Printer Friendly

Associations among international CIMMYT bread wheat yield testing locations in high rainfall areas and their implications for wheat breeding.

THE BREAD WHEAT BREEDING PROGRAM of the International Maize and Wheat Improvement Center (CIMMYT) breeds spring wheat lines for all major wheat growing areas in the developing world (Rajaram and van Ginkel, 2001). On a yearly basis, about 2000 advanced lines are distributed to collaborators in more than 60 countries.

To better target germplasm adapted to different environmental conditions, various agroecological zones or megaenvironments have been defined which represent similar biotic and abiotic stresses, cropping system requirements, and consumer preferences (Rajaram et al., 1994; Rajaram and van Ginkel, 2001). One of these major megaenvironments is characterized by average cropping season rainfall above 500 mm. Representative regions include high rainfall sites in West Asia and North Africa (WANA), the central highlands of eastern and central Africa, the southern cone and Andean highlands of South America, and the highlands of central Mexico. The total area in developing countries exceeds 8 million hectares.

Spring bread wheat (Triticum aestivum L.) germplasm targeted to this high rainfall mega-environment is developed by shuttling segregating generations between two contrasting environments in Mexico; a fully irrigated, high-yield potential site located near Ciudad Obregon in north-western Mexico and a high-rainfall, high disease incidence site at Toluca in the Central Mexican Highlands (Braun et al., 1996). Since 1992, advanced bread wheat lines targeted to this megaenvironment have been distributed globally through the HRWYT, following yield testing at Toluca.

The selection of superior genotypes is generally complicated by the presence of genotype x environment (G x E) interactions, whereby the relative yields of genotypes vary across different environments. A useful way to deal with G x E interactions in a breeding program is to characterize the crop environments in terms of the way they influence the relative performance of genotypes. Pattern analysis, as defined by Williams (1976), is the joint use of classification and ordination methods. Many models have been proposed for extraction and interpretation of grouping patterns (see DeLacy et al. (1996a), for review). The shifted multiplicative model (SHMM) is a clustering method that identifies subsets of locations with negligible crossover interaction, i.e., locations that give the same relative ranking of genotypes (Cornelius et al., 1992; Crossa et al., 1993). However, it requires balanced data sets where the same locations and genotypes are repeated over years. Another, highly recommended classification method for multienvironment trials is the incremental sum of squares (ISS) or Ward's strategy (Ward, 1963), which searches to minimize the incremental sum of squares within each group. ISS has a strong clustering property which tends to minimize the growth of large groups and produces groups of relatively even size (DeLacy et al., 1996a). In multienvironmental trials, where the composition of genotypes change from year to year, but many of the same locations are repeated, a cumulative analysis can be performed by averaging the environmental distance matrices over years and then eliminating rows and columns with empty cells (DeLacy et al., 1996b).

DeLacy et al. (1994) used pattern analysis based on ISS to examine associations among environments over time for the International Spring Wheat Yield Nursery (ISWYN), targeted to all the worlds spring bread wheat growing areas. Recently, we have used both SHMM and ISS classification methods to analyze the relationships among international testing sites for the Semi-Arid Wheat Yield Trial (SAWYT) (Trethowan et al., 2001) and the Elite Spring Wheat Yield Trial (ESWYT) targeted to irrigated environments (Trethowan et al., 2003).

Our objective in the present study was to evaluate the associations among test locations where the HRWYT nursery was grown and to attempt to explain the underlying causes of these associations.

MATERIALS AND METHODS

Locations and Genotypes

Genotypes yield-tested in HRWYTs 1 to 8 (1992-1999) were bred in Mexico for high-rainfall environments by shuttle breeding as described by Braun et al. (1996). Segregating materials were shuttled between the Centro de Investigaciones Agricolas del Noroeste (CIANO) (27[degrees]23'N and elevation 38 m above sea level) near Ciudad Obregon, a dry, fully irrigated site in northwestern Mexico, and CIMMYT's research station at Atizapan, Toluca, in the central Mexican Highlands (19[degrees]16'N and elevation 2640 m above sea level). Leaf rust [caused by Puccinia recondita Roberge ex Desmaz. f. sp. tritici (Eriks. & E. Henri.) D.M. Henderson] and stem rust (caused by P. graminis Pers.:Pers.) are the prevalent diseases at CIANO and stripe rust (caused by P. striiformis Westend.), Septoria blotch (caused by Septoria tritici Roberge in Desmaz.), leaf rust, Fusarium head blight (caused by Fusarium graminearum Schwabe), Barley yellow dwarf virus (BYDV), and intermittent water-logging are common at Toluca. The final yield trials for selecting germplasm to enter the HRWYT nursery were conducted across 2 to 3 yr at the research station in Toluca.

Each year the HRWYT nursery was assembled from seed increased under fungicide application at Mexicali, a disease free site located in northwestern Mexico and distributed globally upon request to international collaborators. Each trial consisted of between 30 and 50 entries and was planted on the basis of local agronomic practices. Two-replicate [alpha]-lattice designs were used (Barreto et al., 1997). The composition of lines varied from year to year, representing newly developed germplasm, and a local check variety representing the best locally adapted germplasm was included at each site each year. The local check varied among locations and in some instances changed between years at the same location. Genotypes were considered as fixed effects and replicates and subblocks within replicates as random effects. Adjusted means were calculated and used in all subsequent SHMM and cumulative cluster analyzes to examine site clustering or grouping. A total of 187 location years or individual yield trials were used for the analysis and are listed in Table 1. Except for the cumulative cluster analysis, all other statistical analyses of the yield data were performed with SAS 8.1 (SAS, 1999).

Although the HRWYT entries were developed for high rainfall conditions with more than 500 mm of rain during the cropping season, many collaborators grew them at locations with lower rainfall, with consequently lower yield levels. Some collaborators in dry areas also grew the nursery under irrigation.

SHMM Analysis

The SHMM clustering procedure (Crossa et al., 1993) was used to examine the associations among sites for each of the eight years of HRWYT and to identify groups of sites with reduced COI. The methods were the same as previously outlined in Trethowan et al. (2001 and 2003). The SHMM model for the mean of the ith genotype (i = 1, 2, ... g) in the jth site (j = 1, 2, ... s) ([[bar]y.sub.ij]) can be represented [[bar]y.sub.ij] = [beta] + [[SIGMA].sup.t.sub.k=1] [[lambda].sub.k] [[alpha].sub.ik] [[gamma].sub.jk] + [[bar][epsilon].sub.ij]. (Seyedsadr and Cornelius, 1992), where [beta] is the shift parameter; [[lambda].sub.k]k([[lambda].sub.1] [greater than or equal to] [[lambda].sub.2] [greater than or equal to] ... [greater than or equal to] [[lambda].sub.t]) are the singular values (scale parameters) that allow imposition of orthonormality constraints on the singular vectors for genotypes, [[alpha].sub.1k], ..., [[alpha].sub.gk] and for sites, [[gamma].sub.1k], ..., [[alpha].sub.sk], such that [[SIGMA].sub.i][[alpha].sup.2.sub.ik] = [[SIGMA].sub.j] [[gamma].sup.2.sub.jk] and [[SIGMA].sub.i][[alpha].sub.ik][[alpha].sub.ik'] = [[SIGMA].sub.j] [[gamma].sub.jk] [[gamma].sub.jk'] = 0 for k [not equal to] k'; [[alpha].sub.ik] and [[gamma].sub.jk], for k = 1,2,3, ..., are called "primary," "secondary," "tertiary," ..., effects of the ith genotype and the jth site, respectively; [[bar][epsilon].sub.ij.] is the residual error.

The distances for all possible pairs of sites were calculated, and dcndrograms constructed using the complete linkage (farthest neighbor) clustering method. The third fusion level was selected as an arbitrary cut-off point to determine site clusters, and each site's associations with other sites were calculated as the number of times (in pair vise comparisons) it clustered together with other sites divided by the total number of possible clusters. A summary table was made by adding associations across years, using the procedure described by Trethowan et al. (2001 and 2003).

Cumulative Cluster Analysis

The cumulative cluster analysis was based on the ISS clustering method recommended by DeLacy and Cooper (1990) and used by Abdalla et al. (1996) and Trethowan et al. (2001 and 2003). Dissimilarities between sites were measured by squared Euclidean distance (SED), and distance matrices were calculated for each year for all sites with at least two years of data. An across-year distance matrix was constructed by averaging distances from each year where data was available for any site-by-site comparison. Since clustering algorithms require a complete distance matrix with values for all site-by-site comparisons, sites contributing empty cells were subsequently removed to end up with a complete distance matrix. The statistical software package SEQRET (DeLacy et al., 1998) was used for conducting the cumulative cluster analysis. The most representative site for each cluster in the resulting dendrogram was identified as that with the smallest sum of SED to other sites.

RESULTS

SHMM Analysis

A summary of the dendrogram results for individual years of the SHMM cluster analysis was made to examine the association of various sites with different geographical regions (Table 2). The frequency at which a site clusters together with other sites in different geographical regions is expressed as a fraction of the total number of possible groupings. Because of the inherent uncertainty of associations based on only a few years of data, only sites with data from at least 4 yr are considered in the following discussion, but data from all locations was used to make the summary in Table 2.

Generally, two types of sites were identified: a group of locations highly associated with other sites around the world and two very distinct locations with very poor associations with other sites. Locations like for example Marcos Juarez in Argentina (54%), Kentziko Thermi in Greece (54%), Bethlehem in South Africa (52%), and other sites with high associations with other sites on the global level, can be considered as good predictors of global yield performance for the high rainfall megaenvironment. The temperature profiles of these sites are shown in Fig. 1, and they all share the same characteristics: Relatively low temperature during the vegetative growth stages and a marked increase in temperature toward maturity.

[FIGURE 1 OMITTED]

On the other hand, the remarkably low associations with other sites shown for Sta. Catalina in Ecuador (6%) and Toluca in Mexico (13%) indicate that yield trial data from these sites are irrelevant for predicting global performance within this mega-environment. The temperature profiles of these sites are also different in that the temperature is either stable or decreasing toward maturity (Fig. 1)

Cumulative Cluster Analysis

Since most locations only planted a few of the eight HRWYTs, a complete distance matrix could only be made for 20 of the 46 locations that planted at least 2 yr of the nursery (Fig. 2). On the basis of the average SED to other locations, the two most representative sites in the resulting dendrogram were the Iranian yield testing location at Bayecola and Bethlehem in South Africa.

[FIGURE 2 OMITTED]

Environmental information about the locations in the cumulative cluster analysis is listed in Table 3. Climatic data has been obtained from the nearest occurring meteorological station that could be found in various databases, bearing in mind that for many locations these are only rough estimates of the actual conditions. The data were included to detect major trends among the different groups and precaution should therefore be used when interpreting data from individual sites. Most collaborators who planted the HRWYT also reported data on days to maturity and diseases. If a disease is not listed, it does not necessarily mean that it did not occur, only that the collaborator did not report data for that disease.

The biggest group in the cumulative cluster analysis comprised more than half of the sites, and they were all characterized by increasing temperature toward maturity. The most prevalent disease in this group was leaf rust, but also stripe rust, powdery mildew, and Septoria blotch were frequently reported. For the other groups, none of the environmental aspects could be clearly associated with the groupings.

DISCUSSION

Generally, there are many external or environmental factors that influence the yield ranking of cultivars from site to site. The most common are latitude, altitude, planting date, cultural management, daylength, temperature, water availability, diseases, and specific abiotic stresses such as low pH.

Both the SHMM analysis and the cumulative cluster analysis point to a common environmental feature of sites with good predictability of global yield performance; they all have increasing temperature toward maturity. However, this study does not provide any data to explain whether there is any direct relationship between temperature profile and the ability to predict global yield performance. Different temperature profiles mostly reflect differences in planting dates, and are also driven by daylength variation, rainfall, and solar radiation. It is likely that this association could also reflect some other underlying characteristics of the sites. Although disease data is scarce for some of the locations with good predictive ability, those locations all have favorable conditions for leaf rust, which is globally among the most important biotic stress factors in wheat production.

Except for Marcos Juarez, which did not occur in the cumulative cluster analysis, all globally good predictors identified from the SHMM summary grouped into group two of the cumulative cluster analysis. The general similarity of these sites and their high association with global performance, as indicated from both analyses, make them good indicators for the identification of germplasm with broad adaptability. On the other hand, Toluca and Sta. Catalina, which were identified from the SHMM analysis as poor predictors of global yield performance, clustered into separate groups of the cumulative cluster analysis, which indicates the more specific adaptability required for these sites.

Sta. Catalina, located in the highlands of Ecuador, has a high incidence of stripe rust, and is characterized by a different, more virulent race composition (Broers and Danial, 1994). There are also indications that the soil at this site is infected with root lesion nematodes (Pratylenchus thornei Sher and Allen; Trethowan, pers. comm.). A similarly low association between Sta. Catalina and other international yield trial sites was also found in the analysis of the ESWYT nursery (Trethowan et al., 2003).

Toluca's low association with global yield performance is also in accordance with earlier findings (Braun et al., 1992). Apart from cooler conditions and shorter days during grain filling with occasional night frosts, Toluca experiences other extremes; about 850 mm of rain falls during the growing season and serious disease epidemics such as stripe rust, Septoria blotch, BYDV, Fusarium head scab, and late-arriving leaf rust occur. Soils are frequently water logged, and crop lodging and preharvest sprouting are constraints.

It is therefore not surprising that the very special conditions at these two locations resulted in a different yield ranking of lines compared with other global test sites which have more favorable conditions for wheat cultivation. Although such extreme locations can be excellent for disease screening (e.g., stripe rust in Sta. Catalina and stripe rust, Septoria blotch and Fusarium head scab in Toluca), it is clear from this analysis that their yield data is not relevant for identification of genotypes with global adaptation. Nevertheless, it is likely that the high rainfall germplasm has benefited from several generations of selection at Toluca, since this ensures photoperiod insensitivity (being part of the Cd. Obregon-Toluca breeding shuttle), and good resistance to the most important diseases and abiotic stresses for high rainfall areas around the world (Braun et al., 1992; Campuzano 1997; Rajaram and van Ginkel, 2001). Further work should aim to identify more representative yield testing locations in Mexico for the high rainfall breeding material.

CONCLUSIONS

This is the first study of the relationships among yield testing sites for the high-rainfall germplasm since the partition of the CIMMYT breeding material into megaenvironments and the establishment of the HRWYT nursery. This paper shows that within the high-rainfall megaenvironment, there are at least two subgroups. The largest subgroup consists of autumn- and/or early spring-planted sites characterized by increasing temperature as the crop approaches maturity and generally high association with global yield performance. The second, and smaller subgroup, consists of spring-planted sites with either stable or decreasing temperature in the later stages of development and low association with global yield performance.

The SHMM analysis identified sites that associated well with overall global yield ranking, thereby facilitating the identification of representative or key yield testing locations. The methods applied in this study are not only relevant to international wheat breeding but can be used to analyze any breeding program, regardless of crop species, as long as a sufficient number of yield trials are sown at representative locations throughout the target area.
Table 1. Summary of locations used in the analysis of HRWYT's
1-8 and their latitude, longitude, altitude and frequency of
occurrence.

Region                     Site                    Country

North
America

              Charlottetown, PEI                Canada
              Saskatoon, SK                     Canada
              Swift Current, SK                 Canada
              Apizaco, Tlaxcala                 Mexico
              Calpulalpan, Tlaxcala             Mexico
              Cd. Obregon                       Mexico
              Chapingo, Texcoco                 Mexico
              El Bajio, Celaya                  Mexico
              El Batan, Texcoco                 Mexico
              Ex-Hacienda El Copal, Irapuato    Mexico
              Juchitepec                        Mexico
              La Barca                          Mexico
              Montecillo, Texcoco               Mexico
              Atizapan, Toluca                  Mexico
              Tepatitlan, Jalisco               Mexico
              Zaragoza                          Mexico
              Plains, GA                        United States

Central
America

              Labor Ovalle, Quezaltenango       Guatemala
              Zamorano                          Honduras

Andes

              San Benito, Cochabamba            Bolivia
              Tibaitata, Bogota                 Colombia
              Sta. Catalina, Cutuglagua         Ecuador
              Cusco                             Peru

Southern
Cone

              La Ballenera, Miramar             Argentina
              Marcos Juarez                     Argentina
              Parana, Entre Rios                Argentina
              Pergamino                         Argentina
              San Miguel de Tucuman             Argentina
              Apucarana                         Brazil
              Bela Vista Do Paraiso             Brazil
              Cruz Alta                         Brazil
              Londrina                          Brazil
              Palotina                          Brazil
              Passo Fundo                       Brazil
              Pelotas                           Brazil
              Graneros, Rancagua                Chile
              Hidango, Litueche                 Chile
              La Platina, Santiago              Chile
              Quilamapu, Chillan                Chile
              Capitan Miranda                   Paraguay
              Don Esteban, Young                Uruguay
              El Cardo, Young                   Uruguay
              Erro, Dolores                     Uruguay
              La Estanzuela                     Uruguay
              San Patricio, Young               Uruguay

Europe

              Domaine Du Chaumoy, Le Subdray    France
              Ferme De Loudes, Castelnaudary    France
              Lectoure, Castillon-la-Bataille   France
              Orgerus                           France
              Kentziko Thermi, Thessaloniki     Greece
              Tolentino                         Italy
              Vollebekk, [Angstrom]s            Norway
              Elvas                             Portugal
              Alameda Del Obispo, Cordoba       Spain
              Finca La Carrerada, Lleida        Spain
              La Mojonera, Toledo               Spain
              Rancho De La Merced, Cadiz        Spain
              Torregrossa/Belloc, Lleida        Spain
              Kharkov                           Ukraine
              Odessa                            Ukraine
              Ustymovska                        Ukraine

West Asia
and North
Africa

              Guelma                            Algeria
              Baku                              Azerbaijan
              Komombo, Aswan                    Egypt
              Araghi Mahaleh, Gorgan            Iran
              Bayecola, Sari                    Iran
              Darab                             Iran
              Karaj, Tehran                     Iran
              Mazraeh Nemoneh, Gorgan           Iran
              Moghan, Ardabil                   Iran
              Al-Tuwaitha, Baghdad              Iraq
              Tel Hadya, Aleppo                 Syria
              Beja, Tunis                       Tunisia
              Aydin                             Turkey
              Bornova, Izmir                    Turkey
              Edirne                            Turkey
              Menemen, Izmir                    Turkey
              Samsun                            Turkey
              Bishkek                           Kyrgyzstan

Southern
and Eastern
Africa

              Munanira                          Burundi
              Holetta, Addis Ababa              Ethiopia
              Njoro                             Kenya
              Bembeke                           Malawi
              Bethlehem                         South Africa
              Houthaaldoorns, Lichtenburg       South Africa
              Langgewens, Gouda                 South Africa
              Moredou, Gouda                    South Africa
              Lyamungo                          Tanzania
              Simba-Tilotanga, Lyamungo         Tanzania
              Mbala                             Zambia
              Harare                            Zimbabwe

South Asia

              New Delhi                         India
              Islamabad                         Pakistan
              Mingora, Swat                     Pakistan
              Quota                             Pakistan

East Asia

              Harbin                            China
              Hongxinglong                      China
              Lanzhou, Gansu                    China
              Kitami, Kunneppu                  Japan
              Dan Phung                         Viet Nam

Oceania

              Lincoln, Christchurch             New Zealand

Region                     Site                 Latitude

North
America

              Charlottetown, PEI                46[degrees]20'N
              Saskatoon, SK                     52[degrees]9'N
              Swift Current, SK                 50[degrees]17'N
              Apizaco, Tlaxcala                 19[degrees]25'N
              Calpulalpan, Tlaxcala             19[degrees]35'N
              Cd. Obregon                       27[degrees]23'N
              Chapingo, Texcoco                 19[degrees]17'N
              El Bajio, Celaya                  20[degrees]32'N
              El Batan, Texcoco                 19[degrees]31'N
              Ex-Hacienda El Copal, Irapuato    20[degrees]45'N
              Juchitepec                        19[degrees]6'N
              La Barca                          20[degrees]15'N
              Montecillo, Texcoco               19[degrees]26'N
              Atizapan, Toluca                  19[degrees]16'N
              Tepatitlan, Jalisco               20[degrees]51'N
              Zaragoza                          28[degrees]33'N
              Plains, GA                        32[degrees]28'N

Central
America

              Labor Ovalle, Quezaltenango       14[degrees]52'N
              Zamorano                          14[degrees]0'N

Andes

              San Benito, Cochabamba            17[degrees]30'S
              Tibaitata, Bogota                 4[degrees]4'N
              Sta. Catalina, Cutuglagua         0[degrees]22'S
              Cusco                             13[degrees]24'S

Southern
Cone

              La Ballenera, Miramar             38[degrees]8'S
              Marcos Juarez                     32[degrees]42'S
              Parana, Entre Rios                31[degrees]50'S
              Pergamino                         33[degrees]56'S
              San Miguel de Tucuman             26[degrees]48'S
              Apucarana                         23[degrees]36'S
              Bela Vista Do Paraiso             23[degrees]0'S
              Cruz Alta                         28[degrees]38'S
              Londrina                          23[degrees]22'S
              Palotina                          24[degrees]17'S
              Passo Fundo                       28[degrees]15'S
              Pelotas                           31[degrees]52'S
              Graneros, Rancagua                34[degrees]3'S
              Hidango, Litueche                 34[degrees]6'S
              La Platina, Santiago              33[degrees]27'S
              Quilamapu, Chillan                36[degrees]31'S
              Capitan Miranda                   27[degrees]17'S
              Don Esteban, Young                32[degrees]40'S
              El Cardo, Young                   32[degrees]41'S
              Erro, Dolores                     33[degrees]43'S
              La Estanzuela                     34[degrees]20'S
              San Patricio, Young               33[degrees]41'S

Europe

              Domaine Du Chaumoy, Le Subdray    47[degrees]2'N
              Ferme De Loudes, Castelnaudary    43[degrees]30'N
              Lectoure, Castillon-la-Bataille   44[degrees]50'N
              Orgerus                           48[degrees]50'N
              Kentziko Thermi, Thessaloniki     40[degrees]38'N
              Tolentino                         43[degrees]15'N
              Vollebekk, [Angstrom]s            59[degrees]40'N
              Elvas                             38[degrees]54'N
              Alameda Del Obispo, Cordoba       37[degrees]53'N
              Finca La Carrerada, Lleida        41[degrees]35'N
              La Mojonera, Toledo               39[degrees]58'N
              Rancho De La Merced, Cadiz        36[degrees]43'N
              Torregrossa/Belloc, Lleida        41[degrees]35'N
              Kharkov                           50[degrees]0'N
              Odessa                            46[degrees]27'N
              Ustymovska                        49[degrees]22'N

West Asia
and North
Africa

              Guelma                            36[degrees]28'N
              Baku                              40[degrees]5'N
              Komombo, Aswan                    23[degrees]8'N
              Araghi Mahaleh, Gorgan            36[degrees]55'N
              Bayecola, Sari                    36[degrees]42'N
              Darab                             29[degrees]10'N
              Karaj, Tehran                     35[degrees]50'N
              Mazraeh Nemoneh, Gorgan           36[degrees]30'N
              Moghan, Ardabil                   38[degrees]15'N
              Al-Tuwaitha, Baghdad              34[degrees]0'N
              Tel Hadya, Aleppo                 36[degrees]1'N
              Beja, Tunis                       36[degrees]44'N
              Aydin                             36[degrees]42'N
              Bornova, Izmir                    38[degrees]27'N
              Edirne                            41[degrees]40'N
              Menemen, Izmir                    38[degrees]40'N
              Samsun                            41[degrees]18'N
              Bishkek                           42[degrees]54'N

Southern
and Eastern
Africa

              Munanira                          2[degrees]55'S
              Holetta, Addis Ababa              9[degrees]3'N
              Njoro                             0[degrees]25'S
              Bembeke                           14[degrees]10'S
              Bethlehem                         28[degrees]11'S
              Houthaaldoorns, Lichtenburg       26[degrees]10'S
              Langgewens, Gouda                 33[degrees]17'S
              Moredou, Gouda                    33[degrees]18'S
              Lyamungo                          3[degrees]14'S
              Simba-Tilotanga, Lyamungo         3[degrees]13'S
              Mbala                             8[degrees]53'S
              Harare                            17[degrees]43'S

South Asia

              New Delhi                         28[degrees]33'N
              Islamabad                         33[degrees]45'N
              Mingora, Swat                     34[degrees]36'N
              Quota                             30[degrees]12'N

East Asia

              Harbin                            45[degrees]41'N
              Hongxinglong                      46[degrees]43'N
              Lanzhou, Gansu                    36[degrees]6'N
              Kitami, Kunneppu                  43[degrees]47'N
              Dan Phung                         21[degrees]5'N

Oceania

              Lincoln, Christchurch             43[degrees]38'S

Region                     Site                 Longitude

North
America

              Charlottetown, PEI                63[degrees]0'W
              Saskatoon, SK                     106[degrees]36'W
              Swift Current, SK                 107[degrees]50'W
              Apizaco, Tlaxcala                 98[degrees]09'W
              Calpulalpan, Tlaxcala             98[degrees]38'W
              Cd. Obregon                       109[degrees]56'W
              Chapingo, Texcoco                 98[degrees]53'W
              El Bajio, Celaya                  100[degrees]49'W
              El Batan, Texcoco                 98[degrees]50'W
              Ex-Hacienda El Copal, Irapuato    101[degrees]20'W
              Juchitepec                        98[degrees]52'W
              La Barca                          102[degrees]33'W
              Montecillo, Texcoco               98[degrees]54'W
              Atizapan, Toluca                  99[degrees]51'W
              Tepatitlan, Jalisco               102[degrees]39'W
              Zaragoza                          100[degrees]55'W
              Plains, GA                        85[degrees]30'W

Central
America

              Labor Ovalle, Quezaltenango       91[degrees]30'W
              Zamorano                          87[degrees]2'W

Andes

              San Benito, Cochabamba            66[degrees]6'W
              Tibaitata, Bogota                 74[degrees]12'W
              Sta. Catalina, Cutuglagua         78[degrees]32'W
              Cusco                             71[degrees]52'W

Southern
Cone

              La Ballenera, Miramar             57[degrees]55'W
              Marcos Juarez                     62[degrees]7'W
              Parana, Entre Rios                60[degrees]31'W
              Pergamino                         60[degrees]33'W
              San Miguel de Tucuman             65[degrees]12'W
              Apucarana                         51[degrees]23'W
              Bela Vista Do Paraiso             51[degrees]12'W
              Cruz Alta                         53[degrees]36'W
              Londrina                          51[degrees]10'W
              Palotina                          53[degrees]50'W
              Passo Fundo                       52[degrees]25'W
              Pelotas                           52[degrees]21'W
              Graneros, Rancagua                70[degrees]42'W
              Hidango, Litueche                 71[degrees]47'W
              La Platina, Santiago              70[degrees]38'W
              Quilamapu, Chillan                71[degrees]55'W
              Capitan Miranda                   55[degrees]49'W
              Don Esteban, Young                57[degrees]23'W
              El Cardo, Young                   57[degrees]40'W
              Erro, Dolores                     58[degrees]5'W
              La Estanzuela                     57[degrees]41'W
              San Patricio, Young               57[degrees]36'W

Europe

              Domaine Du Chaumoy, Le Subdray    2[degrees]20'E
              Ferme De Loudes, Castelnaudary    2[degrees]0'E
              Lectoure, Castillon-la-Bataille   0[degrees]2'E
              Orgerus                           1[degrees]42'E
              Kentziko Thermi, Thessaloniki     22[degrees]57'E
              Tolentino                         13[degrees]30'E
              Vollebekk, [Angstrom]s            10[degrees]47'E
              Elvas                             7[degrees]9'W
              Alameda Del Obispo, Cordoba       4[degrees]47'W
              Finca La Carrerada, Lleida        0[degrees]45'W
              La Mojonera, Toledo               4[degrees]45'W
              Rancho De La Merced, Cadiz        6[degrees]9'W
              Torregrossa/Belloc, Lleida        0[degrees]45'E
              Kharkov                           36[degrees]25'E
              Odessa                            30[degrees]42'E
              Ustymovska                        34[degrees]20'E

West Asia
and North
Africa

              Guelma                            7[degrees]28'E
              Baku                              48[degrees]5'E
              Komombo, Aswan                    32[degrees]47'E
              Araghi Mahaleh, Gorgan            54[degrees]20'E
              Bayecola, Sari                    53[degrees]13'E
              Darab                             55[degrees]13'E
              Karaj, Tehran                     50[degrees]58'E
              Mazraeh Nemoneh, Gorgan           53[degrees]30'E
              Moghan, Ardabil                   48[degrees]18'E
              Al-Tuwaitha, Baghdad              45[degrees]0'E
              Tel Hadya, Aleppo                 36[degrees]56'E
              Beja, Tunis                       9[degrees]8'E
              Aydin                             26[degrees]45'E
              Bornova, Izmir                    27[degrees]14'E
              Edirne                            26[degrees]34'E
              Menemen, Izmir                    27[degrees]4'E
              Samsun                            36[degrees]20'E
              Bishkek                           74[degrees]36'E

Southern
and Eastern
Africa

              Munanira                          29[degrees]34'E
              Holetta, Addis Ababa              38[degrees]30'E
              Njoro                             36[degrees]0'E
              Bembeke                           34[degrees]26'E
              Bethlehem                         28[degrees]11'E
              Houthaaldoorns, Lichtenburg       26[degrees]10'E
              Langgewens, Gouda                 18[degrees]40'E
              Moredou, Gouda                    19[degrees]2'E
              Lyamungo                          37[degrees]53'E
              Simba-Tilotanga, Lyamungo         37[degrees]53'E
              Mbala                             31[degrees]22'E
              Harare                            31[degrees]5'E

South Asia

              New Delhi                         77[degrees]16'E
              Islamabad                         73[degrees]6'E
              Mingora, Swat                     72[degrees]26'E
              Quota                             67[degrees]1'E

East Asia

              Harbin                            126[degrees]37'E
              Hongxinglong                      131[degrees]33'E
              Lanzhou, Gansu                    103[degrees]53'E
              Kitami, Kunneppu                  143[degrees]42'E
              Dan Phung                         105[degrees]38'E

Oceania

              Lincoln, Christchurch             172[degrees]30'E

Region                     Site                 Altitude m

North
America

              Charlottetown, PEI                     15
              Saskatoon, SK                         497
              Swift Current, SK                     825
              Apizaco, Tlaxcala                    2408
              Calpulalpan, Tlaxcala                2580
              Cd. Obregon                            38
              Chapingo, Texcoco                    2249
              El Bajio, Celaya                     1765
              El Batan, Texcoco                    2249
              Ex-Hacienda El Copal, Irapuato       1750
              Juchitepec                           2670
              La Barca                             1517
              Montecillo, Texcoco                  2254
              Atizapan, Toluca                     2640
              Tepatitlan, Jalisco                  1900
              Zaragoza                              350
              Plains, GA                            400

Central
America

              Labor Ovalle, Quezaltenango          2407
              Zamorano                              805

Andes

              San Benito, Cochabamba               2730
              Tibaitata, Bogota                    2550
              Sta. Catalina, Cutuglagua            3050
              Cusco                                2900

Southern
Cone

              La Ballenera, Miramar                  30
              Marcos Juarez                         110
              Parana, Entre Rios                    110
              Pergamino                              65
              San Miguel de Tucuman                 460
              Apucarana                             845
              Bela Vista Do Paraiso                 618
              Cruz Alta                             473
              Londrina                              540
              Palotina                              340
              Passo Fundo                           684
              Pelotas                                12
              Graneros, Rancagua                    479
              Hidango, Litueche                     296
              La Platina, Santiago                  629
              Quilamapu, Chillan                    217
              Capitan Miranda                       200
              Don Esteban, Young                     96
              El Cardo, Young                        80
              Erro, Dolores                          45
              La Estanzuela                          81
              San Patricio, Young                    80

Europe

              Domaine Du Chaumoy, Le Subdray        170
              Ferme De Loudes, Castelnaudary        170
              Lectoure, Castillon-la-Bataille        78
              Orgerus                               120
              Kentziko Thermi, Thessaloniki          10
              Tolentino                             140
              Vollebekk, [Angstrom]s                 90
              Elvas                                 280
              Alameda Del Obispo, Cordoba           110
              Finca La Carrerada, Lleida            360
              La Mojonera, Toledo                   220
              Rancho De La Merced, Cadiz             20
              Torregrossa/Belloc, Lleida            200
              Kharkov                               170
              Odessa                                 34
              Ustymovska                            104

West Asia
and North
Africa

              Guelma                                228
              Baku                                   28
              Komombo, Aswan                        142
              Araghi Mahaleh, Gorgan                  5
              Bayecola, Sari                          3
              Darab                                1100
              Karaj, Tehran                        1321
              Mazraeh Nemoneh, Gorgan              1011
              Moghan, Ardabil                      1343
              Al-Tuwaitha, Baghdad                   62
              Tel Hadya, Aleppo                     292
              Beja, Tunis                           150
              Aydin                                  60
              Bornova, Izmir                         10
              Edirne                                 48
              Menemen, Izmir                         10
              Samsun                                 10
              Bishkek                               813

Southern
and Eastern
Africa

              Munanira                             2120
              Holetta, Addis Ababa                 2390
              Njoro                                2165
              Bembeke                              1560
              Bethlehem                            1687
              Houthaaldoorns, Lichtenburg          1477
              Langgewens, Gouda                      91
              Moredou, Gouda                         82
              Lyamungo                             1280
              Simba-Tilotanga, Lyamungo            1750
              Mbala                                1668
              Harare                               1480

South Asia

              New Delhi                             228
              Islamabad                             683
              Mingora, Swat                        1000
              Quota                                1600

East Asia

              Harbin                                172
              Hongxinglong                           75
              Lanzhou, Gansu                       1517
              Kitami, Kunneppu                      196
              Dan Phung                              10

Oceania

              Lincoln, Christchurch                  11

                                                   HRWYT nursery
Region                     Site                    number (1-8)

North
America

              Charlottetown, PEI                      1, 2, 6
              Saskatoon, SK                              6
              Swift Current, SK                          3
              Apizaco, Tlaxcala                        7, 8
              Calpulalpan, Tlaxcala                      7
              Cd. Obregon                              7, 8
              Chapingo, Texcoco                        3, 7
              El Bajio, Celaya                           6
              El Batan, Texcoco                       2, 3, 5
              Ex-Hacienda El Copal, Irapuato             8
              Juchitepec                                 5
              La Barca                                   1
              Montecillo, Texcoco                      7, 8
              Atizapan, Toluca                   2, 3, 5, 6, 7, 8
              Tepatitlan, Jalisco                      1, 2
              Zaragoza                                   6
              Plains, GA                                 4

Central
America

              Labor Ovalle, Quezaltenango              4, 5
              Zamorano                                 5, 7

Andes

              San Benito, Cochabamba                  2, 4, 6
              Tibaitata, Bogota                          1
              Sta. Catalina, Cutuglagua            1, 2, 4, 5, 6
              Cusco                                      2

Southern
Cone

              La Ballenera, Miramar                      7
              Marcos Juarez                         4, 6, 7, 8
              Parana, Entre Rios                    1, 5, 6, 8
              Pergamino                             2, 3, 7, 8
              San Miguel de Tucuman                      6
              Apucarana                                  2
              Bela Vista Do Paraiso                    1, 7
              Cruz Alta                               1, 4, 5
              Londrina                                 2, 5
              Palotina                                 4, 8
              Passo Fundo                                7
              Pelotas                                    1
              Graneros, Rancagua                         5
              Hidango, Litueche                       4, 5, 7
              La Platina, Santiago                       2
              Quilamapu, Chillan                      1, 7, 8
              Capitan Miranda                         2, 4, 5
              Don Esteban, Young                         5
              El Cardo, Young                            7
              Erro, Dolores                              6
              La Estanzuela                         1, 2, 4, 5
              San Patricio, Young                        2

Europe

              Domaine Du Chaumoy, Le Subdray             2
              Ferme De Loudes, Castelnaudary           1, 2
              Lectoure, Castillon-la-Bataille            3
              Orgerus                                  1, 2
              Kentziko Thermi, Thessaloniki        1, 2, 4, 5, 6
              Tolentino                                  1
              Vollebekk, [Angstrom]s                     2
              Elvas                                1, 2, 4, 5, 6
              Alameda Del Obispo, Cordoba                4
              Finca La Carrerada, Lleida                 5
              La Mojonera, Toledo                        1
              Rancho De La Merced, Cadiz              4, 5, 6
              Torregrossa/Belloc, Lleida                 2
              Kharkov                                  4, 5
              Odessa                                     5
              Ustymovska                               6, 7

West Asia
and North
Africa

              Guelma                                     1
              Baku                                5 (sown twice)
              Komombo, Aswan                             6
              Araghi Mahaleh, Gorgan                     7
              Bayecola, Sari                        1, 2, 3, 7
              Darab                                    1, 2
              Karaj, Tehran                            1, 2
              Mazraeh Nemoneh, Gorgan                    2
              Moghan, Ardabil                            7
              Al-Tuwaitha, Baghdad                       6
              Tel Hadya, Aleppo                       5, 6, 7
              Beja, Tunis                              1, 4
              Aydin                                      8
              Bornova, Izmir                             8
              Edirne                                     8
              Menemen, Izmir                           4, 5
              Samsun                                     7
              Bishkek                                    7

Southern
and Eastern
Africa

              Munanira                                   3
              Holetta, Addis Ababa                       6
              Njoro                                    5, 6
              Bembeke                                    5
              Bethlehem                         1, 2, 3, 5, 6, 7, 8
              Houthaaldoorns, Lichtenburg              3, 5
              Langgewens, Gouda                          3
              Moredou, Gouda                           2, 4
              Lyamungo                                1, 2, 3
              Simba-Tilotanga, Lyamungo                6, 7
              Mbala                                      1
              Harare                                     6

South Asia

              New Delhi                                  8
              Islamabad                               6, 7, 8
              Mingora, Swat                            6, 7
              Quota                                      6

East Asia

              Harbin                                     1
              Hongxinglong                               1
              Lanzhou, Gansu                             2
              Kitami, Kunneppu                         3, 4
              Dan Phung                                  4

Oceania

              Lincoln, Christchurch                    4, 5

Table 2. Summary of regional associations for individual sites in
the SHMM analysis that planted at least 50% of the yield trials.

                   Number of groupings with the region/Total
                             number of groupings

                              Sta.      Marcos
Sites              Toluca   Catalina    Juarez      Parana

Country            Mexico   Ecuador    Argentina   Argentina
Number of
  yield trials       6         5           4           4
North
  America           2/21     1/16        6/17        5/16
Central America     2/3      0/3         1/2         0/2
Andes               1/6      0/5         2/4         1/5
Southern Cone       4/33     3/31       10/19        7/19
Europe              0/19     2/28        4/10        9/16
North Africa
  and West Asia     5/21     0/18        9/14       10/15
Southern and
  Eastern Africa    1/20     0/16        7/9        10/13
South Asia          2/7      0/3         6/7         4/5
East Asia           0/2      1/5         0/2         0/2
New Zealand         0/1      0/2         1/1         1/1
Total              17/133    7/127      46/85       47/94
%                    13       6          54          50

                      Number of groupings with the
                         region/Total number of
                               groupings

                                   La       Kentziko
     Sites         Pergamino   Estanzuela    Thermi

Country            Argentina    Uruguay      Greece
Number of
   yield trials        4           4           5
North
  America            6/19        4/11         8/16
Central America      1/1         1/3          0/3
Andes                1/3         2/8          2/10
Southern Cone       10/17       13/23        15/31
Europe               8/9        12/24        14/23
North Africa
  and West Asia      4/14       12/15        12/18
Southern and
  Eastern Africa     8/11        5/11        12/16
South Asia           1/4         0/0          3/3
East Asia            1/2         1/5          1/5
New Zealand          0/0         1/2          1/2
Total               40/80       51/102       68/127
%                     50          50           54

                        Number of groupings with
                       the region/Total number of
                              groupings

     Sites          Elvas     Bayecola    Bethlehem

Country            Portugal     Iran     South Africa
Number of
   yield trials       5          4            7
North
  America            4/16       6/17       11/30
Central America      1/3        0/1         1/3
Andes                3/10       1/5         2/8
Southern Cone       18/31      12/22       21/39
Europe               9/23       9/15       18/25
North Africa
  and West Asia     12/18       9/12       13/26
Southern and
  Eastern Africa     5/16       4/13       10/16
South Asia           0/3        2/2         4/7
East Asia            1/5        1/4         2/4
New Zealand          1/2        0/0         1/1
Total               54/127     44/91       83/159
%                    43         48          52

Table 3. Summary of environmental data for locations in the
cumulative cluster analysis.

Group       Site name          Country          Season

1       San Benito           Bolivia        January-May
1       Toluca               Mexico         June-October

2       Darab                Iran           December-May
2       Elvas                Portugal       December-June
2       Capitan Miranda      Paraguay       June-October
2       Kentziko Thermi      Greece         December-June
2       Bethlehem            South Africa   August-December
2       Karaj, Teheran       Iran           December-May
2       Parana               Argentina      July-November
2       Pergamino            Argentina      July-December
2       Lyamungo             Tanzania       May-October
2       Bayecola, Sari       Iran           December-May
2       La Estanzuela        Uruguay        July-December

3       Tepatitlan           Mexico         July-November
3       Charlottetown, PEI   Canada         May-September
3       Sta. Catalina        Ecuador        January-July

4       Orgerus              France         March-July
4       Ferme De Loudes      France         November-July
4       Londrina             Brazil         April-August
4       El Batan             Mexico         June-October

                              Season       Season
                             rainfall      temp.
Group       Site name           mm       [degrees]C

1       San Benito              559         17.8
1       Toluca                  847         13.7

2       Darab                irrigated      13.3
2       Elvas                   381         12.6
2       Capitan Miranda         677         18.0
2       Kentziko Thermi         252         12.3
2       Bethlehem            irrigated      14.3
2       Karaj, Teheran       irrigated      10.3
2       Parana                  343         15.7
2       Pergamino               397         15.1
2       Lyamungo                808         17.7
2       Bayecola, Sari          330         10.8
2       La Estanzuela           534         16.1

3       Tepatitlan              674         20.4
3       Charlottetown, PEI      409         14.8
3       Sta. Catalina           761         13.2

4       Orgerus                 262         12.1
4       Ferme De Loudes         310         14.8
4       Londrina                435         18.5
4       El Batan                561         16.7

                               Temp.       Source
                              profile     ([double   Yield
Group       Site name        ([dagger])   dagger])   Mg/ha

1       San Benito               D           5        2.5
1       Toluca                   D           6        6.0

2       Darab                    I           2        7.0
2       Elvas                    I           2        2.9
2       Capitan Miranda          I           1        2.7
2       Kentziko Thermi          I           1        3.8
2       Bethlehem                I           1        3.6
2       Karaj, Teheran           I           1        6.5
2       Parana                   I           1        2.0
2       Pergamino                I           3        3.5
2       Lyamungo                 I           3        3.3
2       Bayecola, Sari           I           2        7.2
2       La Estanzuela            I           1        5.2

3       Tepatitlan               D           1        4.1
3       Charlottetown, PEI       D           1        3.7
3       Sta. Catalina            S           1        3.3

4       Orgerus                  I           1        4.9
4       Ferme De Loudes          I           1        6.1
4       Londrina                 S           4        3.7
4       El Batan                 D           6        3.8

                             Days to     Diseases reported
Group       Site name        maturity       ([section])

1       San Benito              --
1       Toluca                 139      LR, YR, SFD

2       Darab                  156      LR, YR, ST, SFD
2       Elvas                  181      LR, PM, ST
2       Capitan Miranda         --      LR, PM
2       Kentziko Thermi        191      PM
2       Bethlehem              155      LR, YR, PM
2       Karaj, Teheran         173      LR, YR
2       Parana                 123      LR
2       Pergamino               --      LR, ST, SFD
2       Lyamungo                --      LR, YR, PM
2       Bayecola, Sari         180      LR, YR, PM, ST, SFD
2       La Estanzuela           --      LR, ST

3       Tepatitlan             109      LR
3       Charlottetown, PEI     110      PM, SFD
3       Sta. Catalina           --      YR, SFD

4       Orgerus                 --
4       Ferme De Loudes         --      PM
4       Londrina                --      LR
4       El Batan               123      LR, YR

([dagger]) Tendencies over the three last months of the growing
season: D = Decreasing temperature, S = Stable temperature,
I = Increasing temperature

([double dagger]) These are the sources used for obtaining long-term
averages for rainfall and temperature:

1. World Climate at: http://www.worldclimate.com; verified 12 March
2004.

2. Weather Base at: http://www.weatherbase.com/; verified 12 March
2004.

3. Worldwide Bioclimatic Classification System at:
http://www.globalbioclimatics.org/data/indice1_1.html; verified 12
March 2004.

4. Major World Crop Areas and Climatic Profiles at:
http://www.usda.gov/oce/waob/jawf/profiles/mwcacp2.htm; verified
12 March 2004.

5. Monthly Climate Profiles at:
http://www.bestplaces.net/html/climatewld1.asp; verified
12 March 2004.

6. CIMMYT experimental stations.

([section]) LR = Leaf rust, YR = Stripe rust, PM = Powdery mildew,
ST = Septoria tritici, SFD = Severe foliar diseases.


ACKNOWLEDGMENTS

This study was conducted during the first author's stay at CIMMYT in Mexico, which was made possible by a grant from the Research Council of Norway. The authors are thankful to Tom Payne for providing valuable information about the international yield testing locations, and to Jose Crossa for advise on the use of statistical methods.

REFERENCES

Abdalla, O.S., J. Crossa, E. Autrique, and 1.H. DeLacy. 1996. Relationships among international testing sites of spring durum wheat. Crop Sci. 36:33-40.

Barreto, H.J., G.O. Edmeades, S.C. Chapman, and J. Crossa. 1997. The alpha lattice design in plant breeding and agronomy: Generation and analysis, p. 544-551. In G.O. Edmeades et al. (ed.) Developing drought- and low N-tolerant maize. Mexico, D.F., Mexico.

Braun, H.J., W.H. Pfeiffer, and W.G. Pollmer. 1992. Environments for selecting widely adapted spring wheat. Crop Sci. 32:1420-1427.

Braun, H.J., S. Rajaram, and M. van Ginkel. 1996. CIMMYT's approach to breeding for wide adaptation. Euphytica 92:175-183.

Broers, L.H.M., and D.L. Danial. 1994. Stability of resistance to yellow rust in spring bread wheat: Field observations at three highland locations, p. 91-96. In D.L. Danial (ed.) Aspects of durable resistance in wheat to yellow rust. Ph.D. Thesis. Wageningen Agricultural University. Wageningen, the Netherlands.

Campuzano, L.F. 1997. Selection systems for wheat (Triticum aestivum L.) in alternate enviroments and in situ. (In Spanish, with English abstract). Ph.D. Thesis. Colegio de Postgraduados, Montecillos, Mexico.

Cornelius, P.L., M. Seyedsadr, and J. Crossa. 1992. Using the shifted multiplicative model to search for "separability" in crop cultivar trials. Theor. Appl. Genet. 84:161-172.

Crossa, J., P.L. Cornelius, M. Seyedsadr, and P. Byrne. 1993. A shifted multiplicative model cluster analysis for grouping environments without genotypic rank change. Theor. Appl. Genet. 85:577-386.

DeLacy, I.H., K.E. Basford, M. Cooper, J.K. Bull, and C.G. McLaren. 1996a. Analysis of multi-environment trials an historical perspective. p. 39-124. In M. Cooper and G.L. Hammer (ed.) Plant adaptation and crop improvement. CAB International. Wallingford, UK.

DeLacy, I.H., K.E. Basford, M. Cooper, and P.N. Fox. 1996b. Retrospective analysis of historical data sets from multi-environment trials-theoretical development, p. 243-267. In M. Cooper and G.L. Hammer (ed.) Plant adaptation and crop improvement. CAB International. Wallingford, UK.

DeLacy, I.H., and M. Cooper. 1990. Pattern analysis for the analysis of regional variety trials, p. 301-334. In M.S. Kang (ed.) Genotype-by-environment interaction in plant breeding. Louisiana State Univ, Baton Rouge, LA, USA.

DeLacy, I.H., M. Cooper, K.E. Basford, and P.N. Fox. 1998. The SEORET package. Computer programs for retrospective pattern analysis, p. 39. In Plant improvement group research Report No 1. School of land and food, The University of Queensland, Brisbane, Australia.

DeLacy, I.H., P.N. Fox, J.D. Corben, J. Crossa, S. Rajaram, R.A. Fischer, and M. van Ginkel. 1994. Long-term association of locations for testing spring bread wheat. Euphytica 72:95-106.

Rajaram, S., and M. van Ginkel. 2001. Mexico, 50 years of International Wheat Breeding. p. 579-608 (chapter 22) In A.P. Bonjean and W.J. Angus (cd.) The world wheat book, A history of wheat breeding. Lavoisier Publishing, Paris.

Rajaram, S., M. van Ginkel, and R.A. Fischer. 1994. CIMMYT's wheal breeding mega-environments (ME). p. 1101 1106 In Proceedings of the 8th International Wheat Genetics Symposium, Beijing, China. SAS. 1999. Version 8.1. SAS Institute Inc., Cary, NC, USA.

Seyedsadr, M., and P.L. Cornelius. 1992. Shifted multiplicative model for nonadditive two way tables. Commu. Statist. B. Simulation Comput. 21:807-822.

Trethowan, R.M., J. Crossa, M. van Ginkel, and S. Rajaram. 2001. Relationships among bread wheat international yield testing locations in dry areas. Crop Sci. 41:1461-1469.

Trethowan, R.M., M. van Ginkel, K. Ammar, J. Crossa, B. Cukadar, S. Rajaram, and E, Hernandez. 2003. Relationships among twenty years of high yielding international bread wheat yield evaluation environments. Crop Sci. 43:1698-1711.

Ward, J.H. 1963. Hierarchical grouping to optimize an objective function. J. Am. Stat. Assoc. 58:236-244.

Williams, W.T. 1976. Pattern analysis in agricultural science, Elsevier, Amsterdam, the Netherlands.

M. Lillemo, * M. van Ginkel, R. M. Trethowan, E. Hernandez, and S. Rajaram

M. Lillemo, Dep. of Plant and Environmental Sciences, Agricultural Univ. of Norway, P.O. Box 5003, N-1432 As, Norway; M. van Ginkel, R.M. Trethowan, E. Hernandez, and S. Rajaram, Wheat Program, International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, 06600 Mexico DF, Mexico. Received 10 Mar. 2003. * Corresponding author (morten.lillemo@nlh.no).
COPYRIGHT 2004 Crop Science Society of America
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2004 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:Crop Breeding, Genetics & Cytology
Author:Lillemo, M.; van Ginkel, M.; Trethowan, R.M.; Hernandez, E.; Rajaram, S.
Publication:Crop Science
Article Type:Author Abstract
Date:Jul 1, 2004
Words:6784
Previous Article:Inheritance of high levels of adult-plant resistance to stripe rust in five spring wheat genotypes.
Next Article:Geographical parameters and proximity to related species predict genetic variation in the inbred potato species Solanum verrucosum Schlechtd.
Topics:

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters