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Phenotypic effects of introgressing French winter germplasm into hybrid spring canola.

ONE OF THE MOST remarkable achievements of modern plant breeding was the development of canola quality Brassica napus from rapeseed by the reduction of erucic acid content in the oil and glucosinolates in the meal (Becker et al., 1999; Buzza, 1995; Hickling, 2001). Two forms of canola cultivars are grown in temperate regions worldwide: those that require or respond to vernalization (winter cultivars) and are widely grown in Europe and Asia as fall-seeded crops and those that behave as annuals (spring cultivars) and are grown extensively in Canada, Australia, and northern Europe as spring-seeded crops. Winter canola cultivars usually outyield spring types, when they are grown in optimal environments (Downey and Rakow, 1987; Thomas, 1984). Although most of the seed is produced by open-pollinated cultivars, it is well known that canola has sufficient heterosis to justify the effort to develop hybrid cultivars (Sernyk and Stefansson, 1983; Grant and Beversdorf, 1985; Lefort-Buson et al., 1986, 1987; Brandle and McVetty, 1989). Several systems for commercial production of [F.sub.1] hybrid seed are now available, including cytoplasmic male-sterility (CMS) systems (Buzza, 1995; Becker et al., 1999) and the dominant genic male-sterility Seedlink (Plant Genetic Systems, NV, Gent, Belgium) system (Mariani et al., 1990, 1992; Goldberg et al., 1993).

Most studies on heterosis in canola have been conducted within either spring types (Sernyk and Stefansson, 1983; Grant and Beversdorf, 1985; Brandle and McVetty, 1989; Diers et al., 1996; Starmer et al., 1998) or winter types (Lefort-Buson et al., 1986, 1987; Leon, 1991; Ali et al., 1995). In a genetic diversity study based on RFLP markers, Diers and Osborn (1994) were able to separate the germplasm of oilseed B. napus into three main groups of cultivars. One group included only spring cultivars, a second included mostly winter accessions, and a third consisted of intermediate types from Asia and Australia which had characteristics of both growth habits (spring and winter). These results indicate that winter and spring forms of oilseed rape represent very distinct genetic groups. Diers and Osborn (1994) suggested that breeders have maintained the spring and winter forms as distinct gene pools, intercrossing them only when they need to introduce major genes through backcrossing for traits, such as canola quality. Therefore, the winter germplasm may represent an unexploited source of genetic diversity to introgress into the spring-canola germplasm to broaden its genetic base and potentially boost seed yield of hybrids.

On the basis of this premise, Butruille et al. (1999a) used an introgression approach to develop spring-type hybrids of B. napus with genes coming from winter germplasm. They evaluated 19 DH lines, derived from a cross between a spring canola and a winter rapeseed cultivar, and their testcrosses to two spring canola cultivars and found that the average yield of the experimental hybrids was higher than the yield of hybrid cultivars, inbreds and spring x spring hybrids included in these trials every year. The same authors (Butruille et al., 1999b) developed and analyzed four populations of inbred backcross lines (IBLs) and their testcrosses to a spring canola cultivar to map genomic regions introgressed from the German winter cultivar Ceres that affect agronomic traits in spring-type inbreds and hybrids. In the testcross populations, they found two putative quantitative trait loci (QTL) for seed yield that explained about 10% of the observed genetic variation, for which the donor alleles positively contributed to seed yield. These two results indicate that winter rapeseed may be a valuable source of germplasm for spring hybrid improvement in B. napus.

The purpose of this research was to determine the potential for improving spring canola hybrids by introgressing germplasm from two French winter cultivars. Two large segregating populations of DH lines were evaluated per se and in testcrosses with a spring canola line used in commercial canola hybrids. The testcross populations were compared with the starting hybrid combination, and with commercial hybrid cultivars being used in the canola growing regions of Canada and the USA.

MATERIALS AND METHODS

Plant Materials

The hybrid P124 x P1804 (T x P) was used as a reference hybrid combination to test the effects of introgressing winter germplasm. The line P124 and sister lines of P1804 have been used as parents of commercial hybrids by Bayer CropScience and represent the Canadian x European heterotic pattern. According to results reported here and by Udall et al. (2004), this hybrid shows a midparent heterosis of 11%. P124 is a line segregating for male-sterility due to the dominant Ms gene included in the Seedlink transgenic system, and P1804 is a DH line having the restorer gene (Rf) of the same genetically engineered male-sterility system (Mariani et al., 1990; Mariani et al., 1992; Goldberg et al., 1993).

The lines MF216 and RV128 were selected as donors of winter germplasm. MF216 is a non-canola quality DH line with about 60% of its genes coming from Major and was derived from a cross between the cultivars Major and Stellar (Ferreira et al., 1994). MF216 was the male parent of the highest yielding hybrid evaluated in Wisconsin for 3 yr by Butruille et al. (1999a). RV128 was developed by backcrossing alleles for spring growth habit from 'Westar' (a Canadian spring canola) into 'Samourai' (a French winter canola cultivat) using RFLP marker loci to select for spring alleles at the major vernalization-requiring flowering time QTL VFN1 and winter alleles at most other marker loci (Osborn et al., 1997; Vogelzang and Osborn, unpublished data). About 85% of the RV128 genome is derived from Samourai.

The DH lines used in this research were derived from [F.sub.1] plants of the crosses MF216 x P1804 (MF population) and RV128 x P1804 (RV population). Haploid plants produced by microspore culture (Chuong and Beversdorf, 1985) from anthers of [F.sub.1] plants of each cross were selected for Rf by screening for the genetically linked herbicide resistance gene (see below). The haploid plants of each cross were treated with colchicine to induce chromosome doubling by immersion in a 0.34% colchicine solution for 1.5 h. About 1000 colchicine-treated haploid plants of each cross were transplanted and covered with Delnet bags (DelStar Technologies, Austin, TX) to allow self-pollination. About 150 DH lines with sufficient seed set were selected in each population.

Seed Production

Hybrid seed was produced from crosses of the MF and RV DH lines with the female tester line P124 (MF and RV testcross populations) during the summers of 1998 in Canada and 1999-2000 in Australia. Each DH line was planted in a crossing cage that included two rows of the line P124 on an irrigated field in Outlook, Saskatchewan, Canada (51[degrees]30'N) in mid May 1998. The Ms (barnase) and Rf (bastar) genes present in line P124 and the DH lines, respectively, are tightly linked to the glufosinate ammonium (bialophos) herbicide resistance gene (Mariani et al., 1990; Mariani et al., 1992; Goldberg et al., 1993). Thus, the seedlings could be sprayed with the herbicide glufosinate ammonium before flowering to eliminate the segregating male-fertile plants in the female parent. When both the pollinator and the female plants started flowering, the cages were covered with pollination bags and leaf-cutter bees (Megachile rotundata F.) were introduced as pollen vectors (Soroka et al., 2001). Hybrid seed was harvested from P124 plants and self-pollinated seed was harvested from each DH line. Some of the lines were included in a second seed production that was planted in November 1999 in Mount Gambier, South Australia (37[degrees]45' S).

Field Trials

The DH lines pcr se were evaluated at the Arlington Agricultural Research Station in Wisconsin, USA (43[degrees]15' N) on a Plano silt loam soil (fine-silty, mixed, mesic Type Arguidoll) in the summer of 1999 and 2000. Because of seed production problems in 1998, only 114 of MF DH lines and 96 of the RV DH lines were analyzed in 1999. The experiments conducted in 2000 included 144 DH lines in each population. Seeds were planted (160 seeds [m.sup.-2]) during the last 3 d of April each year. The genotypes included in each experiment were DH lines, their parents [P1804 (P) and MF216 or RV128], the tester line P124 (T) and several open-pollinated (OP) cultivars as checks, such as 'Crusher' (Svalof-Weibull), 'Phoenix' (Bayer CropScience), 'Ebony' and 'LG3295' (Limagrain Canada), and '45A51' (Pioneer HB). Crusher was the only check used in 2000. Most of these checks were selected on the basis of their high seed yields in canola cultivar trials conducted at different locations and years in Wisconsin (http://osbornlab.agronomy. wisc.edu/research/results.html; verified 22 July 2004). The experimental design was a randomized complete block (RCB) design with two replications. In 1999, the plots were seven rows wide, with 0.15 m between rows and 4.9 m long, and were not trimmed before swathing. In 2000, the seven rows wide plots were 6.1 m long and were trimmed to 4.9 m long 2 wk before swathing.

The MF and RV testcross populations were evaluated during 1999 and 2000 at the same location as the inbreds and at Saskatoon, SK, Canada (52[degrees]10' N) on a Dark brown clay loam Chernozemic soil. The genotypes analyzed in each field trial were the testcrosses (114-150 hybrids), the reference hybrids T x P and T x Donor (T x D), the parents of the DH lines and the tester line. The checks included in 1999 were the same OP cultivars used in the DH line trials, plus the commercial hybrids 'Hyola 401' (Advanta Seeds) and 'InVigor 2373' (Bayer CropScience); in 2000 the OP cultivar checks were 45A51 and LG3295 in Wisconsin, and '45A02' (Pioneer HB) and 'LG3222' in Saskatchewan, and the hybrid checks were Hyola 401, 'Hyola 420' and InVigor 2373. The experimental design at both locations was an RCB with two replications. In Wisconsin, planting dates and plot sizes were the same as for the inbred experiments conducted during the same years. In the field trials conducted at Saskatchewan, the plots were six rows wide, with 0.25 m between rows and 6 m long, and plots were not trimmed before swathing. The seeding rate was 187 seeds [m.sub.-2], equivalent to 5 kg [ha.sup.-1], the seeding rate recommended for this region (http://www.canola-council.org/; verified 22 July 2004). Seeds were planted on 28 May 1999 and on 20 May 2000. Conventional field practices were used in each trial; seed treatment with the fungicide benomyl [methyl 1-(butylcarbamoyl)-2-benzimidazole carbamate], and the insecticide imidacloprid {1-[(6-chloro-3-pyridinyl)methyl]N-nitro-2-imidazolidinimine}; fields were treated with preplant incorporated trifluralin ([alpha], [alpha], [alpha]-trifluoro-2,6-dinitro-N, N-dipropyl-p-toluidine) herbicide (1.2 L [ha.sup.-l]), and nitrogen (150 kg [ha.sup.-1]) was applied about 2 wk before planting. The plots were also hand weeded during the season, before flowering and about 2 wk before the first plot was swathed.

Trait Measurements

The traits evaluated in each experiment included days to flowering, plant height, lodging, seed yield, test weight, and seed weight. Days to flowering (DTF) was recorded when about 10% of the plants in a plot had at least one flower open. Plant height (PH) was measured on a few randomly selected plants from the center of each plot as the distance from the ground to the apex of the extended plants. Lodging (L) was recorded using a scale from 1 to 5, where 1 = completely upright and 5 = completely prone. When seeds matured, the plots were swathed and left to dry on the field for about two weeks, after which each plot was combined with a small plot combine (Hege Equipment, Inc., Colwich, KS). The seed samples of each plot were dried at 39[degrees]C for 10 d or until their moisture were 50 g [kg.sup.-1] and then were cleaned and weighed. Seed yield was recorded as total seed weight per plot. The test weight (TW) for each plot was measured as the weight of seeds in a 71.6-mL sample. For field trails in Wisconsin, seed weight (SW) was recorded for each plot as 1000-seed weight. The oil content of seed samples from each plot in the Wisconsin field trials in 1999 was determined by David Syme, Bayer CropScience Saskatoon, Canada, by NMR analysis following conventional protocols. In the DH lines trials, bacterial leaf blight disease (BLB) caused by Pseudomonas syringae pv. maculicola (McCulloch) Young et al. was recorded about 40 d after planting using a disease severity scale of 1 to 5, where 1 = 0-20% of the plants had small necrotic spots on their leaves, and 5 = 80-100% of the plants had their leaves almost completely covered by lesions caused by the bacterium. This disease did not occur on any of the testcrosses in either location, and therefore, these data were not collected for testcross populations.

Statistical Analysis

Data were tested for homogeneity of error variance by Bartlett's [chi square] test (Steel et al., 1997) and the Levene's test. The second test was performed with the Statistical Analysis System (SAS, Cary, NC) Generalized Linear Models (GLM) procedure using the option "Hovtest" in the statement "Means" (SAS Institute, 2000). The data were analyzed with the SAS MIXED procedure (Littell et al., 1996) including the "Repeated" statement for the traits with heterogeneous error variance across environment. Genotypes, environment, and the genotype x environment interaction (G x E) were considered as fixed effects, and replications within environment as random effects. Phenotypic correlations were computed using the SAS CORR procedure (SAS Institute, 2000) using the least squares means estimates of each trait in each population.

RESULTS AND DISCUSSION Lines per se

Results from the combined analysis of variance indicated a highly significant G x E for seed yield (SY) and most other traits analyzed in the MF population, whereas SY and DTF were the only traits that showed a highly significant G x E in the RV population (Table 1). However, highly significant phenotypic correlations were detected for seed yield in the two environments within each population (0.72 for the MF population and 0.61 for the RV population), perhaps an indication of quantitative or non-crossover G x E (Baker, 1990). Seed yield (Fig. 1), days to flowering, plant height, and most other traits showed highly significant differences (P < 0.001) among lines in both DH populations each year (Table 1).

The mean SYs of the DH populations were higher than those of the donor parent and significantly lower than those of P1804 in three of the four field tests. Only for the RV population in Wisconsin in 2000 did some lines (about 15%) significantly out-yield P1804 (Fig. 1). Thus, there was little indication that introgression of winter germplasm improved seed yield of the DH lines per se. The mean seed yield of the RV DH lines was higher than that of the MF DH lines by 303 kg [ha.sup.-1] in 1999 and 630 kg [ha.sup.-1] in 2000, and the RV DH lines also flowered earlier and had less lodging in 2000 (Table 2). Two potential reasons for the poor SY of MF216 and many of the MF DH lines were their higher susceptibility to BLB and their later flowering time which coincided with a period of higher temperatures, especially during 1999. Temperatures higher than 29.5[degrees]C have been shown to cause flower abortion in B. napus and therefore lowers seed yields (Morrison and Stewart, 2002).

Testeross populations

The testcross populations, grown at two locations (Wisconsin and Saskatchewan) in 1999 and 2000, showed greater differences among environments than the population of DH lines grown only in Wisconsin, an expected result because these two locations are very different. Saskatoon is located in one the most important canola growing regions in Canada. In 1999, the weather during the growing season in Saskatchewan was cooler than at the Wisconsin location, allowing an overall better performance of the different genotypes. However, in 2000 the Canadian environment was affected by a prolonged drought during the first 50 d of the field trials that severely lowered seed yields of the populations. An overall better performance was observed in the field trials conducted in Wisconsin during the same year.

Genotype x environment interaction was highly significant for SY and most other traits in both testcross populations (Table 1). The phenotypic correlations for seed yield among environments were very low within both testcross populations (seven were not significant, r = 0.00 to 0.16, P > 0.05; and five were significant, r = 0.20 to 0.49, P < 0.05) suggesting that qualitative or crossover G x E was more predominant than quantitative or noncrossover G x E (Baker, 1990) in the testcross populations. There were highly significant differences among hybrids for SY and most other traits in both populations in each field trial (Tables 3 and 4; Fig. 1). The lowest seed yields in each population were those from the Wisconsin location in 1999. This year was very warm with temperatures higher than 30[degrees]C at the time when most of the hybrids started to flower. In addition, strong storms in mid-July caused heavy lodging in these experiments. In the other environments, which had growing conditions more suitable for canola, the mean of the testcrosses had a similar or higher yield than the mean of commercial hybrid cultivars and the T x P hybrid (Tables 3 and 4).

In the Canadian environments, a high percentage (average of about 30%) of the testcrosses significantly (P < 0.05) out-yielded the T x P hybrid and the average of hybrid cultivars (Fig. 1), and the means of both testcross populations were higher than the means of T x P hybrid, the hybrid cultivars, and the OP cultivars (Tables 3 and 4). In the Wisconsin environments, a much lower percentage of the hybrids were significantly higher yielding than the T x P hybrid and the average of hybrid cultivars. Across environments, 34% of the MF testcrosses and 35% of the RV testcrosses had higher mean seed yields than the mean seed yield of the T x P hybrids. With regard to the other measured traits, the testcrosses were, on average, taller and flowered later than the T x P hybrid, the OP, and hybrid cultivars, but they had similar mean values for lodging, test weight, and seed weight in each trial (Tables 3 and 4).

Phenotypic Correlations

Phenotypic correlations between seed yield and the other traits were estimated in both DH and testcross populations by the least-squares means of each characteristic. In general, the most significant correlations were found in the DH populations. Seed yield was negatively correlated with DTF in both DH and testcross populations (Table 5), and for most populations, this association was higher in 1999 than in 2000. The higher negative correlations between SY and DTF are perhaps an indication of how the heat stress affected B. napus. In both years in Wisconsin, the late-flowering DH lines were in flower during late June and the first half of July when temperatures often exceeded 29.5[degrees]C, the threshold temperature for flower fertility (Morrison and Stewart, 2002). In the testcross populations, the correlations between SY and DTF were much lower, with the exception of the MF testcross population in 1999. The hybrids flowered earlier than the DH lines (Tables 2, 3, and 4) and most may have escaped the heat stress. The hybrids also may be able to withstand the effects of heat stress better than the DH lines, as reported by Butruille et al. (1999a).

Seed yield and lodging were not correlated in the DH populations and in the testcross populations in Saskatchewan; however, these traits were negatively correlated in both testcross populations in Wisconsin each year. The highest association between SY and L was observed in the MF testcross population in 1999, which was severely affected by two storms in mid-July. Test weight showed a strong positive (P < 0.001) association with SY in both DH populations, while it was much lower in the testcross experiments (Table 5). Seed weight showed a low association with SY in the testcross populations and none in the DH populations. Oil content, measured only in Wisconsin 1999, was positively and significantly correlated with seed yield in both testcross populations (0.24 and 0.38 for the MF and RV testcross population, respectively). These results are similar to those reported by Butruille et al. (1999a) and by Udall et al. (2004) for other spring hybrids containing winter germplasm, and they suggest that increases in seed yield from winter germplasm introgression are not achieved at the expense of reduced oil content. A highly significant correlation (Table 5) was detected between SY and BLB in the DH populations. This bacterial disease severely affected SY of the DH lines each year; however, the T x DH hybrids were not affected, apparently because the tester parent was resistant to this disease.

CONCLUSIONS

Our results illustrate that the introgression of these winter germplasms can improve SY in spring canola hybrids. This was especially apparent in field trials conducted in Saskatchewan, an important canola region in western Canada, where the populations performed well and many hybrids had significantly higher seed yield than the starting hybrid and hybrid cultivars. These populations are suitable for developing linkage maps using molecular markers and for testing associations between these markers and the phenotypic traits analyzed in this study. This analysis may allow detection of genomic segments introgressed from winter germplasm into spring B. napus that improve seed yield and other agronomic traits of spring hybrids. Manipulation of these favorable alleles through marker-assisted selection, after their confirmation, may result in improved populations for use in hybrid breeding programs of spring oilseed B. napus.

Abbreviations: BLB, bacterial leaf blight; DH. doubled haploid: DTF, days to flowering; L, lodging; PH, plant height: SW, seed weight: SY, seed yield: TW, test weight.
Table 1. Significance of effects from analysis of variance for seed
yield and other traits measured in field trials of DH lines and
testcross populations.

                                             Seed    Days to
Effects                 Population      DF   yield  flowering

Genotypes               MF DH lines     164   ***      ***
                        RV DH lines     156   ***      ***
                        MF testcrosses  168   ***      ***
                        RV testcrosses  168   ***      ***
Genotype X environment  MF DH lines     102   ***      ***
                        RV DH lines     94    ***      ***
                        MF testcrosses  424   ***      ***
                        RV testcrosses  398   ***      ***

                            Plant                  Test
Effects                    height       Lodging   weight

Genotypes                    ***          ***      ***
                        ns ([dagger])     ***      ***
                             ***          ***      ***
                             ***          ***      ***
Genotype X environment       ***          ***       *
                             ns           ns        ns
                             ***          **       ***
                             ***          ***       ns

                                       Bacterial
                            Seed         leaf
Effects                    weight       blight

Genotypes                    ***          ***
                             ***          ***
                             ***          na ([double dagger])
                             ***          na
Genotype X environment       **           **
                             **           ns
                              *           na
                             **           na

* Significant differences among DH lines at the 0.05 probability level.

** Significant differences among DH lines at the 0.01 probability
level.

*** Significant differences among DH lines at the 0.001 probability
level.

([dagger]) ns = nonsignificant at the 0.05 probability level.

([double dagger]) na = data not available.

Table 2. Least square means for seed yield and other traits of
germplasms included in trials of two populations (MF and RV) of
doubled haploid (DH) lines each grown in two environments.

             Germplasm     n ([double
Environment  ([dagger])     dagger])     Seed yield

                                       kg [ha.sup.-1]

WI 1999      MF DH lines      114      1051 [+ or -]  121 (#) ***
             MF216              1       285 [+ or -]  212
             P1804              1      2458 [+ or -]  212
             P124               1      1773 [+ or -]  212
             OP cultivars       5      1876 [+ or -]  143
WI 2000      MF DH lines      144      1518 [+ or -]  122 ***
             MF216              1       386 [+ or -]  287
             P1804              1      3147 [+ or -]  287
             P124               1      1692 [+ or -]  287
             OP cultivars       1      2414 [+ or -]  287

WI 1999      RV DH lines       96      1354 [+ or -]  097 ***
             RV128              1       902 [+ or -]  257
             P1804              1      2256 [+ or -]  257
             P124               1      1461 [+ or -]  257
             OP cultivars       5      1413 [+ or -]  142
WI 2000      RV DH lines      144      2148 [+ or -]  097 ***
             RV 128             1      1947 [+ or -]  302
             P1804              1      2527 [+ or -]  302
             P124               1      1586 [+ or -]  302
             OP cultivars       1      2545 [+ or -]  302

                                                Bacterial
              Days to    Plant     Lodging     leaf blight
Environment  flowering  height   ([section])  ([paragraph])

                 d        cm

              MF216 population

WI 1999       57 ***    136 ***    1.5 ***       2.9 ***
              66        161        1.0           3.5
              51        125        1.5           2.0
              51        125        3.0           1.0
              52        132        1.4           1.5
WI 2000       64 ***    131 ***    1.7 ***       2.4 ***
              76        158        1.5           3.0
              56        122        1.0           2.0
              56        109        3.0           1.3
              50        106        4.5           1.5

              RV128 population

WI 1999       55 ***    145 ***    1.7 ***       2.3 ***
              59        158        1.0           1.0
              52        136        1.0           2.0
              50        123        3.5           1.5
              51        136        2.3           1.7
WI 2000       59 ***    148 ***    1.3 ***       1.9 ***
              66        167        1.0           2.5
              54        137        1.3           1.5
              53        149        2.8           1.7
              49        155        2.3           1.3

Environment  Test weight    Seed weight

             g [L.sup.-1]     g 1000
                           see[d.sup.-1]

WI 1999        583 ***       2.56 ***
               530           2.09
               618           2.77
               601           2.68
               599           2.56
WI 2000        621 ***       2.92 ***
               613           2.98
               658           2.97
               628           3.08
               636           3.13

WI 1999        588 ***       2.48 ***
               593           2.77
               618           2.78
               575           2.54
               581           2.45
WI 2000        636 **        2.88 ***
               641           2.77
               654           2.78
               625           2.91
               615           3.05

* Significant differences among DH lines at the 0.05 probability level.

** Significant differences among DH lines at the 0.01 probability
level.

*** Significant differences among DH lines at the 0.001 probability
level.

([dagger]) OP =open pollinated.

([double dagger]) n = number of entries in each germplasm class.

([section]) Scored on a 1 (no lodging) to 5 (completely lodged)
scale.

([paragraph]) Scored on a 1 (0-20% severity) to 5 (80-100% severity)
scale.

(#) Standard error.

Table 3. Least square means for seed yield and other traits of
germplasms included in trials of MF testcrosses (T x MF hybrids)
grown in four environments.

               Germplasm       n ([double
Environment    ([dagger])       dagger])

WI 1999      T x MF hybrids       126
             T x MF216              1
             T x P1804              1
             Hybrid cultivars       2
             OP cultivars           5
SK 1999      T x MF hybrids       128
             T x MF216              1
             T x P1804              1
             Hybrid cultivars       2
             OP cultivars           5
WI 2000      T x MF hybrids       147
             T x MF216              1
             T x P1804              1
             Hybrid cultivars       3
             OP cultivars           2
SK 2000      T x MF hybrids       147
             T x MF216              1
             T x P1804              1
             Hybrid cultivars       3
             OP cultivars           1

               Germplasm
Environment    ([dagger])              Seed yield

                                     kg [ha.sup.-1]

WI 1999      T x MF hybrids    1505 [+ or -] 125 ([paragraph] ***
             T x MF216          931 [+ or -] 242
             T x P1804         2012 [+ or -] 242
             Hybrid cultivars  1832 [+ or -] 192
             OP cultivars      1281 [+ or -] 155
SK 1999      T x MF hybrids    3125 [+ or -] 126 ***
             T x MF216         2861 [+ or -] 309
             T x P1804         2710 [+ or -] 309
             Hybrid cultivars  3036 [+ or -] 235
             OP cultivars      2568 [+ or -] 177
WI 2000      T x MF hybrids    2790 [+ or -] 126 ***
             T x MF216         2861 [+ or -] 276
             T x P1804         3026 [+ or -] 276
             Hybrid cultivars  2686 [+ or -] 189
             OP cultivars      1634 [+ or -] 214
SK 2000      T x MF hybrids    2421 [+ or -] 127 ***
             T x MF216         3069 [+ or -] 349
             T x P1804         1718 [+ or -] 349
             Hybrid cultivars  2066 [+ or -] 241
             OP cultivars      1766 [+ or -] 349

               Germplasm        Days to    Plant     Lodging
Environment    ([dagger])      flowering  height   ([section])

                                   d        cm

WI 1999      T x MF hybrids     53 ***    162 **     4.3 **
             T x MF216          57        183        4.5
             T x P1804          51        153        3.5
             Hybrid cultivars   48        144        3.8
             OP cultivars       51        150        4.4
SK 1999      T x MF hybrids     47 ***    146ns      2.5ns
             T x MF216          48        145        2.5
             T x P1804          44        157        2.0
             Hybrid cultivars   43        145        3.0
             OP cultivars       45        141        2.4
WI 2000      T x MF hybrids     58 ***    142 ***    1.4 **
             T x MF216          66        178        1.0
             T x P1804          54        140        1.0
             Hybrid cultivars   51        116        1.4
             OP cultivars       52        113        1.3
SK 2000      T x MF hybrids     52 ***    131 ***    2.0ns
             T x MF216          53        150        2.0
             T x P1804          50        123        3.0
             Hybrid cultivars   48        129        2.3
             OP cultivars       50        123        2.0

               Germplasm           Test              Seed
Environment    ([dagger])         weight            weight

                               g [L.sup.-1]  g 1000 see[d.sup.-1]

WI  1999     T x MF hybrids      610ns (#)   2.46ns
             T x MF216           600         2.51
             T x P1804           630         2.48
             Hybrid cultivars    610         2.84
             OP cultivars        605         2.47
SK  1999     T x MF hybrids      619 ***       na ([dagger])([dagger])
             T x MF216           625           na
             T x P1804           630           na
             Hybrid cultivars    625           na
             OP cultivars        627           na
WI  2000     T x MF hybrids      629ns       2.76 ***
             T x MF216           625         2.42
             T x P1804           645         2.75
             Hybrid cultivars    632         2.9
             OP cultivars        620         2.55
SK  2000     T x MF hybrids      617 ***       na
             T x MF216           605           na
             T x P1804           640           na
             Hybrid cultivars    617           na
             OP cultivars        615           na

* Significant differences among DH lines at the 0.05 probability
level.

** Significant differences among DH lines at the 0.01 probability
level.

*** Significant differences among DH lines at the 0.001 probability
level.

([dagger]) OP = open pollinated.

([double dagger]) n = number of entries in each germplasm class.

([section]) Scored on a 1 (no lodging) to 5 (completely lodged) scale.

([paragraph]) Standard error.

(#) ns = not significant at the 0.05 level.

([dagger])([dagger]) na = data not available.

Table 4. Least square means for seed yield and other traits of
germplasms included in trials of testcrosses populations (T x RV
hybrids) grown in four environments.

                Germplasm      n ([double
Environment     ([dagger])      dagger])

WI 1999      T x RV hybrids       114
             T x RV128              1
             T x P1804              1
             Hybrid cultivars       2
             OP cultivars           5
SK 1999      T x RV hybrids       114
             T x RV128              1
             T x P1804              1
             Hybrid cultivars       2
             OP cultivars           5
WI 2000      T x RV hybrids       150
             T x RV128              1
             T x P1804              1
             Hybrid cultivars       3
             OP cultivars           2
SK 2000      T x RV hybrids       149
             T x RV128              1
             T x P1804              1
             Hybrid cultivars       4
             OP cultivars           2

                Germplasm
Environment     ([dagger])          Seed yield

                                    kg [ha.sup.-1]

WI 1999      T x RV hybrids    1758 [+ or -] 181 ([paragraph]) ***
             T x RV128         1089 [+ or -] 272
             T x P1804         1609 [+ or -] 272
             Hybrid cultivars  1896 [+ or -] 231
             OP cultivars      1381 [+ or -] 202
SK 1999      T x RV hybrids    3046 [+ or -] 181 ***
             T x RV128         3151 [+ or -] 313
             T x P1804         2589 [+ or -] 313
             Hybrid cultivars  2741 [+ or -] 256
             OP cultivars      2505 [+ or -] 213
WI 2000      T x RV hybrids    2715 [+ or -] 181 ***
             T x RV128         2444 [+ or -] 300
             T x P1804         3024 [+ or -] 300
             Hybrid cultivars  2453 [+ or -] 227
             OP cultivars      2008 [+ or -] 247
SK 2000      T x RV hybrids    2349 [+ or -] 183 ***
             T x RV128         2852 [+ or -] 446
             T x P1804         2107 [+ or -] 606
             Hybrid cultivars  2257 [+ or -] 283
             OP cultivars      1909 [+ or -] 379

                Germplasm       Days to     Plant      Lodging
Environment     ([dagger])     flowering   height    ([section])

                                   d         cm

WI 1999      T x RV hybrids     51 ***     155 **      3.6 *
             T x RV128          55         174         3.5
             T x P1804          50         150         1.5
             Hybrid cultivars   48         138         3.0
             OP cultivars       50         142         3.5
SK 1999      T x RV hybrids     45 ***     145ns (#)   2.5ns
             T x RV128          48         153         2.0
             T x P1804          45         145         3.0
             Hybrid cultivars   44         138         2.3
             OP cultivars       45         146         2.3
WI 2000      T x RV hybrids     57 ***     144 ***     1.4 ***
             T x RV128          59         163         1.0
             T x P1804          55         143         1.5
             Hybrid cultivars   52         115         1.7
             OP cultivars       53         124         1.5
SK 2000      T x RV hybrids     52 ***     140 ***     2.2 ***
             T x RV128          53         155         2.0
             T x P1804          50         130         2.0
             Hybrid cultivars   49         130         2.3
             OP cultivars       50         120         2.5

                Germplasm
Environment     ([dagger])     Test weight          Seed weight

                               g [L.sup.-1]           g 1000
                                                   see[d.sup.-1]

WI 1999      T x RV hybrids      590 ***     2.60 ***
             T x RV128           581         2.37
             T x P1804           599         2.52
             Hybrid cultivars    597         2.88
             OP cultivars        578         2.56
SK 1999      T x RV hybrids      624ns         na ([dagger])([dagger])
             T x RV128           623           na
             T x P1804           655           na
             Hybrid cultivars    641           na
             OP cultivars        623           na
WI 2000      T x RV hybrids      638 *       2.76 ***
             T x RV128           642         2.53
             T x P1804           646         2.84
             Hybrid cultivars    638         3.03
             OP cultivars        643         2.70
SK 2000      T x RV hybrids      606 ***       na
             T x RV128           594           na
             T x P1804           624           na
             Hybrid cultivars    602           na
             OP cultivars        602           na

* Significant differences among DH lines at the 0.05 probability level.

** Significant differences among DH lines at the 0.01 probability
level.

*** Significant differences among DH lines at the 0.001 probability
level.

([dagger]) OP = open pollinated.

([double dagger]) n = number of entries in each germplasm class.

([section]) Scored on a 1 (no lodging) to 5 (completely lodged) scale.

([paragraph]) Standard error.

(#) ns = not significant at the 0.05 level.

([dagger])([dagger]) na = data not available.

Table 5. Phenotypic correlation coefficients between seed yield and
other traits for two populations (MF and RV) consisting of doubled
haploid (DH) lines and two testcross populations derived from crossing
the DH lines to a tester (T).

                 n        Days to    Plant
Environment  ([dagger])  flowering   height    Lodging

                                        MF DH lines

WI 1999         114      -0.38 ***  0.25 **    -0.08ns

WI 2000         146      -0.21 **   0.67 ***   -0.11ns

                                        RV DH lines

WI 1999          95      -0.49 ***  0.09ns     -0.07ns
WI 2000         144      -0.36 ***  0.37 ***   -0.04ns

                                       MF testcrosses

WI 1999         126      -0.48 ***  -0.17 *    -0.54 ***
SK 1999         128      -0.13ns     0.04ns     0.00ns
WI 2000         147      -0.21 **    0.17 *    -0.29 ***
SK 2000         147      -0.18 *     0.33 ***   0.11ns

                                       RV testcrosses

WI 1999         114       -0.20 *   -0.13ns    -0.31 ***
SK 1999         114        0.01ns    0.11ns     0.07ns
WI 2000         149       -0.19 *    0.31 ***  -0.31 ***
SK 2000         148       -0.17 *   -0.08ns     0.03ns

                                                Bacterial
Environment  Test weight    Seed weight        leaf blight

WI 1999       0.56 ***    0.16ns ([double   -0.73 ***
                              dagger])
WI 2000       0.50 ***    0.12ns            -0.70 ***

WI 1999       0.62 ***   -0.12ns            -0.45 ***
WI 2000       0.46 ***    0.15ns            -0.69 ***

WI 1999       0.20 *      0.25 **              na ([section])
SK 1999       0.45 ***      na                 na
WI 2000       0.30 ***    0.28 ***             na
SK 2000      -0.11ns        na                 na

WI 1999       0.36 ***    0.24 **              na
SK 1999      -0.13ns        na                 na
WI 2000       0.15ns      0.29 ***             na
SK 2000      -0.05ns        na                 na

* Significant differences among DH lines at the 0.05 probability level.

** Significant differences among DH lines at the 0.01 probability
level.

*** Significant differences among DH lines at the 0.001 probability
level.

([dagger]) n = number of entries used to calculate the correlation
coefficients.

([double dagger]) ns = nonsignificant at the 0.05 probability level.

([section]) na = data not available.


ACKNOWLEDGMENTS

We thank researchers at Bayer CropScience for their assistance, particularly Debbie Doell for haploid plant production, Tom Shuler and Stewart Brandt for their assistance with hybrid seed production and field trials in Canada and David Syme for oil analysis. Funding was provided by the North Central Biotechnology Initiative and a USDA-NRI grant # 98-353006-6286 to T.C.O.P.A.Q. was supported in part by a scholarship from CDCH-UCV, Government of Venezuela, and J.A.U. was supported by UW Pioneer Plant Breeding Fellowship 1999-2000.

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Pablo A. Quijada, Joshua A. Udall, Hieronim Polewicz, Robert D. Vogelzang, and Thomas C. Osbron *

Pablo A. Quijada, Robert D. Vogelzang, and Thomas C. Osborn, Plant Breeding and Plant Genetics Program, and Department of Agronomy, 1575 Linden Dr., University of Wisconsin-Madison, Madison, WI 53706, USA: Joshua A. Udall, Ecology, Evolution, and Organismal Biology Dep. Iowa State University, Ames, IA 50011, USA: Hieronim Polewicz, Bayer CropScience Inc., Site 600, Box 117, RR. #6, Saskatoon, SK S7K 3J9, Canada. Received 7 Nov. 2003. * Corresponding author (tcosborn@wisc.edu)
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Title Annotation:Crop Breeding, Genetics & Cytology
Author:Quijada, Pablo A.; Udall, Joshua A.; Polewicz, Hieronim; Vogelzang, Robert D.; Osbosn, Thomas C.
Publication:Crop Science
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Date:Nov 1, 2004
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