Printer Friendly

Plant Genetic Resources and Breeding: Current Scenario and Future Prospects.

Byline: HAKAN ULUKAN

ABSTRACT

Variation in any plant population is very important for breeders. Basic aim(s) of the plant breeding is/are high yield, quality and quantity, development, resistance or tolerance of adaptation ability to stress factors, etc. They are being utilized from the genetic variation to be able to manage all these component(s). On the other hand, an accomplished adaptation to environmental conditions and 'success' of the plant breeding is limited with genetic base (or gene pools) of the organism. Therefore, this wideness is measured by density of the biological diversity or biodiversity/bioversity. Aboveall, variation (genetic, among species, ecosystems, etc.) is essential for all kind of the plant breeding activities and obtained from the PGRs fundamentally (such as breeding lines, landraces, local varieties, primitive forms, wild and wide relatives, weed races, etc.). (c) 2011 Friends Science Publishers

Key Words: Genetic resources; Biodiversity; Biotechnology; Yield; Yield formation

Abbreviations:

PGRs, plant genetic resources; CGIAR, Consultative Group on International Agricultural Researches; CWR, crop wild relatives; MA, marker-assited PCR; GMOs, genetically modified organisms; DNA, Deoxyribonucleic acid; PCR, polymerase chain reaction; AFLP, amplified fragment length polymorphism; QTL, quantitative trait locus; eQTL, expression quantitative trait loci; SNP, single nucleotide polymorphism

INTRODUCTION

Plant breeding is an art and science, and it describes related methods for the creation, selection, and fixation of superior plants in the development of improved cultivars suited to the needs of growers and consumers (Moose and Muhm, 2008). About 250,000 angiosperms, 650,000 gymnosperms, 12,000 ferns, 14,000 bryophytes and 40,000 algae are taxonomically studies up to now (Govaerts, 2001; Hodkinson et al., 2007). But, less than 3% plants are available to agriculture, and economically important 15-30 species responsible for the world's food, schelters, etc. (wheat, rice, maize, sorghum, cotton, lentil, flax, sunflower, tobacco, etc.). Especially, from them, cereals are very important, and this has a very significant and strategic role.

It is estimated that some cereals such as rice (Oryza sativa L.), wheat (Triticum spp.) and only maize (Zea mays L.) provide about 50% of the calories people consume each day (Anonymous, 2007b; Bertrand and Mackill, 2008; Mondeil and Setboonsarng, 2009). But, about 840 million people (about 14% of the total population) have no adequate food (Anonymous, 2008a and 2008c) and more than 700 million people suffer from malnutration in the world. Since 1960, world food production has been grown faster than the human population. The main reason of this positive development is green revolution; introgression of genes reduced the plant height and increased the disease and viral resistance in wheat (Poehlman, 1979).

According to the FAO (1999) (Cited by Mondeil and Setboonsarng, 2009), major causes of genetic erosion in crops are land clearing, population pressure, environmental and land degredation, pest/weeds/diseases, over-exploitation of species, overgrazing, collateral damages caused by conventional agriculture, contamination by genetically engineered or transgenic crops, and finally global climate change replacement local cultivars and changing agricultural systems.

Importance of plant biodiversity:

The term of "biodiversity" is not only limited to "plant species richness", but are also related to all living components in the flora (Buchs, 2003). The diversity of PGRs from which the world's food crops are derived is steadily declining, due in part to the reliance of modern agriculture on a limited number of improved varieties (Mondeil and Setboonsarng, 2009). There are three types of biological diversity in the nature (i) intraspecific (genetic), (ii) species and (iii) ecosystem diversity (Hammer, 2000). The importance of genetic diversity (biodiversity) in plant breeding was recognized by the 1960s and Sir Otto Frankel coined the term "genetic resources" in 1967 to highlight the relevance and need to consider germplasm as natural resource for the long-term breeding of crop plants (Yunbi, 2010).

Nevertheless, the global spread of commercial cultivars is reducing the genetic diversity that needed to continue crop improvement. The overall objective of the plant breeding is to improve of the agro-economic traits such as yield and yield components in the plant species' parts like leaf, stem, tuber, root, flower, fruit, seed etc (Gepts, 2002; Ulukan, 2008). From them, plant genetic diversity refers to any variation in the nucleotides of genomes of organisms (Hawkes, 1991; Kasha, 1999; Ulukan, 2008). Genetic studies, therefore cannot be conducted if no variation exists within plant species. The germplasm centre(s) of cultivated plants species was/were for the first time offered by a researcher la Candolle (Engels et al., 2006), later, after the publication of Vavilov's "On the Origin of Cultivated Plants" and some researchers suggested sub-centers of origin (or gene centers) and totally their number has reached to 13-14, but mainly its number is 8 (Vavilov, 1926, 1951; Perrino, 2005; Ulukan, 2010; Fig. 1).

However, these centers are not always equivalent to the biodiversity centers, because they may have originated in one geographic area, but domesticated elsewhere. Today, many plant species have been lost or under threat for their genetical components and their genetic bases have narrowed or are being narrowed. Several species have lost their resistance potential against biotic and abiotic stresses. This point is especially important for minimizing the effects of stress factor(s). A clear category of plant genetic diversity has been summarized in Fig. 2. Two approaches are accepted for the maintaining techniques of the germplasms (Table I) and all of them are related with measurement of the genetic variation (Table II) including in situ and ex situ approaches.

In in situ conservation, the maintenance is made in their natural habitat, but in ex situ conservation, the germplasms is collected in proper form and preserved in the chambers (centers, institutes, gene banks, seed banks, etc. Table III) under controlled conditions such as temperature, humidity, light, etc. (Engels et al., 2006). During 1980s and 1990s, application of genetic engineering to crop improvement allowed genes from distantly related and even non-related taxa to be incorporated into crops, thereby broadening the value of CWRs by expanding their usefulness into secondary and tertiary crop gene pools.

Because ex situ conservation is developed as the preferred approach to safeguard the PGRs during the 1970s and 1980s when in situ conservation of landraces in particular was thought to be impractical, the agricultural scientists did not embrace the in situ CWR conservation until the 1990s, despite the fact that influential crop scientists like Frankel (1970) and Jain (1975) (Cited by Meilleur and Hodgkin, 2004) had called for its use earlier.

Table I: Maintenance methods and their relative worth for different categories of diversity (Modified from Hammer et al., 2003)

Category###of###Methods of Maintenance

Diversity###Ex situ (gene###On-farm (agro-###In situ (other

###banks)###ecosystems)###ecosystems)

Intraspecific###C###C###CO

diversity###W###WO###W###

###WP###WP###WP

Species###C###C###CO

diversity###W###WO###W###

###WP###WP###WP

Ecosystem###CO###C###CO

diversity###WO###WO###W###

###WPO###WP###WPO

The relative meaning of the methods for the different categories of diversity is illustrated by the number of stars: =little meaning; =important; =very important; O=unimportant; C=cultivated plants; W=wild plant related to cultivated plants; WP=weedy plants

Role of plants as a member of the PGRs and their utilization:

The plant breeding activities started in its most primitive form since the first farmers saved the seeds of their best plants from one season to the next more than 10,000-12,000 years ago (Hawkes, 1983; Suslov et al., 2002; Fowler and Hodgkin, 2004; Ulukan, 2010). Throughout the centuries, application of selection processes have had gradually become more effective (in a scientific way), bringing great qualitative and quantitative improvements (Hawkes, 1991). The aims are to re-establish or redesign these heritical units for improved productivity (Anonymous,2008d).

Table II: Advantages and disadvantages of some methods of measuring genetic variation (Modified from Hammer et al., 2003)

Method###Variation###Sample###Loci analyzed per###Reproducibility###Analyzed Character###Required

###Detected###through-put###assay###between assays###Type###Inheritance###Techn. level

Morphology###L###H###L number###M###Phenotypic trait###Qual./Quan.###L

Pedigree analysis###M###(n.a.)###(n.a.)###G###Degree of ancestry###(n.a.)###"

Isozymes###"###M###L number###M###Proteins###Co-Dominant###M

RFLP (L copy)###"###L###L number (specific)###G###DNA###"###H

RFLP (H copy)###H###"###H number (specific)###"###"###Dominant###"

RAPD###H to M###H###H number (random)###P###"###"###M

DNA sequencing###H###L###L number (specific)###G###"###Co-Dominant/Dominant H

Seq taq SSRs###"###H###M number (specific)###"###"###Co-Dominant###"

AFLPs###M to H###"###H number (random)###M###"###Dominant###"

(n.a.) = No access; L: Low; H: High; M: Medium; G: Good; P: Poor; Qual.: Qualitative; Quan.: Quantitative

Table III: List of the some biodiversity conservation centers of the CGIAR's (Modified from Anonymous, 2009; Nagel et al., 2009)

Centers###Target

CIAT###(Centro Internacional de Agricultura Tropical)###Rice, Beans, Cassava, Forages, Pasture

CIFOR###(Center for International Forestry Research)###Forest conservation and Sust. Development

CIMMYT (Centro Internacional de Mejoramiento de Maiz y Trigo)###Maize, Wheat, Barley, Triticale.

CIP###(Centro Internacional de la Papa)###Potato and Sweet potato

IPGRI###(International Plant Genetic Resources Institute)###Conservation of gene pools for crops and forages

ICARDA (International Center for Agricultural Researach in the Dry Areas)###Wheat, Barley, Chickpea, Lentil, Pasture, Legumes, Small. ruminants.

ICLARM (International Center for Living Aquatic Resources Management)###Fisheries to imp. efficiency and Productivity of culture and capture fisheries.

ICRAF###(International Centre for Research in Agro-forestry)###Land-use systems in developing countries.0

ICRISAT (International Crops Research Institute for the Semi-Arid Tropics)###Cropping systems in Sorghum, Millet, Chickpea, Pigeonpea and Groundnut.

IFPRI###(International Food Policy Research Institute)###Crop imp. and land manag. in humid and sub-humid tropics, farming sys. in maize, cassava, cowpea, yam, plantain, soybean, rice

IIMI###(International Irrigation Management Institute)###Livestock productivity and animal

IITA###(International Institute of Tropical Agriculture)###health Global rice improvement Strengthening and developing national agricultural research systems

ILRI###(International Livestock Research Institute)###Rice imp. in West Africa with research on rice in mangrove and

IRRI###(International Rice Research Institute)###inland swamps, upland conditions under irrigated conditions.

ISNAR###(International Service for National Agricultural Research)

WARDA###(West Africa Rice Development Association)

In practice, the plant breeding is a very complex and time-consuming procedure. Depending on the crop type, climate, environment, practices and economic or socio-economic conditions forms the similarity or difference in any plant breeding programs. Plant breeders adapt old crops to the new localities increase yields, improve resistance to pest and disease, enhance the nutritional quality and flavor of the fruits and vegetables; and develop traits that are useful for storage, shipping, processing of foods etc., (Prance, 1997; Anonymous, 2008c). Newly developed plants would give more nutritional values and sometimes easier to process, e.g., during cultivation, harvesting and post-harvest. For example, the malting barley (Hordeum vulgare L.) cultivar "Morex" has a high percentage of total malt extract released in 1978 (Hayes et al., 2003). Development of the rapeseed (Brassica rapa) cultivars with a low content of the erucic acid improved the value of oil and extended the under cultivation areas (Jauhar, 2001).

Resistance to various pathotypes is found in a number of different wild species and in the cultivated tetraploid subsp. andigena, which is the originally a tetraploid subspecies of S. tuberosum (Bradshaw et al., 2006). Evidence is building up that this type of resistance has penetrated into the cultigens from a wild resistant tetraploid, S. oplocense Hawkes (Hawkes, 1998). The F1 hybrid of this cross, which has been named S. sucrease, is well-known weed species in Central Bolivia (Bradshaw et al., 2006). The most famous example is the inclusion of eyespot resistance from the wild species (Aegilops ventricosa Tausch.) in wheat (Valkoun, 2001). Again, some resistant genes have been identified against coffee rust (Hemileia vastatrix) in the cultivated coffee (Coffea arabica L.), wild coffee species (C. liberica Hiern.) and (C. canephora L.).

Likewise, resistance to bacterial leaf streak has been found in spontanea varieties of Oryza sativa L., the Asian cultivated rice, and in the related wild rice species (O. rufipogon Griff.) in Southeast Asia (Leroy et al., 2006) (See also Table I). Wild plants have desirable traits but, as known and at the same time, they also contain many undesirable characters such as low yielding, low quality, susceptibility to pests and diseases, etc. Breeding effort to backcross such wild types with commercial varieties to the point where we have the best of both (Ulukan, 2009). In addition to wide crossing, genetic engineering techniques enable of plant breeders to possibily find and introduce many important foreign genes into plants, provides valuable opportunities to modifying theirs genotypes, for resistance to stress factors and improving the quality components such as protein content, fiber content, etc. (Scharma et al., 2002).

The PGRs of wild species and traditionally grown landraces adapted to specific environmentss or showing specific traits, such as resistance to pest and disease or other environmental stresses (heat, drought, cold, etc.) can be pivotal in achieving improvements in crops. For instance, in Africa the use of modern breeding techniques and diversity in Cardaba gaddat and Musa balbisiana allowed for the breeding of improved bananas (Anonymous, 2010a). Maize was originated in Mexico from a weed-grass plant, teosinte (David et al., 1999; Anonymous, 2008d). Tomatoes and potatoes first time appeared in South America. At the time of their origin, tomatoes had small fruits to the size of a grape, and potatoes had knobby tubers with high concentrations of a family of bitter chemicals called glycoalkaloids, toxic to the humans (Hawkes, 1983).

The majority of the traits associated with domestication of the crop plants (such as seed setting, early maturity, easy harvesting, greater size of harvested seeds or fruits, changes in plant growth form, reduction or losing bitter and toxic compounds, etc.) were already accomplished by the time of historic agricultural civilizations such as Egyptian, Chinese, or Mayan (Hawkes, 1983). In addition, these primitive crops were adapted to local ecologies; therefore, they remained genetically diverse for quality and quantity components. Numerous examples are available witnessing the increased productivity of crops. Beginning in the 1930s, plant breeders developed techniques to allow them to develop plants from two parents that could not normally produce viable ancestor. An example is the technique called "embryo rescue" (Anonymous, 2008b; Ulukan, 2009).

In 1950s, plant breeders developed new methods of creating variation in an organism's genetic structure with some physical and chemical agent(s), through "mutation breeding". In addition to this, many techniques have been developed today such as tissue culture, anther culture, genetic engineering, molecular breeding, etc., (Anonymous, 2000; Jauhar, 2001; Suslov et al., 2002; sehirali and ozgen, 2007; Ulukan, 2009; Yunbi, 2010).To provide a stable food supply, agriculture needs diversity in crop plants and cultivars. So, most interesting developments occurred in maize cultivation in this respect. Development of double-cross hybrids to replace allogamaous plants during the 1930s was responsible for about 7.0-12.0% increase in yield. Genetic improvement resulted in a grain yield increase of about 28.0% from 1930s to1960s (Contreras, 2007). The adoption of single-cross hybrids in the 1970s resulted in further improvement in maize yield.

The total yield improvement of single-cross hybrids over open pollinated cultivars were more than 50% (Jain, 1982). Similarly, noticable yield improvements were recorded in wheat and rice during the 1960s and 1970s, which played a major role in increasing of the word food production. On the other hand, huge plant germplasmsor genetic resources enabled the plant breeders to create novel gene combinations and select them according to their necessities in various part of the world (Glaszmann et al., 2010). The diversity and availability of the PGRs are also increases when a crop is attacked by a disease or when unexpected challenges are needed to overcome (Anonymous, 2010a). This trend and the increasing industrialisation of agriculture are key factors in what can only be called genetic erosion and the disapperance and displacement of diverse, local populations of crops (Vernoy and Yiching, 2004).

Cultivated plants under the various effects (especially improvement) of humankind and after 1950, massive genetic erosion begun (Lande, 1998). So, many valuable and desirable traits were lost due to this factor. In many parts of the world, many plants were not properly adapted to diverse cultivation practices. Many local varities or crops were replaced with high yielding (with narrow gene pools) cultivar(s). As a result, many important and local plant gene resources disappeared without recognizing or describing properly from the flora. But, in some areas of the Mediterranean, cultivated land races are still grown on up to 25% of cropland (Hammer, 2000). The PGRs have emerged through years of evolution and natural processes (Linhart and Grant, 1996; Engels et al., 2006).

The cultivated PGRs are classified into three broad categories, namely (i) modern cultivars, (ii) high yielded cultivars (products of plant breeding in the formal system and typically have a high degree of genetic uniformity) and (iii) farmers' cultivars or traditional varieties e.g., product of breeding or selection carried out by farmers, either deliberately or not, continuously over generations (Harlan, 1975). Wild relatives together with weedy species, which have evolved over a long period of time and have coevolved with pests and diseases contributed to plant improvement (Harlan, 1981). It was first time used in 1993 (Hammer, 2000; Hammer et al., 2003) and percieced as "common heritage" agaist to stress factors (Hammer et al., 2003; Rao and Hodgkin, 2004; Buanec, 2005; Faizi and Ravichandran, 2008) and guarantee fighting against agricultural handicap(s).

When called as the common heritage of the PGRs in 1920, they were perceived as national richness of owned country, and still the discussion continu on the ownership of the PGRs. Plant breeders commonly use wild species as gene donors to improve pest and disease resistance among the species and PGRs (Harlan, 1981).

Plant genetic diversity is not only a basis for adapting varieties and agriculture to different environmental conditions and constraints such as drought, outbreaks of pest and disease epidemy(ies) or climatic change, etc. but also a major contributor to the food production (Ulukan, 2010). Breeding new and high yielding crops varieties with better resistance to disease and adaptation to changing climates is important for ensuring the food security (Anonymous, 2010a). But, these crops are known not new. They had derived from currently grown commercial varieties, breeding lines and stocks, induced or natural mutations, old land races, primitive forms, weed races and wild species, etc., (generally from the PGRs) (Fehr, 1987). For instance, from them "weed races" exists as a part of the crop (weed complexes) in gene centers of the world. Similarly, they incorporate useful genes derived from wild types or related wild species that have moved from weedy forms into crops.

In these instances nature has helped the breeder enabling them to insert genes (useful for the agricultural aims) from wild species into a "Cultivated" genetic background (sehirali and ozgen, 2007). "Wild relatives and species" that occur sometimes in the gene centers of cultivated plants, sometimes far outside them, and that can be crossed with the cultigens (which means, Latin cultus-cultivated and genus- kind; a cultivated/domestic organism) and we are already using them as crops and are still dependent upon the broad genetic base that exists in their wild relatives (Hawkes, 1983). Often, however, the term of genetic resources refer more specially to the types of "land races, primitive forms, weeds and wild forms" (Poehlman, 1979; Hawkes, 1983; sehirali and ozgen, 1987; Nevo, 1998; Gepts, 2002; Wale, 2008), but the selected and cultivated form of plant germplasms have originally evolved from a wild plant population called "landrace" (sehirali and ozgen, 1987; Nevo, 1998; Ulukan, 2010).

Before breeding, each crop was a landrace, a mixture of many, sometimes hundreds of cultivars. In addition, they were far away from the uniformity. Despite all negatives, some landraces were better though they had come through selection by farmers over generations and had evolved to survive conditions on that particular farm (Moore, 2001). The maize was threatened by corn blight disease (CBD) in the US. But, thanks to the PGRs, problem was quickly solved by using the PGRs, and transferred the blight resistance genes from its wild form to cultivars in 1970. Similarly, bacterial wilt (Pseudomonas solanacearum E.F. Smith) resistance was re-established in this way using the PGRs in potatoes cultivation. Similarly, the world collection of potatoes was screened for wilt resistance until introduction of six lines of a primitive diploid cultivated species, Solanum phureja. Potatoes breeding for resistance to nematodes followed same pattern.

In that the resistance genes to the potato "Cyst" nematodes are localized to Peru, Bolivia, and Northwestern Argentina (Gepts, 2002). As evident from the models of plant conservation techniques (Fig. 3), the integration of in situ and ex situ conservations of biodiversity (Rao and Hodgkin, 2004; Faizi and Ravichandran, 2008), the possibility of collaboration between plant breeders and growers and the use of the new biotechnological or advanced methods for exploring and manipulating the genetic basis of crop phenotypes are very important (Cleveland, 2001). Of these, ex situ gene banks play a pivotal role in preserving the wild relatives of crop plants as well as local varieties, which are grown in many places. As known, plants are often improved or better protected by using genes from wild species. These species founds in the PGRs and they provide the basic input to all plant breeding programs, whether traditionally or transgenically based (Ullstrup, 1972; Anonymous, 2008f; Ulukan, 2010).

Future prospects of PGRs:

Two major technologies in this regard include biotechnology, molecular biology (Anonymous, 2008c; Fig. 4). In biotechnology, with the advances in genomics, molecular tools for plant breeding are becoming readily accessible and more affordable and useful. Plant breeding informatics will include improved pedigree records, sophisticated statistical designs and analyses, and database management to fully incorporate molecular markers, and to better estimate cultivar performance and breeding methodology used (Edmeades et al., 2004; Anonymous, 2007b; Baenziger et al., 2009; Fig. 4). Molecular biology has become possible to be overcome the obstacles, which can not be overed by classical plant breeding technigues. From them, technology level for the molecular genetics' (esp. molecular marker) (Anonymous, 2007b) enables our understanding of genetic resources more than any other type of genetic data. Relationship(s) among the PGRs, biodiversity and plant breeding were given details in Fig. 5.

The identification of genes and molecular markers underlying these agronomic traits will help accelerate the breeding process and lead to improved varieties with improved yield and quality, tolerance to unfavourable environmental conditions and resistance to disease, etc. (Anonymous, 2007b; Baenziger et al., 2009). All these technological developments are presented in the Fig. 6 as timeline. In days to come, 14 major research areas will be very important in the plant breeding (Gale and Devos, 1998; Ortiz, 1998; Anonymous, 2000; Scharma et al., 2002; Doebley et al., 2006; Anonymous, 2007b; Ozias-Akins and Dijk, 2007; Swaninathan, 2007; Vasil, 2007 and 2008; Schaart and Wisser, 2009).

They are: (i) grafting and apomixis to fix hybrid vigour, (ii) Agro-infiltration, (iii) direct gene transfer, electroporation, polyethylene glycol techniques and DNA-vector Agrobacterium, (iv) in vitro gene shuffling (v) homologous recombination, (vi) male sterility systems with transgenics for hybrid seed in autogams, (vii) DNA methylation, (viii) parthenocarpy for seedless, (ix) induce RNA and silencing by RNA interference, (x) virus-induced gene silencing, (xi) interfering RNAs, (xii) reverse breeding, (xiii) gene Silencing or overexpression, (xiv) genetically modified organisms induction for early flowering, (xv) cisgenesis, (xvi) intragenesis, (xvii) genomics, phenome, metabolomics, QTL, eQTL, transgenics and xenogenics, (xviii) oligonucleotide-mediated mutation induction for the stres factors and finally (xiv) converting annual into perennials.

CONCLUSION

Advanced laboratory techniques are being used in plant biology such as molecular genetics, molecular biology, genomics, metabolomics, preteomics, bioinformatics, DNA sequencing, QTL and eQTL, etc. today. No matter what, certain plant breeding techniques keep their importance as long as the PGRs and and biodiversity. Some of them are tentatively, some of them are not, and some of them are hopeful in the long run and near future. However, it is open that received technology level; obtained information will be help and increase our knowledge in this area, and will bring many solutions to the encountered problems. Thanks to contribution of new findings with the support of scientific tools and techniques such as in vitro breeding, molecular breeding and transgenic breeding, all limits and handicaps could be overcome. But, this point is essential that to be able to get final success identify the aim(s) and study with large, represantative and healty sample(s) as possible as.

REFERENCES

Allard, R.W., 1999. History of plant population genetics. Annu. Rev. Genet., 33:1-27

Anonymous, 2000. Biotechnology Development: Monitor, 40, p: 2

Anonymous, 2007a. Data Base of FAO. http://www.fao.org (accessed 21.12.2008)

Anonymous, 2007b. Breeding with Molecular Markers. http://sbc.ucdavis.edu (accessed 21.09.2010)

Anonymous, 2008a. World Food Supply. http://www.encarta.msn.com/encyclopedia_761576477/world_food_ supply.html (accessed 21.12.2008)

Anonymous, 2008b. Agropolis International, Agriculture, Food, Biodiversity, Environment. Available at http://www.agropolis.fr (accessed 21.12.2009)

Anonymous, 2008c Biotechnology and the World Food Supply. http://www.ucusa.org/food_and_agriculture (accessed 21.12.2008)

Anonymous, 2008d. The Role of Plant Biotechnology in the World's Food System. http://www.4ut.gov.au/usa/english/tech/ijee00903/ shelton.html (accessed 21.12.2008)

Anonymous, 2008f. Media Brifing, Greed or Need? Genetically Modified Crops. http://www.ratical.org/co-globalize/GMcrops.html (accessed 21.12.2009)

Anonymous, 2009. FAO Focus: Biodiversity Preserved: in Situ and ex Situ;CGIAR. http://www.fao.org/focus/e/96/04-e.htm (accessed20.06.2009)

Anonymous, 2010a. Biodiversity and Plant Breeding, pp: 1-6. European Seed Association (ESA) Publication, Brussel, Belgium

Anonymous, 2010b. Dr. Norman E. Borlaug (1914-2009). http://www.saa-tokyo.org/english/pdf/DrNormanBorlaug.pdf (accessed 17.04.2010)

Baenziger, P.S., I. Dweikat and S. Wegulo, 2009. The future of plant breeding. African Crop Sci. Conf. Proc., 9: 537-540

Bertrand, C.Y. and M.D.J. Mackill, 2008. Marker-assisted selection: an approach for precision plant breeding in the twenty-first century.Philosp. Trans. Royal Soc. B: Biol. Sci., 363: 557-572

Bradshaw, J.E., G.L. Brayan and G. Ramsay, 2006. Genetic resources (including wild and cultivated Solanum species) and progress in their utilisation in potato breeding. Potato Res., 1: 49-65

Buanec, B.L., 2005. Plant genetic resources and freedom to operate. Euphytica. 146: 1-8

Buchs, W., 2003. Biodiversity and agri-environmental indicators-general scopes and skills with special reference to the habitat level. Agric. Ecosys. Environ., 1-3: 35-78

Cleveland, D.A., 2001. Is plant breeding science objective truth or social construction? The case of yield stability. Agric. Human Values., 18: 251-270

Contreras, S., 2007. Fundamentals of Seed Production I: Genetics, Breeding and Seed Production, pp: 1-10. Departamento de Ciencias Vegetales Pontificia Universidad Catolica de Chile Santiago, Chile

David, H., M.K. Timothy, R. Ribaut, J.M. Skovmand, B.S. Taba and M. Warburton, 1999. Plant Genetic Resources: What Can They Contribute Toward Increased Crop Productivity?, pp: 5937-5943. the National Academy of Sciences colloquium ''Plants and Population: Is There Time?, held December 5-6, 1998, at the Arnold and Mabel Beckman Center in Irvine, CA. USA, May 1999, 96

Doebley, J.F., S.B. Gaut and B.D. Smith, 2006. The molecular genetics of crop domestication. Cell. 7: 1309-1321

Edmeades, G.O., G.S. McMaster, J.W. White and H. Campos, 2004. Genomics and the physiologist: bridging the gap between genes and crop response. Field Crops Res., 90: 5-18

Engels, J.M.M., A.W. Ebert, I. Thormann and M.C. deVicente, 2006. Centres of crop diversity and/or origin, genetically modified crops and implications for plant genetics resources conservation. Genet. Resour. Crop Evol., 8: 1675-1688

Faizi, S. and M. Ravichandran, 2008. Biodiversity and land reforms: A neglected linkage. Biodiver. Conserv., 17: 2817-2819

Fehr, W.R., 1987. Principles of Cultivar Development, p: 524. Macmillan Publishing Company, A Division of Macmillan Inc. New York

Fernie, A.R. and N. Schauer, 2008. Metabolomics-assisted breeding: a viable option for crop improvement?. Trends Genetics, 1: 39-48

Fowler, C. and T. Hodgkin, 2004. Plant genetic resources for food and agriculture: Assessing global availability. Ann. Rev. Environ. Res., 29: 143-179

Gale, M.D. and K.M. Devos, 1998. Plant Comparative Genetics after 10 Years. Science, 282: 656-658

Gepts, P., 2002. A comparison between crop domestication, plant breeding and genetic engineering. Crop Sci., 42: 1780-1790

Glaszmann J.C., B. Kilian, H.D. Upadhyaya and R.K. Varshney, 2010. Accessing genetic diversity for crop improvement. Current Opinion Plant Biol., 13: 167-170

Govaerts, R., 2001. How Many Species of Seed Plants Are There?. Taxon, 4: 1085-1090

Hammer, K., 2000. A paradigm shift in the discipline of plant genetic resources. Genet. Resour. Crop Evol., 50: 3-10

Hammer, K., T.H. Gladis and A. Diederichsen, 2003. In situ and on-farm management of plant genetic resources. Eurpean J. Agron., 19: 509- 517

Harlan, J.R., 1975. Our Vanishing Genetic Resources. Science, 188: 618- 621

Harlan, J.R., 1981. Evaluation of Wild Relatives of Crop Plants, pp: 6-10. Report of the FAO/UNEP/IBPGR Technical Conference on Crop Genetic Resources, Rome

Hawkes, J.G., 1983. The Diversity of Crop Plants, pp: 91-103. Harvard University Press, Cambridge, Massachusetts, London, England

Hawkes, J.G., 1988. The evolution of cultivated potatoes and their tuber-bearing wild relatives. Kulturpftanze, 36: 189-208

Hawkes, J.G., 1991. The importance of genetic resources in plant breeding. Biol. J. Linnean Soc., 43: 3-10

Hayes, P.M., A. Castro, L. Marquez-Cedill, A. Corey, C. Henson, B.L. Jones, I. Matus, C. Rossi and S. Kazuhiro, 2003. Genetic diversity for quantatively inherited agronomic and malting quality traits. In: Von Brothmer, R. and T.V. Hintum (eds.), Diversity in Barley. (Hordeum vulgare L.), pp: 201-315. Linnean Soc

Hodkinson, T.R., S. Waldren, J.A.N. Parnell, C.T. Kelleher, K. Salamin and N. Salamin, 2007. DNA banking for plant breeding, biotechnology and biodiversity evaluation. J. Plant Res., 120: 17-29

Jain, H.K., 1982. Plant breeders' rights and genetic resources. Indian J. Genet., 42: 121-128

Jauhar, P.P., 2001. Genetic engineering and accelerated plant improvement: Opportunities and challenges. Plant Cell. Tiss. Org. Cult., 64: 87-91 Kasha K.J., 1999. Biotechnology and world food supply. Genome, 42: 642- 645

Lande, R., 1998. Anthropogenic, ecological and genetic factors in extinction and conservation. Res. Pop. Ecol., 3: 259-269

Leroy, T., F. Ribeyre, B. Bertrand, P. Charmetant, M. Dufour, C. Montagnon, P. Marraccini and P. David, 2006. Genetics of coffee quality. Brazilian J. Plant Physiol., 1: 229-242

Linhart, B.Y. and M.C. Grant, 1996. Evolutionary signicance of local genetics differentiation in plants. Annu. Rev. Ecol. Syst., 27: 223-227 Maxted, N., J.M. Iriondo, M.E. Dulloo and A. Lane, 2008. The integration of PGR conservation with protected area management, Conserving plant genetic diversity in protected areas. In: Iriondo, J.M., N. Maxted and M.E. Dulloo (eds.), Population Management of Crop

Wild Relatives CAB International, pp: 1-21. CAB Head Office UK Meilleur, B.A. and T. Hodgkin, 2004. In situ conservation of crop wild relatives: status and trends. Biodiver. Conserv., 13: 663-684 Merezhko, A.F., 1998. Impact of plant genetic resources on wheat breeding. Euphytica, 100: 295-303

Mondeil, M. and S. Setboonsarng, 2009. Enhancing Biodiversity Through Market-Based Strategy: Organic Agriculture. ADBI Working Paper 155. Tokyo: Asian Development Bank Institute. http://www.adbi.org/workingpaper/2009/10/15/3347.biodiversity. organic.agriculture (accessed 21.12.2008)

Moore, M., 2001. Securing the building blocks for tomorrow's crops. The Furrow, 2: 6-8

Moose, S.P. and R.H. Muhm, 2008. Molecular breeding as the foundation for 21st century crop improvement. Plant Physiol., 147: 969-977

Nagel, M., H. Vogel, S. Landjeva, G. Buck-Sorlin, U. Lohwasser, U. Scholz and A. Borner, 2009. Seed conservation in ex situ genebanks-genetic studies on longevity in barley. Euphytica, 170: 5-14

Nevo, E., 1998. Genetic diversity in wild cereals: Regional and local studies and their bearing on conservation ex situ and in situ. Genet. Resour. Crop Evol., 45: 355-370

Ortiz, R., 1998. Critical role of plant biotechnology for the genetic improvement of food crops: perspectives for the next millennium. EJB Electronic J. Biotechnol., 3: 1-8

Ozias-Akins, P. and P.J. Dijk, 2007. Mendelian genetics of apomixis in plants. Annu. Rev. Genet., 41: 509-537

Perrino, P., 2005. The diversity in Vavilov's Mediterrenean gene center. Genet. Resour. Crop Evol., 1988: 85-105

Poehlman, J.M., 1979. Breeding field crops. In: The Avi Publ. Co. Inc. Westport, pp: 277-320. Connecticut

Prance, G.T., 1997. The conservation of botanical diversity. In: Maxted, N., V. Ford-Lloyd and J.G. Hawkes (eds.), Plant Conservation: The in situ Approach, pp: 3-14. Chapman and Hall, London

Rao, V.R. and T. Hodgkin, 2004. Genetic diversity and conservation and utilization of plant genetic resources. Plant Cell. Tiss. Org. Cult., 68: 1-19

Schaart, J.G. and F.G.F. Wisser, 2009. Novel Plant Breeding Techniques: Consequences of New Genetic Modification-based Plant Breeding Techniques in Comparison to Conventional Plant Breeding, pp: 1- 60. Vu and Wageningen University. COGEM. VROM. RIMV/CSR Bureo GGO, The Netherlands

Scharma, H.C., J.H. Crouch, K.K. Sharma, N. Seetharama and C.T. Hash, 2002. Applications of biotechnology for crop improvement: prospects and constraints. Plant Sci., 163: 381-395

Suslov, V., R.T. Bruce and K.J. Bradfort, 2002. Biotechnology Provides New Tools for Plant Breeding, Vol. 8043, pp: 1-19. Agricultural Biotechnology in California Series, Publication, California

Swaminathan, M.S., 2007. Can science and technology feed the world in 2005. Field Crops Res., 1-3: 3-9

sehirali, S. and M. ozgen, 1987. Plant Gene Sources, p: 293. Ank. University of Agriculure Fac. Publication No. 1020/294. Ankara. Turkey

sehirali, S. and M. ozgen, 2007. Plant Breeding, p: 270. Ank. University of Agriculture Fac. Publication No. 1533/506. Ankara. Turkiye

Ullstrup, A.J., 1972. The impacts of the southorn corn leaf epidemics of 1970-71. Ann. Rev. Phytopatol., 10: 37-50

Ulukan, H., 2008. Agronomic adaptation of some field crops: A general approach. J. Agron. Crop Sci., 194: 169-179

Ulukan, H., 2010. The use of plant genetic resources and biodiversity in classical plant breeding, Acta Agric. Scan. Sec. B-Plant Soil Sci., doi: 10.1080/09064710903573390

Ulukan, H., 2009. The evolution of cultivated plant species: Classical plant breeding versus genetic engineering. Plant Sys. Evol., 280: 133-142

Valkoun, J.J., 2001. Wheat Pre-Breeding Using Wild Progenitors. Euphytica, 119: 17-23

Vernoy R. and S. Yiching, 2004. New approaches to supporting the agricultural biodiversity important sustainable rural livelihoods. Int. J. Agric. Sustain., 1: 5-66

Vasil, I.K., 2007. Molecular genetic improvement of cereals: transgenic wheat (Triticum aestivum L.). Plant Cell Rep., 26: 1133-1154

Vasil, I.K., 2008. A history of plant biotechnology: From the cell theory of schleiden and schwann to biotech crops. Plant Cell Rep., 27: 1423- 1440

Vavilov, N.I., 1926. Studies on the origin of cultivated plants. Bull. Appl. Bot., 16: 139-245

Vavilov, N.I., 1951. The Origin, Variation, Immunity and Breeding of Cultivated Plants, pp: 1-16. Chronica-Botanica Co., Inc

Wale, E., 2008. Challanges in genetic resources policy making: Some lessons from participatory policy research with a special reference to Ethiopia. Biodiv. Conser., 17: 21-33

Yunbi, X.U., 2010. Molecular Plant Breeding, pp: 1-38. International Maize and Wheat Improvement Center (CIMMIYT), Mexico DF., Mexico

University of Ankara, Faculty of Agriculture, Department of Field Crops, 06110, Ankara, Turkey
COPYRIGHT 2011 Asianet-Pakistan
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2011 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Ulukan, Hakan
Publication:International Journal of Agriculture and Biology
Article Type:Report
Geographic Code:7TURK
Date:Jun 30, 2011
Words:5820
Previous Article:Synthesis and Toxicity Evaluation of Cinnamyl Acetate: A New Phytotoxin Produced by a Strain of Verticillium dahliae Pathogenic on Olive Tree.
Next Article:Antioxidant Enzyme Activity during Postharvest Deterioration of Cassava (Manihot esculenta) Root Tubers.
Topics:

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