Genetic Diversity In Crop Plants Research Articles

Experiment on long-term storage of vegetable seeds under natural conditions

Preservation of the genetic diversity of crop plants and genetic collections of cultivated plants in a living state is an important state task. Seeds are a convenient form of storing genetic material, as the specimens are small in volume, require relatively little care, and remain viable for a long period. The genetically determined period of seed viability can be signifi cantly extended by creating optimal storage conditions. Therefore, it is necessary to search for or create environmental conditions under which seeds could remain viable for as long as possible. There are modern high-tech seed storage facilities in the world, but in the event of emergency situations, natural storage facilities, one of which is located on the Taymyr Peninsula, will be in a more advantageous position. Since 1974, an experiment has been carried out to study the safety of various products in diff erent types of packaging in permafrost conditions with the participation of a number of research institutions. Employees of the breeding laboratories selected seeds of 27 varieties of seven main types of vegetable crops; the samples were planted in triplicate, in accordance with the planned three extraction dates: in 2022, 2028, and 2034.

Genoplasmics: Advancing Plant Germplasm Research through Genomics

Plant genetic resources (PGR) are crucial for crop improvement programs. The National Genebank (NGB) at ICAR-NBPGR is responsible for collecting, conserving, and facilitating the utilization of genetic diversity in crop plants. Plant germplasm forms the foundation for plant genetic improvement. Extensive germplasm collections have been amassed and stored, presenting the challenge of effectively harnessing and exploiting this valuable resource. Genomics-based plant germplasm research (GPGR), or genoplasmics, is an emerging interdisciplinary field that applies genomic principles and methods to germplasm study. This article outlines the concept, strategy, and approach of GPGR, highlighting recent advancements in core collection creation, germplasm enhancement through core collections, and gene discovery from core collections. GPGR represents a significant milestone in germplasm research, ushering in a new scientific investigation and innovation era.

Effect of ethyl methanesulfonate mediated mutation for enhancing morpho-physio-biochemical and yield contributing traits of fragrant rice.

Chemical mutagenesis has been successfully used for increasing genetic diversity in crop plants. More than 800 novel mutant types of rice (Oryza sativa L.) have been developed through the successful application of numerous mutagenic agents. Among a wide variety of chemical mutagens, ethyl-methane-sulfonate (EMS) is the alkylating agent that is most commonly employed in crop plants because it frequently induces nucleotide substitutions as detected in numerous genomes. In this study, seeds of the widely consumed Basmati rice variety (Super Basmati, Oryza sativa L.) were treated with EMS at concentrations of 0.25%, 0.50%, 0.75%, 1.0%, and 1.25% to broaden its narrow genetic base. Sensitivity to a chemical mutagen such as ethyl methanesulfonate (EMS) was determined in the M1 generation. Results in M1 generation revealed that as the levels of applied EMS increased, there was a significant reduction in the germination percent, root length, shoot length, plant height, productive tillers, panicle length, sterile spikelet, total spikelet, and fertility percent as compared to the control under field conditions. All the aforementioned parameters decreased but there was an increase in EMS mutagens in an approximately linear fashion. Furthermore, there was no germination at 1.25% of EMS treatment for seed germination. A 50% germination was recorded between 0.50% and 0.75% EMS treatments. After germination, the subsequent parameters, viz. root length and shoot length had LD50 between 05.0% and 0.75% EMS dose levels. Significant variation was noticed in the photosynthetic and water related attributes of fragrant rice. The linear increase in the enzymatic attributes was noticed by the EMS mediated treatments. After the establishment of the plants in the M1 generation in the field, it was observed that LD50 for fertility percentage was at EMS 1.0% level, for the rice variety. Hence, it is concluded that for creating genetic variability in the rice variety (Super Basmati), EMS doses from 0.5% to 0.75% are the most efficient, and effective.

Assessment of Tomato (Solanum lycopersicum) Landraces for Their Agronomic, Biochemical Characteristics and Resistance to Phytophthora infestans

Genetic diversity in crop plants is the conditio sine qua non for sustainable agriculture and long-term food security. Our research carried out the morphological, agronomic, and physico-chemical characterization and resistance to late blight of 35 tomato landraces from seven countries. These landraces have been approved and appear in the Official Catalog of Varieties. The International Plant Genetic Resources Institute (IPGRI) descriptors have been used to describe the tomato’s morphological and agronomic characteristics. For the physico-chemical characteristics, the dry matter, the pH, and the carotenoid content (lycopene, lutein, and β-carotene)) were analyzed. Carotenoids were monitored by high-performance liquid chromatography (HPLC). The results showed that the morphological diversity of landraces was very high. Three landraces of remarkable commercial value have shown increased resistance to late blight caused by Phytophthora infestans, one of the most damaging diseases of tomato. Also, six landraces had a lycopene content exceeding 100 µg/g sample. The carotenoid content ranged between 0.769 (Marmande-FR 166) and 140.328 mg kg−1 FW (Răscruci). The landrace with the highest β carotene content was PT 308 with 65.499 mg kg−1 FW, while the lowest values were registered for Marmande-FR 166 with 0.105 mg kg−1 FW. The present study provides essential information on the morphological and agronomic qualities of these tomato landraces and their lycopene and other carotenoid content. The results are discussed in light of the importance of tomato landraces in meeting the preferences of different producers and consumers, the choice of the most suitable landraces for specific pedoclimatic conditions, and the supply of carotenoid pigment sources for the pharmaceutical industry. Our research responds to humanity’s great global challenges: preserving agricultural biodiversity, protecting the environment by identifying pest-resistant varieties, and also protecting consumer health by finding important sources of antioxidants.

Biocultural diversity of common walnut (Juglans regia L.) and sweet chestnut (Castanea sativa Mill.) across Eurasia.

A biocultural diversity approach integrates plant biology and germplasm dispersal processes with human cultural diversity. An increasing number of studies have identified cultural factors and ethnolinguistic barriers as the main drivers of the genetic diversity in crop plants. Little is known about how anthropogenic processes have affected the evolution of tree crops over the entire time scale of their interaction with humans. In Asia and the Mediterranean, common walnut (Juglans regia L.) and sweet chestnut (Castanea sativa Mill.) have been economically and culturally important crops for millennia; there, in ancient times, they were invested with symbolic and religious significance. In this study, we detected a partial geographic congruence between the ethno‐linguistic repartition of human communities, the distribution of major cognitive sets of word‐related terms, and the inferred genetic clusters of common walnut and sweet chestnut populations across Eurasia. Our data indicated that isolation by distance processes, landscape heterogeneity and cultural boundaries might have promoted simultaneously human language diversification and walnut/chestnut differentiation across the same geographic macro‐regions. Hotspots of common walnut and sweet chestnut genetic diversity were associated with areas of linguistic enrichment in the Himalayas, Trans‐Caucasus, and Pyrenees Mountains, where common walnuts and sweet chestnuts had sustained ties to human culture since the Early Bronze Age. Our multidisciplinary approach supported the indirect and direct role of humans in shaping walnut and chestnut diversity across Eurasia from the EBA (e.g., Persian Empire and Greek–Roman colonization) until the first evidence of active selection and clonal propagation by grafting of both species. Our findings highlighted the benefit of an efficient integration of the relevant cultural factors in the classical genome (G) × environmental (E) model and the urgency of a systematic application of the biocultural diversity concept in the reconstruction of the evolutionary history of tree species.

Introgression Breeding in Barley: Perspectives and Case Studies.

Changing production scenarios resulting from unstable climatic conditions are challenging crop improvement efforts. A deeper and more practical understanding of plant genetic resources is necessary if these assets are to be used effectively in developing improved varieties. In general, current varieties and potential varieties have a narrow genetic base, making them prone to suffer the consequences of new and different abiotic and biotic stresses that can reduce crop yield and quality. The deployment of genomic technologies and sophisticated statistical analysis procedures has generated a dramatic change in the way we characterize and access genetic diversity in crop plants, including barley. Various mapping strategies can be used to identify the genetic variants that lead to target phenotypes and these variants can be assigned coordinates in reference genomes. In this way, new genes and/or new alleles at known loci present in wild ancestors, germplasm accessions, land races, and un-adapted introductions can be located and targeted for introgression. In principle, the introgression process can now be streamlined and linkage drag reduced. In this review, we present an overview of (1) past and current efforts to identify diversity that can be tapped to improve barley yield and quality, and (2) case studies of our efforts to introgress resistance to stripe and stem rust from un-adapted germplasm. We conclude with a description of a modified Nested Association Mapping (NAM) population strategy that we are implementing for the development of multi-use naked barley for organic systems and share perspectives on the use of genome editing in introgression breeding.

Diversity analysis of selected rice landraces from West Bengal and their linked molecular markers for salinity tolerance.

Study of genetic diversity in crop plants is essential for the selection of appropriate germplasm for crop improvement. As salinity posses a serious environmental challenge to rice production globally and especially in India, it is imperative that the study of large collections of germplasms be undertaken to search for salt tolerant stocks. In the present study, 64 indica germplasms were collected from different agro-climatic zones of West Bengal, India, from the Himalayan foothills in the northern part down to the southern saline belt of the state keeping in view the soil characteristics and other edaphic factors prevailing in the region. Salt tolerance parameters were used to screen the large set of germplasms in terms of root-shoot length, fresh-dry weight, chlorophyll content, Na+/K+ ratio and germination potential in presence of salt. Standard evaluation score or SES was calculated to find out tolerant to sensitive cultivar. Twenty-one SSR markers, some associated with the Saltol QTL and others being candidate gene based SSR (cgSSR) were used to study the polymorphism of collected germplasm. A wide diversity was detected among the collected germplasms at the phenotypic as well as molecular level. Of the 21 SSR markers, 15 markers were found to be polymorphic with 88 alleles. Based on phenotypic and biochemical results, 21 genotypes were identified as salinity tolerant, whereas 40 genotypes turned out to be salt susceptible. The present study shows that apart from the established salt tolerant lines, several other landraces like Bonkanta, Morisal, Ghiosh, Patni may be the source of salt tolerant donor in future breeding programs.

Genetic diversity and domestication of hazelnut (Corylus avellana L.) in Turkey

Societal Impact StatementHazelnut is consumed worldwide and is of critical economic importance to the rural communities of Turkey's northern coast. A new disease outbreak has drastically decreased yields across Turkey and climate change is emerging as a new threat to cultivation. Our study is the first to provide a genomic perspective on diversity in this vulnerable crop, which will prove valuable for future breeding efforts. Such research into perennial crops like hazelnut can help to improve farmer livelihoods and ensure the sustainability of crop production in a changing world. Summary Assessing and describing genetic diversity in crop plants is a crucial first step toward their improvement. The European hazelnut, Corylus avellana L., is one of the most economically important tree nut crops worldwide. It is primarily produced in Turkey where rural communities depend on it for their livelihoods. Despite this, we know little about its domestication history and the genetic diversity it holds. We use double digest restriction‐site associated DNA (ddRAD) sequencing to produce a genome‐wide dataset containing wild and domesticated hazelnut. We uncover patterns of population structure and diversity, determine levels of crop‐wild gene flow, and estimate the relationships among different genetic clusters. We use a dataset of over 60k single nucleotide polymorphisms to find that genetic clusters of cultivars do not reflect their given names and that there is limited evidence for a reduction in genetic diversity in domesticated individuals. We find evidence that hazelnut may have been domesticated more than once and that admixture has likely occurred multiple times between wild and domesticated hazelnut. We provide the first genomic assessment of Turkish hazelnut diversity and suggest that there has not been an extreme bottleneck during the domestication of this crop, leading to cultivars at different stages of domestication. Our study provides a platform for further research that will protect hazelnut from the threats of climate change and an emerging fungal disease.

Cas Endonuclease Technology-A Quantum Leap in the Advancement of Barley and Wheat Genetic Engineering.

Domestication and breeding have created productive crops that are adapted to the climatic conditions of their growing regions. Initially, this process solely relied on the frequent occurrence of spontaneous mutations and the recombination of resultant gene variants. Later, treatments with ionizing radiation or mutagenic chemicals facilitated dramatically increased mutation rates, which remarkably extended the genetic diversity of crop plants. However, a major drawback of conventionally induced mutagenesis is that genetic alterations occur simultaneously across the whole genome and at very high numbers per individual plant. By contrast, the newly emerging Cas endonuclease technology allows for the induction of mutations at user-defined positions in the plant genome. In fundamental and breeding-oriented research, this opens up unprecedented opportunities for the elucidation of gene functions and the targeted improvement of plant performance. This review covers historical aspects of the development of customizable endonucleases, information on the mechanisms of targeted genome modification, as well as hitherto reported applications of Cas endonuclease technology in barley and wheat that are the agronomically most important members of the temperate cereals. Finally, current trends in the further development of this technology and some ensuing future opportunities for research and biotechnological application are presented.

Molecular breeding approaches involving physiological and reproductive traits for heat tolerance in food crops

Heat stress is a significant threat that limits crop yield and fecundity all over the world. Prevalent strategies for heat adaptation that alter technical and management systems are inadequate to sustain yield. As such, the identification of heat-tolerant genotypes with improved yield potential is crucial. Raising tolerant and stable cultivars can be tedious as heat-stress responses are highly variable across different developmental stages. While molecular breeding has progressed in engineering heat-tolerant lines, the complexity of genetic networks and divergence of heat tolerance mechanisms is the main hindrance for plant breeders. Hence, insight into the physiological and reproductive traits associated with heat tolerance could assist in the development of strategies to screen germplasm for heat tolerance. Exploitation and use of landraces and wild relatives in breeding may enhance favorable genetic diversity in crop plants. A holistic approach to delineate molecular markers, where quantitative trait loci (QTLs) for different traits linked to heat tolerance involving physiological and reproductive traits are characterized in well-controlled field environments, may be an option for optimizing germplasm under heat stress. Here, we present an outline of the effects of heat stress and its associated tolerance mechanisms in food crops, along with some physiological, molecular and reproductive characteristics such as ‘stay-green,’ membrane thermostability, canopy temperature depression, metabolites, genes, QTLs, and pollen fertility. Further, we provide information on conventional and molecular breeding approaches as well as different selection strategies for heat stress tolerance.

Assessment of Genetic Diversity in Crop Plants - An Overview

Assessment of Genetic Diversity in Crop Plants - An Overview

From working collections to the World Germplasm Project: agricultural modernization and genetic conservation at the Rockefeller Foundation

This paper charts the history of the Rockefeller Foundation’s participation in the collection and long-term preservation of genetic diversity in crop plants from the 1940s through the 1970s. In the decades following the launch of its agricultural program in Mexico in 1943, the Rockefeller Foundation figured prominently in the creation of world collections of key economic crops. Through the efforts of its administrators and staff, the foundation subsequently parlayed this experience into a leadership role in international efforts to conserve so-called plant genetic resources. Previous accounts of the Rockefeller Foundation’s interventions in international agricultural development have focused on the outcomes prioritized by foundation staff and administrators as they launched assistance programs and especially their characterization of the peoples and “problems” they encountered abroad. This paper highlights instead how foundation administrators and staff responded to a newly emergent international agricultural concern—the loss of crop genetic diversity. Charting the foundation’s responses to this concern, which developed only after agricultural modernization had begun and was understood to be produced by the successes of the foundation’s own agricultural assistance programs, allows for greater interrogation of how the foundation understood and projected its central position in international agricultural research activities by the 1970s.

Managing Biodiversity with Emphasis on Sustainable Development

The biodiversity, which makes our lives both pleasurable and probable. No one knows precisely how many species arise on our world. According to specialist the total number of species on earth is in between 10 million to 80 million. We have been capable to procure only 1.4 million species so far. India has a flora of its possess and concerning 15000 species are widespread in this region. However biodiversity loss is continuing as a serious worry in many countries including India. Human population increase, indefensible consumerism, augmenting liberate of waste and pollutants, urbanization, international conflicts and unfairness in giving out of wealth and resources are presently being viewed in totality to ameliorate environmental problems as well as to make sure the potential of life on earth. Biodiversity is an umbrella expression acceptance numbers, assortment and variability of living organisms, the sum total of genetic materials within the organisms and the ecosystems in which they take place. Asia was the most horrible influence in terms of casualties owing to natural disasters - 65% of those killed in 2012 were Asians. Study conducted by specialist that 70% of worldwide genetic diversity of crop plants has already been gone during the last century owing to preface of elevated yielding and hybrid varieties of crops. Pollution has risen in numerous developing countries including India with elevated economic growth, as superiority of environment is ignored in favor of economic achievement. According to Global Ecology and Biogeography that global warming will make quite a lot of species of lizard go away extinct within the next 50 years. In India biodiversity is critical not only because it provides rather a few goods as well as services indispensable for human endurance, other than as well for the reason that it is unswervingly associated by means of as long as livelihoods on the way to along with improving socio-economic conditions of millions of our populace, consequently contributing to sustainable development in adding together to scarcity alleviation.

Genomics of crop wild relatives: expanding the gene pool for crop improvement.

Plant breeders require access to new genetic diversity to satisfy the demands of a growing human population for more food that can be produced in a variable or changing climate and to deliver the high-quality food with nutritional and health benefits demanded by consumers. The close relatives of domesticated plants, crop wild relatives (CWRs), represent a practical gene pool for use by plant breeders. Genomics of CWR generates data that support the use of CWR to expand the genetic diversity of crop plants. Advances in DNA sequencing technology are enabling the efficient sequencing of CWR and their increased use in crop improvement. As the sequencing of genomes of major crop species is completed, attention has shifted to analysis of the wider gene pool of major crops including CWR. A combination of de novo sequencing and resequencing is required to efficiently explore useful genetic variation in CWR. Analysis of the nuclear genome, transcriptome and maternal (chloroplast and mitochondrial) genome of CWR is facilitating their use in crop improvement. Genome analysis results in discovery of useful alleles in CWR and identification of regions of the genome in which diversity has been lost in domestication bottlenecks. Targeting of high priority CWR for sequencing will maximize the contribution of genome sequencing of CWR. Coordination of global efforts to apply genomics has the potential to accelerate access to and conservation of the biodiversity essential to the sustainability of agriculture and food production.

Plant domestication and resistance to herbivory.

Transformation of wild species into elite cultivars through “domestication” entails evolutionary responses in which plant populations adapt to selection. Domestication is a process characterized by the occurrence of key mutations in morphological, phenological, or utility genes, which leads to the increased adaptation and use of the plant; however, this process followed by modern plant breeding practices has presumably narrowed the genetic diversity in crop plants. The reduction of genetic diversity could result in “broad susceptibility” to newly emerging herbivores and pathogens, thereby threatening long-term crop retention. Different QTLs influencing herbivore resistance have also been identified, which overlap with other genes of small effect regulating resistance indicating the presence of pleiotropism or linkage between such genes. However, this reduction in genetic variability could be remunerated by introgression of novel traits from wild perhaps with antifeedant and antinutritional toxic components. Thus it is strongly believed that transgenic technologies may provide a radical and promising solution to combat herbivory as these avoid linkage drag and also the antifeedant angle. Here, important questions related to the temporal dynamics of resistance to herbivory and intricate genetic phenomenon with their impact on crop evolution are addressed and at times hypothesized for future validation.

Processos evolutivos e a origem das plantas cultivadas

A evolução das plantas cultivadas, que teve início há cerca de 13.000 anos, está sujeita aos mesmos processos evolutivos naturais, aliada à ação do homem de forma consciente ou inconsciente, levando à domesticação. Nesta revisão, são apresentados os principais fatores evolutivos, tais como mutação, hibridação, migração, seleção e deriva genética, que, de alguma maneira, estão envolvidos com a origem, evolução e domesticação de plantas cultivadas. São apresentados também exemplos de como esses processos influenciaram na diversidade intra e interespecífica de plantas cultivadas, com o aparecimento de novas variedades ou mesmo de novas espécies. De modo geral, tais processos atuaram na ampliação, na manutenção, bem como na redução da variabilidade genética das plantas cultivadas.

Evaluation of variability in five linseed (Linum usitatissimum L.) genotypes using agro‐morphological characters and RAPD analysis

Analysis of the extent and distribution of genetic diversity in crop plants is essential for optimizing sampling and breeding strategies. Morphological characters and Randomly amplified polymorphic DNA (RAPD) was used to estimate genetic variability among 5 genotypes of linseed (Linum usitatissimum L). Selected four RAPD primers generated 140 bands, 80 of which were found to be polymorphic. All the primers produced polymorphic amplification products, however the extent of polymorphism varied with each primer .The percentage of polymorphism generated by primer was OPG‐03 (85.029%), OPH‐12(45.94%), OPC‐02(45.94%) and OPG‐18(64.28%). Great variation among morphological characters viz., root length, stem diameter, number of leaves, germination percentage and radicle length was observed. UPGMA (Unweighted Pair Group Method with Arithmetic Mean) dendrogram obtained from cluster analysis using Jaccard’s similarity coefficient resulted into three clusters. Cluster1 comprised of two genotypes (Jawhar and saharda), cluster II also comprised of two genotypes (T‐397 and KL‐1) and cluster III consisted of only one genotype Garima, which was interesting to observe that the Garima was distinct from all other four experimental varieties and sole constituent of cluster III. All the genotypes could be discriminated from one another using combined profiles of 4 primers.

Herbarium specimens expand the geographical and temporal range of germplasm data in phylogeographic studies

As the world faces a burgeoning human population and changing climate, the sustainability of its food resources are of key importance. Humans rely on an extremely narrow range of food plants: three species of cereals (maize, rice, wheat) make up approximately 50 percent of the world's calorific con sumption (FAOSTAT, 2009). Plant breeding practices since the 1950s have reduced the genetic diversity of crop plants in western agriculture to a drastic level. The preservation of the remaining genetic diversity in crop plants, and its conserva tion and management, are core goals of the coming decades. Phylogeography, the mapping of geographical and temporal patterns in genetic diversity, is an important tool in this process. Phylogeography can help us explore the processes that affected crop biodiversity in the past, e.g., where and when a crop was domesticated, how many times it was domesticated, what were the initial routes of spread of its cultivation and the effects of subsequent prehistoric and historic processes.

Tobacco cultivar and type mediated effects on the population of aphid parasitoid, Aphidius sp. (Hymenoptera: Aphidiinae) and predator, Cheilomenes sexmaculata (Fabricius) (Coleoptera: Coccinellidae).

During 1998-2002, three experiments Were conducted under net housc house conditions to determine the tritrphie interactions involving certain tobacco varieties, aphid, Myzus nicotianae and the aphidophagous species, Aphidius sp. and Cheilomens sexmaculata . The results revealed that C. Sexmaculata population on tobacco cultivars, CM-12 with dark cast leaf character and VT-1158 with open typc leaf character, was higher than in Gouthami with semi-erect and light cast leaf character and Jayasri (erect type). Among the tobacco types, Lanka special (cheroot) followed by Kumkumadri (beedi) were more attractive to the beetle than Badami local ( rustica ) and Samsun (Aromatic). Highest amount of leaf surface waxes detrimental to movement of coccinellids was observed in rustica tobacco (225μg/cm<SUP2) and the lowest in Lanka special (42μg/cm<SUP2). It was also observed that nutritional status of aphids fed on Lanka tobacco was superior to those fed on least preferred varieties. In the casc of Aphidius sp. parasitization involving different tobacco types, significant differences were not observed at top lear position. In Ihe middle leaf position, highest percent parasitization (80.40) was noticed in variety Kanchan followed by Samsun (70.00) and DR-I Lanka (69.54). Except in varieties GT-4 and Kumkumadri (beedi), higher parasitization on bottom leaves was recorded in the rest. The opportunities for utilizing genetic diversity in crop plants for enhancing natural enemy activity are elucilhlted.

Assessing genetic potential in germplasm collections of crop plants by marker-trait association: a case study for potatoes with quantitative variation of resistance to late blight and maturity type

Genetic diversity of crop plants resulting from breeding and selection is preserved in gene banks. Utilization of such materials for further crop improvement depends on knowledge of agronomic performance and useful traits, which is usually obtained by phenotypic evaluation. Associations between DNA markers and agronomic characters in collections of crop plants would (i) allow assessment of the genetic potential of specific genotypes prior to phenotypic evaluation, (ii) identify superior trait alleles in germplasm collections, (iii) facilitate high resolution QTL mapping and (iv) validate candidate genes responsible for quantitative agronomic characters. The feasibility of association mapping was tested in a gene bank collection of 600 potato cultivars bred between 1850 and 1990 in different countries. The cultivars were genotyped with five DNA markers linked to previously mapped QTL for resistance to late blight and plant maturity. Specific DNA fragments were tested for association with these quantitative characters based on passport evaluation data. Highly significant association with QTL for resistance to late blight and plant maturity was detected with PCR markers specific for R1, a major gene for resistance to late blight, and anonymous PCR markers flanking the R1 locus at 0.2 Centimorgan genetic distance. The marker alleles associated with increased resistance and later plant maturity were traced to an introgression from the wild species S. demissum. These DNA markers are the first marker that are diagnostic for quantitative agronomic characters in a large collection of cultivars.