A drought stress panel composed of diverse accessions selected from upland, aerobic, rainfed lowland and irrigated lowland environments, was assembled to serve as germplasm for aerobic adaptation breeding. Aerobic rice requires significant levels of tolerance to drought stress due to intermittent water deficit and high soil impedance caused by aerobic conditions. Genomic information may be utilized to investigate the nature of the panel to guide varietal improvement. Using 153 simple sequence repeat and 384 single nucleotide polymorphism markers, the aim of the study was to compare the allelic properties of the two marker types, infer population structure of the panel, and estimate kinship among the accessions. There was a general agreement between the results derived from the two marker types. Marker alleles were found to occur at low frequencies, as the panel was composed mostly of improved accessions with some landraces. The panel clustered into japonica (JA), aus (AU), upland-adapted indica (UL) and lowland-adapted indica (LL) subpopulations. The AU and JA subpopulations were more divergent from the rest of the subpopulations than were the LL and UL subpopulations. Average marker-based kinship for related accessions was less than 0.20, indicating a low degree of genetic relatedness in the panel. Within the LL and UL subpopulations, the low levels of kinship imply that there is still much genetic gain to be expected from utilizing the accessions in breeding. Thus, an understanding of the genetic variation in the panel suggests focusing on improving the mean in the short term, and tapping into the exotic alleles from the AU and JA subpopulations when genetic gain declines.

To preliminarily evaluate the genetic diversity of the Iranian diploid Triticum L. gene pool, in this study, a total of 176 individuals belonging to T. monococcum L. ssp. aegilopoides (Link) Thell. and T. urartu Thum. ex Gandil. were pre-screened using single-strand conformation polymorphism (SSCP) analysis of the Acc-1 and Pgk-1 loci. A selected set of 76 DNA samples corresponding to the observed SSCP variants were sequenced for both loci and evaluated for nucleotide diversity associated with the taxonomic groups and geographical regions. We found three haplotypes, including one that was new for Iran, at each locus. Population structure and analysis of molecular variation results proved that the collection evaluated could be genetically divided into two distinct groups, which to a great extent was in accordance with the taxonomic classification. A genetic leakage from T. monococcum ssp. aegilopoides into T. urartu was observed during structure analysis, which was inferred on the basis of occasional outcrossing, despite their inbreeding nature. The results revealed that there was no variation within the populations belonging to T. urartu, while a meaningful variation was found between the geographical regions for T. monococcum ssp. aegilopoides. The median-joining networks revealed a conflict between morphology and haplotype variation, which was interpreted on the basis of introgressive hybridization, recombination signature and rapid speciation. In conclusion, we suggest that SSCP analysis is a useful tool in regions where thorough sequencing of an enormous number of DNA samples is time consuming and not affordable.

To investigate the genetic diversity and structure of Jatropha curcas L. oilseed plant, in this study, native populations from Chiapas, Mexico, were evaluated, using microsatellite DNA markers. A total of 93 representative samples were selected from seven sites in two regions in the state of Chiapas grouped by geographical proximity, where leaf samples were collected to isolate the genomic DNA. Individual polymerase chain reactions were carried out with ten pairs of specific oligonucleotides for the microsatellites of J. curcas, separating the products of amplification by acrylamide electrophoresis. Twenty-seven fragments were detected (77% polymorphic) with which heterozygous individuals were distinguished. The most informative microsatellite was Jcps20 (nine alleles, polymorphic index content 0.354). The average polymorphism per population was 58%. The Hardy–Weinberg tests revealed a reproductive pattern of non-random mating. The diversity descriptors and the analysis of molecular variance revealed that the populations were structured and moderately differentiated (FST 0.087) and that this differentiation was not due to isolation by distance, as the Mantel test was not significant (P= 0.137), but rather due to allopatry. Bayesian analysis revealed that the accessions belonged to only four genetic groups and confirmed the differentiation between the regions. Because some loci were in Hardy–Weinberg disequilibrium, it is proposed that differentiation is due to the clonal reproduction of J. curcas practised by farmers in Chiapas, along with the anthropogenic dispersion at regional levels. The results of this study reveal that J. curcas in Chiapas has genetic diversity that is greater than that reported in other parts of the world, which represents a potential germplasm pool for the selection of genotypes.

Local upland rice germplasm is an invaluable resource for farmers who grow rice on acidic soils without flooding that benefits wetland rice. In this study, we evaluated the adaptation to soil acidity in common local upland rice varieties from an area with acidic soil in Thailand. Tolerance to hydrogen and aluminium (Al) toxicity was determined by measuring root growth, plant dry weight and phosphorus (P) uptake in aerated solution culture without the supplementation of Al (0 mg/l) at pH 7 and 4 and with the supplementation of 10, 20 and 30 mg Al/l at pH 4. The root growth of upland rice plants grown from farmers' seed was depressed less by Al than that of common wetland rice varieties. Pure-line genotypes of upland rice varieties were differentiated into several classes of Al tolerance, with frequency distribution of the classes that sometimes differed between the accessions of the same varieties. The effect of Al tolerance on root length was closely correlated with depression by Al in root dry weight and whole-plant P content. A source for adaptation to soil acidity for exploitation in the genetic improvement of aerobic and rainfed rice is clearly found among local upland rice varieties grown on acidic soils. However, the variation in tolerance to soil acidity within and among the seed lots of the same varieties maintained by individual farmers as well as among the varieties needs to be taken into consideration.

Development of a representative and well-diversified core with minimum duplicate accessions and maximum diversity from a larger population of germplasm is highly essential for breeders involved in crop improvement programmes. Most of the existing methodologies for the identification of a core set are either based on qualitative or quantitative data. In this study, an approach to the identification of a core set of germplasm based on the response from a mixture of qualitative (single nucleotide polymorphism genotyping) and quantitative data was proposed. For this purpose, six different combined distance measures, three for quantitative data and two for qualitative data, were proposed and evaluated. The combined distance matrices were used as inputs to seven different clustering procedures for classifying the population of germplasm into homogeneous groups. Subsequently, an optimum number of clusters based on all clustering methodologies using different combined distance measures were identified on a consensus basis. Average cluster robustness values across all the identified optimum number of clusters under each clustering methodology were calculated. Overall, three different allocation methods were applied to sample the accessions that were selected from the clusters identified under each clustering methodology, with the highest average cluster robustness value being used to formulate a core set. Furthermore, an index was proposed for the evaluation of diversity in the core set. The results reveal that the combined distance measure A 1 B 2 – the distance based on the average of the range-standardized absolute difference for quantitative data with the rescaled distance based on the average absolute difference for qualitative data – from which three clusters that were identified by using the k-means clustering algorithm along with the proportional allocation method was suitable for the identification of a core set from a collection of rice germplasm.

Chilli (Capsicum spp.) is an economically important vegetable and spice. The Tropical Vegetable Research and Development Center, Kasetsart University, Kamphaeng Saen Campus has collected more than 2500 chilli germplasm accessions since 1989. Investment to maintain and evaluate such a large germplasm collection is high. For efficient germplasm management and to reduce the cost of germplasm maintenance, a core collection needs to be established. Therefore, this study aimed to investigate the genetic diversity of chilli germplasm using microsatellites. A total of 230 chilli germplasm accessions were evaluated using ten anchored Capsicum microsatellite loci. These loci generated 42 alleles with a size ranging from 87 to 323 bp. The average polymorphic information content was 0.57, ranging from 0.414 to 0.681, and the probability of identity (PI) ranged from 0.17 to 0.49. The combined PI of the ten microsatellite loci was 2.30 × 10− 6. The similarity index ranged from 0.29 to 1.00. The 230 chilli accessions were divided into two major groups. Group I comprised mainly C. annuum, and group II comprised all four Capsicum species with the majority being C. frutescens, C. chinense and C. baccatum. The matrix comparison showed that a cophenetic correlation of 0.798 indicated the best fit of the obtained dendrogram. The PowerCore program selected 28 representative chilli accessions to form a core collection, which maintained a similar level of diversity to that of the overall 230 chilli accessions. The representative alleles in those 28 core accessions equalled all the alleles present in the entire collection.

Plant genetic resources are conserved by genebanks mainly in the form of seeds. In most of the cases, the dried seeds can be stored for a considerable period of time, but eventually seed deterioration results in the inability to generate healthy seedlings. Prolonging seed longevity during storage reduces the frequency of regeneration, which is beneficial from a genetic as well as a management point of view. To reduce the rate of deterioration, cool and dry storage conditions are usually practised for long-term seed storage. In spite of the growing body of evidence that seed deterioration is predominantly caused by oxidative processes, the importance of seed storage under anoxic conditions has received little attention from the genebank community. Herein, we report on the effects of anoxia on seed viability, the oxygen uptake by dry seeds in closed containers and the permeability for oxygen of various seed storage containers. Our results confirm that the ageing of dry seeds is accelerated by the presence of oxygen in the storage environment. Therefore, we recommend that genebanks store dry seeds under anoxic conditions to prolong their longevity during ex situ conservation. To reduce the initial rate of viability loss, we further recommend that the period of temporary storage after seed harvest be minimized and also that the seeds are kept during this period under controlled conditions, including anoxia.

Cultivated soybeans [Glycinemax (L.) Merr.] have various flower colours such as dark purple, purple, light purple, pink, magenta, near white and white. About one-third of the soybean accessions in the United States Department of Agriculture – Germplasm Resource Information Network (USDA-GRIN) Soybean Germplasm Collections have white flowers and are the second dominant accessions after the purple-flowered accessions. Earlier studies have shown that the w1 recessive allele of the W1 gene encoding flavonoid 3′,5′-hydroxylase produces white flowers. In the present study, we aimed to understand why the white-flowered accessions have become abundant among the cultivated soybeans and what their genetic and regional origin is. For this purpose, 99 landraces with white flowers and 39 landraces with purple flowers from eight Asian countries and Russia were analysed with regard to the nucleotide sequences of the W1 locus. We not only found that the w1 alleles of the 99 white-flowered landraces were identical to those of the white-flowered Williams 82, but also found that these w1 alleles displayed no polymorphism at all. By carrying out a phylogenetic analysis, we were able to identify a group with W1 alleles from which the w1 allele might have diverged.

Cultivars of Miscanthus used as bioenergy crops or tested in trials are largely clonally propagated, wild sourced genotypes or clonally propagated F1 hybrids. One of the most productive taxa is the sterile triploid M. × giganteus. Little domestication or breeding has been undertaken and there is huge potential to utilize the extensive genetic resources of the genus for crop improvement. The challenge is to generate new highly adapted genotypes suitable for a range of environments. Production on marginal land, not used for food crops, is particularly desirable, but presents many barriers to crop breeders, as these are largely unproductive and/or stressful environments. This article outlines progress made in characterizing natural genetic variation in Miscanthus including next-generation single-nucleotide polymorphism genotyping, quantitative trait locus analysis and association mapping. It also explains how this knowledge is being used to develop novel genotypes suited for growth in a broad range of agricultural and marginal lands by defining breeding pools, generating novel crosses, manipulating polyploidy and applying genomic selection approaches.

In this study, the genetic constitution of wild grape populations distributed in the Zagros Mountains in the north-west part of Iran was investigated to assess their risk of extinction and to identify the most suitable conservation strategy. A total of 65 wild grapevine samples from five different populations were analysed using 23 SSR loci. Consistent allelic richness was detected in all the analysed populations (from 4.01 to 5.35). The observed heterozygosity and expected heterozygosity were high with mean values of 0.67 and 0.69, respectively. A modest heterozygosity deficiency was detected only in the Piranshahr and Sardasht-Shalmash populations. The neighbour-joining dendrogram clustered the accessions into three groups corresponding to the geographical distribution of the populations. Molecular data combined with field evaluation revealed that an ex situ conservation approach is the most suitable strategy for preserving the genetic richness of Iranian wild grape populations with consistent rare alleles (about 20%). We propose in situ preservation only in the case of the Sardasht-Ghasmarash population to ensure that evolutionary dynamic forces continue to influence plant adaptation and survival in response to environmental alterations.

Accurate knowledge of intra-specific diversity of underutilized crop species is a prerequisite for their genetic improvement and utilization. The diversity of 77 accessions of African yam bean (AYB, Sphenostylis stenocarpa) was assessed by amplified fragment length polymorphism (AFLP) markers. A total of EcoRI/MseI primer pairs were selected and 227 AFLP bands were generated, of which 59(26%) were found to be polymorphic in the 77 accessions of AYB. The most efficient primer combination for polymorphic detection was E-ACT/M-CAG with a polymorphic efficiency of 85.5%, while the least efficient was E-AGC/M-CAG with a polymorphic efficiency of 80.6%. The Jaccard genetic distance among the accessions of AYB ranged between 0.048 and 0.842 with a mean of 0.444. TSs98 and TSs104B were found to be the most similar accessions with a genetic similarity of 0.952. The neighbour-joining dendrogram grouped the 77 accessions of AYB into four distinct clusters comprising 8, 20, 21 and 28 accessions. The major clustering of the accessions was not related to their geographical origin. Cluster I was found to be the most diverse. The mean fixation index (0.203) and the mean expected heterozygosity (0.284) revealed a broad genetic base of the AYB accessions. The same germplasm set was previously evaluated for several agro-morphological traits. As the collection of additional AYB germplasm continues, the phenotypic profile, the clustering of the accessions and the AFLP primer combinations from this study can be used to augment breeding programmes.

Old germplasm is an important genetic resource for enhancing modern crops with new alleles. In the present study, the genetic diversity of 52 historic varieties and landraces of bread wheat originated from the Western (Bulgaria) and Northeastern (Ukraine, Russia and Georgia) regions of the Black Sea basin was assessed based on microsatellite markers and agronomic characteristics. A set of 24 markers detected a total of 263 alleles at 25 microsatellite loci, with an average number of 10.5 alleles per locus and an average polymorphic information content (PIC) of 0.74. A total of 63 alleles at 22 loci were unique, being specific to a particular accession. Half of the alleles (132) were regionally specific, and the rest were common between the Western and Northeastern accessions. The latter group was characterized with greater total and private allelic richness, a higher number of unique alleles and a higher average PIC. The population was found to be very heterogeneous (average heterogeneity 41%), with the Northeastern pool (52.8%) being more diverse than the Western pool (30.9%). Most of the accessions of the Western group clustered together, and the rest were distributed among the subclusters of the Northeastern germplasm. Large inter-group differences in the frequencies of alleles ranging from 3.1 at Xgwm294-2A to 16.7 at Xgwm333-7B were observed. This variation might partly account for the differences in certain yield-related traits. The Northeastern accessions had significantly longer spikes with more number of spikelets. Some issues related to germplasm preservation in seed genebanks are discussed herein. The large molecular variation observed could be utilized by breeders for the selection of diverse parents, or by researchers for the production of mapping populations.

Millions of farmers depend on the use of local crops and varieties for their food and livelihood. These resources constitute a reservoir of alternative traits and characteristics, which allow us to diversify crops, foods and farming methods and provide material for targeted plant breeding. Still, many countries lag behind in providing support to farming communities for the maintenance and use of plant genetic resources for food and agriculture (PGRFA). A global survey was conducted among a wide range of stakeholders to gain insights into the state of on-farm management (OFM) as a strategy for enhancing the maintenance and sustainable use of PGRFA. The survey showed that a wide range of stakeholders provide de facto support to OFM and that the practices they consider critical are focused on building capabilities in local communities. This supports the fact that the management of crop diversity on farm can be promoted in a variety of ways, depending on the specific context, and that local solutions are needed to successfully support OFM. Partnerships and networks should be considered as one of the critical means to promote OFM, as they involve a diversity of stakeholders working towards common goals. The survey further showed that many respondents currently contribute to existing networks relevant to OFM, but that these networks are mainly nationally or internationally oriented and might therefore exclude crucial local stakeholders, such as community-based organizations. Therefore, mechanisms should be put in place to strengthen the collaboration between stakeholders and networks, especially at the local level.

In Uruguay, onion (Allium cepa L.) germplasm is mainly derived from the genetic material introduced by several waves of European immigrants and subsequently multiplied by household farmers, resulting in a wealth of locally adapted populations. This study examined the genetic diversity in a collection of 27 local onion populations and two cultivars derived from them. A total of 843 onion plants were fingerprinted, and 83 inter-simple sequence repeat polymorphic bands were generated. Analysis of molecular variance showed high diversity within the populations (66% of the total variation). Some short-day populations from different geographical origins were grouped together by the unweighted pair-group method using arithmetic averages, principal coordinate analysis and cluster analysis, while the more extensively sampled long- and intermediate-day populations showed a widespread distribution, with no significant subgrouping among them. This weakly structured gene pool is probably the consequence of seed and bulb exchange between farmers and natural inter-pollination. Nevertheless, a Bayesian analysis allowed the distinction of four genetic backgrounds of alleles in the whole collection, and populations were predominately assigned to each genetic background. In addition, mitochondrial variants determining normal (N) pollen fertility or the sterile S or T types were analysed for the same set of plants using specific primers. Most accessions showed a proportion of male-sterile individuals. Cytoplasm type T was the most represented (26 out of 29 accessions), and cytoplasm type S was found in a low proportion of individuals in seven populations. Uruguayan onion germplasm maintains a low degree of genetic differentiation despite the small cultivated area and intense seed exchange, probably due in part to different market purposes based on the growing cycle.

In this study, genetic diversity in 340 finger millet accessions from Kenya, Tanzania and Uganda and 15 minicore accessions was assessed using 23 single-sequence repeat markers and five qualitative traits. Nineteen markers were polymorphic with a mean polymorphic information content value of 0.606 and a range of 0.035–0.889, with allele size ranging from 148 to 478. A total of 195 alleles were detected (range of 3–23 and average of 10.3 alleles per locus), with 57.7% being rare and 17.4% being private. Differentiation between the accessions of the three countries was weak, with most of the genetic diversity being explained by variability within the countries and subregions than by that among the countries and subregions. The highest genetic diversity was observed in the Kenyan accessions (0.638 ± 0.283) and the least in the Ugandan accessions (0.583 ± 0.264). The highest differentiation based on Wright's fixation index was observed between the Ugandan and Tanzanian accessions (FST= 0.117; P< 0.001). There was no association between the morphological traits assessed and the genetic classes observed. The low variability between the countries could be attributed to a shared gene pool, as the crop originated from the East African region. Farmers' selection for adaptation and end use could have contributed to the high diversity within the countries. Concerted efforts need to be made to characterize the large germplasm stocks in East Africa for their effective conservation and utilization. The lack of representation of accessions from the three countries in all global minicore diversity clusters points to the need to explore the East African germplasm to identify the diversity not captured earlier to be included in the global repository.

The genebank at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, India holds a collection of 542 accessions from the Caribbean and Central American (CCA) regions, of which 424 were evaluated for eight qualitative and 17 quantitative traits at ICRISAT farm. A hierarchical cluster analysis was performed using the scores of the first nine principal components that resulted in four clusters. The accessions of these four clusters exhibited the following good characteristics: cluster 1 had high pod-bearing length and high seed protein content; those of cluster 2 had high degree of branching, large number of pods per plant and high seed yield per plant; those of cluster 3 had long pods; and those of cluster 4 had larger seeds. In the whole collection of accessions, diversity was found to be maximum (H′ = 0.630+0.026) for plant height and minimum for tertiary branches per plant (H′ = 0.259+0.026). The highest correlation coefficient was observed between racemes per plant and pods per plant (r= 0.914) followed by between pods per plant and seed yield per plant (r= 0.744), and between shelling percentage and the harvest index (r= 0.703). In view of the poor representation of the world collection of pigeonpea (13,771 accessions) from the CCA regions, launching of collection missions in these countries has been suggested to fill gaps and increase the variability. Multi-location evaluation of the collections for agronomic traits at potential locations in the CCA regions and systematic evaluation for nutritional traits and resistance to biotic and abiotic stress could result in the identification of useful genotypes, particularly vegetable types, for use in breeding programmes to develop high-yielding cultivars as well as to release as varieties in these regions.

The regions of north-eastern Ethiopia are known for their high levels of sorghum genetic diversity, and for being drought prone. For centuries, sorghum has been developed and maintained by farmers for its adaptation to the marginal and heterogeneous environment of these regions. The objective of this study was to examine the genetic diversity and population structure of 200 sorghum landraces collected from seven lowland districts, using 30 microsatellite markers sampled from all linkage groups of the sorghum genome. Both distance-based and model-based analytical approaches were used to analyse the data. The data analysis revealed that there was a large variation among all the markers under study. The values of polymorphic information content ranged from 0.26 to 0.88, with a mean value of 0.61, reflecting the high discriminating ability of the markers studied. The mean value of total gene diversity was 0.69, which partitioned 86% among the landraces and 14% within the landraces. Gene diversity among the landraces was largely due to the variation among the genotypes within the geographic origins. Landraces sampled from different collection sites appeared to cluster together, indicating the existence of a high level of gene flow among the sites of collection. This indicates that a relatively small, random collection of landraces would capture the bulk of genetic diversity in the target area. A moderately high level of genetic differentiation and a relatively low level of gene flow were observed between sorghum races and maturity groups. Given that the target area is marginal, drought prone and heterogeneous, the study of genetic diversity among sorghum landraces could serve as an important indicator of valuable alleles for drought tolerance in future sorghum improvement programmes.

To maximize heterosis, it is important to understand the genetic diversity of germplasm and associate useful phenotypic traits such as fertility restoration for hybrid rice breeding. The objectives of the present study were to characterize genetic diversity within a set of rice germplasm groups using coefficient of parentage (COP) values and 58 simple sequence repeat (SSR) markers for 124 genotypes having different attributes such as resistance/tolerance to various biotic and abiotic stresses. These lines were also used for identifying prospective restorers and maintainers for wild abortive-cytoplasmic male sterile (CMS) line. The mean COP value for all the lines was 0.11, indicating that the genotypes do not share common ancestry. The SSR analysis generated a total of 268 alleles with an average of 4.62 alleles per locus. The mean polymorphism information content value was 0.53, indicating that the markers selected were highly polymorphic. Grouping based on COP analysis revealed three major clusters pertaining to the indica, tropical japonica and japonica lines. A similar grouping pattern with some variation was also observed for the SSR markers. Fertility restoration phenotype based on the test cross of the 124 genotypes with a CMS line helped identify 23 maintainers, 58 restorers and 43 genotypes as either partial maintainers or partial restorers. This study demonstrates that COP analysis along with molecular marker analysis might encourage better organization of germplasm diversity and its use in hybrid rice breeding. Potential restorers identified in the study can be used for breeding high-yielding stress-tolerant medium-duration rice hybrids, while maintainers would prove useful for developing new rice CMS lines.

Understanding of genetic diversity and its distribution is essential for promoting the use of genetic resources. The development of core collections using molecular tools has been proposed as a strategy for increasing the economical use and conservation of genetic resources. In this study, we investigated the genetic variation among different geographical origins and potential entries that constituted a core collection of oil palm, using 29 microsatellite markers and by evaluating 788 oil palm accessions. Our results revealed important genetic diversity (HT= 0.759) between oil palm accessions from Angola and Cameroon, which exhibited a low coefficient of genetic differentiation between populations (GST= 0.022). However, the inclusion of oil palm accessions from Indonesia in the analysis resulted in a high coefficient of genetic differentiation between populations (GST= 0.251). We found that the combination of stratified sampling based on a sorting method and a heuristic algorithm was the most effective method for the development of an oil palm core collection set. Using this method, two core collections were identified. The first core collection, comprising 289 entries, contained 271 retained alleles in a sample representing 37% of the entire collection. The second one is a mini core collection, comprising 91 entries, that contained 271 retained alleles with a total He value of 0.72 in a sample representing 11% of the entire collection. The information reported in this study will be of great interest to oil palm researchers because new strategies for breeding programmes can be developed based on these advances.