Common bean (Phaseolus vulgaris L.) is a highly economically important crop worldwide and a particularly important source of protein and minerals for people in less developed countries. Improving yield is a vital objective to meet the increasing demand for food due to the expanding human population. The present study was undertaken to study the genetic architecture of agronomic traits of common bean in India, particularly in the north-western Himalayan region. Marker-trait association (MTA) analysis was performed in a population of 100 common bean accessions using polymorphic microsatellite markers. Population structure analysis based on SSR markers divided the accessions into three main subpopulations. Ten significant MTAs were found using general linear model (GLM) and mixed linear model (MLM) approaches. We found two markers i.e. BM142 and J04555 associated with 100 seed weight and pods per plant common in both the GLM and MLM approach markers. All the MTAs were considered as major MTAs contributing more than 25% phenotypic variation. The significant quantitative trait loci identified in this study could be used in marker-assisted breeding to accelerate the genetic improvement of yield and development of high yielding common beans lines.

The Sikkim-Himalaya represents one of the unique reservoirs of rice genetic resources in India owing to the presence of a large number of landraces adapted to extreme climatic and edaphic conditions. This valuable gene pool is now under threat due to the introduction of high-yielding varieties, wanting suitable genetic intervention for enhancing their productivity, and thus economic viability. Development of lodging resistant, high-yielding varieties tolerant to soil acidity through association mapping aided marker-assisted breeding programmes can help achieve this in a fast and efficient manner. But this requires information on genetic diversity, population structure, etc., of the germplasm collection, which is strikingly lacking. We, therefore, characterized a set of 53 rice landraces from Sikkim to address the above issues. The results revealed moderate diversity, poor divergence and high gene flow in our germplasm collection attesting its utility as an association mapping panel. Further, a total of 115 putative marker-trait associations (P < 0.05, R2 ≥ 10%) were obtained using the general linear model and mixed linear models of which 25 were identical in both. Some of the associated markers were positioned in those regions where Qualitative Trait Loci have been previously identified in rice, providing credence to our results. The resources generated from this study will benefit the rice breeders from this region and elsewhere for targeting the yield and related traits, in addition to conservation efforts by the interested researchers.

Improving plant resistance against Fusarium wilt (FW) is key to sustaining chickpea production worldwide. Given this, the current study tested a set of 75 FW-responsive chickpea breeding lines including checks in a wilt-sick plot for two consecutive years (2016 and 2017). Genetic diversity analysis using 75 simple sequence repeats (SSRs) revealed a total of 267 alleles with an average of 3.56 alleles per marker. The entire set was divided into two major classes based on clustering method and factorial analysis. Similarly, STRUCTURE analysis placed the 75 genotypes into three distinct sub-groups (K = 3). Marker-trait association (MTA) analysis using the generalized linear model approach revealed nine and eight significant MTAs for FW resistance in the years 2016 and 2017, respectively. Three significant MTAs were obtained for FW resistance following the mixed linear model approach for both years. The SSR markers CESSR433, NCPGR21 and ICCM0284 could be potentially employed for targeted and accelerated improvement of FW resistance in chickpea. To the best of our knowledge, this is the first report on association mapping of the genomic loci controlling FW (Foc2) resistance in chickpea.

Bread wheat (Triticum aestivum) is one of the most important food crops in the world. Its physiological and morphological traits are closely related to yield. Therefore, it is generally important to discover the genomic region associated with these traits. In this research, associations between 21 simple sequence repeat (SSR) markers and 10 inter-simple sequence repeat (ISSR) markers with some traits related to root structure at the embryonic and seedling stages and also some agromorphological traits at the whole plant stage were evaluated on a set of 102 wheat genotypes. A highly significant coefficient of variation among different genotypes was observed in all measured traits. A high level of polymorphism with SSR and ISSR markers was obtained. Genetic structure analysis revealed two distinct subpopulations. Significant correlations were found between genomic markers and evaluated traits. A total of nine markers, including four SSR markers in 1A, 3A, 5A and 2B chromosomal regions and five different ISSR markers were related to the studied traits. Several molecular markers were significantly associated with more than one phenotypic trait, suggesting the possible presence of pleiotropic or indirect effects. The phenotypic variation justified by these alleles ranged from 4 to 15%. Obtained genetic information can be targeted for further validation and genetic analysis in the relevant populations or other breeding sets.

Association mapping (AM), an alternative method of quantitative trait loci (QTL) discovery, exploits historic linkage disequilibrium (LD) present in natural populations. AM is effective in self-pollinated crops such as Dolichos bean as LD extends over longer genomic distance driven-by low rate of recombination and thereby requiring fewer markers for exploring marker-traits associations. A core set of Dolichos bean germplasm consisting of 64 accessions was evaluated for nine quantitative traits (QTs) during 2014 and 2015 rainy seasons and genotyped using 234 simple sequence repeats (SSR) markers. Substantial diversity was observed among the core set accessions at loci controlling QTs and 95 of the 234 SSR markers were found polymorphic. The structure analysis and low magnitude of fixation indices suggested weak population structure, which in-turn indicated the low possibility of false discovery rates in the marker-QTs association. The marker allele's scores were regressed onto phenotypes at nine QTs following general linear model and mixed linear model for exploring marker-QTs associations. Significantly higher number of SSR markers was found associated with genomic regions controlling nine QTs. A few of the markers such as KT Dolichos (KTD) 200 for days to 50% flowering, KTD 273 for fresh pod yield per plant and KTD 130 for fresh pods per plant explained ≥10% of the trait variations. The study could also identify a few SSR markers such as KTD 273, KTD 271 and KTD 130 linked to multiple traits. These linked SSR markers are suggested for validation for their use in marker-assisted Dolichos bean improvement programmes.

Fe and Zn deficiency are widespread worldwide. As wheat is the primary food for the majority of the world people, producing wheat grains with high mineral content can ameliorate the problem of mineral hunger. However, the genetic variation available for breeders is limited. The aim of this study was to assess the genetic variation in grain Fe and Zn contents in 47 synthetic hexaploid wheats and to identify marker loci associated with Fe and Zn contents. We measured the grain Fe and Zn contents using inductively coupled plasma atomic emission spectroscopy and performed genotyping using SSR markers. The results showed considerable genetic variation for these minerals. We identified three lines with high Fe and Zn contents and six quantitative trait loci of which three were associated with Fe content and the other three with Zn content. The minerals showed positive phenotypic and genotypic correlation and high heritability (>60%). The ratio of the σ2g to the σ2g×e was ≥1 for the two mineral contents indicating that breeding for increasing mineral content within the synthetic lines is possible. The synthetic wheat lines identified in this study are valuable genetic resources, and can be utilized for breeding wheat cultivars with high mineral content.

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.

The present study was undertaken to examine the population structure of the Solanum pimpinellifolium collection maintained by AVRDC – The World Vegetable Center – and to construct a core set of this collection. Out of the entire collection of 322 accessions, a diverse subset of 190 accessions was chosen representing 14 countries of origin. Data on 32 qualitative and 22 quantitative phenotypic traits (IPGRI–AVRDC descriptor traits) and 48 simple sequence repeat markers evenly distributed over the genome were used to develop the core set. A total of 377 alleles were detected with 7.85 alleles per locus, on average. Of these, 52 alleles at 28 loci were extremely rare-frequency alleles. The 190 accessions clustered into two main populations and an admixture group. Population I (PopI) included 99 accessions, 93 of which originated from Peru. Population II (PopII) contained 49 accessions, the majority of which originated from Ecuador and Mexico. The remaining 42 accessions were classified as admixture group. The two main populations were further subdivided into five subgroups. Values of Fst among the five sub-populations were significant (average pairwise Fst of 0.296), suggesting a real difference between these populations. A clear differentiation was observed among and within populations based on geography. Peruvian accessions were genetically more diverse than accessions originating in Ecuador and Mexico. Within the Peruvian group, a gradual increase in genetic diversity was observed from southern to northern Peru. The constructed core collection consists of 75 accessions representing 23.4% of AVRDC's entire S. pimpinellifolium collection and 39.5% of the subset used in this study. It is a well-balanced core with a good representation of the different populations (31 accessions from PopI, 22 from PopII and 22 from the Admixture group) and geographic origins (40 accessions from Peru, 17 from Ecuador, 14 from Mexico and four from other countries).

In South Europe, rice is grown as an irrigated crop in river deltas where it plays an important role in soil desalinization. Specific varieties are needed for these tough conditions. We analyzed the genetic structure of a set of 305 varieties coming from the European Rice Germplasm Collection (ERGC) with 90 single nucleotide polymorphisms and compared it with a reference set representative of the diversity of Oryza sativa (mini-Germplasm Bank (GB)). These accessions had been characterized for their grain type and growth cycle duration. The polymorphism information contents of the ERGC were lower than those of the mini-GB, indicating a narrower genetic basis. Indeed, almost all ERGC accessions belong to the japonica group. Within the japonica group, both a dendrogram and a Bayesian clustering identified two major clusters. The first cluster encompassed tropical japonicas and American varieties from USA and Argentina characterized by long and narrow grains and medium to long duration. On a finer level, tropical japonicas appear separated from the other accessions. The second cluster is composed of European varieties mostly early or medium in duration and Asian temperate accessions, with a subgrouping based on grain format. A set of 200 accessions was composed for association mapping studies on traits such as salt tolerance.

Response to selection is fundamental to plant breeding. To gain insight into the genetic basis of response to selection, we propose a new experimental genetic framework allowing for the identification of trait-specific genomic loci underlying population improvement and the characterization of allelic frequency responses at those loci. This is achieved by employing a sampling scheme for recurrently selected populations that allows for the simultaneous application of genetic association mapping and analysis of allelic frequency change across generations of selection. The combined method unites advantages of the two approaches, permitting the estimation of trait-specific allelic effects by association mapping and the detection of rare favourable alleles by their significant enrichment over generations of selection. Our aim is to develop a framework applicable for many crop species in order to gain a broader and deeper understanding of the genetic architecture of response to artificial selection.

The aim of this study was to establish associations of kernel weight and colour with ecogeographic factors and molecular markers, based on ten wild barley [Hordeum spontaneum (C. Koch) Thell.] populations sampled in Israel across a southward transect of increasing aridity. Kernel weight and colour category were scored using barley kernels (naked caryopsis). Small kernel sizes (0.011 g kernel–1) and dark kernels were found in xeric populations. A higher variation of kernel weight was observed in xeric populations. A higher proportion of variation occurred within, rather than among, populations. Water, temperature and soil factors were associated with kernel size variation. Among 18 simple sequence repeats (SSRs) investigated, HVM14, HVM36, HVM43, BMS64 and BMS90 were associated with kernel weight, and HVM68 with kernel colour. The results indicated that high phenotypic variation and genetic diversity are related to ecological stress, and that the association of phenotypic traits with molecular markers, based on natural plant populations, should be interpreted cautiously due to the high chance of spurious associations between traits and molecular markers.

The effectiveness of association mapping (AM) based on linkage disequilibrium (LD) is currently being tested in a number of crops. An important prerequisite for the application of AM is the availability of collections of accessions with a suitable level of genetic variation for target traits and with limited spurious LD due to the presence of population structure. Herein, the results of a genome-wide molecular characterization of a collection of elite durum wheat accessions well-adapted to Mediterranean environments are presented. Ninety-seven highly polymorphic simple sequence repeats and 166 amplified fragment length polymorphism markers were used to characterize 189 durum accessions, mainly cultivars and advanced breeding lines. Genome-wide significant and sizeable LD indices at a centimorgan scale were observed, while LD mainly decayed within 10 cM. On the other hand, effects due to spurious LD were notably lower than those previously observed in a durum wheat collection sampling durum gene pools of more diverse origin. These results, coupled with the high level of genetic variability detected for a number of important morpho-physiological traits and their high heritability, indicate the suitability of this collection for AM studies targeting agronomically important traits.