BackgroundGenetic diversity is the main source of variability in any crop improvement program. It serves as a reservoir for identifying superior alleles controlling key agronomic and quality traits through allele mining/association mapping. Association mapping based on LD (Linkage dis-equilibrium), non-random associations between causative loci and phenotype in natural population is highly useful in dissecting out genetic basis of complex traits. For any successful association mapping program, understanding the population structure and assessing the kinship relatedness is essential before making correlation between superior alleles and traits. The present study was aimed at evaluating the genetic variation and population structure in a collection of 192 rice germplasm lines including local landraces, improved varieties and exotic lines from diverse origin.ResultsA set of 192 diverse rice germplasm lines were genotyped using 61 genome wide SSR markers to assess the molecular genetic diversity and genetic relatedness. Genotyping of 192 rice lines using 61 SSRs produced a total of 205 alleles with the PIC value of 0.756. Population structure analysis using model based and distance based approaches revealed that the germplasm lines were grouped into two distinct subgroups. AMOVA analysis has explained that 14 % of variation was due to difference between with the remaining 86 % variation may be attributed by difference within groups.ConclusionsBased on these above analysis viz., population structure and genetic relatedness, a core collection of 150 rice germplasm lines were assembled as an association mapping panel for establishing marker trait associations.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-015-0062-5) contains supplementary material, which is available to authorized users.

Limiting transpiration rate under high vapor pressure deficit (VPD) and/or progressive soil drying conditions are soil water conservation mechanisms that can play an important drought-adaptive role if water is limiting to support crops at its full potential. In this study, these two important physiological mechanisms were measured on parental pairs of existing Recombinant Inbred Lines (RILs) of sorghum mapping populations; both in experiments run in the glasshouse and growth chambers, and outdoors. In controlled environmental conditions, the RIL1, RIL2, RIL6 and RIL8 showed contrasting transpiration response to increasing VPD. The difference in the soil moisture fractions of transpirable soil water threshold where transpiration initiated a decline were high in RIL1, RIL3 and RIL8 respectively. The exploration of the variation of the evapotranspiration response to VPD was also carried out in a high throughput phenotyping facility in which plants were grown similar to field density conditions. Under high VPD conditions, the RIL parental pairs showed usual transpiration peak during the midday period. At this time period, genotypic differences within parental pairs were observed in RIL1, RIL2, RIL6 and RIL8. The donor parent had lower transpiration than the recurrent parents during the midday/high VPD period. Also, we found variation among parental pairs in leaf area normalized with received radiation and measured plant architecture traits. Across studied genotypes, RIL1, RIL2 and RIL8 showed differences in the plant canopy architecture and the transpiration response to an increasing VPD. Collectively, these results open the opportunity to phenotype the RIL progenies of contrasting parents and genetically map the traits controlling plant water use. In turn, this can act as an important genetic resource for identification and incorporation of terminal drought tolerance components in marker-assisted breeding.

Nine rice genotypes were evaluated for this present study. Genetic variability parameters, correlation and path coefficient analysis were estimated for eleven agronomic and quality traits. Among all the genotypes, ASD 16 recorded highest significant grain yield per plant. In this present study, the PCV was higher than GCV for all the characters studied. The grain yield per plant recorded highest GCV, high heritability coupled with high genetic advance which indicates that the trait were governed by epistasis and dominant gene action. Number of productive tillers per plant and thousand grain weight showed positive significant correlation and direct effects on grain yield per plant. The purpose of this study is to estimate the amount of variability present in this material, which in turn helps to select these material for further breeding programme to develop high yield hybrids combine with blast and leaf folder resistance.

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