Association mapping is a powerful approach to detect associations between traits of interest and genetic markers based on linkage disequilibrium (LD) in molecular plant breeding. In this study, 150 accessions of worldwide originated durum wheat germplasm (Triticum turgidum spp. durum) were genotyped using 1,366 SNP markers. The extent of LD on each chromosome was evaluated. Association of single nucleotide polymorphisms (SNP) markers with ten agronomic traits measured in four consecutive years was analyzed under a mix linear model (MLM). Two hundred and one significant association pairs were detected in the four years. Several markers were associated with one trait, and also some markers were associated with multiple traits. Some of the associated markers were in agreement with previous quantitative trait loci (QTL) analyses. The function and homology analyses of the corresponding ESTs of some SNP markers could explain many of the associations for plant height, length of main spike, number of spikelets on main spike, grain number per plant, and 1000-grain weight, etc. The SNP associations for the observed traits are generally clustered in specific chromosome regions of the wheat genome, mainly in 2A, 5A, 6A, 7A, 1B, and 6B chromosomes. This study demonstrates that association mapping can complement and enhance previous QTL analyses and provide additional information for marker-assisted selection.

In the present study, 150 accessions of worldwide originated durum wheat germplasm (Triticum turgidum spp. durum) were observed for major seedling traits and their growth. The accessions were evaluated for major seedling traits under controlled conditions of hydroponics at the 13th, 20th, 27th and 34th day-after germination. Biomass traits were measured at the 34th day-after germination. Correlation analysis was conducted among the seedling traits and three field traits at maturity, plant height, grain weight and 1000-grain weight observed in four consecutive years. Associations of the measured seedling traits and SNP markers were analyzed based on the mixed linear model (MLM). The results indicated that highly significant genetic variation and robust heritability were found for the seedling and field mature traits. In total, 259 significant associations were detected for all the traits and four growth stages. The phenotypic variation explained (R2) by a single SNP marker is higher than 10% for most (84%) of the significant SNP markers. Forty-six SNP markers associated with multiple traits, indicating non-neglectable pleiotropy in seedling stage. The associated SNP markers could be helpful for genetic analysis of seedling traits, and marker-assisted breeding of new wheat varieties with strong seedling vigor.

Twelve genotypes of groundnut (Arachis hypogaea L.) were executed under rain-fed conditions in a semi-arid zone at the Research farm of El Fasher Research Station, Sudan for two consecutive seasons 2006 and 2007. Genotypic and phenotypic variability, heritability in a broad sense and genetic advance were estimated in a randomized complete block design with four replications. High heritability estimate (above 95 %) was recorded by hay yield (kg/ha) in both seasons and 100- seed weight in season 2006. Moreover, the high genetic advance was recorded for hay yield (kg/ha) and pod yield (kg/ha) in both seasons. However, a day to 50% flowering was expressed low genotypic coefficient of variation with low genetic advances in both seasons. Highly significant different among genotypes were found for days to 50% flowering, hay yield (kg/ha), shelling (%), while pod yield (kg/ha) and 100- seed weight were observed non-significant. The high yielding genotype was ICGV93260 with a pod yield of 1389.1 kg/ha. Pod yield (kg/ha) was highly significantly and positively correlated with hay yield (kg/ha), shelling (%) and 100- seed weight, while non-significant and negative correlated with days to 50% flowering. Based on the results the characters hay yield (kg/ha), shelling (%), 100- seed weight and days to 50% flowering to be the important characters which would be used in selection for groundnut improvement. The promising genotype identified in this study could provide valuable sources of resistance to climate-change-related stresses and for other consequent breeding activities in groundnut improvement. DOI: http://dx.doi.org/10.3126/ije.v3i3.11060 International Journal of Environment Vol.3(3) 2014: 16-23

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