Genetic Diversity Analysis In Spring Wheat Triticum Aestivum L PDF Download

Early maturity, grain yield and grain protein content are some of the important traits in western Canadian wheat breeding programs. A series of experiments were conducted to explore the genetic basis of days to heading, and maturity, plant height, grain protein, grain yield and related traits. In a spring wheat population of 187 recombinant inbred lines genotyped with 341 Diversity Array Technology (DArT) polymorphic markers, a total of 21 quantitative trait loci (QTLs) were identified for all phenotypic traits recorded, except plant height and grain protein content. Two earliness per se QTLs were mapped on chromosomes 1A (QEps.dms-1A) and 4A (QEps.dms-4A) in all three growing seasons, contributing 15-27% and 8-10%, respectively, to the total genetic variation in days to maturity. The two earliness QTLs and Vrn-B1 exhibited additive interaction. In the same population, lines carrying the resistant allele of Lr34/Yr18 were taller, matured earlier, yielded less grain with lower test weights than lines without Lr34/Yr18. Lines with Lr34/Yr18 also exhibited lower leaf and stripe rust infection than lines with the susceptible allele. The failure to combine Lr34/Yr18 with high yield, protein, and SDS sedimentation suggested single seed descent or doubled haploid populations for the combined selection of multiple quantitatively inherited traits, and simply one molecular marker, would require population sizes in excess of at least 500 to have any possibility of selection success. Genetic diversity analysis for earliness related and plant height reducing genes in 82 spring wheat cultivars registered in western Canada through eight diagnostic DNA markers suggested breeding efforts in western Canada have resulted in the incorporation of vernalization and photoperiod insensitive and height reducing genes in modern cultivars to promote early maturity, to make use of off-season nurseries in other parts of the world and to improve lodging tolerance. Using genome-wide association mapping (GWAS). we identified a total of 152 significant marker-trait associations; however, there were only 18 genomic regions that consisted of clusters of 3 to 20 significant single nucleotide polymorphisms (SNPs) across 12 chromosomes, including two regions each for grain yield, test weight and protein content, six regions for plant height and six other coincident regions that were associated with two or three traits. The genomic region associated with plant height on chromosome 4B showed high linkage disequilibrium (r2 > 0.80) with the semi-dwarfing gene Rht-B1. Results of these studies suggest that besides the widely used semi-dwarf and early maturity related genes, there is a wide spectrum of loci available that could be used for modulating plant height, days to maturity, grain yield and grain protein content in western Canadian wheat germplasm.