Association Mapping of Root Traits for Drought Tolerance in Bread Wheat

Triticum aestivum (Bread wheat 2n=6x=42) belongs to family Poaceae having hexaploid genome (AABBDD) of 17 Gb. Wheat is the staple food of Pakistan and covers 37% of the cultivable land and contributes 80% of the grains for human consumption while shares 70% grains for food production. The major constraint to wheat production around the world is drought stress and is most serious problem to agriculture of Pakistan. Drought is the main environmental problem that causes high negative effect on cereals crops particularly wheat. Drought could shake morphophysiological features of plant growth, anatomy, morphology, physiology, biochemistry and finally the yield of crop.

It is a great challenge for crop breeders to produce cultivars having good potential of survival in drought stress environment. Drought tolerance breeding may be effective if the marker assisted selection based molecular linkage maps for crop species are available.

The hundred wheat genotypes were screened with 102 SSR markers. Most of the markers were showed high level of polymorphism. Total of 271 polymorphic alleles generated. The alleles per locus was ranged from 1-3 and an average of 2.63 per locus. Polymorphic information content (PIC) values of the markers was calculated in the range of 0.03–0.59. The association analysis revealed that one hundred genotypes having different genetic background were classified into thirteen distinct groups. Total of 12 MTAs were recorded for root traits in GLM and MLM models. The genetic information obtained in the present study in the form of MTAs/QTLs could be utilized for breeding programs to improve drought stress tolerance.

Furthermore, the genome wide association mapping (GWAS) are strongly depend on choice of material, population size and number of markers to be used. Large population and large number of molecular markers are needed to investigate genetic diversity.