Assessing genetic variation for heat tolerance in synthetic wheat lines using phenotypic data and molecular markers

High temperature is a major environmental stress factor limiting wheat productivity in India. Therefore, improvement for heat tolerance in wheat is an important breeding objective. A number of synthetic wheat hexaploids have shown resistance to major wheat diseases and tolerance to abiotic stresses such as drought, waterlogging and salinity. This study was conduct to assess heat tolerance and genetic variation among twenty-four heat tolerant synthetic wheat lines in order to identify new sources of diversity that could accelerate the development of improved wheat genotypes better suited to meet the challenges posed by changing climate in India. Phenotypic data of nine traits of synthetic wheat lines were evaluated for heat tolerance under non-stress (timely sown) and stress (late sown) field conditions. The heat tolerance and stress susceptibility indices were calculated for Thousand-grain weight (TGW) and genotypes differed significantly for stress indices. A hierarchical cluster analysis was conducted based on phenotypic traits and among 24 synthetics lines, three accessions were classified as highly tolerant, 9 as medium tolerant and 12 as susceptible. Fifteen polymorphic ISSR markers were used to evaluate the diversity profile of synthetic hexaploid wheats (2n=6x=42, AABBDD). In total, 75 alleles were detected (five bands/primer), out of which 36 were polymorphic across the lines and the percentage of polymorphism was 80%. The polymorphic information content value for ISSR markers was calculated in the range of 0.39 to 0.88 with an average of 0.65. Genotypes (SNY 11, SNY 36 SNY 44) characterized as highly heat tolerance were distributed among the ISSR cluster groups. It implies that genetic basis of heat tolerance in synthetic wheat lines was different, therefore enabling wheat breeders to combine these diverse sources of genetic variability to improve heat tolerance in their breeding program.