Identification of novel sources of genetic variation for the improvement of cold germination ability in upland cotton (Gossypium hirsutum)

Upland cotton (Gossypium hirsutum) is inherently susceptible to low temperature stress especially during the early seedling growth and boll maturation stages. The goal of the study is to identify novel sources of genetic variation that can be used to improve cold tolerance of cotton during seed germination. Genetic diversity analysis of thirty accessions from the core Gossypium Diversity Reference Set (GDRS) and twenty recombinant inbred lines derived from intercrossing cotton mutants with altered fatty acid content profiles established genetic variation in the test germplasm based on simple sequence repeat (SSR) genotyping. The mutants clustered in a single clade, whereas the GDRS accessions were separated into four different clades. Screening for germination ability at 12 °C and 15 °C showed that the fatty acid mutants had a significantly better overall germination compared to the GDRS accessions. Hydropriming improved the germination rate and uniformity of the GDRS accessions at 12 °C and 15 °C but not those of the fatty acid mutants, which recorded a better overall germination at 15 °C even without hydropriming. The tolerance of the FA mutants to cold stress during germination is proposed to be conferred by the higher proportion of unsaturated to saturated fatty acids in the mutants compared to the GDRS accessions. Principal component analysis established phenotypic patterns of variation that is consistent with the observed genotypic variation in the test germplasm. Results of the study indicate the potential of the mutants and select GDRS accessions as donors in breeding for cold germination ability.