Genetic diversity and genome-wide associations for frost survival in sorghum.

Background: The ability to withstand periods of light frost during juvenile development is an important adaptive trait for sorghum (Sorghum bicolor L. Moench) production in high-latitude temperate areas. Frost tolerance would allow for earlier sowing and prolongation of growing season and maturity, thereby increasing yield potential. Using a broad diversity set (n = 285), a field cold emergence trial and two semi-controlled frost survival experiments were conducted to investigate the phenotypic diversity and genetic architecture of frost survival traits.

Results: The results show high phenotypic diversity for frost survival, including superior genotypes combining high frost tolerance and cold emergence levels via quantitative trait inheritance. Tolerance to temperatures above and below 0 °C was not correlated, suggesting separate genetic control. The found QTL do not overlap for the traits of frost survival and plant emergence under cold sowing conditions. Genome-wide association studies revealed four significant associations for frost survival, where the QTLs are located on chromosomes Sb02, Sb07, and Sb08. For the trait of emergence under cold sowing conditions, a total of 12 QTLs were found on chromosomes Sb01, Sb03, Sb04, Sb05, and Sb06.

Conclusion: A good overview regarding the suitability of the tested genotypes for early sowing was obtained due to the large diversity investigated in this study, with surprisingly high survival rates of numerous genotypes after frost stress. These results will contribute to the breeding of cultivars with improved cold and frost tolerance, facilitating better adaptation for production in high-latitude temperate areas, as well as earlier sowing to avoid summer drought.