Registration of sorghum nested association mapping population in BTx623 background as pre‐breeding germplasm for early‐season cold tolerance

The sorghum [ Sorghum bicolor (L.) Moench] nested association mapping (NAM) population is a germplasm resource for genetic improvement of early‐season cold tolerance (ESCT) developed and released by the USDA, ARS at Lubbock, TX. The sorghum ARS_BTX623_NAM_ESCT (Reg. No. MP‐7 NSL 558860 MAP) population consists of three biparental parental subpopulations comprising a total of 771 recombinant inbred lines (F 6 –F 7 generations). The recombinant inbred lines were derived from the inbred line BTx623, which was crossed separately to the cold‐tolerant HongKeZi (PI 567946), NiushengZui (PI 568016), and Kaoliang (PI 562744) lines. The ARS_BTX623_NAM_ESCT was used as a genetic resource to dissect quantitative trait loci and identify DNA markers useful for improving sorghum cold tolerance. Notably, ARS_BTX623_NAM_ESCT includes new sorghum germplasm that exhibits transgressive segregation compared with its founders for enhanced ESCT based on germinability, field emergence, and seedling vigor—traits that are needed for ESCT in a production setting. The populations were shown to be useful for validating quantitative trait loci for cold tolerance and served as a resource for identifying DNA markers for cold tolerance that are now being applied for breeding purposes. The current NAM population in the BTx623 background is an enduring approach toward capturing genetic variation and genotype information from Chinese landrace germplasm to introduce, create variation in, and recombine genes for ESCT to produce a usable pre‐breeding germplasm resource for downstream improvement of sorghum ESCT.