Screening of Adaptive Cultivars and Identification of QTNs Associated With Flowering Time and Related Traits of Diverse Soybean Cultivars Grown in Low-Latitude, High-Altitude Regions.

Soybean has been grown across diverse latitudes; however, its adaptation to low-latitude, high-altitude environments with short days and low temperature remains unclear. To understand the genetic basis of adaptation, we screened 200 diverse cultivars and conducted genome-wide association studies (GWAS) in Bamei and Xianshui, Daofu country, Sichuan Province, China, in 2019 and 2023, respectively. Six agronomic traits: flowering time (DTF), maturity time, node number on main stem (NNM), plant height (PH), effective number of pods per plant and 100-seed weight (HGW) were evaluated. Five MG I-II cultivars (Bamei) and 17 MG II-V cultivars (Xianshui) were screened as adaptive, exhibiting late flowering and maturity, tall stature, and high node and pod numbers. Adaptive cultivars predominantly carried the allelic combinations E1/e2-ns/e3-tr/E4 and E1/e2-ns/E3/E4 (Bamei), and only E1/e2-ns/E3/E4 (Xianshui). GWAS identified 9, 6, and 2 genomic regions associated with DTF, NNM and PH, respectively, with two regions linked to both DTF and PH. Most QTNs associated with DTF were located near known loci or Arabidopsis flowering gene homologues. Non-synonymous mutations in GmPIE1, GmFY and GmIAA31 were associated with delayed flowering and taller plants. The adaptive cultivars, markers, and genes identified offer valuable resources for improving soybean adaptation to low-latitude, high-altitude regions.