Exploring the QTL–allele constitution of main stem node number and its differentiation among maturity groups in a Northeast China soybean population

Abstract

AbstractNortheast China (NEC) is a major soybean [Glycine max (L.) Merr.] production region in China, where the germplasm of American soybeans are mainly from. The main stem node number (MSN) is a trait related to plant type and yield potential. With the soybeans expanded to higher latitudes in NEC, earlier maturity groups (MG 0, MG 00, and MG 000) formed based on MG I + MG II (MG I+II), and correspondingly the MSN decreased. To explore the MSN quantitative trait locus (QTL)–allele constitution, 306 accessions from NEC were studied using the restricted two‐stage multilocus genome‐wide association study (RTM‐GWAS) procedure. In total, 76 MSN QTLs and 183 alleles were identified, with their genetic contribution about 0.04–9.83% per locus for a total of 65.63% for all loci. With the MSN reduction from MG I+II to MG 0, MG 00, and MG 000 (17.89 to 13.11), the changed alleles accounted for 28.42% of all alleles (6.56% for new allele emergence plus 21.86% for old allele exclusion), whereas the major part of the alleles were those inherited from MG I+II (71.58%). Thus in the evolution of MSN in the NEC soybean population, inheritance is the first genetic motivation, exclusion and selection (positive allele exclusion, 65.00%) is the second, emergence and mutation (negative allele emergence, 95.67%) is the third, and recombination among retained alleles is the fourth. A potential of 2–5 MSN improvement keeping the MG earliness was predicted, and 49 candidate genes were identified.