QTL-based analysis of heterosis for number of grains per spike in wheat using DH and immortalized F2 populations

To map quantitative trait loci (QTL) and heterotic loci (HL) related to grain number per spike (GNS), 168 double haploid (DH) populations derived from Huapei 3 x Yumai 57 and an immortalized F (2) population (IF (2)) generated by randomly permutated intermating of these DH populations were investigated. Using inclusive composite interval mapping (ICIM), a total of nine and eight significant QTLs for GNS were detected in three different environments in DH and IF (2) populations, respectively. QTLs on chromosomes 1A, 2B, 3B, and 6A were observed between two populations. Five QTLs were detected on chromosome 1A. Of these QTLs, QGns1A-1 was a major QTL explaining 31.25 % of phenotypic variation. QGns2B-2 detected on chromosome 2B had the most significant additive effects, explaining 46.75 % of phenotypic variation with the favorable allele contributed by Yumai 57 corresponding to an increase of 5.69 kernels. Mid-parent heterosis of each cross in the IF (2) population was used to map heterotic quantitative trait loci. A total of 17 HLs were detected. QTLs and HLs on chromosomes 2B and 6A were observed in the IF (2) population. Three HLs, QHgns1B-2, QHgns2B, and QHgns6A-1, were detected in two environments and expressed stably. These results showed that some intervals on chromosomes 1B, 2B, and 6A play an important role in GNS heterosis in wheat, improving understanding of this phenomenon.