Diversity of Puroindoline genes and their association with kernel hardness in Chinese wheat cultivars and landraces

Abstract

Kernel hardness is a key trait that greatly affects the milling and baking qualities of common wheat. Kernel hardness is largely controlled by Pina and Pinb genes. Here, we investigate the allelic diversity of Pina and Pinb genes in a collection of 107 Chinese wheat cultivars and landraces. The kernel hardness values of these accessions were determined in two field seasons (2016/2017 and 2017/2018 seasons), and they were strongly correlated between the 2 years, with hardness indexes ranging from 5.4 to 91.8. Five known Pina-D1 alleles and four known Pinb-D1 alleles were detected. In particular, we identified a novel Pina-null allele (designated Pina-D1z) with a 3382-bp deletion that can be detected by the new molecular marker Pina-N5. We also identified a Pina/Pinb double null allele containing a ~ 29-kb deletion. They are useful genotypes for kernel texture improvement. The most frequent genotypes in these accessions were Pina-D1a/Pinb-D1a and Pina-D1a/Pinb-D1b (39.3% and 34.6%, respectively), followed by Pina-D1a/Pinb-D1p (13.2%). A comparison of genotypes between the present study and previous studies suggests that Chinese wheat landraces have more allelic variations in the Pina gene than do cultivars. An association analysis of Puroindolines with kernel hardness shows that 15 Pina-D1 alleles and 6 Pinb-D1 alleles could be associated with hard-kernel phenotypes in common wheat. Notably, this study suggests that Chinese landraces are a valuable resource of genetic variability in Puroindoline genes and provides a deeper understanding of the genotype-to-phenotype association of Puroindoline genes.