Identification and Characterization of Near‐Isogenic Hard and Soft Hexaploid Wheats

Abstract

A complete understanding of the physical–chemical mechanism and underlying genetic control of wheat (Triticum aestivum L.) endosperm texture will contribute to defining optimal grain utilization while assisting the breeding and development of new cultivars. World trade in wheat grain primarily is based on the two main market classes, “soft” and “hard,” which are mostly determined by the expression of the puroindoline genes at the Hardness (Ha) locus. Here we identify and characterize new genetic stocks (near isogenic lines, NILs) in four different genetic backgrounds (20 NILs total, nine hard and 11 soft). Methods included identifying homogenous or mixed texture lines by Single Kernel Characterization System and Near‐Infrared Reflectance Spectroscopy. Puroindoline genes and Ha alleles were determined through nucleic acid sequence analysis. The four different genetic sources for NILs were (i) accessions of ‘Gamenya’ cultivar which were physical mixtures of hard and soft types, (ii) existing near‐isogenic lines from the cultivars Heron and Falcon, (iii) advanced‐generation backcross lines involving ‘Paha’ and ‘Early Blackhull,’ and (iv) ‘Nugaines’ and ‘Early Blackhull Derivative’. The NILs reported here provide new genetic materials for the study of wheat grain texture and the effect of puroindolines and the Hardness gene on end‐use quality. Two of the four sets of NILs possess the Gly‐46 to Ser‐46 Pinb‐D1b hardness allele which has not been previously available in NILs. The results corroborate a model of wheat grain texture that identifies two major hardness classes, as opposed to one that accommodates intermediate texture classes such as “semi‐hard” and “medium‐soft.” A direct role of the puroindoline proteins in conferring soft grain phenotype is supported; conversely, no genetic basis for intermediate hardness was found. Rather, intermediate hardness resulted from mixtures of the soft and hard classes.