Identification and characterization of near-isogenic hard and soft hexaploid wheats

A complete understanding of the physical-chemical mechanism and underlying genetic control of wheat (Triticum aestivum L,) endosperm texture will cont ribute to defining optimal grain utilization while assisting the breeding a nd development of new cultivars, World trade in wheat grain primarily is ba sed on the two main market classes, "soft" and "hard," which are mostly det ermined by the expression of the puroindoline genes at the Hardness (Ha) lo cus, Here we identify and characterize new genetic stocks (near isogenic li nes, NILs) in four different genetic backgrounds (20 NILs total, nine hard and 11 soft). Methods included identifying homogenous or mixed texture line s by Single Kernel Characterization System and Near-Infrared Reflectance Sp ectroscopy. Puroindoline genes and Ha alleles were determined through nucle ic 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'. Th e NILs reported here provide new genetic materials for the study of wheat g rain texture and the effect of puroindolines and the Hardness gene on end-u se 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 re sults 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 puroind oline 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.