Development of soft kernel durum wheat

Authors: Morris, Craig

Submitted to: Frontiers of Agricultural Science and Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2019
Publication Date: 7/31/2019
Publication URL: https://handle.nal.usda.gov/10113/6961209
Citation: Morris, C.F. 2019. Development of soft kernel durum wheat. Frontiers of Agricultural Science and Engineering. 6(3):273-278. https://doi.org/10.15302/J-FASE-2019259.
DOI: https://doi.org/10.15302/J-FASE-2019259

Interpretive Summary: Kernel texture (grain hardness) is a fundamental and determining factor related to wheat (Triticum spp.) milling, baking and flour utilization. Generally speaking, there are three kernel texture classes: soft and hard hexaploid (T. aestivum), and very hard durum (T. turgidum subsp. durum). The genetic basis for these three classes lies with the Puroindoline genes, Puroindoline a and Puroindoline b (Pina and Pinb, respectively). A fourth class exists, “Super Soft”, but it has not been commercialized and its genetic basis is incompletely understood. This chapter focuses on the development of soft kernel durum wheat, an endeavor led by the author at the USDA Western Wheat Quality Laboratory, but one that required the talents and contributions of numerous collaborators.

Technical Abstract: Kernel texture (grain hardness) is a fundamental and determining factor related to wheat (Triticum spp.) milling, baking and flour utilization. There are three kernel texture classes in wheat: soft and hard hexaploid (T. aestivum), and very hard durum (T. turgidum subsp. durum). The genetic basis for these three classes lies with the Puroindoline genes. Phenotypically, the easiest means of quantifying kernel texture is with the Single Kernel Characterization System (SKCS), although other means are valid and can provide fundamental material properties. Typical SKCS values for soft wheat would be around 25 and for durum wheat = 80. Soft kernel durum wheat was created via homoeologous recombination using the ph1b mutation, which facilitated the transfer of ca. 28 Mbp of 5DS that replaced ca. 21 Mbp of 5BS. The 5DS translocation contained a complete and intact Hardness locus and both puroindoline genes. Expression of the puroindoline genes in durum grain resulted in kernel texture and flour milling characteristics nearly identical to that of soft wheat, with high yields of break and straight-grade flours, which had small particle size and low starch damage. Dough water absorption was markedly reduced compared to durum flour and semolina. Dough strength was essentially unchanged and reflected the inherent gluten properties of the durum background. Pasta quality was essentially equal-to-or-better than pasta made from semolina. Agronomically, soft durum germplasm showed good potential with moderate grain yield and resistance to a number of fungal pathogens and insects. Future breeding efforts will no doubt further improve the quality and competitiveness of soft durum cultivars.