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Relationship Between Wheat (Triticum aestivum L.) Grain Hardness and Wet-Milling Quality¹

¹This research was supported by USDA-ARS National Research Initiative Competitive Grants Program grant 2004-35301-14538 and by the Montana Agricultural Experiment Station. ²Department of Plant Sciences and Plant Pathology, Montana State University, 119 Plant Bioscience Building, Bozeman, MT 59717-3150. ³Corresponding author. Phone: (406) 994-7877. Fax: (406) 994-7600. E-mail address: mgiroux@montana.edu

Grain hardness variation has large effects on many different end-use properties of wheat (Triticum aestivum). The Hardness (Ha) locus consisting of the Puroindoline a and b genes (Pina and Pinb) controls the majority of grain hardness variation. Starch production is a growing end-use of wheat. The objective of this study was to estimate the differences in starch yield due to natural and transgenically conditioned grain hardness differences. To accomplish this goal, a small-scale wet-milling protocol was used to characterize the wet-milling properties of two independent groups of isogenic materials varying in grain hardness and in Pin expression level. The first group of lines consisted of hard/soft near-isogenic lines created in cultivars Falcon or Gamenya in which lines carried either the Pina-D1a (functional) or the Pina-D1b (null) alleles of Pina. The second group of lines consisted of Pina, Pinb, or Pina and Pinb overexpressing lines created in Hi-Line, a hard red spring wheat. Soft near-isogenic lines had higher starch extractability than the hard Pina null counterparts. This difference in starch extractability was more pronounced between Hi-Line and its transgenic isolines, with highest levels of extractable starch observed in the transgenic isoline with intermediate grain texture. The results demonstrate that the Ha locus and puroindoline expression are both linked to wet-milling starch yield and that selection for increased Ha function increases starch yield through the enhanced separation of starch granules and the protein matrix during wet milling.