Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2006
Publication Date: 4/1/2007
Citation: Martin, J.M., Morris, C.F., Giroux, M.J. 2007. Pilot scale milling characteristics of transgenic isolines of a hard wheat over-expressing puroindolines. Crop Sci. 47(2):1-10. Interpretive Summary: Whether wheat is classified as hard or soft is based on the texture of the grain and ultimately determines milling and end-use characteristics. Puroindolines are responsible for much genetic variation in texture, and to better understand this variance milling characteristics were examined in transgenic wheats derived from the hard red spring wheat cultivar Hi-Line. The transgenic wheat lines over-expressed either one of the puroindoline proteins, or both proteins. The lines with over-expressed puroindoline b or both puroindolines a and b were softest, had the greatest break flour yield, lowest starch damage and largest cookie diameter. Any additional puroindolines led to smaller bread loaves then was seen for Hi-Line. Whether these differences are due to the puroindolines themselves, or to secondary water hydration effects remains to be seen. Over-expressed puroindolines were shown to have larger impacts on textural, milling and baking traits.
Technical Abstract: Wheat (Triticum aestivum L.) grain texture is an important determinant of milling properties and ultimately end product use. Two tightly linked genes, puroindoline a (Pina)and puroindoline b (Pinb), control most of the genetic variation in wheat grain texture. Our goal was to examine milling characteristics of transgenic isolines of the hard red spring wheat cultivar Hi-Line over-expressing Pina (HGA), Pinb (HGB), or both (HGAB), giving grain texture very soft (HGAB and HGB), intermediate (HGA) and hard (Hi-Line). A second goal was to evaluate the flour quality of the genotypes for cookies and bread. The four genotypes were grown in replicated trials in rain-fed and irrigated environments. Grain from each replicate was milled in a Miag Multomat pilot scale flour mill. Stream yield and ash and protein content were determined from ten flour streams and four bran streams. Cookie and bread quality was determined from straight grade flour. Break flour yield ranged from 404 g kg-1 for HGAB to 202 g kg-1 for Hi-Line. Straight grade flour yield ranged from 711 g kg-1 for HGAB to 744 g kg-1 for Hi-Line. Cumulative ash curves showed harder textured wheats, (Hi-Line and HGA) had greater ash content from break streams, but more horizontal slope than soft wheats (HGAB and HGB) for the portion of the curve describing the relation between ash and flour extracted from the endosperm. Flours from the soft wheat isolines, HGAB and HGB, suffered less starch damage than flour from intermediate HGA or hard Hi-Line. Flours from HGAB and HGB were best suited for cookies. All three transgenic isolines over-expressing either or both puroindolines had smaller loaves of bread that Hi-Line. It is not clear whether the changes in end use properties such as cookie properties and loaf volume are due to puroindolines themselves or the effects on water hydration traits brought about by changes in grain texture.