Pilot Scale Milling Characteristics of Transgenic Isolines of a Hard Wheat Over-Expressing Puroindolines

Wheat (Triticum aestivum L.) grain texture is an important determinant of milling properties and end product use. Two 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 overexpressing Pina (HGA), Pinb (HGB), or both (HGAB), which have soft (HGAB and HGB), intermediate (HGA), and hard (Hi-Line) grain texture. A second goal was to evaluate the flour quality of the genotypes for cookies and bread. Genotypes were grown in replicated trials in two environments. Grain was milled in a Miag Multomat pilot scale flour mill which closely emulates a commercial long flow mill. Stream yield and ash and protein content were determined from 10 flour 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 relationship between ash and flour extracted from the endosperm. Flours from the soft 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 overexpressing either or both puroindolines had smaller loaves of bread than Hi-Line. Puroindolines directly impact milling properties and may indirectly affect end use properties such as cookie properties and loaf volume by modifying water hydration traits.