MOLECULAR CHARACTERIZATION OF RECOMBINANT LINES OF CHROMOSOME 7 BETWEEN L. Elongatum AND WHEAT

¹ Department of Agronomy and Range Science, University of California Davis, One shields Avenue, Davis, CA 95616, USA

² Department of Botany and Plant Sciences, University of California Riverside, CA 92521, USA

The distal region of the chromosome arm 7EL from L. elongatum carries the leaf rust resistant gene Lr19 and a gene designated Yp that increases yellow pigment in the endosperm. Lr19 gene has not been used in common wheat because of linkage in all existing transfers with Yp. Yp tints flour yellow reducing its appeal in bread making. However, the increase of yellow pigment is a desirable trait in durum wheat. We produced 96 recombinant chromosomes between E.R. Sears transfer 7D.7E#1 and its wheat homoeologous using the ph1b mutation that promotes homeologous pairing. We characterized a subset of 37 of these lines with nine molecular markers and evaluated their resistance to leaf rust and the presence of Yp. Most recombination events occurred between 7E and 7D chromosomes but approximately 20% were recombinants between 7E and non-7D chromosomes, mostly 7A. Recombinant chromosome designated 1-23 carrying a short terminal 7E segment translocated to 7A is being transferred to durum wheat by backcrossing. Three recombinants with small terminal 7E segments were isolated that carry Yp but not Lr19. Lr19 was mapped distal to Xwg420; Yp was mapped distal to Lr19 and to Xpsr121. No reciprocals with Lr19 present and Yp absent have been identified so far, presumably because of GISH resolution limits in detection of distal breakpoints in configurations where alien segments are proximal and wheat segments are terminal. We are producing new recombinants in bread wheat to find the desirable combination that will facilitate the use of Lr19 in bread wheat.