DETECTION OF QUANTITATIVE TRAIT LOCI ASSOCIATED WITH LEAF RUST RESISTANCE IN BREAD WHEAT

Leaf rust, caused by Puccinia recondita Rob. ex Desm., is a common dis ease in wheat. The objective of this study was to develop molecular ma rkers associated with the quantitative trait loci (QTLs) putatively co nferring durable leaf rust resistance in Triticum aestivum L. em. Thel l. A population of 77 recombinant inbred lines (RILs) developed from ' Parula' (resistant) and 'Siete Cerros' (moderately susceptible) was us ed. Bulked segregant analysis was done using random amplified polymorp hic DNAs (RAPDs) with DNA enriched for low-copy sequences using hydrox yapatite chromatography. Out of 400 decamer primers screened, 3 RAPD m arkers were identified between the bulk of the most resistant and the bulk of the most susceptible lines. These were cloned and used as prob es on the RILs in Southern hybridizations. Two probes revealed two tig htly linked loci. One-way analysis of variance showed that these two l oci, and another revealed by the third probe, were linked to QTLs cont rolling leaf rust resistance based on data taken from 2 years of repli cated field trials. Cytogenetic analysis placed the two tightly linked loci on the long arm of chromosome 7B. The third probe detected loci located on the short arms of chromosomes 1B and 1D. It is suggested th at the QTL detected on 7BL may well be homoeoallelic to Lr34.