Microsatellite tagging of the stripe-rust resistance gene YrH52 derived from wild emmer wheat, Trificum dicoccoides, and suggestive negative crossover interference on chromosome 1B

Stripe rust caused by Puccinia striiformis West. is one of the most devasta ting diseases relating to wheat production. Wild emmer wheat. Triticum dico ccoides, the tetraploid progenitor of cultivated wheat, has proven to be a valuable source of novel stripe-rust resistance genes for wheat breeding. F or example, T. dicoccoides accessions from Mt. Hermon. Israel. are uniforml y and highly resistant to stripe-rust. The main objective of the present st udy is to map a stripe-rust resistance gene, derived from the unique Mt. He rmon population of wild emmer, using microsatellite markers. An FZ mapping population was established by crossing stripe-rust resistant T. dicoccoides accession H52 from Mt. Hermon with the Triticum durum cultivar Langdon. Th e stripe-rust resistance derived from accession H52 was found to be control led by a single dominant gene which was temporarily designated as YrH52. Ou t of 120 microsatellite markers tested. 109 (91%) showed polymorphism betwe en the parental lines. Among 79 segregating microsatellite loci generated f rom 56 microsatellite primer pairs: nine were linked to YrH52 with recombin ation frequencies of 0.02-0.35, and LOD scores of 3.56-54.22. A genetic map of chromosome 1B, consisting of ten microsatellite loci and the stripe-lus t resistance gene YrH52, was constructed with a total map length of 101.5 c M. YrH52 is also closely linked to RFLP marker Nor1 with a map distance of 1.4 cM and a LOD value of 29.62. Apparent negative crossover interference w as observed in chromosome 1B, especially in the region spanning the centrom ere. Negative crossover interference may be a common characteristic of gene -rich regions or gene clusters in specific chromosomes.