RESISTANCE TO LEAF RUST IN A SET OF DURUM WHEAT CULTIVARS AND LANDRACES IN SPAIN

Abstract

SUMMARY Durum wheat (Triticum turgidum var. durum) is an important crop in the Mediterranean basin, and in southern Spain. One of the most important biotic constraints to durum wheat production is leaf rust. Breeder deployed resistant cultivars, but mutations in the pathogen create new virulent pathotypes that erode resistance. In this work, two collections of genotypes have been characterized for their leaf rust resistance both in field trials (in Spain and Mexico) and in the greenhouse (with an array of Spanish pathotypes). The first collection included 14 cultivars and lines, mostly from CIMMYT origin, plus six genotypes with known resistance genes. The second collection comprised 29 cultivars commercially available in Spain, plus 11 landraces from the Spanish germplasm bank. Besides, six resistant cultivars of particular importance were crossed with two cultivars with known effective genes (Lr14a and Lr27 + Lr31), and a susceptible one to infer the genetic basis of their resistance. F2 populations were analyzed. At adult plant stage, 20 genotypes including four landraces were resistant in greenhouse to all Spanish pathotypes. In field trials, 24 genotypes were resistant in Spain, and 22 genotypes in Mexico. The presence of resistant genes Lr14a and the complementary genes Lr27+Lr31 has been deduced in some cultivars either by gene postulation or by genetic analysis. These results provide an opportunity for breeding programs in Spain and elsewhere to target their crossing and selection activities so they can yield lines with effective resistance in the Mediterranean region.