Genomic constitution and expression of disease resistance in Agropyron cristatum x durum wheat derivatives

Abstract

Septoria leaf blotch, powdery mildew and yellow and brown rusts are major wheat diseases characterized by a worldwide distribution. The level of genetic resistance against these diseases is low in durum wheat (Triticum turgidum) germplasm, while some wheat relatives, such as crested wheatgrass (Agropyron cristatum), are resistant. In an attempt to incorporate resistance genes into durum wheat, crosses were carried out between durum wheat and a fertile allotetraploid (2n = 4x = 28; DDPP) previously obtained from a cross between diploid wheat (T. tauschii) and crested wheatgrass (A. cristatum). The plants were backcrossed twice to durum wheat and studied for their reaction to the diseases. The genomic constitution of all the backcross derivatives from these crosses were analyzed by fluorescence in situ hybridization (FISH) using both total genomic DNA of A. cristatum and the pAs1 repetitive DNA sequence isolated from T. tauschii. All of them retained chromosomes or chromosome segments of A. cristatum. All the analyzed plants were immune to septoria leaf blotch and powdery mildew and showed a high level of resistance to yellow and brown rusts.