Evaluation of Wheat Wild Relatives for Resistance to Septoria Tritici Blotch

Abstract

Septoria tritici blotch (STB), caused by the fungus Mycosphaerella graminicola (Fuckel) Schroeter (anamorph: Septoria tritici Roberge in Desmaz), is a major disease of wheat (Triticum aestivum L. em. Thell) world wide. The susceptibility of most commercial cultivars to STB has led to the need to identify new sources of resistance to this disease. Although the wild relatives of wheat have provided a valuable source of many new resistance genes, they have not been widely screened for resistance to STB. The objectives of this study were to identify new sources of STB resistance from the wild relatives of common wheat and to examine relationships among frequency of STB resistant accessions and ecogeographieal parameters. Two hundred and fifty‐four accessions, with genomes homologous to those of hexaploid wheat, were inoculated in the greenhouse with a spore suspension of a mixture of 14 S. tritici isolates collected in Missouri. Accessions with a mean disease reaction <1 on a 0 to 9 scale, ranging from no visible symptoms (0) to complete necrosis of the inoculated leaf (9), were considered resistant. Pearson product‐moment correlation coefficients were determined for seedling disease susceptibility scores and environmental variables measured at the site of collection of each accession. Eighteen of the 19 resistant accessions identified were from T. speltoides and T. tauschii. The frequency of resistant accessions was highest in areas of high rainfall and temperature. Targeting areas with these environmental conditions should facilitate future collection of STB resistant germplasm.