Dasypyrum villosum come fonte di geni di resistenza a oidio e ruggine bruna per il miglioramento dei frumenti coltivati

Abstract

The wild species of cereals comprised in the secondary gene pool (GP 2)of wheat have received specific attention mainly with a view to widening the narrow genetic basis of cultivated wheats. Dasypyrum villosum Candargy (syn. Haynaldia villosa) (Dv) is an annual, diploid (2n=14), allogamous grass species, belonging to the GP 2 of wheat. This species, originating from Southern Europe and South-Western Asia, is widespread in the Mediterranean region and has been reported as carrying genes for enhancing agronomic and grain quality traits. A study has been carried out on two wheat aneuploid lines (CS V32 and CS V63) obtained after introgression of chromosome 6V # 4 into the T. aestivum cv. Chinese Spring (CS) nuclear genome by interspecific hybridization with a D. villosum population collected in Latium. The disomic addition line CS+6V carrying chromosome 6V#1 and bred by the late E.R. Sears, was also included in the study. The two aneuploid lines resulted completely resistant to Blumeria graminis f. sp. tritici (Bgt) at adult and seedling plant stage. The CS V63 line was crossed to the susceptible disomic addition line 6V # 1 and a suitable mapping population, segregating for powdery mildew resistance, was produced. The F2:3 progenies were studied both by phytopathological (with selected pathotypes of Bgt) and molecular (PCR marker) analyses in order to assess the genetic basis of resistance. The observed resistant: susceptible phenotypic ratio fitted the 3:1 ratio expected for the segregation of the resistance/susceptible alleles at one locus named “PmVt”, presumably located in 6VS. The resistant phenotype was dominant. Molecular analyses using the RAPD marker OPH171900 were carried out to confirm the location of this gene on 6VS and to verify its relationship with the Pm21 locus and association to the gliadin-encoding locus Gli-V2. The line CS V63 was tested also for resistance to Puccinia triticina (Pt): it resulted susceptible in the experiments carried out at the seedling stage with different selected Pt pathotypes. When tested with the same pathotypes in controlled infection at the adult plant stage, and in the field, in multilocation epidemiological trials, the line showed a complete or moderate resistance to this disease, thus indicating the possible presence in 6V # 4 of gene(s) for adult plant resistance to Pt.