Molecular Identification of a Plasmopara halstedii Isolate and Assessment of Sunflower Hybrid Resistance to Race 330 in Kazakhstan

Abstract

The oomycete Plasmopara halstedii is the causal agent of sunflower Downy mildew and plays a key role in identifying races and assessing the resistance of Kazakhstan’s sunflower hybrids to this pathogen. The relevance of the research is due to the high pathogenicity of the disease and the variability of the pathogen’s racial composition. The pathogen was isolated by in vitro cultivation on potato-glucose agar supplemented with sunflower sprout juice. Molecular identification was performed based on the analysis of the 28S rDNA region using PCR followed by sequencing. Race identification was carried out by artificial inoculation of differential sunflower lines under controlled conditions. The results of morphological and molecular-genetic analyses confirmed that the isolate belonged to the species Pl. halstedii. Based on the reaction of differential lines, the studied isolate was identified as race 330. Screening of 70 sunflower hybrids of Kazakhstani breeding revealed a predominance of susceptible genotypes and a limited number of resistant forms. The obtained data indicate the distribution of Pl. halstedii race 330 in the East Kazakhstan region and highlight the necessity of regular phytopathological monitoring. The identified resistant genotypes are of practical interest for breeding programs aimed at improving sunflower resistance to downy mildew.