Application of a new approach for study of virulence variation in cucurbit powdery mildew populations
Ales Lebeda: Palacky Univ in Olomouc
<div>Cucurbit powdery mildew (CPM) is caused by two obligate ectoparasites, <em>Golovinomyces orontii s.l.</em> (Go) and<em> Podosphaera xanthii</em> (Px), that are highly variable in virulence. Various systems of CPM race determination and denomination were used (Lebeda et al. 2011). We developed new tools to enhance research of CPM virulence variation (Lebeda et al. 2016). Diversity models were applied to analyses of virulence (disease reaction patterns) variation of 115 isolates of two CPM species, Go and Px, collected in the Czech Republic from 2010 through 2012. Diversity within and distances between Go and Px populations and each other in spatio-temporal context and with regard of original host plant species were analyzed, based on virulence patterns of individual isolates (races) on a set of 21 melon (<em>Cucumis melo</em> L.) race differential genotypes (Lebeda et al. 2016). Significant differentiation among the Go and Px pathogen populations was revealed, and the results clearly demonstrate and confirm that the set of differential <em>C. melo</em> genotypes is well composed because of high differentiation capacity. Differentiation of pathogens among years was significant for both species. No significant difference between Go isolates from different host plant species was established due to high variability among Go isolates, but there was significant host-specific differentiation among Px isolates. The results revealed high virulence variation in isolates of Go and Px, and their spatio-temporal fluctuations. Approach applied in this study provides a complex view of virulence structures of CPM populations, and when completed by race determination and denomination on melon, it may serve as a base to understand virulence variation of these CPM species from a spatio-temporal viewpoint, as well as application of this system in breeding, seed production and cucurbit growing.</div>
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