Multivariate analysis of Diversity in Botrytis cinerea Isolates from Israel
The necrotrophic fungus Botrytis cinerea, known as the causal agent of gray mold, is ranked second for its phytopathological global-impact. The disease is controlled by agrotechnical means and fungicides, however, these techniques have a variable effect on different fungal isolates. Several studies have scanned for resistance in wild-type tomato lines, however, these works utilized one or few fungal isolates, and plant organs. Here we studied and characterized B. cinerea isolates from different sources and conditions.
We characterized 31 B. cinerea isolates, collected from six hosts in different locations of Israel. Based on the initial screening on leaves and stems, ten isolates that exhibited significant phytopathogenic variability were selected for further study. Two genetic markers (microsatellite) Bc-1 and Bc-7, were able to differentiate between these isolates. Characterization of these isolates showed 178, 68, 142, and 62% (maximal) differences in the rate of necrosis on detached leaves or stems, infection-rate on plants, and saprophytic growth-rate on the solid substrate, respectively. When necrosis-rate was normalized by saprophytic growth-rate, we found 156 and 86% differences among isolates inoculated on leaves and stems, respectively, which could not be related to host-free growth capacity. These isolates also show wide variation in resistance to oxidizing paraquat previously correlated with virulence. Based on these results hierarchical clustering enabled highlighting isolates with higher virulence and paraquat resistance. Further analysis demonstrated that these isolates had higher expression of superoxide dismutase (SOD1), which was previously shown to play an important role in pathogenicity, then an isolate demonstrating lower virulence and paraquat resistance.
In line with reported plasticity for B. cinerea, isolates from different sources showed genetic, physiologic and phytopathogenic variability. Selected isolates containing significant variability will facilitate future research aimed to identify and subsequently breed for sustainable resistance in cultivated tomato.