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Population structure and fungicide resistance profile of Botrytis spp. causing damping-off disease in stone- and pome fruit rootstock seedlings
S. KONSTANTINOU (1), G. Sarmis (1), G. S. Karaoglanidis (2). (1) Aristotelian University of Thessaloniki, Faculty of Agriculture, Plant Pathology Laboratory, Thessaloniki, Greece; (2) Aristotelian Univ of Thessaloniki, Thessaloniki, Greece

<i>Botrytis</i> spp. is the main causal agent of damping-off in micro-propagated pome and stone fruit rootstock seedlings in greenhouse nurseries. The study was conducted to investigate the fungal population structure and fungicide resistance profile. Population structure was investigated in 134 isolates, using 2 molecular markers, the presence of transposable elements (TEs, Boty and Flipper) and the presence of a 21bp insertion in the <i>mrr1</i> gene, encoding a transcription factor, that distinct <i>B.</i> <i>cinerea sensu stricto</i>, from <i>Botrytis</i> Group S, a novel clade within <i>Botrytis </i>populations. Results showed that transposa isolates (both TEs present) were predominant (83.6%), while Boty, Flipper or vacuma (both TEs absent) isolates were found at frequencies of 11.9, 1.5 and 3%, respectively. Similarly, was found that <i>B. cinerea sensu stricto</i> was predominant in the population (69.7%). However a significant proportion of the isolates were identified as <i>Botrytis </i>group S (29.6%), while 1 isolate was identified as <i>B. pseudocinerea</i>. Measurements of fungicide sensitivity revealed the presence of high frequencies of multiple resistance to more than 2 different fungicide classes, mostly associated with target site mutations. The higher frequencies of resistance were observed for QoIs, SDHIs and benzimidazoles with values of 89.8, 73 and 64.6%, respectively, while frequencies of resistance to anilinopyrimidines, hydroxyanilides, dicarboximides and phenylpyrroles were lower.

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