Plant Pathology (2022) 71, 1369-1380

Stefania Pollastro, Cataldo Laguardia, Crescenza Dongiovanni, Palma Rosa Rotondo, Rita Milvia De Miccolis Angelini, Celeste Raguseo, Caterina Rotolo, Donato Gerin and Francesco Faretra (2022)
Mating type and fungicide resistance in populations of Podosphaera xanthii in south Italy
Plant Pathology 71 (6), 1369-1380
Abstract: Powdery mildew is one of the most common and severe diseases of cucurbits, causing heavy yield losses in all growing areas when not successfully controlled. Two different fungal species, Podosphaera xanthii and Golovinomyces orontii, are generally recognized as causal agents. The results of monitoring carried out in 2016 and 2018 confirmed that P. xanthii is the exclusive pathogen causing cucurbit powdery mildew (CPM) in southern Italy. P. xanthii is a bipolar heterothallic fungus; a PCR-based method for distinguishing MAT1-1 and MAT1-2 idiomorphs was applied for assessing mating type distribution in fungal populations present on cucurbits in different sites. The idiomorph MAT1-2 was prevalent over the MAT1-1 in 2016, whereas they were approximately in a 1:1 ratio in 2018; this finding corroborated the hypothesis that the MAT1-1 idiomorph was more recently introduced in the area. Cyflufenamid-resistant isolates were widespread in commercial greenhouses and field plantings even though use of this fungicide had been drastically reduced by the farmers 1 year before the monitoring due to the effectiveness losses observed in CPM control. Occurrence of cyflufenamid resistance and its impact on efficacy were evaluated in a field trial comparing different fungicide spray schedules. Cyflufenamid-resistant isolates were detected even at the first appearance of symptoms on leaves, increasing over time. Isolates resistant to cyflufenamid showed a resistance factor as high as 900. Generally, P. xanthii was better controlled when cyflufenamid was used in integrated strategies rather than in spray schedules based on the exclusive use of the fungicide.
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Database assignments for author(s): Francesco Faretra

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Podosphaera xanthii	Cucumber (Cucumis sativus)	Italy
	Podosphaera xanthii	Melon (Cucumis melo)	Italy
	Podosphaera xanthii	Watermelon/colocynth (Citrullus)	Italy
	Podosphaera xanthii	Squash/pumpkin (Cucurbita)	Italy