Screening Fungicide Resistance of Alternaria Pathogens Causing Alternaria Blight of Pistachio in Turkey

Abstract

Alternaria blight is one of the important diseases of pistachio and wild relatives, and its management in pistachio orchards mainly relies on fungicide applications. But, it is observed the disease cannot be declined or controlled by fungicide treatment that might be due to development of fungicide resistance in Alternaria pathogens. On the other hand, wild Pistacia species and some pistachio trees which cultural practices are not applied are not exposed to fungicide treatments in nature. Isolates from orchards and wild systems may show difference in their sensitivities to fungicides. In this study, twenty-two isolates of Alternaria species from different hosts of Pistacia species were investigated in vitro for their sensitivity to different fungicides having different mode of action. Fungicide sensitivity were evaluated based on mycelial growth and spore germination of the isolates by using effective concentrations. The least effective fungicide was azoxystrobin and the most effective one was boscalid + pyraclostrobin among the fungicides tested in this study. Partial gene sequencing of succinate dehydrogenase genes presented boscalid sensitivity of the isolates according to the specific mutations related with boscalid resistance. This study is the first initiation to observe sensitivity of Alternaria pathogens from pistachio and wild relatives against to the most commonly used commercial fungicides in Turkey.

Keywords

• Alternaria,Pistachio,Fungicide

Türkiye’de Antepfıstığı’nda Alternaria Yanıklık Etmeni Alternaria Patojenlerinin Fungisit Direncinin İncelenmesi

Öz

Alternaria yanıklığı, Antepfıstığı ve yabani akrabalarını etkileyen önemli hastalıklardan biridir ve Antepfıstığı bahçelerinde hastalık kontrolü fungisit uygulamalarına dayalı olarak yürütülmektedir. Fakat, fungisit kullanımı ile hastalığın azalmadığı veya kontrol edilemediği görülmüştür ki bu durum Alternaria patojenlerinde fungisit direnci gelişmiş olmasından dolayı olabilir. Diger taraftan, yabani Pistacia türleri ve kültürel pratiklerin uygulanmadığı bazı Antepfıstığı ağaçları doğada fungisit uygulamalarına maruz kalmamaktadır. Kültür bahcelerindeki ve yabani ekosistemdeki izolatlar, fungisitlere karşı duyarlılıkta farklılık gösterebilir. Bu çalışmada, Pistacia türlerinin farklı konukçularından örneklenmiş yirmi iki izolatın, farklı etki mekanizmasına sahip fungisitlere karşı in vitro duyarlılıkları araştırılmıştır. Fungisit duyarlılıkları izolatların miselyal gelişim ve spor çimlenmesi üzerinden etkili konsantrasyon verileri ile değerlendirilmiştir. Test edilen fungisitler arasında izolatlar üzerinde etkisi en düşük olan fungisit azoxystrobin, en etkili olan ise boscalid+pyraclostrobin olarak bulunmuştur. Boscalid direnci ile ilişkilendirilen polimorfizmlere göre suksinat dehidrogenaz genlerinin kısmi baz dizilim verileri izolatların duyarlı olduğunu göstermistir. Bu çalışma, Türkiye’de, Antepfıstığı ve yabani akrabalarından örneklenmis Alternaria izolatlarının yaygın ticari kullanımı olan fungisitlere karşı duyarlılıklarını belirlemek üzere yapılan ilk başlangıç çalısmasıdır.

Anahtar Kelimeler

• Alternaria,Antepfıstığı,Fungisit

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