Liu Qiong, Ravanlou Abbasali, Babadoost Mohammad
Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana 61801.
Plant Dis. 2016 Dec;100(12):2377-2382. doi: 10.1094/PDIS-01-16-0107-RE. Epub 2016 Sep 28.
Since 2006, a bacterial spot disease has been widely observed on pumpkin and squash fruit in the North Central region (NCR) of the United States. Surveys were conducted during 2011 to 2013 to determine the occurrence of the disease on pumpkin and winter squash in the NCR. In each state, at least five commercial pumpkin and squash fields were visited each year within 3 weeks of harvest, and 60 fruit were inspected in each field. In nine states surveyed, 217 of 245 fields had fruit with bacterial spot. The average incidence of the symptomatic fruit in all pumpkin fields surveyed was 27.1, 30.3, and 25.3% in 2011, 2012, and 2013, respectively. The average incidence of fruit with bacterial spot in all squash fields surveyed was 20.2% in 2012 and 16.9% in 2013. The incidence of symptomatic fruit was more than 90% in some fields. Xanthomonas cucurbitae and non-X. cucurbitae bacteria were isolated from all of the symptomatic fruit collected. X. cucurbitae was identified based on colony characteristics on yeast extract-dextrose-CaCO agar, a polymerase chain reaction test using primers RST2 and RST3, and pathogenicity on pumpkin leaves. All X. cucurbitae isolates tested were pathogenic on 'Howden' pumpkin. In total, 312 non-X. cucurbitae isolates were identified into 10 genera based on the restriction fragment length polymorphism analysis. None of the non-X. cucurbitae isolates was pathogenic on Howden. In vitro studies of interactions between non-X. cucurbitae and X. cucurbitae showed that Pantoea isolates had antagonistic activity against X. cucurbitae. Identified Pantoea agglomerans showed the highest antagonistic activity against X. cucurbitae.
自2006年以来，在美国中北部地区（NCR）的南瓜和西葫芦果实上广泛观察到一种细菌性斑点病。在2011年至2013年期间进行了调查，以确定NCR地区南瓜和西葫芦上该病的发生情况。在每个州，每年在收获前3周内走访至少5个商业南瓜和西葫芦田，每个田检查60个果实。在调查的9个州中，245个田中有217个田的果实带有细菌性斑点。在2011年、2012年和2013年，所有被调查南瓜田中有症状果实的平均发病率分别为27.1%、30.3%和25.3%。在2012年和2013年，所有被调查西葫芦田中带有细菌性斑点果实的平均发病率分别为20.2%和16.9%。在一些田块中，有症状果实的发病率超过90%。从所有收集的有症状果实中分离出了西葫芦黄单胞菌和非西葫芦黄单胞菌。根据酵母提取物 - 葡萄糖 - 碳酸钙琼脂上的菌落特征、使用引物RST2和RST3的聚合酶链反应试验以及对南瓜叶片的致病性来鉴定西葫芦黄单胞菌。所有测试的西葫芦黄单胞菌分离株对“Howden”南瓜都具有致病性。总共，基于限制性片段长度多态性分析，将312株非西葫芦黄单胞菌分离株鉴定为10个属。没有一株非西葫芦黄单胞菌分离株对Howden具有致病性。非西葫芦黄单胞菌与西葫芦黄单胞菌之间相互作用的体外研究表明，泛菌属分离株对西葫芦黄单胞菌具有拮抗活性。鉴定出的成团泛菌对西葫芦黄单胞菌表现出最高的拮抗活性。
