Carr Eric A, Zaid Ali M, Bonasera Jean M, Lorbeer James W, Beer Steven V
Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853.
Plant Dis. 2013 Dec;97(12):1524-1528. doi: 10.1094/PDIS-06-12-0597-RE.
Pantoea ananatis has been identified as a cause of center rot of onion. In the field, onion leaves can become infected with P. ananatis and lead to leaf blight. Infected bulbs often are detected only after harvest; however, it has not been demonstrated experimentally that leaf infection by P. ananatis can lead to bulb infection. In this study, onion leaf infection by P. ananatis leading to bulb infection was investigated. Of 18 strains of P. ananatis isolated from symptomatic onion bulbs grown in New York, 14 were pathogenic in bulb and leaf tissue. Pathogenic strains of P. ananatis caused nonmacerated, yellow-brown coloration in fleshy bulb scales following inoculation of bulbs and incubation for 2 days at 28°C. Subepidermal inoculation of onion leaves with pathogenic strains of P. ananatis resulted in gray-white foliar lesions that extended acropetally and basipetally from the points of inoculation. In all, 16% of leaf lesions extended to the onion neck and 11% continued into the bulbs, which developed nonmacerated, yellow-brown scales. Bacteria recovered from the leading edges of lesions had microbiological and molecular characteristics of P. ananatis. This is the first experimental evidence that infection of onion leaves by P. ananatis can lead to bulb infection.
菠萝泛菌已被确认为洋葱中心腐烂病的病因。在田间，洋葱叶片可被菠萝泛菌感染并导致叶枯病。受感染的鳞茎通常在收获后才被检测到；然而，尚未通过实验证明菠萝泛菌对叶片的感染会导致鳞茎感染。在本研究中，对菠萝泛菌感染洋葱叶片导致鳞茎感染的情况进行了调查。从纽约种植的有症状洋葱鳞茎中分离出的18株菠萝泛菌中，有14株对鳞茎和叶片组织具有致病性。将致病性菠萝泛菌菌株接种到鳞茎上，并在28℃下培养2天后，在肉质鳞茎鳞片上引起了未软化的黄棕色变色。用致病性菠萝泛菌菌株对洋葱叶片进行表皮下接种，导致灰白色叶斑从接种点向顶端和基部扩展。总共有16%的叶斑扩展到洋葱颈部，11%延伸到鳞茎，鳞茎上出现未软化的黄棕色鳞片。从病斑前沿分离出的细菌具有菠萝泛菌的微生物学和分子特征。这是菠萝泛菌感染洋葱叶片可导致鳞茎感染的首个实验证据。
