First report of sesame spot caused by Xanthomonas campestris pv. sesami in Sinaloa, Mexico

A new disease on sesame (Sesamum indicum L.) plants was observed in the municipalities of Ahome, El Fuerte and Choix in the state of Sinaloa, Mexico during the summer of 2014. The disease occurred during the rainy season (August–September) when temperatures ranged between 27–40°C. The symptoms were lesions on leaves, petioles, stems and capsules. Up to 100% incidence was observed, and up to 50% of the foliage exhibited symptoms under field conditions. Isolations were made from leaves and a bacterium was consistently recovered on nutrient agar medium. Based on physiological and biochemical tests, as well as sequences from three different DNA regions, the bacterium was identified as Xanthomonas campestris pv. sesami. Pathogenicity tests confirmed the ability of select isolates to cause symptoms similar to those observed under field conditions.2014年夏季，科研人员在墨西哥锡那罗亚州的阿霍梅、埃尔富尔特与乔伊什自治市镇的芝麻（Sesamum indicum L.）植株上发现了一种新型病害。该病于雨季（8月至9月）发生，此时气温介于27℃至40℃之间。其症状表现为叶片、叶柄、茎秆及蒴果出现病斑。田间调查显示，该病发病率最高可达100%，且多达50%的植株叶片显现病症。研究人员从病叶中进行分离，可在营养琼脂培养基上稳定获得该细菌。综合生理生化试验结果与三个不同DNA区段的序列分析，该细菌被鉴定为油菜黄单胞菌芝麻致病变种（Xanthomonas campestris pv. sesami）。致病性试验证实，所选分离菌株均可诱发与田间自然发病症状一致的病征。