Alternaria leaf spot of Ailanthus excelsa is generally considered as minor disease in India. Recently, severe disease outbreaks were recorded in the nursery of the Forest Research Institute, Dehradun, progeny trial at Jhumpa, Haryana, and in a nearby farm field. Leaf symptoms included small circular, brown, necrotic spots with a chlorotic halo. With severe infections, leaf spots coalesced and resulted in leaf blight. A small‐spored Alternaria with concatenated conidia was isolated consistently from the leaf samples with spot symptoms. Sequence analyses of the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) and the translation elongation factor 1‐alpha (tef‐1α) gene region of two fungal isolates confirmed the species as A. alternata. In detached leaf assays, both isolates produced symptoms similar to those observed on the nursery/field‐grown plants. To validate the detached leaf assay result, pathogenicity was also demonstrated on whole plants in a glasshouse. Koch's postulates were fulfilled by re‐isolating A. alternata from the inoculated leaves. This work is the first to confirm that A. alternata is associated with leaf spot and blight disease of A. excelsa in India.

中文翻译：

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引起印度臭椿叶斑病和枯萎病的链格孢的鉴定及致病性

臭椿的链格孢叶斑病在印度一般被认为是小病。最近，在德拉敦森林研究所的苗圃、哈里亚纳邦 Jhumpa 的后代试验以及附近的农田中记录了严重的疾病爆发。叶片症状包括带有褪绿光晕的小圆形、棕色、坏死斑点。随着严重感染，叶斑合并并导致叶枯病。从具有斑点症状的叶子样品中一致地分离出具有串联分生孢子的小孢子链格孢。对核糖体 DNA (rDNA) 的内部转录间隔区 (ITS) 区域和两个真菌分离株的翻译延伸因子 1-α (tef-1α) 基因区域的序列分析证实，该物种为 A. alternata。在离体叶分析中，两种分离株产生的症状与在苗圃/田间种植的植物上观察到的症状相似。为了验证离体叶测定结果，还在温室中的整株植物上证明了致病性。Koch 的假设通过从接种的叶子中重新分离 A. alternata 得到满足。这项工作首次证实了 A. alternata 与印度 A. excelsa 的叶斑病和枯萎病有关。