Javier-Alva J, Gramaje D, Alvarez L A, Armengol J
Departamento de Sanidad Vegetal, Universidad Nacional de Piura, Campus Universitario, Urb. Miraflores s/n, Piura - Peru.
Instituto Agroforestal Mediterráneo, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain.
Plant Dis. 2009 Apr;93(4):426. doi: 10.1094/PDIS-93-4-0426B.
Mango (Mangifera indica L) is one of the most important cash crops of northern Peru. Since 2003, adult mango trees (cvs. Criollo and Kent) located in Piura Province developed symptoms of dieback characterized by the death of twigs and branches in the tree canopy. Additional disease symptoms involved darkened, elongated lesions on the peduncle, causing an early maturation of the fruit, and in advanced symptoms, stem-end rot of fruits. Symptoms were frequent in the spring months (September to November) when the lesions expand rapidly. Diseased tissues from branches and fruits were collected and small pieces of necrotic tissues were surface disinfected and plated onto potato dextrose agar (PDA) with 0.5 g L streptomycin sulfate. Plates were incubated at 25°C in the dark. All affected tissues consistently developed colonies with a white mycelium, moderately dense, and becoming olivaceous gray after 5 to 6 days. Pycnidia were produced on sterile mango twigs placed on the surface of potato carrot agar (PCA) after 10 days. Conidia were hyaline, guttulate, aseptate, measuring (15-) 18.5 (-22.5) × (4-) 5.2 (-7.5) μm. Conidia became olivaceous and developed one or two septa before germination. Isolates were identified as Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers, & A.J.L. Phillips (1). DNA sequences of the rDNA internal transcribed spacer region (ITS) and part of the translation elongation factor 1-alpha (EF1-α) genes were used to confirm the identification through BLAST searches in GenBank (ITS: 99% identity to Accession No. EU080928; EF1-α: 98% identity to Accession No. AY343367). Representative sequences of the studied DNA regions were deposited at GenBank (ITS: Accession No. FJ528596; EF1-α: Accession No. FJ528597). Pathogenicity tests were conducted on 18-month-old potted mango plants cv. Kent with two N. parvum strains (A4 and A5). A mycelial plug (3 cm in diameter) taken from the margin of an actively growing colony of each isolate was put in a wound made with a cork borer of the same diameter on the stem of each plant. Inoculation wounds were wrapped with Parafilm. Controls were inoculated with sterile PDA plugs. Ten replicates for each isolate were used with an equal number of control plants. Plants were maintained in a greenhouse with a temperature range of 22 to 28°C. After 4 weeks, mango plants showed necrotic stem lesions originating from the inoculation point affecting also the branches of the inoculated plants. No differences in lesion area between strains were obtained. No lesions developed in the control plants. Reisolations from necrotic tissues were successful and both isolates were morphologically identical to those used for inoculations. N. parvum was isolated from all symptomatic trees in all surveyed areas. This pathogen has already been reported on mango (2) and currently represents a serious problem in the mango-producing areas of Peru. To our knowledge, this is the first report of N. parvum affecting mango in Peru. References: (1) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (2) B. Slippers et al. Mycologia 97:99, 2005.
芒果（Mangifera indica L）是秘鲁北部最重要的经济作物之一。自2003年以来，位于皮斯科省的成年芒果树（品种为克里奥罗和肯特）出现了枝枯病症状，表现为树冠中的嫩枝和枝条死亡。其他病害症状包括花梗上出现变黑、拉长的病斑，导致果实早熟，在病情严重时，果实会出现茎端腐烂。这些症状在春季月份（9月至11月）较为常见，此时病斑会迅速扩大。采集了树枝和果实上的患病组织，将小块坏死组织进行表面消毒后，接种到添加了0.5 g/L硫酸链霉素的马铃薯葡萄糖琼脂（PDA）培养基上。平板在25°C黑暗条件下培养。所有受感染的组织均持续长出带有白色菌丝体的菌落，菌丝体密度适中，5至6天后变为橄榄灰色。10天后，在放置于马铃薯胡萝卜琼脂（PCA）表面的无菌芒果嫩枝上产生了分生孢子器。分生孢子无色透明，具油滴，无隔膜，大小为（15 -）18.5（-22.5）×（4 -）5.2（-7.5）μm。分生孢子在萌发前变为橄榄色并形成一至两个隔膜。分离菌株被鉴定为微小新壳梭孢（Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers, & A.J.L. Phillips (1)）。通过在GenBank中进行BLAST搜索，利用核糖体DNA内部转录间隔区（ITS）和翻译延伸因子1-α（EF1-α）基因的部分DNA序列来确认鉴定结果（ITS：与登录号EU080928的序列相似度为99%；EF1-α：与登录号AY343367的序列相似度为98%）。所研究DNA区域的代表性序列已提交至GenBank（ITS：登录号FJ528596；EF1-α：登录号FJ528597）。对18个月大的盆栽肯特品种芒果植株进行了致病性测试，使用了两个微小新壳梭孢菌株（A4和A5）。从每个分离菌株活跃生长菌落的边缘取一个直径为3 cm的菌丝块，放置在用相同直径的打孔器在每株植物茎干上造成的伤口处。接种伤口用Parafilm包裹。对照组接种无菌PDA块。每个分离菌株设置10个重复，并设置相同数量的对照植株。植株置于温度范围为22至28°C的温室中。4周后，芒果植株在接种点出现坏死茎斑，受影响的还包括接种植株的枝条。两个菌株在病斑面积上没有差异。对照植株未出现病斑。从坏死组织中再次分离成功，且两个分离菌株在形态上与用于接种的菌株相同。在所有调查区域的所有有症状的树上均分离到了微小新壳梭孢。这种病原菌已在芒果上有过报道（2），目前在秘鲁的芒果产区是一个严重问题。据我们所知，这是微小新壳梭孢在秘鲁影响芒果的首次报道。参考文献：(1) P. W. Crous等人，《Stud. Mycol.》55:235, 2006。(2) B. Slippers等人，《Mycologia》97:99, 2005。
