Tomato (Lycopersicon esculentum Mill.) is an important vegetable crop grown in Liaoning Province, China. In May 2012, dark brown, angular lesions were observed on lower, older leaves of 5-month-old tomato plants of cv. Bi Jiao in commercial greenhouses in Dawa County, which is administered by Panjin City in Liaoning Province. The irregularly shaped lesions varied in size from 1 to 7 mm in diameter. The necrotic lesions were usually surrounded by a yellow halo. Sporulation was rarely seen on the leaf surfaces. This contrasts with tomato leaf mold caused by Passalora fulva, in which the conidia develop as a velvety brown patch in lesions. By July 2012, the same disease was found in research greenhouses of Shenyang Agriculture University and Liaoning Academy of Agricultural Sciences. The incidence of symptoms was 30 to 40%. To identify the pathogen, leaf pieces (3 to 5 mm) with both infected and healthy portions were taken at the edge of lesions and surface-disinfected by placing them in 75% ethanol for 5 s, then transferred to a 0.1% aqueous mercuric chloride solution for 30 s and rinsed with sterilized water three times. The sections were placed on potato dextrose agar (PDA) at 25°C in the dark. Ten pure fungal cultures were obtained from single spores. For studies of microscopic morphology, isolates were grown on synthetic nutrient agar (SNA) in slide cultures. Conidia ranged in shape from subglobose or ovoid (2 to 4 × 2 to 3 μm) to subcylindrical (4.5 to 17.8 × 2.4 to 4.5 μm). Conidiophores were straight to slightly flexuous with typical nodes. The internal transcribed spacer (ITS) region from isolate PJ12-36 was amplified using primers ITS1 and ITS4 and sequenced (GenBank Accession No. KC137278). The 560-bp amplicons had 99% identity to C. oxysporum (JQ775499). On the basis of morphological characteristics (1) and nucleotide homology, the isolate was identified as C. oxysporum. Koch's postulates were fulfilled in the laboratory on fully expanded leaves of 5-week-old tomato plants 'Moneymaker' inoculated with C. oxysporum conidial suspensions (107 conidia ml-1). Eight seedlings were incubated in an illuminated incubator at 25°C for 8 to 10 days with 85% relative humidity. Characteristic lesions that developed on inoculated leaves were similar in appearance to those observed on diseased tomato plants in the greenhouse. C. oxysporum was reisolated from lesions and its identity was confirmed by morphological characteristics. C. oxysporum was previously reported as the causal agent of a leaf spot disease of pepper (2) and greenhouse tomato (4). To our knowledge, this is the first report of C. oxysporum causing disease on tomato foliage in China. It is noteworthy that C. oxysporum has led to a decline in pepper yield in northern regions of China (3). In addition, pathogenicity tests showed that the isolate W10-02 from pepper and the isolate PJ12-36 from tomato could each cause damage to the opposite host, producing symptoms similar to those observed on the host of origin. Studies are needed on strategies to manage C. oxysporum in crops, because its prevalence may cause yield loss both on tomato and pepper in northern regions of China. References: (1) K. Bensch et al. Stud. Mycol. 67:1, 2010. (2) A. M. Hammouda. Plant Dis. 76:536, 1992. (3) X. Y. Huang et al. Plant Dis. 96:1072, 2012. (4) J. S. Lamboy and H. R. Dillard. Plant Dis. 81:228, 1997.

译文

番茄 (Lycopersicon esculentum Mill。) 是中国辽宁省种植的重要蔬菜作物。在2012年5月中,在5个月大的cv番茄植株的下部,较老的叶子上观察到深棕色的角状病变。辽宁省盘锦市管辖的大洼县商业大棚中的毕娇。不规则形状的病变的直径从1到7毫米不等。坏死性病变通常被黄色光环包围。在叶片表面很少见到孢子形成。这与Passalora fulva引起的番茄叶霉菌形成对比,其中分生孢子在病变中发展为天鹅绒般的棕色斑块。经2012年7月,在沈阳农业大学和辽宁省农业科学院的研究温室中发现了相同的疾病。症状发生率为30 ~ 40%。为了鉴定病原体,将具有感染和健康部分的叶块 (3至5毫米) 在病变边缘处取出,并通过将其置于75% 乙醇中5 s进行表面消毒,然后转移到0.1% 的氯化汞水溶液中30 s,并用无菌水冲洗三次。将切片在黑暗中于25 °C放置在马铃薯葡萄糖琼脂 (PDA) 上。从单个孢子中获得十种纯真菌培养物。为了研究微观形态,在玻片培养物中的合成营养琼脂 (SNA) 上生长了分离株。分生孢子的形状范围从近球形或卵形 (2至4 × 2至3μm) 到近圆柱形 (4.5至17.8 × 2.4至4.5 μ m)。分生孢子笔直至略带弯曲,具有典型的节。使用引物ITS1和ITS4扩增来自分离PJ12-36的内部转录间隔区 (ITS) 区域并测序 (GenBank登录号KC137278)。560 bp扩增子与尖孢菌 (JQ775499) 具有99% 的同一性。根据形态学特征 (1) 和核苷酸同源性,分离株被鉴定为尖孢杆菌。Koch的假设是在实验室中对5周龄番茄植物 “moneymaker” 的完全膨胀的叶子进行的,该叶子接种了C. oxysporum分生孢子悬浮液 (107 conidi 1毫升-1)。将八个幼苗在25 °C的照明培养箱中于85% 相对湿度下孵育8至10天。在接种的叶子上形成的特征性病变在外观上与在温室中患病的番茄植物上观察到的相似。从病变中重新分离出C. oxysporum,并通过形态学特征确认其身份。C. oxysporum以前被报道为辣椒 (2) 和温室番茄 (4) 的叶斑病的病原体。据我们所知,这是中国首次报道的C. oxysporum引起番茄叶片疾病。值得注意的是,尖孢菌导致中国北方地区辣椒产量下降 (3)。此外,致病性测试表明,从胡椒中W10-02的分离物和从番茄中PJ12-36的分离物都可能对相反的宿主造成损害,产生与在来源宿主上观察到的症状相似的症状。需要对农作物中处理C. oxysporum的策略进行研究,因为它的流行可能会导致中国北部地区番茄和辣椒的单产损失。参考文献 :( 1) K。Bensch等人。Mycol。67:1,2010。(2) A.M。哈姆穆达。植物Dis。76:536,1992。(3) X。Y。黄等人。植物Dis。96:1072,2012。(4) J。S。Lamboy和h.r.迪拉德。植物Dis。81:228,1997。

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