Department of Mycology & Microbiology, Tea Research Association, North Bengal Regional, R & D Center, Nagrakata, Jalpaiguri, West Bengal, 735225, India.
Department of Plant Pathology, University of Horticultural Sciences, Navanagar, Udyanagiri, Bagalkot, Karnataka, 587104, India.
World J Microbiol Biotechnol. 2022 Dec 5;39(1):34. doi: 10.1007/s11274-022-03474-3.
Gray blight, a fungal disease caused by Pestalotiopsis-like species, is a widespread disease affecting tea crop (Camellia sinensis (L.) Kuntze) in many tea-growing countries, including India, resulting in huge losses in tea production. In India, several studies have been conducted to understand the fungal diseases of tea crop, but gray blight has not been well described in major tea growing areas such as in North Bengal, based on its geographic distribution, molecular analysis, or pathogenicity, and even fungicide resistance. The objective of this study was to identify and characterize the causative agents of gray blight disease in symptomatic leaf sample of tea crop collected from 27 tea gardens located in North Bengal, India and to evaluate some common fungicides against them in order to understand the resistance mechanism. In this study, we characterized Pestalotiopsis-like species based on the phylogenies of DNA sequences (internal transcribed spacers) and assessment of conidial characteristics. The study revealed that out of 27 isolates of gray blight pathogens, 17 belonged to the genus Pseudopestalotiopsis (Ps.), six isolates were Neopestalotiopsis, and four were Pestalotiopsis. Two novel species, Ps. thailandica and N. natalensis were introduced through this study. The most frequently isolated genus from C. chinensis was Pseudopestalotiopsis. Pathogenicity tests showed that the isolates displayed significantly different virulence when inoculated onto wounded tea leaves and the mycelial growth rate was positively correlated with pathogenicity (P < 0.01). Based on the 13 ISSR (Inter Simple Sequence Repeat) markers used and principal coordinate analysis, it was found that isolates were very diverse. Out of 27 isolates, IND0P2, DLG0P10, and BHAT0P11 isolates were insensitive against both MBC + M3 (Carbendazim + Mancozeb) and DMI (Hexaconazole) fungicides, while isolates SANY0P18, PAHG0P19, RANG0P24, and SING0P25 were insensitive only against MBC + M3 fungicide. Further, these insensitive isolates were grouped into separate clusters by ISSR, indicating their distinctiveness. However, all the evaluated isolates were susceptible to M1 (copper oxychloride) and another DMI (propiconazole) fungicides. Therefore, to manage gray blight, fungicide resistance management strategies as recommended by Fungicide Resistance Action Committee should be implemented.
灰疫病，一种由拟盘多毛孢属物种引起的真菌病害，是一种广泛影响茶叶作物（Camellia sinensis (L.) Kuntze）的疾病，在包括印度在内的许多产茶国家造成了巨大的茶叶产量损失。在印度，已经进行了几项研究来了解茶叶作物的真菌病害，但根据其地理分布、分子分析或致病性，甚至抗药性，在北孟加拉等主要产茶地区并没有很好地描述灰疫病，即使是在杀菌剂方面。本研究的目的是从印度北孟加拉的 27 个茶园采集的有症状的茶叶叶片样本中鉴定和表征灰疫病的病原体，并评估一些常用的杀菌剂对它们的作用，以了解抗药性机制。在这项研究中，我们根据 DNA 序列（内部转录间隔区）的系统发育和对分生孢子特征的评估来描述拟盘多毛孢属物种。研究表明，在 27 个灰疫病病原菌分离物中，有 17 个属于拟盘多毛孢属（Ps.），6 个分离物为新拟盘多毛孢属（Neopestalotiopsis），4 个为拟盘多毛孢属（Pestalotiopsis）。通过这项研究，引入了两个新种，即泰国拟盘多毛孢（Ps. thailandica）和新热带拟盘多毛孢（N. natalensis）。从 C. chinensis 中分离到的最常见的属是拟盘多毛孢属。致病性试验表明，接种在受伤叶片上的分离物表现出明显不同的毒力，菌丝生长率与致病性呈正相关（P < 0.01）。基于使用的 13 个 ISSR（简单重复间序列）标记和主坐标分析，发现分离物非常多样化。在 27 个分离物中，IND0P2、DLG0P10 和 BHAT0P11 分离物对 MBC+M3（多菌灵+代森锰锌）和 DMI（戊唑醇）杀菌剂均不敏感，而 SANY0P18、PAHG0P19、RANG0P24 和 SING0P25 分离物仅对 MBC+M3 杀菌剂不敏感。此外，这些不敏感的分离物通过 ISSR 被分组到不同的聚类中，表明它们的独特性。然而，所有评估的分离物均对 M1（氧化亚铜）和另一种 DMI（丙环唑）杀菌剂敏感。因此，为了管理灰疫病，应根据杀菌剂抗药性行动委员会的建议实施杀菌剂抗药性管理策略。
