Fungitoxic effect of essential oils on Phakopsora euvitis, causal agent of grape rust

ABSTRACT Knowledge about undesirable effects of conventional fungicides, and concern from consumers and Regulatory Agencies about food quality have encouraged the research on new alternatives for controlling plant diseases. The objective of this study was to evaluate the antifungal activity of 16 essential oils on Phakopsora euvitis , causal agent of grape rust in vitro and under field conditions. The essential oils tested were oregano, peppermint, black pepper, neem, eucalyptus globulus , citronella, cinnamon, marjoram, rosemary, basil, blue chamomile, white camphor, clove, ginger, tea tree and white thyme. In vitro , two experiments were carried: (i) evaluation of spores germination in water agar media amended with essential oil at 0 (control), 0.1, 0.5, 1, 2 and 4% (v/v). (ii) Evaluation of spores germination on detached leaves of vine previously treated with a solution of essential oils at 0, 0.1, 0.5, 1, 2 and 4%. The percentage of inhibition in the spores germination and LD90 values were calculated. Under field conditions, essential oils 1% (v/v) were sprayed on vine plants, and rust severity was evaluated twice, 15 and 30 days post application. In in vitro tests, the LD90 values ranged from 0.39 (neem) to 3.9% (oregano). The most efficient essential oils on Phakpsora euvitis were blue chamomile, citronella, eucalyptus globulus , ginger, neem and white thyme. Under field conditions, all essential oils reduced rust severity and among them, those from cinnamon, citronella, neem and white thyme showed the highest level of rust control. Our results show that the essential oils tested are effective for the management of grape rust. However, further studies on the phytotoxicity of these compounds are still required.

摘要：传统杀菌剂的不良副作用，以及消费者与监管机构对食品品质的担忧，推动了植物病害防控新型替代方案的研究。本研究旨在评价16种精油（essential oils）对葡萄锈病菌（Phakopsora euvitis，该病的病原菌）的体外及田间抑菌活性。供试精油包括牛至油、薄荷精油、黑胡椒精油、印楝精油、蓝桉（Eucalyptus globulus）精油、香茅精油、肉桂精油、马郁兰精油、迷迭香精油、罗勒精油、蓝甘菊精油、白樟精油、丁香精油、生姜精油、茶树精油及白百里香精油。
体外试验共设置两组：① 在添加体积比（v/v）0（对照）、0.1、0.5、1、2及4%精油的水琼脂培养基上评价孢子萌发情况；② 在预先经0、0.1、0.5、1、2及4%精油溶液处理的葡萄离体叶片上评价孢子萌发情况。计算孢子萌发抑制率及90%致死剂量（LD90）值。
田间试验中，将体积比1%的精油溶液喷施于葡萄植株，分别于施药后15天和30天两次评估锈病病情严重度。体外试验结果显示，LD90值范围为0.39%（印楝精油）至3.9%（牛至油）。对葡萄锈病菌抑制效果最优的精油为蓝甘菊、香茅、蓝桉、生姜、印楝及白百里香精油。田间试验中，所有供试精油均可降低锈病病情严重度，其中肉桂、香茅、印楝及白百里香精油的锈病防控效果最佳。本研究结果表明，供试精油可有效用于葡萄锈病的防控，但仍需开展上述化合物的植物毒性相关后续研究。