Bacterial blight in pomegranate is a devastating disease caused by bacterial pathogen Xanthomonas axonopodis pv. punicae (XAP), recording huge damage to pomegranate crop worldwide. Antibiotics and copper-based chemicals are being used for the management of this blight, while in this present work, we investigated the effect of eugenol and clove oil either singly or in combination with copper oxychloride (COC) on the induction of plant defense responses and concomitant prevention of bacterial blight. Our results provided evidence that clove oil (0.2%–1%) and eugenol (0.1% and 0.2%) successfully inhibit the growth of XAP in paper disk diffusion assay. Strikingly under the greenhouse condition, clove oil (0.2%) as foliar application 24 h before XAP inoculation recorded the lowest disease severity of 7.34%, whereas eugenol (0.2%) recorded maximum disease severity of 14.56%. However, the combination of clove oil (0.2%) and copper oxychloride (0.3%) recorded the least disease severity of 2.38%. A similar trend was observed in field conditions. Prophylactic application of clove oil leads to enhanced nitrate reductase activity and nitric oxide production which was further enhanced in clove oil pre-treated plants challenged with XAP. Strikingly, the total ROS and H₂O₂ levels were reduced in response to clove oil application. Clove oil also induced the systemic response by inducing expression levels of defense genes. The reduction of disease severity by clove oil and COC combination also reflected on total yield recording via large-scale field experiments where maximum yield of 14.04 tonnes/acre was observed, whereas streptocycline application recorded 11.12 tonnes/acre. Application of COC and clove oil resulted in a high remunerative value of ₹ 1:5.6, compared to streptocycline (1:4.85) and control (1:1.85). The present study revealed that clove oil as a plant derivative and eugenol as a synthetic option can be effectively used for the successful management of bacterial blight in pomegranate.

中文翻译：

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温室和田间试验表明丁香油可以有效减少白叶枯病，提高石榴产量

石榴细菌性枯萎病是由细菌病原体Xanthomonas axonopodis pv 引起的一种破坏性疾病。石榴(XAP)，记录了全球石榴作物遭受的巨大破坏。抗生素和铜基化学品被用于管理这种枯萎病，而在目前的工作中，我们研究了丁香酚和丁香油单独或与氯氧化铜 (COC) 组合对植物防御反应的诱导和同时预防细菌性枯萎病。我们的结果提供了证据表明丁香油 (0.2%–1%) 和丁香酚 (0.1% 和 0.2%) 在纸盘扩散试验中成功地抑制了 XAP 的生长。引人注目的是，在温室条件下，在 XAP 接种前 24 小时叶面喷施丁香油 (0.2%) 的病害严重程度最低，为 7.34%，而丁香酚 (0.2%) 的病害严重程度最高，为 14.56%。然而，丁香油 (0.2%) 和氯氧化铜 (0. 3%) 记录的疾病严重程度最低，为 2.38%。在野外条件下也观察到了类似的趋势。丁香油的预防性应用导致硝酸还原酶活性和一氧化氮产生增强，这在用 XAP 攻击的丁香油预处理植物中进一步增强。引人注目的是，总 ROS 和 H₂ O ₂水平响应丁香油应用而降低。丁香油还通过诱导防御基因的表达水平来诱导全身反应。丁香油和 COC 组合对疾病严重程度的降低也反映在通过大规模田间试验记录的总产量上，其中观察到最大产量为 14.04 吨/英亩，而链环素的应用记录为 11.12 吨/英亩。与链环素 (1:4.85) 和对照 (1:1.85) 相比，COC 和丁香油的应用产生了 1:5.6 的高回报价值。本研究表明，丁香油作为植物衍生物和丁香酚作为合成选择可以有效地用于成功管理石榴中的白叶枯病。