Asghar Muhammad, Atiq Muhammad, Ali Muhammad Usman, Kachelo Ghalib Ayaz, Khan Nasir Ahmad, Naveed Khalid, Usman Muhammad, Nawaz Ahmad, Iqbal Owais, Rajput Nasir Ahmed
Department of Plant Pathology, University of Agriculture Faisalabad, Faisalabad, Pakistan.
Crop Disease Research Institute, Southern Zone Agricultural Research Center, PARC, Karachi, Pakistan.
PLoS One. 2025 May 9;20(5):e0323067. doi: 10.1371/journal.pone.0323067. eCollection 2025.
Purple blotch (PB), caused by Alternaria porri (Ellis) ciferri, poses a significant threat to onion crop, resulting in major economic losses in both bulb and seed production globally. The incidence of this disease underscores the critical need for an effective management. In the present study, screening of onion genotypes for PB under field conditions revealed that the genotypes like Phulkara and Ceylon expressed resistant, response with 8.21 and 8.91% disease severity index (DSI) respectively, whereas Desi Black and Red Imposta were highly susceptible, with DSI of 67.38 - 79.41%. Furthermore, resistant and susceptible genotypes were also evaluated for biochemical variation analysis. Significant variations (p ≤ 0.05) in antioxidant enzymes were observed across reaction groups (inoculated and un-inoculated), types (resistant and susceptible), and onion varieties in response to A. porri infection. The analysis of variance showed significant changes in antioxidant enzymes level of onion leaves, including catalase (CAT), peroxidase (POD), and super dismutase (SOD). Results indicated that the concentration of SOD (55.37%), POD (41.87%) and CAT (37.92), respectively, in resistant plant leaves, whereas susceptible varieties showed SOD (43.71%), POD (28.3%) and CAT (26.59%). Furthermore, the amount of antioxidant enzymes was reduced in both resistant as well as susceptible varieties of onion after inoculation. Amount of SOD (68.04%), POD (57.45%) and CAT (50.87%) were recorded in un-inoculated group of onion plants that reduced to 31.05, 12.98 and 13.64% in inoculated group respectively. For the management of A. porri four different plant activators (salicylic acid, benzoic acid, citric acid and di-potassium hydrogen phosphate) at three different concentrations (0.5, 0.75 and 1%) were evaluated under greenhouse and field conditions. Among all salicylic acid was found to be most effective in controlling this disease under greenhouse and field conditions. The present study revealed that purple blotch affects the biochemical mechanism of the plants, which helps in activating the resistance process against pathogens through various enzymes. Additionally, salicylic acid demonstrated significant efficacy in controlling purple blotch in onions.
紫斑病（PB）由葱链格孢（Alternaria porri (Ellis) ciferri）引起，对洋葱作物构成重大威胁，在全球鳞茎和种子生产中均造成重大经济损失。这种病害的发生率凸显了有效防治的迫切需求。在本研究中，在田间条件下对洋葱基因型进行紫斑病筛选发现，像Phulkara和锡兰洋葱这样的基因型表现出抗性，病情严重指数（DSI）分别为8.21%和8.91%，而Desi Black和Red Imposta高度易感，DSI为67.38 - 79.41%。此外，还对抗性和易感基因型进行了生化变异分析。在不同反应组（接种和未接种）、类型（抗性和易感）以及洋葱品种中，对抗葱链格孢感染的抗氧化酶进行观察，发现存在显著差异（p≤0.05）。方差分析表明洋葱叶片中抗氧化酶水平发生了显著变化，包括过氧化氢酶（CAT）、过氧化物酶（POD）和超氧化物歧化酶（SOD）。结果表明，抗性植株叶片中SOD、POD和CAT的浓度分别为55.37%、41.87%和37.92%，而易感品种中SOD、POD和CAT的浓度分别为43.71%、28.3%和26.59%。此外，接种后抗性和易感洋葱品种中的抗氧化酶含量均有所降低。未接种洋葱植株组中SOD、POD和CAT的含量分别为68.04%、57.45%和50.87%，接种组中分别降至31.05%、12.98%和13.64%。为防治葱链格孢，在温室和田间条件下评估了三种不同浓度（0.5%、0.75%和1%）的四种不同植物激活剂（水杨酸、苯甲酸、柠檬酸和磷酸二氢钾）。在所有激活剂中，发现水杨酸在温室和田间条件下对防治这种病害最有效。本研究表明，紫斑病影响植物的生化机制，通过各种酶有助于激活对病原体的抗性过程。此外，水杨酸在防治洋葱紫斑病方面显示出显著效果。
