Control of Alternaria brassicicola with thermotherapy and propolis and effect on the physiological quality of kale seeds

ABSTRACT In the organic production system, the use of agrochemicals for seed treatment is prohibited. This study was carried out to evaluate the effect of heat treatment and propolis on the germination and vigor of kale seeds and the effect on the control of Alternaria brassicicola. In the treatment with wet thermotherapy, three temperatures (50, 55 and 60°C) were evaluated in separated experiments. For each temperature, five immersion times [0 (control), 15, 30, 45 and 60 minutes] were evaluated. In the dry thermotherapy treatment, seeds were submitted to constant 70ºC temperature and five times [0 (control), 24, 48, 72 and 96 hours] were evaluated. In the treatment with propolis, six concentrations (0.0, 0.2, 0.4, 0.6, 0.8 and 1.0%) were studied, with subsequent washing or not washing of the seeds. Then, seeds were inoculated with A. brassicicola and submitted to the following treatments: wet thermotherapy at 50°C for 60 minutes and at 55°C for 15 minutes and propolis at 1.0% with and without further washing. Two control treatments were included in the experiment (inoculated untreated seeds; and not inoculated and untreated seeds), totalizing six treatments. After inoculation and treatments, the incidence of the fungus on the seeds was evaluated and the effect on the physiological quality of the seeds. Both thermotherapy treatments (50°C for 60 minutes and 55°C for 15 minutes) reduced the pathogen incidence significantly. Both propolis treatments at 1% (with and without subsequent washing) did not provide a satisfactory reduction on A. brassicicola incidence in kale seeds. Thermotherapy at 55°C for 15 minutes is the best option for A. brassicicola control in kale seeds, because it does not affect seed physiological quality.

摘要：在有机生产体系中，禁止使用农用化学品进行种子处理。本研究旨在评估热处理与蜂胶对羽衣甘蓝种子萌发及活力的影响，以及其对芸苔链格孢（Alternaria brassicicola）的防控效果。在湿热处理组中，分别设置50、55、60℃三个温度开展独立实验，每个温度下设置5个浸种时长：0（对照组）、15、30、45及60分钟。干热处理组采用恒定70℃温度，设置5个处理时长：0（对照组）、24、48、72及96小时。蜂胶处理组设置6个浓度梯度（0.0、0.2、0.4、0.6、0.8及1.0%），并分别对处理后的种子进行清洗或不清洗操作。随后将种子接种芸苔链格孢，并施加以下处理：50℃湿热处理60分钟、55℃湿热处理15分钟，以及1.0%蜂胶处理（含后续清洗与不清洗两组）。本实验共设置6个处理组，包括两个对照组：接种但未处理的种子，以及未接种且未处理的种子。接种与处理完成后，评估种子表面的真菌侵染率及处理对种子生理品质的影响。结果表明，两种热处理方案（50℃处理60分钟、55℃处理15分钟）均可显著降低病原菌侵染率。而1.0%浓度的两种蜂胶处理（清洗与不清洗组）均未能有效降低羽衣甘蓝种子中芸苔链格孢的侵染率。其中，55℃湿热处理15分钟是防控羽衣甘蓝种子中芸苔链格孢的最优方案，因其不会对种子生理品质产生负面影响。