弱毒黄萎病菌的筛选及诱导向日葵交互保护作用的条件优化

向日葵黄萎病是一种难以防治的土传病害。本研究通过毒力和致病力双重评价标准筛选得到一株弱毒黄萎病菌菌株Vn-1，采用诱导接种和挑战接种方法，明确了弱毒菌株Vn-1可以诱导向日葵产生对黄萎病菌的交互保护作用。本试验进一步对菌株Vn-1诱导间隔期和诱导浓度进行了条件优化，并在最优条件下探究其交互保护作用的持效性以及对向日葵植株生长情况的影响。结果表明，菌株Vn-1诱导向日葵交互保护的最佳诱导间隔为5 d，最佳诱导浓度为1×10⁶孢子/mL；在最佳诱导条件下，防效最大可达72.27%，且在挑战接种44 d后维持防效在30%以上；对比直接接种强毒菌株处理，最佳诱导条件下，向日葵株高和根长显著提高，表明菌株Vn-1诱导能够减小强毒菌株对向日葵植株生长的抑制作用。

Screening of Hypovirulent Strains and Optimization of Induction Condition for Its Cross-Protection against Verticillium Wilt on Sunflower

Sunflower Verticillium wilt is one of soil-borne diseases which are difficult to control. In this study, a hypovirulent strain Vn-1 of Gibellulopsis nigrescens. was screened and obtained by virulence index and disease index evaluation. It was the first time to clarify that strain Vn-1 can induce the cross-protection against sunflower Verticillium wilt. In order to find the best conditions for cross-protection of strain Vn-1, interval days and induced concentration were optimized. Under the optimal conditions, it was conducted to test the persistence of the cross-protection and its effect on sunflower growth. The results showed that the optimized condition was 5 d as interval days and 1×10⁶ cfu/mL as induced concentration. Under the optimized condition, the highest control efficacy of strain Vn-1 against sunflower Verticillium wilt reached up to 72.27%, and the efficacy could maintain over 30% after 44 days by challenge inoculation. Under the optimal condition, plant height and root length of the sunflower were significantly improved, indicating that strain Vn-1 can reduce the inhibitory effect of virulent strains on the growth of sunflower plants.