寡雄腐霉GAQ1对辣椒疫病的防效及对辣椒的促生作用

Biological control and growth-promotion effects of mycoparasitic fungus Pythium oligandrum GAQ1 against Phytophthora blight in pepper

为明确自主分离的生防菌株寡雄腐霉Pythium oligandrum GAQ1对辣椒疫病的生防效果及其防御机制,通过平板拮抗和盆栽防效试验测定寡雄腐霉菌株GAQ1对辣椒疫霉Phytophthora capsici菌丝的拮抗作用、对辣椒疫病的防效和对辣椒的促生效果,同时应用实时荧光定量PCR技术检测菌株GAQ1处理后辣椒抗性基因表达的变化。结果表明,寡雄腐霉菌株GAQ1的菌丝可以缠绕并吸附寄生在辣椒疫霉菌丝表面或穿入菌丝体内,使辣椒疫霉菌丝细胞死亡;菌株GAQ1发酵液处理辣椒离体叶片再接种辣椒疫霉后产生的病斑直径较对照组显著减少,离体防效为30.79%;接种菌株GAQ1菌丝球后,辣椒疫病的病情指数较对照组显著降低,盆栽防效达69.16%;经菌株GAQ1处理辣椒后可诱导相关抗性基因PR1、WRKY40、WRKY53、ACCO和GST的相对表达量出现不同程度的升高,说明菌株GAQ1可诱导辣椒植株产生不同程度的防御系统应答。菌株GAQ1对辣椒具有良好的促生效果,处理后第5周其株高、株重及根重分别较对照组提高10.11%、33.23%和24.72%,其叶片中叶绿素a、叶绿素b及类胡萝卜素的含量分别较对照组提高13.72%、12.13%和15.99%。表明寡雄腐霉菌株GAQ1对辣椒疫病具有显著的防效并能促进辣椒生长,在生物防治方面有一定的应用前景。

In order to clarify the biocontrol effects and mechanisms of the newly isolated mycoparasitic fungus strain Pythium oligandrum GAQ1 against pepper blight caused by Phytophthora capsica,the antagonistic effect of GAQ1 against P.capsici,the control effect on Phytophthora blight,and the growth promotion effect of GAQ1 on pepper were investigated,and the expression levels of defense-related genes induced by GAQ1 were determined by quantitative real time PCR(qPCR).The results showed that GAQ1 hyphae could entangle,adsorb and parasitize on the surface and penetrate the body of P.capsica hyphae,causing cell death.Dipping the detached pepper leaves in the fermentation broth of GAQ1 before inoculation with P.capsici significantly reduced the leaf lesions diameter compared with the untreated control,and the in vitro biocontrol effect was 30.79%.Pot trial results showed that after inoculation with GAQ1 mycelium,the disease index of pepper blight was significantly lower than that of the control,and the potted biocontrol effect was 69.16%.qPCR results revealed that GAQ1 induced the relative expression levels of the plant defense related genes PR1,WRKY40,WRKY53,ACCO and GST.Moreover,GAQ1 could promote pepper growth in the pot assay in which at the 5th week after GAQ1 treatment,pepper plant height,above-ground weight,and root weight were increased by 10.11%,33.23%,and 24.72%,respectively.Meanwhile,the leaf contents of chlorophyll a,chlorophyll b,and carotenoids were increased by 13.72%,12.13%,and 15.99%,respectively.Taken together,Pythium oligandrum GAQ1 is a promising biocontrol agent with the capacity to control Phytophthora blight effectively and promote plant growth of pepper.