向日葵菌核病生防菌株的筛选及防效分析

为了从内生菌资源中筛选出对向日葵菌核病有防效的生防菌株，本研究从12个向日葵品种籽粒中分离获得不同菌落形态的33株内生菌株，在此基础上，利用纸杯法进行初筛，从中选出两株对菌核病具有良好防效的菌株，进而采用离体叶片接种试验进行复筛，筛选出一株对菌核病离体防效达100%的内生菌菌株KB3(Bacillus subtilis)。温室盆栽条件下KB3能够显著降低向日葵苗期菌核病的病情指数，防治效果达79.47%。含菌培养基接菌试验表明菌株KB3发酵滤液对核盘菌的抑菌率为68.46%,分皿试验发现KB3能够抑制核盘菌黑色菌核的形成。通过全基因组测序，分析预测到KB3中有7个次级代谢产物合成基因簇。本研究所采取的纸杯法和离体叶片接种相结合的筛菌方法将对菌核病生防菌株的筛选具有参考意义，所获KB3菌株对于向日葵菌核病的防治具有一定的应用前景。

Screening of biocontrol strains against sunflower white mold and analysis of its control effect

To exploit effective microbial resource for sunflower white mold control, 33 endogenous strains with different colony phenotypes were isolated from 12 sunflower cultivars. Their function of sunflower white mold control caused by Sclerotinia sclerotiorum were analyzed via a paper cup system combined with in vitro leaves inoculation method. The only strain named as KB3 (Bacillus subtilis) protected sunflower seedlings from the destruction by S. sclerotiorum absolutely during the experiment period. Its sunflower white mold control effect was 79.47% under greenhouse condition. Its culture filtrate inhibited the growth of S. sclerotiorum on antagonism plate significantly (68.46%) and suppressed the black sclerotia formation severely, which was probably attributed to its various category of secondary metabolites production, indicated by whole genome sequencing and unidentified volatiles respectively. The microbial screening method used in this study could be an important refe-rence for biocontrol agent exploration and strain KB3 was a potent resource for the suppression of sunflower white mold.