向日葵列当的内生细菌分离筛选与初步鉴定

Isolation and identification of antagonistic endophytic bacteria from Orobanche cumana

为获得对向日葵菌核病有较强生防效果的拮抗细菌,从向日葵根部一年生全寄生杂草向日葵列当植株内分离纯化得到135株内生细菌菌株。依次采用平板对峙法、生长速率法、离体叶片防效试验、菌核萌发抑制试验筛选得到2株对核盘菌拮抗活性较好的内生细菌LIEH 92和LIEB54,用内生拮抗细菌菌株发酵液无菌滤液进行离体叶片防效试验发现,2个菌株的离体防效分别达68.48%和62.33%;LIEH 92和LIEB 54滤液处理过的菌核均不萌发,在防治向日葵菌核病方面具有良好的生防潜力。除木糖利用和V.P试验(Vopes-prokauer test)外,菌株LIEH 92与粘质沙雷氏菌的生理生化特征一致。16S r DNA序列分析鉴定,与菌株LIEH 92相似性大于99%的菌株归于肠杆菌科的沙雷氏菌属。以16S r DNA序列为基础构建系统发育树,发现菌株LIEH 92与各粘质沙雷氏菌同源性最高,因此认为菌株LIEH 92可能为粘质沙雷氏菌(Serratia marcescens)的新亚种。

To biocontrol the sunflower Sclerotinia rot,135 endophytic bacteria strains were isolated from Orobanche cumana,a kind of root- holoparasitic weed of sunflower. The bacteria were dual cultured to investigate the inhibition rate of Sclerotinia mycelia growth. Then antagonistic effects were tested on leaves in vitro,and sclerotia germination were screened under bacteria against Sclerotinia sclerotiorum of sunflower. Strains LIEH 92 and LIEB54 were found efficiently suppressing S. sclerotiorum with efficacy of 68. 48% and 62. 33% on detached leaves.Sclerotia did not germinate under sterile fermentation filtrate treatment. Thus the 2 endophytic bacteria had great potentials in biocontrol on sunflower sclerotinia rot. Except ositive xylose fermentation and negative Vopes- prokauer test,strain LIEH 92 had the same morphological and physio- biochemical characteristics as Serratia marcescens. 16 S r DNA phylogenetic analysis showed that the majority of strains belonging to Serratia of enterobacteriaceae had over99% similarity with LIEH 92. Thus the strain LIEH 92 was putatively identified as a new subspecies of S. marcescens.