腐霉菌对荧光假单胞菌株LT6代谢物的敏感性变异

Variation in sensitivity of Pythium spp.to metabolite produced by Pseudomonas fluorescent LT6

为了探明不同靶标病原菌对生防菌荧光假单胞菌株LT6及其代谢物的敏感性差异,在1/5TSA平板上测定了荧光假单胞菌株LT6对69株腐霉菌的拮抗效果,在试验中观察到菌株LT6对不同种腐霉与同种腐霉不同菌株的拮抗效果存在明显差异,抑菌带最宽的为终极腐霉Pythiumulti-mum菌株,达7.5mm,对未知种腐霉菌株抑菌带宽最小,均小于3.0mm。腐霉菌株对由LT6产生的抗生素吩嗪-1-羧酸(PCA)的敏感性存在变异,被测的54株腐霉,当PCA浓度为7.0μg/mL时,敏感的为28株,高抗的为15株。用不同的培养液培养LT6所得的代谢物,在相同浓度下,对同一腐霉菌菌丝体生长的抑制效果不同,培养液1/5TSB和NB明显强于KMB。综合所获结果可以看出,靶标病原菌对生防菌敏感性不一致;不同的培养基产生不同的代谢产物,对病原菌的抑制作用有明显差异。

In order to investigate the variation in sensitivity of different target pathogens to the biocontrol agent, Pseudomonas fluorescent LT6 and it＇s metabolite, the antagonistic effect of Pseudomonas fluorescent LT6 on 69 isolates of Pythium spp. was tested on a 1/5 TSA plate. Strain LT6 exhibited significantly dif- ferent antagonistic activities against different species of Pythium or different isolates of the same species. It showed the widest inhibition zone against Pythium ultimum （7.5 mm） , while it was lest effective to unknown species. The size of inhibition zones on those eleven tested isolates were all less than 3.0 mm. The sensitivity of Pythium spp. to PCA （phenazine-1-carboxylic acid）, produced by Pseudomonasfluorescent LT6 was variant. When the concentration of PCA was 7.0μg/mL, there were 28 sensitive isolates and 15 highly resistant isolates among the 54 tested isolates. These results demonstrated that the sensitivity of target pathogens to the biocontrol agent varies, and that the metabolite produced in different culture media exhibit distinctly different levels of suppression to pathogens.