The Disease Prevention And Growth Promoting Effects Of Eight Biocontrol Agents

In order to popularizing the biocontrol strains which have excellent effects in laboratory into field agricultural production, this paper selected wheat and Chinese cabbage as the two research materials, to exploring the growth promoting effect on these two crops in field for two consecutive years and the control efficacy against wheat take-all and cabbage downy mildew. This paper selected three wheat varieties(xinong 979, xiaoyan 15 and S016-19) by means of petri dish standoff experiment, shake flask co-culture fermentation, pot experiment, hydroponic experiment and two consecutive years of field trials(a year in progressing), obtained strain SC11 which has good prevention effect and strain 153 which could applying in field stable and have ideal effect of growth promoting. The main results obtained as follows:1.Petri dish standoff experiment and shake flask co-culture fermentation showed that both five biocontrol strains and its fermentation filtrate have good inhibition on pathogen of wheat take all disease, both strain SC11 and 153 have the highest inhibition rate were 78.43% and 75.68% respectively. Strain SC11 in liquid culture environment can effectively inhibit the growth of hypha of Gaeumannomyces graminis var. tritici, the inhibition effect on the mycelial dry weight under the condition of 20 and 50 times dilution are 88.16% and 71.57% respectively.2.Indoor potted experiment of wheat showed that both five biocontrol strains can increase root length and leaf length under the premise of does not affect the seedling emergence, and further study on mechanism found that they not only directly promoting growth by increasing the root activity and chlorophyll content, but also improving the inducible resistance of wheat via increasing the Proline content and decrease MDA content. Strain SC11 has good control effect on wheat take-all disease, the inhibition rate is 33.16%.3.Two consecutive years of field trials showed that both seven strains can increase wheat tiller number, plant height, main root length and leaf area via improve resistance in jointing stage and booting stage, finally adding spike grain number, grain weight and grain, the mechanism of growth promoting as same as potted wheat. Strain 153 showed excellent stability and ideal for increasing production effect among single growth index, the same index of different varieties, different years and dosage forms, has certain value of commercial development.4.Indoor potted experiment of Chinese cabbage showed that all the five biocontrol strains can prevent and control Chinese cabbage downy mildew, both strain SC11 and 153 have excellent effect which close to the fungicide dimethomorph, the control effect are 59.38% and 37.5% respectively. All the strains also can improve Chinese cabbage growth and enhance the vitamin C content in the leaves. Strain AM3 and 153 can significantly improve the root activity of Chinese cabbage, close to the compound fertilizer, the largest increase 195.80% and 175.23% respectively.5.Chinese cabbage hydroponic experiment showed that biocontrol strain 153 could not play the ideal effect as in soil, further study showed that Hoagland nutrient solution is not be suitable to the live of strain 153, the best application way of 153 is root irrigation with fermented liquid.This study provide sufficient theoretical basis and practical guidance to applying strain 153 into agricultural production via two consecutive years of field trials.