Screening Of Biocontrol Strains Against Four Plant Fungal Diseases

In order to screen the antagonistic antibiotics against some important pathogenic fungis such as Alternaria solani,Phytophthora capsici,Fusarium oxysprizan,Botryosphaeria berengerianade and Glomerella cingulate,the agar plate method,growth rate method,tissue experiment and pot experiments were systematically used to filter the 454 strains of actinomycetes and 30 strains of bacterium.And one strain bacteria B1409 with good antifungal activity was studied to reveal the biocontrol mechanism using the pot experiments to detect its effect on the growth potential and activities of defense-related enzymes in tomato plants and pepper plants.The main results are as follows:1.Five pathogenic fungis: Alternaria solani,Phytophthora capsici,Fusarium oxysprizan,Botryosphaeria berengerianade and Glomerella cingulate were used for the first screening by the agar plate method.The results were that: 19 strains actinomycetes posses activity against Alternaria solani and Botryosphaeria berengerianade,in which 7 strains were effective to both pathogenic fungins,8 strains were only effective to Alternaria solani,and 4 strains were only effective to Botryosphaeria berengerianade.Bactiria B1409 has better activity against pathogenic fungins offered.Four pathogenic fungis: Alternaria solani,Phytophthora capsici,Fusarium oxysprizan and Botryosphaeria berengerianade were used for the secondary screening by the growth rate method.The results were that: 7 strains actinomycetes possess inhibition activity against pathogenic fungin Alternaria solani,in which the inhibition efficacy of strains YC-15,YC-18 and HN-5 reached to 80.0 %.Strains YC-15,YC-18,YC-36,EC-13,EC-24 and HN-5 have good activity against Botryosphaeria berengerianade which inhibition efficacy arrived to 70.0 %.The inhibition efficacy of strains YC-15 and YC-18 against Phytophthora capsici arrived to 60.0 %.And bactiria B1409 showed best activity against 4 pathogenic fungis,the inhibition rates of which all reached to 80.0 %.2.7 strains actinomycetes including YC-15,YC-18,YC-28,YC-36,EC-13,EC-24 and HN-5 and bacteria B1409 were revealed the the inhibition effect to Alternaria solani and Botryosphaeria berengerianade using tissue experiment.The results were that: the control efficacy of fermentation broth to Alternaria solani of both YC-18 and EC-24 reached to 50 %,and which of HN-5 and EC-13 arrived respectively to 60.0 % and 71.7 %.The control efficacy of fermentation broth to Botryosphaeria berengerianade of YC-18 and EC-24 both exceeded 60.0 %,and which of HN-5 achieved 82.5 %.Bactiria B1409 had the best efficacy to all the fungins which all exceeded 80.0 %.3.Pot experiments of B1409 against tomato early blight,phytophthora root rot and cucumber Fusarium wilt were also tested.The results were that: the preventive efficacy and therapeutic efficacy of B1409 to tomato early blight were 67.8 % and 41.2 %;the preventive efficacy and therapeutic efficacy of B1409 to phytophthora root rot were 61.2 % and 56.4 %;the preventive efficacy and therapeutic efficacy of B1409 to cucumber Fusarium wilt were 47.0 % and 22.5 %.4.The mechanism of bacterial B1409 was further discussed.Electron microscopy showed that B1409 could inhibit the growth of mycelium and deform the mycelium.Different concentration of fermentation broth of B1409 was also tested to reveal its effect on the growth potential and activities of defense-related enzymes in tomato plants and pepper plants using pot experiments.The results were that: the growth potential and activities of defense-related enzymes in both tomato plants and pepper plants chronically irrigated with different concentration of fermentation broth could be enhanced proportionally.The activities of defense-related enzymes in both tomato plants and pepper plants once irrigated with different concentration of fermentation broth could be influenced differently.In summary,antagonize bacteria B1409 could effectively inhibit three pathogenic fungal diseases: tomato early blight,phytophthora root rot and cucumber Fusarium wilt in pot experiments by inhibiting pathogenic fungis hyphae growing,promoting plants growing and activities of defense-related enzymes in plants so that B1409 should be further studied.