The Study Of Screening And Anti-efifciency Of Mancozeb Resistant Antimicrobials Against Potato Early Blight

Trichoderma has been widely used worldwide for crop disease control. Trichodrema antagonists, whichprepared using Trichoderma conidia, however, are very sensitive to environmental conditions, resulting in theinstability of biocontrol effect. Therefore, it will be immense promising if antimicrobial strain with bothantagonism and resistance can be selected, thus while improving the biocontrol effect of Trichoderma, thedoses of chemical pesticides can be reduced, thereby the biocontrol of pathogens induced by the collaborativeeffect of bio-pesticides and chemical pesticides.In the presenting study,25mutant Trichoderma strains, which were remarkably mancozeb-resistant, wereselected through ultraviolet mutagenesis and drug-containing medium screen. Among the25mutants,7strainswith the growth rates more than20.00mmï¹'d^-1 were screened using growth potential method, and the Th-25had the highest average growth rate of27.00mmï¹'d^-1; In the tests to determine the resistance of Trichodermamutants, Th-13had the highest resistance with12.10gï¹'L^-1, all the6mutants had relatively stable resistantexcept for Th-17; Through plate confrontation tests, the7mutants had the abilities of antagonistic to5pathogens which were inherited from their parent strains, and Th-25had the most obvious antagonism to earlyblight, besides, its antagonistic effects to the other4pathogens were also comparatively higher than the othermutants; Th-25had the highest effect against early blight, both in vitro and in vivo tests, with the controleffects of88.23%and81.6%respectively. Hence, the Th-25was chosen as the suitable strain for furtherresearch.Th-25spore germination conditions analysis revealed significant relationships between spore germinationand medium components, temperature, and pH, but indirectly related to illumination. The optimal temperaturefor the germination of Th-25spore was around28℃, with pH5-6; the suitable nitrogen and carbon sourcewere peptone and lactose respectively. The results may not only provide reference for Trichoderma sprayingtime, but also the theoretical basis for the research of Trichoderma preparation.In field trials, conclusions were conducted according to survey on the incidence and disease index: thedisease indices of early blight in the fields sprayed with chemical bactericides, Trichoderma spore suspension and the mixture of the first two were1, while the indices in control fields were4; through post-harvest yieldmonitor, the yield of the fields sprayed with mancozeb, Trichoderma spore suspension and the mixtures ofmancozeb and spore suspension were increased by23.5-32.5%compared to the control fields, which indicatedthat the usage of mancozeb will reduced by using Trichoderma spore suspension without affecting the controleffects on potato early blight.