Study On Resistance Of Colletotrichum Glosoporioides (Penz.) Sacc. To Prochloraz

Prochloraz is an effective fungicide to control mango anthracnose disease causedby Colletotrichum glosoporioides （Penz.） Sacc.. But the study of prochloraz-resistanceof C.glosoporioides is still in blank. The resistance of C.glosoporioides to prochlorazwas studied in this paper. Prochloraz-resistant mutant（MCGM） was obtained from wildisolate （MCGW） through prochloraz-taming.By comparing the fitness of MCGM andMCGW, the resistance risk of prochloraz was preliminary assessed. And the resistancemechanisms were also studied. The results could be summarized as follows:MCGM was obtained through prochloraz-taming at the concentration of12g·mL^-1. After successively cultured for9generations on fungicide free PDA, theresistance of the mutant was basically stable.Compared with MCGW, dry weight of mycelia, size of mycelia and conidiumgermination rate of MCGM were significantly increased. However, the growth rate,sporulation, appressorium formation, conidium and appressorium average size ofMCGM were inordinately decreased.Pathogenicity of MCGM to the flowers of mango was higher than MCGW.However, the pathogenicity of MCGM to the young fruits were significantly lowerthan MCGW.There were no cross resistance between benzimidazole, obvious positive crossresistance between hexaconazole, triadimefon, imazalil. So the mechanisms offungicides similar with prochloraz should be avoided in the process of field control.The phenomenon of growth inhibition at the tip of the hyphae and excessivebranching of MCGM was observed, after treated with different concentrations ofprochloraz. It showed that prochloraz inhibited the tip growth, but promoted thebranching. Effects of prochloraz on the change of cell structure were examined byusing electron microscopy techniques, the result show that prochloraz causedsignificantly changes which included irregular thickening of cell walls, increasingvacuoles, lipoids and mitochondria. It was assumed that these changes were aimed toexcrete the prochloraz.The data of electrical conductivity showed that cell membrane permeability ofMCGM is significantly higher than MCGW. Osmotic pressure sensitivity revealedthat both MCGW and MCGM were not sensitive to high osmotic pressure of salt andsugar. Respiration of MCGM was increased after treated with different concentrationsof prochloraz. Prochloraz had dual influences on MCGM.The sequence of CYP51gene with1720bp was cloned and blasted. The resultsshowed that the reason of resistance to prochioraz was point mutation of amino acid.The expression analysis of mRNA of CYP51gene was conducted by qPCR，Theresult showed the excessive expression of CYP51gene was also the resistantmolecular mechanism of C.glosoporioides to prochloraz.