Study On The Resistance Of Mango Anthracnose Pathogen Colletotrichum Gloeosporioides To Several Fungicides

Mango anthracnose disease, which occurs commonly in mango producing area, is an important factor restricting the mango production in our country. At present, the main strategy to control the disease still relies on fungicide application. It was reported that mango anthracnose pathogen had evolved a resistance to the fungicide carbendazim, which brings a new threat to mango industry. The sensitivities of C. gloeosporioides isolates to thiophanate-methyl, thiabendazole and prochloraz were tested by mycelial growth rate method. The sensitivities of C. gloeosporioides isolates to azoxystrobin were tested by spore germination method. The sensitivities, and occurrence of C. gloeosporioides isolates to the 4 fungicides, including thiophanate-methyl, thiabendazole, prochloraz and azoxystrobin were evaluated in this paper. The biological characteristics, cross-resistance to different fungicides, and the molecular mechanism of resistace of C. gloeosporioides were also studied. The main results were as follows :1. The sensitivity baseline of isolates of C. gloeosporioides to thiophanatemethyl and thiabendazole were 0.9244±0.0262 ?g/m L and 0.1699±0.0048 ?g/m L, respectively. The results showed that 5 of 181 isolates were resistant to thiophanate-methyl, and 5 of 105 isolates were resistant to thiabendazole, accounted for 2.76% and 4.76%, respectively. The resistant isolates had no significant differences in biological characteristics such as colony morphology, mycelium growth rate, spore germination, sporulation and pathogenicity. There was a positive cross resistance between thiophanate-methyl and thiabendazole, while no cross resistance among the fungicides thiophanate-methyl, prochloraz, chlorothalonil, azoxystrobin, difenoconazole and fludioxonil. A 1837 bp DNA fragment from the ?2-tubulin gene was cloned and sequenced, and the result indicated that resistance of C. gloeosporioides to thiophanate-methyl was caused by point mutation at codon 198(GAG? GCG, E198A).2. The sensitivity baseline of isolates of C. gloeosporioides to prochloraz was 0.0666±0.0019 ?g/m L.The results showed that the vast majority of 214 isolates were sensitive isolates and only 32 low-resistance isolates were found, accounted for 15%. Mutants resistant to prochloraz were obtained through UV irradiation and fungicide induction. After 9 generations of transfer, the mutants showed a stable resistance, while the level of resistance was somewhat lowered. Compared with sensitive strains, resistant mutants had significant decreased in mycelium growth rate, sporulation, spore germination and pathogenicity. There was no cross resistance among the fungicides prochloraz, thiophanate-methyl, chlorothalonil and fludioxonil.3. The sensitivity baseline of isolates of C. gloeosporioides to azoxystrobin was 4.4803±1.4715 ?g/m L. The results proved that SHAM had a synergistic effect to azoxystrobin.