Studies On Carbendazim-resistance Of Colletotrichum Gloeosporioides Penz On Mango

The samples of Colletotrichum gloeosporioides of mango in different orchards in Guangdong and Hainan were collected and their resistance to carbendazim was tested in vitro. The results showed that the resistance to carbendazim was correlative to the times of applying fungicide.Percentage of resistant isolates from the orchards to which carbendazim has been applied frequently was higher than the ones seldom applied. The assay of sensitivity to carbendazim showed the lowest MIC of sensitive isolate was 0.110g/mL. However, resistant isolates were able to grow well on carbendazim as high as 500 g/mL,and the average, inhibiting rate on all tested isolates were lower than 6.5%. The resistance to carbendazim was stably inherited for 10 continuous transfers on earbendazim-free PDA medium. Biological characters of resistant and sensitive isolates were tested and compared thoroughly. The results showed that these biological characters were appeared no correlation of resistance to carbendazim. Resistant isolates were also resistant to thiophanate-methyl, benomyl and thiabendazole, but sensitive to diethofencarb and prochloraz. The resistant and sensitive isolates were inoculated on mango fruits which were soaked in carbendazim solution in vitro. Mango fruits were treated with the fungicide and then inoculated with resistant or sensitive isolates. The fruits inoculated with resistant isolates showed disease symptoms as severe as the control, while the fruits inoculated with sensitive ones didn't.The total DNA isolated from MBC-resistant and MBC-sensitive isolates of Colletotrichum gloeosporioides Penz(C.g.m.) of mango were used as templates in PCR amplification using consensus oligo nucleotide primers designed according to the known sequence data of tubulin-encoding gene (tub\ and tub2) of Colletotrichum gloeosporioides f.sp. aeschynomene (C.g.a. ). Only the primers designed according to C.g.a. tub2 amplified specific fragments.These amplifiedfragments were cloned and sequenced. The results showed that these 6-tubulin-coding gene have 1344bp and deduced 447 amino acid, and these sequences were highly homologous to C.g.a. tubl. MBC-resistant isolates did not carry the allelic mutation at amino acid codes 198 and 200 of 13-tubulin gene in comparison with the sensitive isolates. However, the amino acid altered in codes 181, 237 and 363. These results strongly suggested that the resistance of C.g.m. to carbendazim had the molecular mechanism similar to other known fungi, i.e. single base-pair point mutation in 6-tubulin gene resulted in resistance, except for C.g.m. mutant points were different.