Detection Of Resistance To Azoxystrobin And Biochemical Characterization Of The Botryodiplodia Theobromae From Mango In Hainan

Mango(Martgifera indica L.)is an important economic crop in the tropics and subtropics.The production and planting area of Mango in Hainan are all ranked first in China.But the occurrence of Mango diseases is very serious,directly restricting the production of mangoes.Studies have shown that mango stem end rot is an important post-harvest disease in the world,which is less serious than mango anthracnose.These pathogens have the characteristics of latent infection,which brings lot difficulty to the control of mango stem end rot.The strobiurin fungicide is a kind of cell respiratory inhibitor.Because of its broad inhibitory spectrum,it is widely used for controling agriculture diseases.However,due to its relatively single action site,fungicide resistance has become an important issue of this kind of fungicide.In order to understand the resistance status of strobiurin fungicides and the characteristics of isolates and the mechanism of resistance,we conducted researches in the following aspects.Firstly,the isolates of mango stem end rot were isolated and collected from Hainan mango orchard,and the resistance to pyraclostrobin and azoxystrobin was determined by differentiating dose method.The possible resistance mechanisms were investigated by the differences between the biological characteristics,osmotic pressure,enzyme activity and hypha relative conductivity of the azoxystrobi-resistantl isolate.The results show:1.The strains of Botryodiplodia theobromae were resistant to pyraclostrobin.The frequency of resistance was 58.95%.The frequency of resistant isolates to azoxystrobin was 91.58%.The ECso values are ranging from 3.12 mg/1 to 1525.43 mg/l,and it's a continuous normal distribution.Most isolates showed intermediate or high resistance to pyraclostrobin.2.The results of culture and biochemical characteristics of isolates showed that both high and low temperature environment can inhibit the growth of the isolates.The inhibitory effect of low temperature environment to resistant isolates was significantly greater than that of sensitive isolates.Low concentration of glucose inhibited the growth of the isolates as well as low concentration of sodium.The difference between different resistant isolates was not significant.The relative conductivity of the resistant isolates changes slowly and the permeability of the cell membrane decreases,which may be related to the resistance of the isolate.3.The results of the enzyme activities of the isolates showed that the POD,CAT and PAL activity of the resistant isolates increased,the GST activity decreased.The change of the enzyme activity under the stress of pyraclostrobin,the results showed that the GST activity of the isolates after treatment with a high concentration of pyraclostrobin became smaller.