Pathogenicity of Cell Wall Degrading Enzymes Produced by Botryodiplodia theobromae Pat. against Mangoes

[ Objective ] This study aimed to confirm the roles of cell wall degrading enzymes （CWDEs） produced by Botryodiplodia theobromae Pat. in the infec- tion of mango fruits. [ Method] Change of activities of five types of CWDEs produced by B. theobromae Pat. were studied under both in vitro culture and inocula- tion conditions, along with the pathogenicity and the ability of producing CWDEs of four post-harvest fangal pathogens（B, theobromae Pat. , Colletotrichum gloeos- porioides Penz. , Phomopsis mangiferae Ahmad and Dothiorella dominicana Pet. et Cif. ） which cause stem-end rot of mangoes. [ Result] B. theobromae Pat. was a- ble to produce polygalacturonase（PG）, pectinmethylgalacturonase（PMG）, polygalacturonic acid trans-eliminase （PGTE）, pectin methyltrans-eliminase （PMTE） and cellulase （ Cx. ） under both in vitro culture and inoculation conditions, of which activities of PG, Cx and PMG were significantly higher in than that in either PGTE or PMTE. Among three primary CWDEs, the peak of activities of PG and Cx appeared earlier and that of PMG occured later. The pathogenicity of B. theo- bromae Pat. was significantly higher than that of any other three pathogens; it is the same with the abilities of producing pectinase. [ Conclusion] This paper pro- vides theoretical bases for further exploring the mechanism of host-pathogen interaction and decreasing the post-harvest loss of mango fruits.

The quantity of OA and activity of cellulase and polygalacturonase are involved in variation of virulence in Sclerotium rolfsii

In order to understand the pathogenic mechanisms of Sclerotium rolfsii on peanut and to analyze the variation of virulence in S.rolfsii strains,the highly virulent strain(ZY2)and weakly virulent strain(GP3-1)were investigated under both in vivo and in vitro conditions.The results indicated that S.rolfsii directly infected peanut by producing infection cushions.ZY2 formed infection cushions earlier than GP3-1,and ZY2 produced a greater number of infection cushions compare to GP3-1.Both strains could utilize cellulose,xylose,or polygalacturonic acid in the Czapek medium.The activities of cellulase(CL)and polygalacturonase(PG)in the inoculated peanut stems increased significantly at 9 h after inoculation.The activities of CL and PG produced by ZY2 in the inoculated stems were significantly higher than that produced by GP3-1.Both strains could produce oxalic acid(OA),and the content of OA produced by ZY2 in the inoculated stems was higher than that produced by GP3-1.In summary,it suggested that S.rolfsii destroyed peanut cells through physical and biochemical factors by secreting a large amount of OA,CL and PG during the formation of infection cushions.The difference in OA content,activity of CL and PG produced by highly and weakly virulent strains played important roles in variation of virulence.