Cell-wall Degrading Enzymes Produced By Neofusicoccum Parvum Which Causing Fruit-rotting In Harvested Chinese Olives And Its Pathogenicity

Chinese olive[Canarium album(Lour.)Raeusch.]is a special subtropical fruit in South China,which belongs to Burseraceae Canarium L..Chinese olive is very popular,because of its high nutritional and medical values.However,infections of pathogens seriously affect the quality and yield of olive fruit.During the process of pathogenicity,pathogenic fungi can produce cell wall degrading enzymes(CWDEs).CWDEs are important factors causing plant diseases.In this study,'Tanxiang'Chinese olives were chose as the research material.The dominant pathogenic fungi causing fruit-rotting in harvested Chinese olives,the fermentative conditions and pathogenicity of CWDEs which were produced by the pathogenic fungi were investigated.The results are as follows:1.Pathogenic fungi from Chinese olives were isolated by using tissue isolation methods in some critical growth period of Chinese olive period(blooming period,young fruit period,rapid growth period,the period of pre-maturation and the period of maturation).The dominant pathogenic fungi was identified by its morphological characteristics,pathogenicity and rDNA-ITS sequences.The dominant pathogenic fungi was determined to be Neofusicoccum parvum.2.The improved Czaper cultural medium was used to culture Neofusicoccum parvum.The filtrate was obtained by centrifugation.The supernatant liquid was the crude enzyme solution.The major CWDEs(Cx,?-glucosidase,PMG and PG)were detected in crude enzyme solution.Five factors including cultural time,cultural temperature,the original pH of cultural medium,types of carbon source and nitrogen source were chose to study the effect of CWDEs which were produced by Neofusicoccum parvum.Based on the above results,cultural time,cultural temperature,types of carbon source and concentration of nitrogen source were used to design the L9(34)of orthogonal test.The results showed that the optimum cultural time was 3 d,the optimum cultural temperature was 28?,the optimum original pH of cultural medium was 5.0,the optimum carbon source was 1%CMC or 1%pectin,and the optimum nitrogen source was 1%KNO3.The optimal combinative condition for producing Cx were:3 d,28?,1.0%CMC,0.8%KNO3.The optimal combinative condition for producing PG were:2 d,25?,1.0%pectin,1.2%KNO3.3.Cx,?-glucosidase,PMG and PG activity could be detected from healthy parts,the boundary between diseased and healthy parts,and diseased parts of Chinese olive fruit infected by Neofusicoccum parvum.PG activity was the highest among the four kinds of CWDEs.The four kinds of CWDEs activity in the boundary between diseased and healthy parts were the highest The CWDEs activity in diseased parts were higher than those in healthy parts.Cellulase and pectinase produced by Neofusicoccum parvum could destroy cell membrane and lead to injury of Chinese olive fruit.In addition,the mixed enzyme(cellulase and pectinase in a ratio of 1:1)caused the worst devastating effects to cell membrane,its lesion rate was up to 53.10%,followed by pectinase.The lesion rate of cellulase was the lowest.Chinese olive fruit processed by the CWDEs were appear to different degrees of dark spots and rots.The symptoms of fruits treated with mixed enzymes were more serious than that of pectinase or cellulose respectively.The severity of fruits treated by pectinase or cellulose was little different.