Antagonism Of Endophytic Fungi From Cucurbits Against Three Soil-borne Phytopathogens And Their Inhibitory Effect On Cucumber Rhizoctonia Rot

To understand the effects of endophytic fungi from cucurbits on common soil-borne diseases, the antagonism of459endophytic and12rhizosphere fungal isolates from different tissues of cucurbits, and4endophytic or rhizosphere fungal isolates from bean root was investigated by using the dual culture method against pathogens Fusarium oxysporum f. sp. cucumerinum, Rhizoctonia solani, and Sclemtinia sclerotiorum, respectively. Challenge inoculation into cucumber seedlings was conducted with the endophytic fungal isolates antagonistic against R. solani. The main results obtained are as follows:There were14isolates showed antagonistic against F. oxysporum f. sp. cucumerinum,29isolates against R. solani, and68isolates against S. sclerotiorum, respectively. Among them, there were’ isolates to F. oxysporum f. sp. cucumerinum,22isolates to R. solani, and48isolates to S. sclerotiorum accounted for10.1%,4.6%and1.5%of the tested isolates, respectively, with the colonial growl inhibition rate of50%or above against the pathogenic fungi. The endophytic fungal isolates inhibite growth of the tested pathogenic fungi by antibiosis, competition for substrate, and mycoparasitism. T isolate F30produced the widest inhibition band,19mm in width, against F. oxysporum f. cucumerinum. The isolate JCL143produced the widest inhibition bands,13mm in width, against solani, and16.7mm in width, against S. sclerotiorum.Among the isolates produced the colonial growth inhibition rate of70%or above against e pathogen tested, there were3isolates, belonging to Nigrospora, Penicillium, and Rhizocto a, respectively, against F. oxysporum f. sp. cucumerinum; there were11isolates, belonging to Altern a, Apiospora, Bipolaris, Colletotrichum, Exserohilum, and Fusarium, respectively, against R. solani; re were18isolates, belonging to Fusarium, against S. sclemtiorum.The fermentation broth of the endophytic fungal isolates with obvious antibiosis was test for inhibitory action against colonial growth of the tested pathogenic fungi. There are4isolates a31isolates whose fermentation broth showed inhibitory action to R. solani, and S. scleroi im, respectively. The fermentation broth of the isolates JCL19and3F21reached61.4%and.6%respectively of the colonial growth inhibition rate against R. solani. The fermentation broth the isolates3F9and4F34reached90.9%and89.7%respectively of the colonial growth inhibit:rate against S. sclerotiorum.The hyphal suspensions of the isolates JCL39, JCL143and5F37, were inoculated respectr into cucumber seedlings with different methods. In the inoculation test with the root-wounded me d, the control effects of the isolates JCL39, JCL143and5F37were9.3%,81.3%and67.4%, respe ely,7days after inoculation with R. solani. That the germinated seeds were dipped in a conidial sus ion of isolate JCL39before seeding reduced disease incidence and increased emergence rate of the;umber seedlings. In control without dipping treatment, the disease incidence of the seedlings reacl66.7%, and the disease incidence of the seedlings with dipping treatment was as low as16.7%.The treatment, germinated seeds dipped in a conidial suspension of isolate JCL39or143for30min, showed the best inhibitory effect on seedling Rhizoctonia rot among different di ig times including10,30and60min. The relative control effects of the two isolates were24.1%and58.6%respectively7days after inoculation with R. solani. In the test of different root-wounded inoculation times with hyphal suspension, inoculation with isolate5F37once showed the best control effect on seedling Rhizoctonia rot, which reached61.1%7days after inoculation with the pathogen. Inoculation with isolate JCL143three times showed the best control effect on seedling Rhizoctonia rot, which reached52.8%7days after inoculation with the pathogen.The experimental results proved that some endophytic fungi from cucurbits has antagonistic effects on the tested soil-born pathogens, some endophytic fungal isolates has inhibitory effect on Rhizoctonia rot of cucumber seedlings. The seedlings pre-inoculated with endophytic fungi can inhibit the disease in different degrees in accordance with the endophytic fungal isolates and inoculation methods. These results can contribute to understanding the function of endophytic fungi from cucurbits and their utilization.