Studies On The Relationship Betwween Endophyte Funqi And Allelopathy In Rice (Oryza Sativa L)

Strong allelopathic rice PI312777 and weak allelopathic rice Lemont were used as materials, and they were seeded in wetland and upland respectively, . With the aid of flat-panel culture and T-RFLP technology, endophytic fungi were isolated, and identified respectively, then the community diversities of the endophytic fungi were further studied. Suppression of the fungi's fermentation liquor on the growth of barnyardgrass were tested . The results are summarized as follows:1.A total of 103 endophytic fungi were isolated from the four test samples of the two rice accessions under two soil water conditions ( wetland and upland) by plate culture method. Those endophytic fungi mainly belong to ascomycetes and deuteromycetes. Endophytic fungi isolated from the four tested samples showed regular quantitative changes,showing that 38,26,22 and 17 strains were respectivly isolated from the seedlings of allelopathic rice PI312777 grown in upland and wetland respectively, and from the seedlings of weak allelopathic rice Lemont under wetland and upland conditions. As for two treatments, Fusarium are both the dominant flora in two kinds of rice under the two soil water conditions; separation frequency of P.chrysosporium ( functioning in degradating phenolic acids) and Claviceps ( functioning in producing alkaloids) from PI312777 was higher than that from Lemont, and under drought stress, the separation frequency of the two types of fungi was significantly higher in allelopathic rice accession than that in its counterpart. In addition, specific fungus Chaetomium ( functioning in producing alkaloids) was only isolated from allelopathic rice PI312777.2. Results from the effect of strain fermentation liquor on barnyardgrass and rice indecated that fermentation liquor of more than 85% of sterile endophytic fungi showed inhibited the growth of barnyardgrass roots to different extents, whereas didn't suppress the growth of rice. It was also found that Fusarium spp., Trichoderma, CurvulariaBoed ,Claviceps , and Chaetomium spp. fungi had higher inhibition rate of the target weed, showing more than 50% inhibition rate . Chaetomium fungi was only isolated from PI312777, CurvulariaBoed fungus was specific in the seedling of PI312777 grown in upland, and the separation frequency of Phanerochaete chrysosporium ( the inhibition rates to roots and stem of barnyardgrass were 92.36% and 75.38 %) and Claviceps purpurea in PI312777 was higher than that in Lemont, and the separation frequency of Claviceps purpurea from the same rice was always higher in upland treatment than that in wetland.3. Amplified ITS fragments of the endophytic fungi were respectively digested by restriction endonuclease Haeâ…¢and Hinfâ… , and results analyzed by capillary electrophoresis showed that there were significant differences in endophytic fungi community structures of four samples . T-RFs digested by Haeâ…¢for PI312777 grown in upland and wetland , and for Lemont grown in upland and wetland are 28, 19, 17 and 16 respectively; T-RFs digested by Hinfâ… for PI312777 grown in upland and wetland , and for Lemont grown in upland and wetland are 29, 24 , 26, 13 respectively. The results showed that 22 species of endophytic fungi mainly belong to Basidiomycotina fungi. Bioinformatics analysis of T-RFs showed that quantity of saprophytic fungi which can degrate phenolic acids in allelopathic rice PI312777 was higher than that in Lemont, at the same time, dry condition stress could also induce the increase of some endogenous fungi such as Scleroderma cepa (releasing ergosterol), Cortinarius sp.( releasing Oleh toxins), Amanita (releasing Amanita toxins) are specific fungi in PI312777.In summary, it's a mutual influence entity between rice endophytic fungi and the host.The differences of rice allelopathic potential can obviously affect the community structure of endophytic fungi, and on the contrary, different community structure of endophytic fungi can also affect the intensity of rice allelopathy. Endophytic fungi might affect the intesity of allelpathy in the host rice directly through inhibiting the growth of accompanying weeds by metabolites produced and released from rice.