Isolation Of Endophytic Fungi From Apple Bark And Their Biological Control Effect On Valsa Canker

Apple canker is one of the most serious diseases which occurrs almost all apple production in China. It seriously affect the healthy development of apple industry. As the environmental concern and fruit quality have been emphasized by many people, chemical control is getting restricted. Endophytic fungi which is ubiquity in host plant and can produce many kinds of active material. More and more investigations revealed that many endophytic fungi have great potential of biocontrol on plant diseases. This study focused on endophytic mycobiota and their variation in apple bark, screening endophytic fungi which have inhibitory action to V. ceratosperma, affording a new mentality to the control of apple canker. The main results are as follows.1. 459 strains of endophytic fungi were isolated from healthy apple bark by method of tissue isolation, based on morphological characteristics and 18 SrDNA sequence alignments, 18 genera were identified. They are Alternaria, Phomopsis, Phoma, Coniothyrium, Cladosporium, Penicillium, Fusarium, Myrothecium, Diaporthe, Macrophoma, Nigrospora, Aspergillus, Gibberella, Chaetomium, Setosphaeria, Arthrinium, Trichoderma, Clathrospora. Clathrospora sp. and Setosphaeria sp. have not been known in previous reports about endophytic fungi.2. Alternaria sp. existed universally in every part of apple bark.3. Screening antagonistic endophytic fungi to V. ceratosperma by confrontation test, in the dual culture assays 24 endophytic fungi isolates showed inhibition rate above 40% and 87.5% of them belong to Alternaria sp.. If inoculated endophytic fungi three days earlier, the inhibitory rates of all 11 endophytic Alternaria sp. exceed 80%.4. The inhibitory effect of ME culture filtrate had great difference between different strains, the Al 6 had the highest inhibitory effect to the mycelial growth of V. ceratosperma, the inhibitory rate reached 83.76% when the content of culture filtrate was 10%. The Al 58 had the highest inhibition effect to conidia germination, the inhibition rate was 82.42%.5. The inhibitory effect of volatile compounds produced by endophytic Alternaria sp. to the colonies diameter and mycelia dry weight of V. ceratosperma was increased along with the increase of cultivated time. Al 67 had the highest inhibitory effect to the mycelial growth of V. ceratosperma when being cultivated 8 days. The inhibitory was 24.41%. Al 107 had the highest inhibitory effect to the mycelia dry weight of V. ceratosperma when being cultivated 8 days. The inhibitory rate reached 82.58%.6. When we firstly inoculated the antagonistic endophytic fungi on apple tree, the followed infection and lesion extension of V. ceratosperma could be inhibited effectively. The most effective one was Al 107 which totally inhibited the infection of V. ceratosperma under the condition of artificial inoculation.