Identification Of Endophytic Alternaria From Apple Bark And Their Potential Of Biocontrol Of Apple Tree Valsa Canker

Alternaria a common genus of fungi can produce a variety of toxins. Recently moreand more studies show that Alternaria has great application potential of biocontrol. Ourlaboratory has isolated Alternaria from the apple tree bark which can inhibit Valsa mali.This study focused on further identification of the endophytic Altemaria form apple treebark, and determinating the biocontrol effect of their culture filtrate and the activeingredient in the culture filtrate. In order to provide new materials for biocontrol of appletree Valsa canker.1. The species of endophytic Alternaria was identified by conidium morphology andsporulation pattern after single-spore isolation. Based on morphological characterization,the11isolates of endophytic Alternaria were identified as A. ellisii, A. dictamni, A.tenuissima, A. armeniacae, A. basellae, A. cerasi, A. catalpae, A. abutilonis, A.arborescens, A. destruens and A. typhonii.2. Microscopic observation showed that endophytic Alternaria could significantlyinduce mycelial deformity of V. mali. The main manner of inhibitory effect on V. mali isantagonism.3. The colonization ability test of endophytic Al107, Al67and Al58in appledetached shoots showed that Al107had the highest colonization rate of90%.4. The protective and therapeutic effects of culture filtrate, mycelial disc and sporesuspension of endophytic Al107, Al67and Al58on apple tree Valsa canker in vivo werecarried out. The results showed that different treatments of endophytic Alternaria had someinhibitory effect on lesion expansion. The highest inhibition effect of mycelial disc was Al107, and the highest inhibition effect of culture filtrate was Al67.5. The results of field trail showed that endophytic Alternaria culture filtrate hadprotective and therapeutic inhibitory effects on apple tree Valsa canker. The eradicativeeffect of Al107for the existing lesions reached60%. Wound healing could be formed bytreatments of culture filtrate after90days.6. The culture filtrate of Al67was not stable at the temperature of121℃,while it hada strong ultraviolet irradiation stability. When pH was7, the inhibitory activity of culture filtrate of Al67to V. mali was stable. After both acidic and alkaline treatments, theinhibitory activity was reduced.7. The culture filtrate of Al67was extracted by organic solvents which had differentpolarities. Organic phase of ethyl acetate and chloroform had high inhibition effect on V.mali, and water phase also had inhibition. Under extracting of methyl alcohol, bothprecipitation and supernatant had inhibition. So it described that active materials had bothmacromolecular compound and molecule compound.