Screening fungal endophytes from apple trees and their antagonistic characteristics

Objective To screen fungal endophytes against Valsa malimiyabe and Glomeralla cingulata from apple trees and explore their inhibitory effects.

Method Fungal endophytes were isolated from roots, stems and rhizosphere soil of healthy apple plants. Their antifungal activities against V. malimiyabe and G. cingulata were examined using in vitro dual culture assay. Heat-resistant properties of antifungal substances were tested using the fermentation culture of the isolated fungal endophytes.

Result Eighteen endophytic fungus strains belonging to three genera were isolated and half of the 18 strains were from stem. The dual culture assay showed eight strains had above 60% inhibition rate against V. malimiyabe and G. cingulata. J₂, J₁₆ and J₁₇ strains strongly inhibited V. malimiyabe with the inhibition rates of 82.75%, 84.31% and 82.35% respectively. The inhibition rate of T₁ to G. cingulata reached 80.67%. The culture filtrates of fungal endophytes J₂, J₁₆, J₁₇, J₂₄, T₁ inhibited the conidia germination of both pathogens, and all of the inhibition rates were not less than 39.55% and the highest value was 69.75%. The sterile filtrate of J₁₁ and T₁ showed high heat stability at 121 ℃, while J₂ lost bioactivity at 100 ℃.

Conclusion Fungal endophytes J₂, J₁₁, J₁₆, J₁₇ and T₁ have strong inhibitory effects against V. malimiyabe and G. cingulata, and therefore are potential candidates for biological control of these two pathogens.