Isolation and identification of endophytic fungi resistant to three apple pathogens from the branches of Malus sieversii

Abstract：【Objective】In order to provide new fungi resources for the biological control of apple diseases, the endophytic fungi from healthy branches of Malus sieversii were isolated and identified. 【Methods】Endophytic fungi were isolated from branches of M. sieversii by tissue separation method. Strains were screened out with significant antagonism activity against three pathogens (Botryosphaeria dothidea, Colletotrichum gloeosporioides and Phomopsis mali) of apple trees. The morphology and molecular biology were applied to determine the classification of the strains.【Results】A total of 75 endophytic fungi were isolated, among which 56 strains were from the phloem and 19 strains from the xylem. Five strains (E-m6, S-p5, S-m2, S-p6 and E-p5) were screened out with strong inhibitive effects on mycelia growth of three apple tree pathogens. The highest inhibitory rates of the selected strains against B. dothidea, C. gloeosporioides and P. mali were 73.39% , 73.52% and 82.19% , respectively. The lengths of ITS regions of E-m6, S-p5, S-m2, S-p6 and E-p5 were 593 bp, 554 bp, 585 bp, 430 bp and 575 bp, respectively; and the length of TUB gene of S-p6 was 420 bp. Combined with morphological, ITS and TUB phylogenetic trees analysis, the strains E-m6 and S-p5 were identified as Aspergillus ni-ger, S-m2 was identified as Aspergillus flavus, S-p6 was identified as Rosellinia sp., and E-p5 was identified as Chaetomium globosum.【Conclusion】In this study, five strains of endophytic fungi with biocontrol potential were screened out from M. sieversii branches, which could provide not only new microbial resources for the biological control of apple stem diseases, but also a basis for the study on endophytes of M. sieversii in the future.