Abstract:

Objective: This study aims to investigate the fungal groups associated with pest Agrilus mali (Coleoptera: Buprestidae) in the wild apple (Malus sieversii) forests in Xinjiang and their diversity, and to study the death of trees caused by A. mali and the associated fungi altogether. Method: The strains of the associated fungi were obtained by isolating the tissues of the beetle larvae, pupae, adults and galleries. The identification was conducted based on the molecular data. The diversity of the associated fungi was analyzed using the statistical and graphic software. Result: The result showed that totally 57 genera of the associated fungi, belonging to six classes and eighteen orders, were isolated. Among them, 40 genera were isolated from galleries, 37 genera from adults and 34 genera from larvae+pupae, respectively. As a whole, Alternaria is the dominant genus for all experimental materials, with the relative abundance of 30.58%, followed by Fusarium which was 13.8%. In terms of the isolation materials, Alternaria was also the main group from the adults, Dothiorella was the main group from the larvae+pupae, and Cytospora was the main group from the galleries, with the relative abundance 50.30%, 13.91% and 16.96%, respectively. Besides, in the three experimental materials, the β-dissimilarity index of the fungi from the larvae+pupae and adults were the highest (Jaccard dissimilarity index=0.608, Bray-Curtis dissimilarity index =0.683); the two dissimilarity indices of fungi from the adults and galleries were quite different (Jaccard dissimilarity index = 0. 490, Bray-Curtis dissimilarity index = 0.609); Shannon-Wiener index (H' = 2.949 6) and Richness index (R = 7.206 7) of the fungi from the galleries were the highest, while Pielou index (J=0. 830 2) of the fungi from the larvae +pupae was the highest; adults fungi population diversity index (H' = 2.012 8), Pielou index (J=0.557 4) and Richness index (R=6.214 4) were the lowest, indicating that the adult carried relatively less diverse fungi, however, the proportions of several main fungi species were significantly different among the whole associated fungal groups. Conclusion: The associated fungi of A. mali are diverse, with the various compositions and numbers on three experimental materials. For four main associated genera fungi, Fusarium usually leads to branches withered and rot of their host plants, while Dothiorella and Cytospora cause plants canker. Therefore, we suggest that the wild apple trees are likely endangered by both A. mali and its associated fungi above western Tianshan Mountains in Xinjiang. The result provides insights to the communities and structures of the associated fungi of A. mali. In addition, the findings would be helpful to establish the effective management strategy of the pest insect.

Key words: wild fruit forest, Agrilus mali, associated fungi, diversity