Characteristics of fungal community in stems of pitaya with canker disease

【Objective】 This study clarified the influence of canker on the fungal community in stem tissues of pitaya, to provide theoretical reference for the research on the occurrence and the prevention and control of pitaya canker.【Method】 The stem tissues of healthy and canker diseased plants of pitaya were collected, and the ITS sequences of rDNA of fungi in stem tissue were sequenced using Illumina high-throughput sequencing platform, so as to analyze the characteristics and differences of fungal communities in the stem tissues of healthy and diseased plants.【Result】 The diversity of fungal community in stem tissues of healthy plants was significantly higher than that of diseased plants(P<0.05, the same below), and the composition of fungal community in stem tissues of healthy plants was greatly different from that of diseased plants. Compared with healthy plants, the relative abundance of Ascomycota and Basidiomycota in stem tissues of diseased plants was higher, which were 49.11% and 10.90%, while that of unclassified_k__Fungi at the phylum level was lower(39.97%). At the genus level, there were 8 dominant genera in the stem tissue of the diseased plants. And the relative abundance of Neoscytalidium was the highest(33.29%). The relative abundance of 4 dominant genera, including Hannaella, Dirkmeia, unclassified_f__Nectriaceae, and Colletotrichum was significantly higher than that of the healthy plants, while Neoscytalidium, Vishniacozyma and Meira were not detected in healthy plants. There were 4 dominant genera in the stem tissues of healthy plants, of which the relative abundance of Geotrichum and Alternaria was significantly higher than that of diseased plants. The results of linear discriminant analysis effect size(LEfSe) showed that the difference between healthy and diseased plants could be best explained by Neoscytalidium and Vishniacozyma in diseased plants and Geotrichum in healthy plants. By analyzing the FUNGuild database to predict the trophic types of fungi, it was found that pathotroph(15.46%) contained the highest abundance in diseased plants, while saprotroph(7.95%) contained the highest abundance in healthy plants.【Conclusion】 When the pitaya canker occurred, the diversity of fungal community decreased significantly, and the composition of fungal community changed. When fungi of the pathotroph enriched significantly in stem tissues, the balance of the fungal community would be disturbed and probably trigger stem canker.