| Tuber indicum,belonging to Ascomycete,is precious ectomycorrhizal fungi with important economic,ecological and medicinal value,and distributed widely in China.It is one of the most important edible fungi.The life cycle of T,indicum is mostly buried underground and is closely related to microbes in soil.Studies showed that microbes play an important role in promoting the growth and development of Tuber and the formation of its aromatic odors,but the specific mechanism is still unclear.Currently,the associated microbes of T.indicum from different regions and the possible ecological functions of microbes have not yet been carried out.In this study,we compared the microbial diversity in different regions of.indicum by high-throughput sequencing technology and traditional isolation culture method.We also comparatively analyzed the content of chemical composition(including volatile organic compounds,free sugars,polysaccharides,phenols,flavonoids,etc.)of the fruiting bodies of T.indicum from different geographical regions using GC-MS,HPLC etc.The aims were to clarify the influence of geographical distribution on the associated microbes and contents of chemical composition of T.indicum fruiting bodies and lay a theoretical foundation for the quality evaluation standards for different geographical sources in the future.The main contents were summarized as below:1.The analysis of associated bacterial diversity of T.indicum from 6 regions of southwest,northeast and north China showed that Bradyrhizobium was the dominant genus in fruiting bodies of T.indicum(2.66-47.66%),but the composition of bacteria was regional difference.Streptomyces(4.65%)was dominate in ectomycorrhizae,and Sphingomonas(3.12-6.26%)was dominate in soil.2.The analysis of contents of chemical composition and antioxidant activity of T.indicum fruiting bodies from different regions showed that truffles from Qujing,Yunnan province possessed the highest content of free sugar(23.67 mg/g dw),total phenols(4.46 mg/g dw),flavonoids(2.31 mg/g dw)and the strongest DPPH radical-scavenging activity with EC50 value=0.93±0.11 mg/mL and ABTS scavenging activity with EC50 value=0.68±0.13 mg/mL.Tibetan truffles possessed the highest content of polysaccharides(115.24 mg/g dw).The volatile organic compounds in T.indicum are mainly alcohols(28.30-69.65%),aldehydes(5.35-23.21%),ketones(1.88-16.10%),aromatic compounds(0-0.91%),sulfor compounds(0-0.11%),etc.,and the composition and relative content showed regional differences.3.60 cultural bacteria were isolated from T.indicum fruiting body,belonging to 4 phyla and 24 genera.Among them,Pseudomonas,Alcaligenes faecalis,Microbacterium,Arthrobacter were dominant.Studies on their physiological activities showed that 13 of them could grow on Burk*s nitrogen-free medium,8 had nitrogenase gene nifH,and 1 had phosphorus capacity,implying their potential important functions in truffles' life cycle. |
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