攀枝花白块菌的侵染对美国山核桃生长发育与根际微生态的影响

Tuber panzhihuanense is the most precious commercial white truffle in China and Carya illinoensis is a kind of nut which has been localized and cultivated wildly in China, both of which have high economic value. Due to the natural and anthropogenic factors, the resources of the natural truffles are decreasing year by year and the artificial cultivation is urgently needed. However, because of the long cultivation period and the slow yield of truffles, the acceptance for farmers is very low in China now. Cultivating the ectomycorrhizal seedlings of T. panzhihuanense with C. illinoensis can shorten the yield cycle of truffle cultivation and thus improve farmers’ acceptance. However, the current research on truffle seedlings in China is mainly focused on cultivating techniques, and the effects of T. panzhihuanense infection on the growth of the host plant and rhizosphere microecology of C. illinoensis remain unclear. Therefore, this study intends to investigate the effects of T. melanosporum infection on the growth of C. illinoensis, the physical and chemical changes in rhizosphere soil and the structure of the rhizosphere microbial community using metagenomics and WinRhizo root analysis system as the main methods, combined with convention technologies of the plant and soil. This research would explore the mechanisms of the interactions between the microorganism, C. illinoensis, T. panzhihuanense and ectomycorrhizae, which could provide theoretical guidance for the artificial cultivation of ectomycorrhizal seedlings of T. panzhihuanense with C. illinoensis.

攀枝花白块菌是中国最珍贵的白块菌，美国山核桃是已本土化且大面积栽培的坚果，二者均具有较高的经济价值。由于自然和人为因素影响，野生块菌资源逐年锐减，急需开展人工栽培。然而由于块菌栽培周期过长，收益见效慢，使得其接受度低。而“攀枝花白块菌-美国山核桃”菌根苗的培育则可以缩短块菌栽培的收益周期，提高民众对于块菌栽培的接受度。但是，国内对于块菌根苗的研究主要集中在培育技术上，攀枝花白块菌侵染美国山核桃过程中对宿主植株生长发育及根际微生态的影响规律我们并不清楚和明确。因此，本研究拟以宏基因组学、WinRhizo根系分析系统技术为主要研究手段，结合植物、土壤常规技术，开展攀枝花白块菌侵染美国山核桃对植株生长发育、根际土壤理化变化、根际微生物群落结构等的影响，探索细菌、真菌等微生物与美国山核桃、块菌、外生菌根相互之间的作用机制，从而为“攀枝花白块菌-美国山核桃”菌根苗培育和人工栽培提供理论指导。

块菌是珍贵的外生菌根资源，人工栽培难度大。由于自然和人为因素，野生块菌资源逐年锐减，急需突破对块菌的人工栽培。攀枝花白块菌是中国最珍贵的白块菌，印度块菌是我国目前主要商业块菌。美国山核桃是已本土化大面积栽培的坚果树种，因此开展“攀枝花白块菌、印度块菌-美国山核桃”菌根苗培育，并研究块菌侵染过程中宿主植株生长发育及根际微生态变化规律有助于探索块菌的生长发育及其共生机制，能缩短块菌栽培的收益周期，从而为攀枝花白块菌及印度块菌人工栽培提供理论指导。因此，本研究开展块菌菌根苗培育，研究了攀枝花白块菌及印度块菌侵染对植株生长发育、根际土壤理化性质、根际微生物群落等的影响。研究结果表明，攀枝花白块菌及印度块菌侵染显著影响了宿主植株生长发育及生理水平，提高了宿主茎围和生物量(P<0.05)，尤其显著提高了宿主根系抗氧化酶系统活性(P<0.01)，并能显著提升根系氮代谢水平 (P<0.05)。植株根际理化性质也对两种块菌的侵染有所反馈，全氮、速效氮、全磷、速效磷、速效钾含量在不同测定阶段发生了显著变化(P<0.05)，其中根际有效磷含量在所有测定阶段均显著提升(P<0.01)，说明块菌侵染能促进根际有效磷养分的释放。此外，攀枝花白块菌及印度块菌侵染重塑了宿主根际微生物群落并影响其潜在功能。两种块菌侵染均显著降低了根际微生物群落alpha多样性(P<0.05)，攀枝花白块菌侵染提高了根际总基因数目。Pseudomonas, Archangium, Azospirillum, Hypericibacter, Nitrospira等在攀枝花白块菌侵染后丰度显著提高(P<0.05)。而有些菌群在两种块菌侵染后丰度显著降低，例如Lacunisphaera, Paraflavitalea, Caulobacter, Paraflavitalea, Novosphingobium (P<0.05)，说明块菌与宿主根际其他微生物有强烈的相互作用。两种块菌侵染在根际显著改变了总共23种相关代谢途径，包括花生四烯酸代谢、类黄酮生物合成、碳固定代谢途径等(P<0.05)，体现了块菌侵染对宿主根际发挥的生态功能。此外，攀枝花白块菌及印度块菌侵染显著影响了宿主根系分泌物组成，宿主根系代谢功能发生显著变化。根系果糖和甘露糖代谢、半乳糖代谢、苯丙氨酸、酪氨酸和色氨酸生物合成受到块菌的显著影响(P<0.05)。