甘薯连作障碍机制研究

The large-scale and specialized production in sweet potato (Dioscoreaesculenta (Lour.) Burkill) has developed rapidly in recent years. However, due to the rotation in the main producing areas of sweet potato crop is difficult, and soil-borne disease becomes more serious, the issues on continuous cropping obstacle in the cultivation of sweet potato have become increasingly prominent. So far the researches on its continuous cropping obstacle are very few, mainly focusing on the effects of the single factor on continuous cropping obstacle and control of plant diseases and insect pests rather than internal relation and interaction between the factors. Studying the changes between different varieties during continuous cropping years and exploring the formation mechanism of continuous cropping obstacle in sweet potato are of great significance to control crop diseases, to reduce pesticide use, and to improve quality and yield of sweet potato. In this project, with the sweet potato varieties of both resistance to continuous cropping and low- resistance to continuous cropping as materials, continuous cropping 1~4 years respectively, the technologies of high-throughput sequencing, CG-MS analyzing, conventional determination of enzyme activity and nutrient elements will be utilized to analyze the effects of different types of varieties on soil microbial community, autotoxins, enzyme activities and nutrient elements, and to explore the relationship of sweet potato continuous cropping obstacle factors, and further to reveal the generation mechanism of the continuous cropping obstacle in sweet potato cultivation so as to provide theory support for the prevention and control of sweet potato continuous cropping obstacle.

近年来甘薯规模化和专业化生产发展迅速，然而，由于甘薯主产区轮作困难，土传病害日益严重，导致甘薯栽培中连作障碍问题日益突出。关于甘薯连作障碍的报道很少，并且多集中于单一因素对连作障碍的影响以及病虫害的防治，并未探明因素间的内在联系和相互影响。从微生物群落、自毒物质、养分亏缺等方面研究耐连作与不耐连作品种在不同连作年限间变化，探索甘薯连作障碍的形成机制，对于甘薯连作病害防治、减少农药使用、提升品质及保持产量的持续稳定增长具有非常重要的意义。本项目拟以耐连作与不耐连作甘薯品种为实验材料，分别连作1~4年，采用高通量测序技术、CG-MS技术结合常规酶活、营养元素测定等技术，分析同一年度不同类型品种间以及同一品种不同连作年份对土壤微生物群落、自毒化感物质、土壤酶活、营养元素等的影响，探讨甘薯连作障碍各因素间的相互关系，并进一步揭示甘薯连作障碍产生机制，为甘薯连作障碍防控提供理论支持。

由于甘薯主产区轮作困难，土传病害日益严重，导致甘薯栽培中连作障碍问题日益突出。关于甘薯连作障碍的报道很少，且多集中于单一因素对连作障碍的影响及病虫害防治，并未探明因素间的内在联系和相互影响。探索甘薯连作障碍的形成机制，对于甘薯连作病害防治、减少农药使用、提升品质及保持产量的持续稳定增长具有非常重要的意义。本项目选用耐连作与不耐连作甘薯品种作为试验材料，在壤土和沙土两种条件下，分别连作1-4年，采用高通量测序与CG-MS技术结合土壤酶活、土壤团粒机构测定，分析甘薯连作与土壤微生物群落、根系分泌物、土壤酶活、团粒结构等因素间的互作机制。结果显示：甘薯连作后，两类品种、两种土质均会产生连作障碍，耐连作品种相对来说，连作对产量、品质等影响较小；总体来看，壤土连作障碍比沙土要轻，且随连作时间增加土壤理化性质均呈恶化趋势，团粒结构破坏程度加大，养分转化能力减弱；两类品种共有的根系分泌物包括机酸、醛类、酮类、脂质等，在数量和含量上均存在显著差异；连作后各品种均呈现出镰刀菌、炭疽菌等致病菌含量增加、生防菌相对降低，部分细菌含量降低显著，致使土壤微生态失衡加重。甘薯连作障碍产生的可能机制为：随着连作年限的增加，专性寄生的镰刀菌、炭疽菌等致病菌含量增加，生防菌相对含量降低，Vicinamibacteraceae_norank等细菌含量降低显著，根际土微生态失衡加重，病害加重，但耐连作品种相对较轻，病害加重会诱导根系分泌物发生变化；而微生态失衡导致土壤碱性磷酸酶、蔗糖酶、脱氢酶等活性降低，使土壤养分转化能力降低，团粒结构被破坏，直接影响根系生长发育，致使根系产生应激反应，分泌物中胆碱磷酸、马尿酸等有机酸、磷酸吡哆醛等醛类、黄酮类、脂质类物质增加，反过来又影响了土壤微生物的变化，年复一年，逐年加重，各因素相互制约，一旦发生很难采取化学药剂进行防治。鉴于本研究的局限性，关于连作相关差异分泌物、真菌、细菌相互间的相互制约关系，有待进一步研究。