不同化感潜力水稻苗期根系分布模式及其对抑草圈范围调控机制研究

Paddy weed is a major yield - limiting factor in rice production. Synthetic herbicides are the main tool available for weed control nowadays and will be used more and more. Due to the negative effects of synthetic herbicides, such as herbicide-resistant weeds, environmental contamination, and human health problems, there have been considerable efforts in designing alternative weed management strategies. Improving the inhibiting potential of rice seedlings on paddy weeds is considered as a good weed management pathway for reducing usage of synthetic herbicides and preserving the ecological environment. It has been proved that allelopathic rice plants expressed weed suppression activity at the 3- to 7-leaf stages; while allelopathic characteristic disappears at the mature stages of rice. And rice root exudates is a main pathway for its weed suppression. In this program, ① the temporal-spatial distributions of roots underground at rice seedlings with different allelopathic potential will be explored by Root Scanning Analysis System and Confocal Laser Scanning Microscope; ② the contents of phenolic acids and terpenoids in the soils of the distributed regions of the different allelopathic potential rice roots will be determined by SPE-HPLC and GC-MS techniques; and ③ the contents of the Myxococcus sp. in the soils of the distributed regions of the different allelopathic potential rice roots will be detected by qRT-PCR. The object of this study is to clarify the relationships among the root distribution, allelochemicals, Myxococcus sp., and weed-free zone range, and ascertain the contribution of the temporal - spatial distribution of root growth on the weed suppression. Understanding the root distribution pattern of allelopathic rice seedlings and its regulation mechanisms of weed-free zone range will help us to improve the root growth of allelopathic rice seedlings for enhancing its root exudates and its spread space and increasing the inhibition zone and inhibition potential of allelopathic rice accessions against paddy weeds, thus to provide a new approach for application of rice allelopathy in rice practice.

杂草危害已成为水稻减产的主要因素之一，除草剂仍是农业生产中防除杂草的最主要措施，但其负面作用引起广泛关注。利用化感水稻自身的抑草作用控制杂草是一个重要选择。化感水稻在苗期(3-7叶期)具有抑草作用，而根系分泌物是主要途径。本研究主要内容为①通过根系扫描分析系统和共聚焦激光扫描显微镜分析不同化感潜力水稻苗期根系在土壤中的时空分布规律；②借助于固相萃取法和HPLC、GC/MS等技术测定不同化感潜力水稻根系分布区域内土壤中酚酸和萜类物质的含量；③运用qRT-PCR分析不同化感潜力水稻根系分泌区域内土壤中微生物粘细菌属Myxococcus sp.含量变化。解析“水稻根系-化感物质-粘细菌属-抑草圈范围”之间的相关性，探明不同化感潜力水稻苗期根系分布模式对抑草圈范围的调控机制，为从根系培育角度提高化感水稻根系分泌能力和伸展空间，提高化感水稻抑草空间与抑草能力提供科学依据，是水稻化感作用研究的新思路。

杂草危害已成为水稻减产的主要因素之一，利用化感水稻自身的抑草作用既能有效控制杂草，又能减少稻田除草剂的用量。化感水稻主要通过根系分泌化感物质来实现抑草作用，本项目以国际公认的两种化感水稻PI312777、Taichung Native1和非化感水稻Lemont为种植材料，通过不同种植方法研究不同化感水稻的根系生长形态及其在时间（不同苗期）和空间（土层纵向深度、横向伸展距离）分布上的差异，解析“根系形态和时空分布、化感物质分布、化感潜力和根系土壤微生物多样性”之间的相关性，探明化感水稻苗期根系形态分布模式与抑草作用的关系。主要研究结果如下：（1）明确化感水稻的根系形态特征（细根根长、根尖数、根系生物量）与其化感潜力有一定的相关性。同时探究了化感水稻在土壤介质中的时空分布规律，明确化感水稻苗期根系纵向主要分布在0-5cm深度，且在横向距离水稻6cm以外圈层的根系形态特征值明显高于比非化感水稻。不同化感潜力水稻的这种空间分布差异在五或六叶期表现更明显，且横向距离12cm为化感水稻最佳抑草距离；（2）确定不同化感潜力水稻不同圈层的根系指标、化感潜力和土壤化感物质（酚酸和萜类）含量三者存在相关性，而且不同圈层水稻根系形态与其化感潜力的相关性具有很大差异，其中以6-12cm圈层的各水稻根系生长形态指标与抑制率、苯甲酸型酚酸和含氧单萜含量呈显著正相关；（3）明确了不同化感潜力水稻在不同圈层土壤中的细菌和真菌群落多样性存在差异性，化感水稻的0-6cm根际土壤中的细菌群落多样性高于6-12cm圈层，真菌群落多样性低于6-12cm圈层，且化感水稻PI312777的根际土壤的细菌群落多样性高于非化感水稻Lemont。这些结果暗示水稻根系在水稻化感作用中发挥着重要的调控作用。可以预期，通过苗期促根生长，提高根系分泌能力和伸展空间，可进一步增强苗期化感作用以提高抑草效率，扩大抑草圈范围，减少除草剂用量，保护生态环境，具有重要的科学意义和应用价值。