油菜耐铝性的基因型差异及其耐性机理研究

Aluminum (Al) toxicity is one of the most deleterious factors for plant growth in acidic soils. It is estimated that 30%-40% of arable soils in the world are acidic. Rapeseed is the most important oil crop in china, that mainly grown in south of Yangtze. The strategies for maintaining production on acid soil include lime application to raise soil pH and use of plants with high tolerance to acid soils. Development and planting of Al tolerant cultivars is a cost-effective and practically acceptable approach for full utilization of acid soil. In this study, rapeseed cultivars from red soil area are tested for their reactions to Al toxicity. Under the condition of Al stress, the comprehensive evaluation system will be used to evaluate the Al tolerance of rapeseed cultivars based on the aluminum tolerance coefficients of root morphology, biomass and physiology characteristic. Hydroponic experiments are used to determine the difference in Al and nutrient elements absorption and distribution of rapeseed differing in Al tolerance. We are to study on the changes characteristics of rapeseed root organic acids, and the effects of exogenous organic acids on root exudation under Al stress. In addition, the differentially expressed genes of Al tolerance rapeseed genotype will be also studied by means of real-time PCR and RT-PCR technology. This research will provide a theoretical basis for breeding and planting promotion of high yield and aluminum tolerance rapeseed cultivars, furthermore, be helpful to the sustainable development of rape production in acid soils to some extent.

全世界大约有30%-40%的耕地为酸性土壤，铝毒害是酸性土壤中限制作物生长的主要因素之一。油菜是我国重要的油料作物，主要种植于长江以南区域，属于铝毒害较为严重的区域。为减少和防止铝毒对油菜的危害，培育耐铝品种是最经济、有效的方法，而明确耐铝机制是培育耐铝性油菜品种和制定耐铝栽培技术的基础。本研究以红壤地区主推的油菜品种为材料，研究铝胁迫对不同基因型油菜根系形态、生物量、生理特性的影响，通过综合评价体系筛选耐铝性品种，并提出油菜的耐铝鉴定指标。在此基础上，研究不同耐铝基因型油菜铝和矿质元素吸收、分布的差异，探讨铝胁迫下有机酸的分泌特性及其对铝毒害的缓解效应，初步阐明根系耐铝关键基因转录水平的变化，为高产、高耐铝性油菜品种的选育和种植推广提供科学依据，并在一定程度上促进我国酸性土壤地区油菜生产的可持续发展。

油菜是中国重要的油料作物，主要种植于长江以南区域，该区域铝毒害较为严重，铝毒害已成为限制中国南方油菜产量的重要因素之一。本研究围绕油菜耐铝性，先后开展了油菜耐铝基因型筛选、耐铝性综合评价、不同耐铝品种矿质元素吸收特性、耐铝相关基因表达分析、有机酸分泌特性及其对铝毒害的缓解等研究工作。研究表明，（1）铝胁迫对不同基因型油菜苗期的生长发育和生理特性有不同程度的影响，利用主成分分析法、隶属函数法、聚类分析法，筛选出6个耐铝性油菜品种，以及5个油菜耐铝性鉴定指标，建立耐铝性综合评价体系1个。（2）铝胁迫增加了油菜地上部和根系的铝含量，减少了N、P、K、Ca、Mg、Fe等元素的含量；随着铝胁迫浓度增加和胁迫时间延长各元素含量增加或减小的幅度进一步增强；不同耐铝基因型间存在着明显的差异，敏感型品种各元素的增幅或下降幅度明显大于耐铝型品种。（3）采用RNA-Seq技术对不同耐铝性油菜品种根系转录组基因表达进行研究，发现与铝胁迫相关的差异表达基因富集的14个GO term以及5个KEGG pathway，根据筛选的组间差异基因结果，选取有代表性的铝胁迫相关的9个差异基因进行实时荧光定量PCR（qRT-PCR）的表达量验证。（4）随着铝浓度的增加，油菜根系分泌的苹果酸、柠檬酸、总有机酸和电导率呈先增加后减少的趋势，pH值呈下降的趋势；随着铝处理时间的延长，有机酸含量在高浓度铝胁迫下进一步下降，耐铝性品种有机酸、pH、电导率的降幅小于铝敏感品种。（5）加入外源柠檬酸后，与铝胁迫处理相比，铝+柠檬酸处理的根系分泌物各指标和根系形态指标、生长指标等均增大，外源柠檬酸对铝敏感品种的缓解作用大于耐铝型品种，且铝胁迫浓度越高，缓解效果越显著；随着铝胁迫时间的延长，根系形态指标和生长指标的降幅均减小，柠檬酸的缓解效果进一步增强。综上，本项目可为高产、高耐铝性油菜品种的选育和种植推广提供科学依据，并在一定程度上促进我国酸性土壤地区油菜生产的可持续发展。