水稻化感作用的机制与应用的研究进展

水稻是我国的主要粮食作物,其与周围植物的相生相克作用（化感作用）得到越来越多的重视.简要介绍了近来国内外对水稻对高等植物的化感作用的研究成果,介绍其化感作用途径、化感物质的分离、鉴定、可能的作用原理及在生产实践中的应用.     

不同类型稻种资源对稗草化感潜力差异评价

以120份不同类型稻种资源为研究对象,将田间鉴定和室内叶浸提液处理鉴定方法相结合,对其化感作用差异进行了鉴定评价.结果表明,在田间不同类型稻种资源对稗草生长的抑制效果大小趋势为地方品种＞选育品种(系)＞引进品种(系)＞杂交水稻(恢复系和不育系),对稗草苗鲜重和苗干重的抑制效果大于对苗高的抑制效果.室内叶浸提液处理鉴定结果,不同类型稻种资源间化感作用差异相对较小,但仍以地方品种较强,并对稗草根长的抑制效果大于对稗草苗高的抑制效果.地方品种中具有较强化感作用的种质资源频率高于其他类型品种,今后要加强对地方品种资源的化感潜力鉴定和评价.     

化感作用水稻对无芒稗及相关田间杂草的抑制作用评价

对从500份水稻种质资源中用差时播种共培法的改进方法初步筛选出10份水稻化感抑稗材料进行了田间化感抑草评价研究.结果表明,在直播条件下,化感材料谷梅2号、吓一跳、鸡早籼、赣早籼和商糯1号等对无芒稗的抑制作用显著优于水稻无化感作用材料秀水63和春江11.化感材料Milyang54对田间总量杂草的抑制作用最强.在移栽条件下,化感材料谷梅2号、青困2号、吓一跳和鸡早籼对无芒稗的抑制作用与无化感作用材料秀水63和春江11差异及显著性水平.水稻材料间部分农艺性状差异及显著性水平,化感材料吓一跳和鸡早籼的株高较高,分蘖力较强,但顶三叶叶面积较小.     

水稻化感作用及其分子生态学研究进展

综述了近年来国际上研究水稻化感作用的新进展,比较分析了当前常用于室内评价水稻化感作用潜力的几种生物测试法的优缺点,指出了琼脂迟播共培法是较为理想的室内生物测试法并已广泛应用于化感作用研究中。在此基础上,分析了水稻化感作用的数量遗传特性及其QTL定位的研究现状;阐明了水稻化感作用的遗传多样性及其分子生态特性;并就当前普遍关注的焦点问题：逆境条件（如低氮或高伴生杂草密度胁迫）常引起水稻化感作用潜力增大的生理过程与分子机制作了阐述。结合近年来应用差异蛋白组学和生物信息学的研究实例,阐明了逆境引起水稻化感作用增强与其酚类合成代谢相关酶蛋白表达丰度增加,萜类合成代谢相关酶蛋白表达丰度下降有关。就究竟什么是水稻的化感物质及其作用方式等问题作了分析与讨论．指出水稻的化感抑草效应是其众多化感物质综合作用的结果,应重视区分化感物质对靶标杂草的原生作用和进入土壤生态系统中经生物转化后的次生作用。根据当前植物化感作用研究的发展趋势,阐明了进一步研究水稻化感作用的焦点问题,提出了水稻化感作用的根际生物学特性与分子生态学机制,是未来国际上竞相角逐的重点研究领域,并认为以现代系统生物学理论为指导,运用基因组学、蛋白质组学和代谢组学等技术方法,是揭示这一分子生态学过程与机制的重要技术选择和优先研究领域。     

水稻化感作用研究综述

主要对水稻化感现象发现,化感生物检测,化感物质分离和鉴定,化感种质资源等方面的研究进展了系统的综合论述,在此基础上,进一步对化感作用研究中的主要问题,例如;生物检测手段,化感作用利用途径等进行了分析。并对我国的化感作用研究的存在问题及发展方向作出了论述。     

不同供氮条件下水稻的化感抑草作用与资源竞争分析

为探讨化感水稻在不同氮素水平下的生物干扰现象,提出了一种新的测试方法———化感竞争分离法(allelopathyandcompetitionseparation basedbioassay,ACS),成功地区分了在稻/稗共生系统中水稻化感作用与资源竞争及其在不同N条件下的反应特性.结果表明,水稻PI312777具有较强的生物干扰能力.在不同N水平下,其资源竞争能力较强且表现稳定,但化感作用潜力则随供N水平的下降而明显增强.水稻Lemont不具化感作用潜力,在供N水平正常或充足条件下,其资源竞争能力减弱,但在N胁迫下却明显增强.这是在环境资源贫乏时,稻/稗共生系统中生态位竞争加剧的结果.     

茉莉酮酸甲酯对水稻化感物质的诱导效应

在室内和田间条件下 ,外源茉莉酮酸甲酯均能显著地诱导水稻化感物质的合成 ,而且这种诱导效应与施用茉莉酮酸甲酯的浓度和诱导时间显著相关。 0 .4 m mol/L浓度和处理后 4 8h,茉莉酮酸甲酯对水稻化感物质的诱导效应最强。同样 ,不同的水稻品种对茉莉酮酸甲酯的诱导响应也有显著差异。水稻化感品种 PI312 777和丰华占在茉莉酮酸甲酯的诱导下能很快合成大量的化感物质 ,而水稻非化感品种华粳籼的化感物质的含量虽也有所增加 ,但达不到能显示化感作用的浓度。进一步实验证明 :茉莉酮酸甲酯在处理 4 8h后虽能诱导水稻品种合成大量的化感物质 ,但这一诱导效应并不能长期维持。研究揭示 :水稻化感物质的合成可在外部因子的作用下动态变化 ,这对揭示和充分利用水稻的化感作用机制有重要意义。     

水稻对受体植物化感作用的遗传生态学研究

选用化感作用潜力差异较大的 5个水稻品种 (系 ) ,按不完全双列杂交设计 (4× 5 )配制成一套包括亲本、F1两个世代的遗传材料 ,在不同环境条件下 ,测定其不同叶龄时期对受体植物莴苣幼苗茎长的抑制作用 .采用包括基因型与环境互作的数量性状加性 显性发育遗传模型 ,分析了水稻化感作用的动态遗传及与环境互作效应 .结果表明 ,水稻叶龄在 7叶期对莴苣茎长的化感作用受加性效应的影响 ,在 3叶期和 6叶期由显性效应控制 ,在 5叶期和 8叶期加性和显性效应均有作用 ,以显性效应为主 ,呈现间断表达的遗传特点 .普通狭义遗传率在 5叶期、7叶期和 8叶期达显著水平 ,随叶龄增大趋于下降 .水稻化感作用受基因型与环境互作效应的影响较大 ,应注意控制水稻生长发育的环境 ,以达到最佳利用水稻化感作用潜力的目的 .     

蒙特卡罗法在化感作用全区间抑制强度评估(wholerange assessment)中的应用

植物化感作用的强弱与化感物质的作用浓度相关.化感作用全区间抑制强度指数(Whole-range assessmentindex)是用于评估植物在一定的化感物质作用范围内所受化感作用总体抑制程度的一种方法.在对非线性剂量响应进行曲线拟合的基础上,本研究应用蒙特卡罗模拟法为计算化感作用全区间抑制强度指数提供了一种科学的数学计算方法,并应用该计算方法分析了番茄水浸提液对生菜、萝卜、白菜、菜心、包心菜、豆角和水稻的化感作用强度.     

相同遗传背景不同植株形态水稻等基因系与杂草的竞争及化感作用

利用相同遗传背景不同株形水稻浙辐802等基因系为材料,研究了IG1、IG4、IG25和IG26与无芒稗的竞争和化感作用潜力,探索了二者之间的相互关系.结果表明,IG1和IG4的植株高度和分蘖角度显著大于IG25和IG26,但它们的根系活力却显著小于IG25和IG26.IG1和IG4对无芒稗生物量干重抑制率分别达到15%和17%,显著高于IG26的64%,表明水稻与无芒稗竞争力与水稻植株高度和分蘖角度成正比,而与水稻根系活力成反比.IG1叶片水浸提液对无芒稗根长抑制率为77.6%,显著高于非化感对照品种秀水63,而植株形态相近的IG4的化感作用却未达到显著水平,显示在相同遗传背景下水稻化感作用强弱与水稻株型无相关性.     

水稻品种化感潜力的双重评价与筛选

以初筛获得的7份水稻品种为材料,用特征次生物质标记法在HPLC上测定化感指数AI值并结合田间小区试验进行双重评价与筛选,得到3份既具高化感指数又具较高田间抗草活性的水稻化感品种(系),它们是:我国台湾品种I-Kung-Pao、Parahainakoru和大陆品种HB-1。它们对无芒稗根长抑制率分别达57%、64%、55%,均超过50%;其化感指数分别是0.61、0.56、0.59,均与美国化感潜力品种PI312777的化感指数0.59相近;结果表明,水稻品种I-Kung-Pao、Parahainakoru和HB-1是我国宝贵的化感品种资源。     

Rice allelopathy and the possibility for weed management

In attempts to control weeds in rice, much effort has been focused on rice allelopathy research for more than 30 years. Among screening methods that have been developed, some estimate the allelopathic potential of various rice cultivars in a limited time and space, which is less costly and can be conducted year round. Rice allelopathy activity is variety dependent and origin dependent, where Japonica rice shows greater allelopathic activity than Indica and Japonica–Indica hybrids. Allelopathic characteristics in rice are quantitatively inherited and several allelopathy‐involved traits have been identified. Numerous phytotoxins such as cytokinins, diterpenoids, fatty acids, flavones, glucopyranosides, indoles, momilactones (A and B), oryzalexins, phenols, phenolic acids, resorcinols and stigmastanols have been identified and determined as growth inhibitors in rice. However, the fate and actual modes of action of these compounds as well as other potent rice phytotoxins in nature are not well understood. The question of which compounds play a major role in rice allelopathy has remained obscure; however, rice allelopathy might be attributable to the interaction of all present allelochemicals. Despite locating genes determining or involving allelopathy in rice having attracted much effort, the introduction of these genes into target rice cultivars has not yet been achieved. Success in breeding new rice cultivars having good weed‐suppressing ability would benefit farmers in rice‐cultivating countries and play an important role in sustainable agricultural production.     

Separation of allelopathy from resource competition using rice/barnyardgrass mixed-cultures

Plant-plant interference is the combined effect of allelopathy, resource competition, and many other factors. Separating allelopathy from resource competition is almost impossible in natural systems but it is important to evaluate the relative contribution of each of the two mechanisms on plant interference. Research on allelopathy in natural and cultivated plant communities has been hindered in the absence of a reliable method that can separate allelopathic effect from resource competition. In this paper, the interactions between allelopathic rice accession PI312777, non-allelopathic rice accession Lemont and barnyardgrass were explored respectively by using a target (rice)-neighbor (barnyardgrass) mixed-culture in hydroponic system. The relative competitive intensity (RCI), the relative neighbor effect (RNE) and the competitive ratio (CR) were used to quantify the intensity of competition between each of the two different potentially allelopathic rice accessions and barnyardgrass. Use of hydroponic culture system enabled us to exclude any uncontrolled factors that might operate in the soil and we were able to separate allelopathy from resource competition between each rice accession and barnyardgrass. The RCI and RNE values showed that the plant-plant interaction was positive (facilitation) for PI312777 but that was negative (competition) for Lemont and barnyardgrass in rice/barnyardgrass mixed-cultures. The CR values showed that one PI312777 plant was more competitive than 2 barnyardgrass plants. The allelopathic effects of PI312777 were much more intense than the resource competition in rice/barnyardgrass mixed cultures. The reverse was true for Lemont. These results demonstrate that the allelopathic effect of PI312777 was predominant in rice/barnyardgrass mixed-cultures. The most significant result of our study is the discovery of an experimental design, target-neighbor mixed-culture in combination with competition indices, can successfully separate allelopathic effects from competition.     

The chemical-mediated allelopathic interaction between rice and barnyard grass

Aims

The possible involvement of the chemical-mediated interaction in allelopathy between rice and barnyard grass was investigated.

Methods

Effcts of rice seedlings and rice root exudate on the alleloapthic activity of barnyard grass were determined and a key compound invovled in the allelopathic interaction between rice and barnyard grass was isolated.

Results

Allelopathic activity of barnyard grass was increased by the presence of rice seedlings. Rice root exudates also elevated the allelopahtic activity of barnyard grass. A key compound, which increased the allelopathic activity of barnyard grass, in the rice root exudates was isolated and determined as momilactone B. Momilactone B increased the allelopathic activity of barnyard grass at concentrations greater than 3 μM, and increasing the momilactone B concentration increased the activity.

Conclusions

Momilactone B is known to act as a potent rice allelochemical and to possess strong growth inhibitory activity against barnyard grass. The present research suggests that barnyard grass may response to the presence of neighboring rice by sensing momilactone B in rice root exudates and increase allelopathic activity. Thus, momilactone B may not only act as a rice allelochemical but also play an important role in rice-induced allelopathy of barnyard grass. The induced-allelopathy may provide a competitive advantage for barnyard grass through the growth inhibition of competing plant species including rice. Barnyard grass allelopathy may be one of the inducible defense mechanisms by chemical-mediated plant interaction between rice and barnyard grass. Rice allelopathy was also reported to be increased by the presence of barnyard grass through increasing production and secretion of momilactone B into surrounding environments. During the evolutional process, rice and barnyard grass may have developed the chemical cross talk to activate the defense mechanisms against some biotic stress conditions by detection of certain key compounds.     

Identification and comparative analysis of microRNAs in barnyardgrass (Echinochloa crus‐galli) in response to rice allelopathy

Rice allelopathy is a hot topic in the field of allelopathy, and behaviour of donor allelopathic rice has been well documented. However, few study addresses response of receiver barnyardgrass (BYG). We found that expression of miRNAs relevant to plant hormone signal transduction, nucleotide excision repair and the peroxisome proliferator‐activated receptor and p53 signalling pathways was enhanced in BYG co‐cultured with the allelopathic rice cultivar PI312777, the expression levels of these miRNAs in BYG plants were positively correlated with allelopathic potential of the co‐cultured rice varieties. Treatment of BYG plants with rice‐produced phenolic acids also increased miRNA expression in BYG, while treatment with rice‐produced terpenoids had no obvious effect on miRNA expression. In the hydroponic system, the largest number of Myxococcus sp. was found in the growth medium containing rice with the highest allelopathic potential. The addition of phenolic acids in the hydroponic medium also increased the number of Myxococcus sp. More interestingly, inoculation with Myxococcus xanthus significantly increased miRNA expression in the treated BYG. Jointed treatments of ferulic acid and M. xanthus led to strongest growth inhibition of BYG. The results suggest that there exist involvement of Myxococcus sp. and mediation of miRNA expression in rice allelopathy against BYG.     

水稻化感物质抑草作用机理的分子生物学研究

水稻化感作用是通过水稻植株体向环境中释放化感物质来实现的．水稻化感物质的主要抑草作用机理有：抑制杂草种子的发芽,影响激素平衡,破坏细胞膜系统的完整性,影响光合作用和呼吸作用,干扰对营养和水分的吸收,影响蛋白质合成和基因表达等．水稻化感作用是由多基因控制的,表现为数量性状．利用分子生物学技术和化感生物检测技术等研究手段检测到了多个水稻化感作用的主效应(QTLs)位点,但不同水稻化感种质其主效应QTLs位点明显不同．通过分子辅助选择和建立近等基因系的方法对检测到的QTLs作进一步的精细定位,最终实现水稻化感抑草有利基因的克隆是今后研究的重要方向。     

Genomic analysis of allelopathic response to low nitrogen and barnyardgrass competition in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

To explore the molecular mechanism of allelopathic rice in response to low nitrogen (N) supply or accompanying weed stress, allelopathic rice PI 312777 and its counterpart Lemont were grown under low N supply or co-cultured with barnyardgrass [Echinochloa crus-galli (L.) Beauv.] in hydroponics. The suppression subtractive hybridization (SSH) technique was employed to isolate the up-regulated genes in the treated rice accession. The results indicated that the expression of the genes associated with N utilization was significantly up-regulated in allelopathic rice PI 312777, and the higher efficiency of N uptake and its utilization were also detected in PI 312777 than that in Lemont when the two rice accessions were exposed to low N supply. This result suggested that the allelopathic rice had higher ability to adapt to low N stress than its non-allelopathic counterpart. However, a different response was observed when the allelopathic rice was exposed to accompanying weed (barnyardgrass) co-cultured in full Hoagland solution (normal N supply). It showed that the expression of the genes associated with allelochemical synthesis and its detoxification were all up-regulated in the allelopathic rice when co-cultured with the target weed under normal N supply. The results suggested that the allelopathic rice should be a better competitor in the rice-weed co-culture system, which could be attributed to increasing de novo biosynthesis and detoxification of allelochemicals in rice, consequently resulting in enhanced allelopathic effect on the target and preventing the autotoxicity in this process. These findings suggested that the accompanying weed, barnyardgrass is not only the stressful factor, but also one of the triggers in activating allelopathy in rice. This implies that the allelopathic rice is sensible of the existing target in chemical communication.