Flooding Tolerance in Rice: Focus on Mechanisms and Approaches

Flooding is one of the most hazardous natural disasters and a major stress constraint to rice production throughout the world,which results in huge economic loss.Approximately one-fourth of the global rice crops(approximately 40 million hectares)are grown in rainfed lowland plots that are prone to seasonal flooding.A great progress has been made during last two decades in our understanding of the mechanisms involved in adaptation and tolerance to flooding/submergence in rice.In this review,we summarized the physiological and molecular mechanisms that contribute to tolerance of flooding/submergence in rice.We also covered various features of flooding stress with special reference to rice plants,viz.different types of flooding stress,environmental characterisation of flood water,impact of flooding stress on rice plant and their morphological,physiological and metabolic responses under flooding.A brief discussion on the tolerance mechanism in rice exhibited to different types of flooding will be focused for the future crop improvement programme for development of flooding tolerant rice variety.     

水稻抗旱研究进展与展望

水稻是我国主要粮食作物之一,整个生长阶段对水分的需求远远大于其它作物。然而随着极端气候以及水资源短缺的影响,干旱已经成为造成农作物产量损失最大的非生物胁迫。全面详细地了解水稻抗旱研究相关内容,有助于抗旱水稻品种的培育。本综述从水稻抗旱筛选方法、筛选指标、干旱胁迫条件下产量及其产量相关性状QTL发掘以及抗旱基因的克隆和应用进行论述,并对水稻抗旱品种的培育进行展望。      

Salt Tolerance in Rice:Focus on Mechanisms and Approaches

Salt tolerance is an important constrain for rice, which is generally categorized as a typical glycophyte. Soil salinity is one of the major constraints affecting rice production worldwide, especially in the coastal areas. Susceptibility or tolerance of rice plants to high salinity is a coordinated action of multiple stress responsive genes, which also interacts with other components of stress signal transduction pathways. Salt tolerant varieties can be produced by marker-assisted selection or genetic engineering by introducing salt-tolerance genes. In this review, we have updated on mechanisms and genes which can help in transferring of the salt tolerance into high-yielding rice varieties. We have focused on the need for integrating phenotyping, genomics, metabolic profiling and phenomics into transgenic and breeding approaches to develop high-yielding as well as salt tolerant rice varieties.     

Mapping QTLs for Drought Tolerance at Seedling Stage in Rice Using Doubled Haploid Population

QTLs for drought tolerance at the rice seedling stage were analyzed using a doubled haploid (DH) population consisted of 251 lines from the cross between a japonica parent Maybelle and an indica parent Baiyeqiu. A genetic linkage map with 226 SSR marker loci was constructed. Single-locus analysis following composite interval mapping (CIM) detected a total of five QTLs located on five different chromosomes of rice. Four QTLs were also detected following two-locus analysis, resolving two pairs of epistatic QT...     

Evaluation of Agronomic Traits in Chromosome Segment Substitution Lines of KDML105 Containing Drought Tolerance QTL under Drought Stress

Drought is a major abiotic constraint to rice production in rainfed lowland and insufficiently irrigated areas.The improvement of drought tolerant varieties is one of the strategies to reduce the negative effects of drought.Quantitative trait loci(QTLs) for primary and secondary traits related to drought tolerance(DT) on chromosomes 1,3,4,8 and 9 that determined from double haploid lines derived from a cross between CT9993 and IR62266 were introgressed and dissected into small pieces in the genetic background of Khao Dawk Mali 105(KDML105) to develop chromosome segment substitution line(CSSL) population.The CSSLs were evaluated at the reproductive stage for their agronomic performance and yield components under drought stress,and results were compared with irrigated condition.The flowering of CSSL lines was 6 to 7 d earlier than KDML105.The mean values of grain yields in the CSSLs were higher than KDML105 under drought and irrigated conditions.At irrigated condition,the grain yields of introgression lines carrying DT-QTLs from chromosomes 4 and 8 were higher than that of KDML105,whereas other traits showed little difference with KDML105.Analysis indicated that grain yield has positive correlation with plant height,tiller and panicle number per plant,and total grain weight per plant under drought stress while negatively correlated with days to flowering.As mentioned above,CSSLs showing good adaptation under drought stress can be used as genetic materials to improve drought tolerance in Thai rainfed lowland rice breeding program,and as materials to dissect genes underlying drought tolerance.     

Combined Drought and Heat Stress in Rice: Responses,Phenotyping and Strategies to Improve Tolerance

Simultaneous occurrence of drought and heat stress will have significant negative impact on rice yield, especially under upland conditions. The projected increase in global temperatures and reduced precipitation will increase the frequency of occurrence and intensity of these stresses, threatening rice production. Despite recognizing the importance of combined stress in rice, the knowledge generated in this area is very limited. Though complex, understanding combined stress tolerance of rice under water saving cultivation is more critical towards development of climate resilient rice cultivars. Here, we summarized the effects of combined stress on rice physiology with more emphasis on reproductive stage. Omics responses, phenotyping and physiology challenges and potential strategies for improving combined stress tolerance in rice are also discussed.     

Evaluation of Inherited Resistance Genes of Bacterial Leaf Blight,Blast and Drought Tolerance in Improved Rice Lines

Improved rice lines were developed frome three parents with the resistance or tolerance to bacterial leaf blight, blast and drought stress, respectively, using single-, double- and three-way crosses. The improved lines were assessed for agro-morphological and yield traits under non-drought stress (NS) and reproductive-stage drought stress (RS) treatments. The mean comparison of traits measured between parent plants and progenies (improved lines) were similar, and there were significant and non-significant differences among the parents and improved lines (genotypes) under NS and RS. Smilarly, there was significant and non-significant differences in the interaction among both parent varieties and improved lines for NS and RS. Cluster and 3D-model of principal component analysis did not generate categorical clusters according to crossing methods, and there were no exclusive crossing method inclined variations under the treatments. The improved lines were high-yielding, disease resistant, and drought-tolerant compared with their parents. All the crossing methods were good for this crop improvement program without preference to any, despite the number of genes introgressed.     

植物生长物质冠菌素诱导旱稻、水稻幼苗抗旱性的效应及生理机制

以旱稻 297 和水稻越富幼苗为材料,在 20% PEG 模拟干旱条件下,研究了植物生长物质冠菌素处理对叶片水分状况、质膜透性、渗透调节物质（脯氨酸、可溶性糖和可溶性蛋白）及内源激素（ABA、IAA 和GA3）含量的影响。干旱胁迫下,冠菌素处理可以维持旱稻 297（0.01 μmol/L）和越富（0.1 μmol/L）较高的叶片相对含水量,促进幼苗叶片中脯氨酸、可溶性糖和可溶性蛋白的积累,降低质膜透性,维持细胞质膜的完整性;同时,冠菌素（0.01 和0.1 μmol/L）处理明显促进旱稻 297 和越富幼苗叶片中ABA的积累,并改变了 IAA 和GA3 的浓度及比例。冠菌素处理能改善旱稻和水稻幼苗耐干旱胁迫的能力,最适浓度分别为0.01 μmol/L和0.1 μmol/L。     

玉米抗寒性的研究进展

低温不仅是限制冷敏植物分布及其生长最重要的环境因素,也是影响许多热带或亚热带作物生产的重要气候条件.近年来玉米抗寒性的研究结果表明玉米的抗寒性在自交系间存在明显的差异,冷锻炼或ABA处理也能使抗寒性大为提高.玉米抗寒性的表现有着重要的生理基础,即抗氧化酶的活性维持在较高水平而且其同工酶的表达模式也相应改变;膜类脂降解的程度较轻、光系统II保持较高的活力、膜系统保持较好的通透性和完整性;叶片中ABA、水势和渗透压均维持在较高的水平.玉米抗寒性的遗传分析以及有关基因的克隆和遗传转化的研究结果表明玉米的抗寒性是由多基因控制的数量性状,利用品种改良和生物技术能有效地提高玉米的抗寒性。     

不同时期干旱胁迫对水稻产量和生长特性的影响

为明确水稻生长过程中的水分敏感时期,探索水稻抵御干旱的栽培措施,以常规粳稻楚粳29号和云粳39号为材料,通过盆栽试验准确控制土壤水分(水势),研究不同时期干旱胁迫对水稻产量和生长特性的影响。结果表明,楚粳29号干旱胁迫处理较对照减产10.63%~47.60%,云粳39号干旱胁迫处理较对照减产6.19%~47.27%,减产程度依次为穗分化前期干旱胁迫(T2)﹥有效分蘖期干旱胁迫(T1)﹥穗分化后期干旱胁迫(T3)﹥孕穗期干旱胁迫(T4)。与对照相比,2个品种有效分蘖期干旱胁迫降低了有效穗数,穗分化前期干旱胁迫使每穗粒数明显减少,穗分化后期干旱胁迫使每穗实粒数减少和结实率明显降低,孕穗期干旱胁迫对结实率或千粒重有影响。     

玉米耐旱遗传育种研究及分子育种策略

干旱胁迫一直是玉米产量损失的重要逆境因素。本文结合最新玉米组学研究成果,高通量的数据信息分析平台,从玉米表型和基因型两方面重点讨论耐旱玉米在遗传及育种实践上的研究进展,分子育种技术在进行耐旱玉米新品种的选育过程中的新策略,利用新的技术和平台进行耐旱玉米的创新,为未来提高育种遗传增益以及玉米增产稳产起到重要作用。     

Improvement of Upland Rice Variety by Pyramiding Drought Tolerance QTL with Two Major Blast Resistance Genes for Sustainable Rice Production

Varalu is an early maturing rice variety widely grown in the rainfed ecosystem preferred for its grain type and cooking quality. However, the yield of Varalu is substantially low since it is being affected by reproductive drought stress along with the blast disease. The genetic improvement of Varalu was done by introgressing a major yield QTL, qDTY_12.1, along with two major blast resistance genes i.e. Pi54 and Pi1 through marker-assisted backcross breeding. Both traits were transferred till BC₂ generation and intercrossing was followed to pyramid the two traits. Stringent foreground selection was carried out using linked markers as well as peak markers (RM28099, RM28130, RM511 and RM28163) for the targeted QTL (qDTY_12.1), RM206 for Pi54 and RM224 for Pi1. Extensive background selection was done using genome-wide SSR markers. Six best lines (MSM-36, MSM-49, MSM-53, MSM-57, MSM-60 and MSM-63) having qDTY_12.1 and two blast resistance genes in homozygous condition with recurrent parent genome of 95.0%-96.5% having minimal linkage drag of about 0.1 to 0.7 Mb were identified. These lines showed yield advantage under drought stress as well as irrigated conditions. MSM-36 showed better performance in the national coordinated trials conducted across India, which indicated that improved lines of Varalu expected to replace Varalu and may have an important role in sustaining rice production. The present study demonstrated the successful marker-assisted pyramiding strategy for introgression of genes/QTLs conferring biotic stress resistance and yield under abiotic stress in rice.     

NAC转录因子在水稻抗逆基因工程中的应用进展

水稻经常遭遇干旱、高盐、低温、病原菌等逆境胁迫,影响其生长发育甚至产量。NAC转录因子是植物特有的、最大的转录因子家族之一,在水稻生长发育及抵御多种非生物及生物胁迫反应中具有重要的调控作用。本文阐述了水稻NAC转录因子的结构、分类及染色体定位,并阐述了NAC转录因子在水稻抗旱、耐盐、耐冷及抗病等抗逆基因工程中应用的研究进展,为NAC转录因子的利用及水稻抗逆遗传改良提供参考。     

聚乙二醇模拟干旱对耐低钾水稻幼苗丙二醛、脯氨酸含量和超氧化物歧化酶活性的影响

以早稻品种瑰宝8号及其耐低钾变异后代为材料,用20%PEG6000模拟干旱胁迫,测定丙二醛（MDA）含量、脯氨酸（Pro）含量、超氧化物歧化酶（SOD）活性及质膜相对透性。模拟干旱胁迫后,MDA、Pro含量和质膜相对透性呈急剧上升的趋势,瑰宝8号中的MDA、Pro含量显著高于它的变异后代;SOD活性先迅速上升后急剧下降,变异后代的SOD活性始终高于瑰宝8号。相关性分析表明,Pro含量与MDA含量和质膜相对透性呈显著正相关,而与SOD活性呈一定程度的负相关。     

Engineering for Drought Tolerance in Horticultural and Ornamental Plants

Abstract

Drought is one of the major factors limiting plant growth and productivity. Plant adaptation to drought is dependent on molecular networks for drought perception, signal transduction, expression of a subset of genes and production of metabolites that protect and maintain the structure of cellular components. In general, the drought response pathways can be classified into two categories: one is dependent on the stress hormone abscisic acid (ABA) and the other is ABA-independent. Many genes in these pathways have been identified, thereby providing guidance in choosing genes for engineering of drought tolerance. The review highlights the genes that mediate drought response and tolerance, and discusses lessons learned from engineering for drought tolerance in model plants, such as Arabidopsis, rice and tobacco. Because success of drought tolerance engineering is dependent on not only protein coding regions but also appropriate promoters, this article also reviews the promoters that are crucial for successful engineering of stress tolerance.     

红麻种质资源耐旱性的初步鉴定研究

为鉴定和筛选红麻耐旱种质资源,本研究选用10份红麻野生种和41份红麻栽培品种为材料,51个红麻种质资源进行盆栽和干旱胁迫试验鉴定,根据干旱后叶子的萎蔫程度进行鉴定、比较,获得了51个红麻种质资源的耐旱性评价。已鉴定和筛选出的7个耐旱性较强和8个耐旱性较弱的红麻种质材料,结果对红麻种质资源的评价和进行红麻耐旱性的分子基础研究有一定指导意义。     

广西甘蔗品种抗旱性研究

干旱已成为制约我国甘蔗产量提高的重要因素。研究甘蔗的抗旱机理,选育具备较强抗旱性的甘蔗品种,是降低甘蔗生产成本、提高甘蔗产量的有效途径。为探讨不同甘蔗品种的抗旱性,以桂南亚08-186、桂糖05-3846等7个甘蔗品种为试验材料,采用人工控水桶栽法研究其抗旱性。测定甘蔗+1叶脯氨酸含量、叶片膜透性、过氧化物酶(POD)活性、可溶性蛋白含量4个生理指标的变化,根据抗旱隶属函数加权值大小对其进行抗旱性评价。结果表明,所有甘蔗品种抗旱能力的强弱与脯氨酸含量、过氧化物酶的活性呈正相关;与叶片膜透性、可溶性蛋白含量呈负相关;根据隶属函数分析结果,参试甘蔗品种抗旱性由强到弱依次为:桂糖05-3864>桂南亚08-186>柳城06/241>柳城03/1137>桂糖06-400>ROC22(CK)>桂热2号(凉蔗02-6)。     

开花灌浆期干旱胁迫对水、陆稻细胞膜透性和产量性状的影响

 在开花灌浆期对三个水、陆稻品种进行干旱胁迫处理。结果发现,叶片中自由水含量较高的湘粳2号（粳型水稻）在复水后细胞膜透性仍然较高,束缚水含量下降,平均减产幅度最小,表现出明显的耐旱特性。而湘中籼3号（籼型水稻）的表现相反,是不耐旱品种。陆稻品种奉爱的抗旱性明显较强,但产量较低,有待进一步改良。     

自然干旱胁迫下配方肥增效剂对水稻内源激素的影响

 为揭示土壤自然干旱条件下配方肥增效剂对水稻植株内源激素的影响，以中稻培两优93为材料，采用盆栽法研究了配方肥增效剂对水稻内源脱落酸（ABA）、生长素（IAA）、赤霉酸（GA3）、玉米素核苷（ZR）的影响。干旱处理后，ABA在前期大量积累，后期呈下降趋势。根系和叶片中ABA含量大幅度升高，其中根系中ABA增幅达58~101倍，根源ABA积累幅度远高于叶源ABA积累幅度，而增效剂处理促进了ABA的积累。干旱胁迫前，增效剂处理水稻植株根系IAA、ZR和叶片GA3均显著高于对照；而干旱胁迫后，增效剂处理植株上述激素水平均大幅下降，而对照下降幅度较小。叶中IAA、ZR和GA3的变化则与根系相反。