淹涝胁迫对杂交中稻生长特性及产量形成的影响

以近年审定的20个杂交中稻品种为材料,研究了分蘖期和抽穗期淹涝胁迫对杂交中稻的某些生理指标、生长发育、产量及干物质生产的影响。结果表明:(1)淹没胁迫对杂交中稻的生育期有显著影响。分蘖期受淹没胁迫,头季稻和再生稻的抽穗期分别平均延长了3.25 d和3.95 d,成熟期分别平均延长了1.85 d和2.75 d;而抽穗期受淹没胁迫,成熟期会提前,平均提前1.60 d,且品种间差异较大。(2)淹没胁迫对杂交中稻的产量有显著影响。与对照相比,分蘖期受淹没胁迫,分蘖期叶干重、有效穗数、每穗粒数降低,使其平均减产59.0%;齐穗期受淹没胁迫,每穗粒数和结实率显著降低,使其平均减产57.6%。(3)分蘖期受淹没48 h后,不宜割苗蓄留再生稻,应以加强田间管理保留头季稻为主,耐淹性较强的品种有川谷优6684、冈优169和乐优198;抽穗期受淹没48 h后,则以割苗蓄留再生稻较佳,其中冈优169、内5优317、蓉优22和川谷优6684的产量较高。(4)分蘖期和抽穗期耐淹组合间没有相关性,生产上应分别在各时期筛选相应耐淹能力较强的品种。     

Rayada specialty: the forgotten resource of elite features of rice

Crop domestication and thereafter gradual selection or directional breeding have narrowed the genetic diversity of elite varieties and even promoted gathering of deleterious mutations in their stress response mechanisms, whereas local ecotypes, landraces and wild relatives still growing on native environment and preferences keep the genetic diversities for features like stress tolerance. Rayada is such an exceptional ecotype, variant of typical deepwater rice, completely endemic to certain areas of Madhumati river tracts of Bangladesh and still shares some features of wild rices. Multiple physiological features of Rayadas are distinctly different from typical deepwater rice. Tolerance to prolonged flood, submergence and cold are special features along with strong photoperiod sensitivity and lack of dormancy. Moreover, longer root system and prompt recovery capacity make it as an elite resource of stress tolerance. However, it has long been neglected because of mainly its long life cycle and poor yield. This review examines the specialty of Rayada rice and the potential use of its unique traits.     

Hidden diversity for abiotic and biotic stress tolerances in the primary gene pool of rice revealed by a large backcross breeding program

Low and unstable rice productivity in many areas of Asia is associated with many abiotic and biotic stresses such as drought, salinity, anaerobic conditions during germination, submergence, phosphorus and zinc deficiency, etc. To develop rice varieties with tolerance to these stresses, we undertook a large backcross (BC) breeding effort for the last 6 years, using three recurrent elite rice lines and 203 diverse donors, which represent a significant portion of the genetic diversity in the primary gene pool of rice. Significant progress has been made in the BC breeding program, which resulted in development of large numbers of introgression lines with improved tolerance to these stresses. Promising lines have been developed with excellent tolerances (extreme phenotypes) to salinity, submergence and zinc deficiency; resistance to brown plant hopper, ability to germinate under the anaerobic condition and low temperature. Our results indicated that there exist tremendous amounts of ‘hidden’ diversity for abiotic and biotic stress tolerances in the primary gene pool of rice. Furthermore, we demonstrated that despite the complex genetics and diverse physiological mechanisms underlying the abiotic stress tolerances, introgression of genes from a diverse source of donors into elite genetic backgrounds through BC breeding and efficient selection (careful screening under severe stress) is a powerful way to exploit this hidden diversity for improving abiotic stress tolerances of rice. We have developed three large sets of introgression lines, which not only provide an unique platform of breeding materials for developing new rice cultivars with superior yield and stability by trait/gene pyramiding, but also represent unique genetic stocks for a large-scale discovery of genes/alleles underlying the abiotic and biotic stress tolerances of rice using genomic tools.     

淹涝胁迫对水稻生长发育危害与耐淹性机理研究的进展

评述了淹涝胁迫对水稻生长发育的影响、水稻耐涝的生理机制、淹涝胁迫的基因型差异和耐淹性遗传与减灾措施等方面的一些研究进展,并简要提出了今后的研究方向。     

拔节期杂交中稻对淹水胁迫的响应及指示性指标探讨

长江中下游地区夏季强降水频发,杂交中稻在拔节期易受涝害影响。为定量揭示淹水胁迫对水稻的影响和科学评估灾损,提供形态学、生理特性和产量结构的数据基础,同时筛选拔节期水稻淹水胁迫后受涝及减产程度的指示性指标,在丰两优香1号拔节期设计了不同淹深(1/4PH、1/2PH、3/4PH和全淹)及不同淹水持续时间(3 d、6d和9 d)交互试验。结果表明,拔节期杂交中稻受淹后,株高、节间显著伸长,且第2节间伸长速度快于第1节,植株黄叶数显著增多,最长叶片长度显著增长,且株高增长量(Y_(PH))、节间长度(Y_(IL))、黄叶数(Y_(YL))、最长叶片长度(Y_(LL))均与淹涝天数(D)和淹深(H)呈显著的二元一次关系;同一淹水持续时间处理,随着淹水深度的增加,水稻叶片中叶绿素a、叶绿素b含量和可溶性蛋白含量逐渐降低,而可溶性糖含量呈先增高后降低的趋势;剑叶中MDA含量均随淹水历时和淹水深度的增加而升高,在根系中,当淹水持续时间为3 d和6 d时,其MDA含量随淹水深度的增加而升高,但在淹水持续时间为9 d时,表现为先升高后降低,其拐点在1/2 PH淹水深度;同时,在同一淹水持续时间下,随着淹水深度的增加,叶片和根系中SOD活性先升高后降低,而剑叶中POD活性持续升高,且水稻受淹越深,其增加幅度愈大,但在根系中的变化趋势是先升高后降低,拐点出现在淹水第6 d的1/2 PH淹深;拔节期水稻受到不同程度涝害后,结实率和千粒重显著下降,当淹水深度达到株高的1/4且持续6 d,其结实率降低20%以上,产量减少19%以上。灰色关联度和聚类分析表明,叶绿素b、可溶性蛋白和叶绿素a可作为拔节期水稻受涝后的关键性生理指标,用于指示、监测水稻受涝及减产程度。     

Morpho-Physiological Changes in Roots of Rice Seedling upon Submergence

Submergence is a serious environmental condition that causes large loss in rice production in rain fed lowland and flood affected area. This study evaluated morphological and physiological responses of rice roots to submergence using two tolerant rice genotypes FR13A and Swarna-Sub 1 and two sensitive ones Swarna and IR42. The tolerant genotypes had higher survival rate and less shoot elongation but greater root elongation during submergence than the sensitive ones. After submergence,the tolerant genotypes also had higher root dry weight and more active roots than the sensitive ones.Tolerant genotypes exhibited less root injury, with less malondialdehyde production and slower electrolyte leakage after submergence. Tolerant genotypes also maintained higher concentrations of soluble sugar and starch in roots and shoots and higher chlorophyll retention after submergence than the sensitive ones.Our data showed that root traits such as root activity and root growth are associated with survival rate after submergence. This is probably accomplished through higher energy supply, and membrane integrity is necessary to preserve root function and reduce injury during submergence. These root traits are important for submergence tolerance in rice.     

Assessment of Variation in Morpho-Physiological Traits and Genetic Diversity in Relation to Submergence Tolerance of Five Indigenous Lowland Rice Landraces

The present study evaluated submergence responses in 88 lowland indigenous rice(Oryza sativa L.) landraces from Koraput, India, to identify submergence-tolerant rice genotypes. In pot experiments, variations in survival rate, shoot elongation, relative growth index, dry matter, chlorophyll, soluble sugar and starch contents were evaluated in two consecutive years under well-drained and completely submerged conditions. Principal component analysis showed that the first three axes contributed 96.820% of the total variation among the landraces, indicating wide variation between genotypes. Major traits such as survival rate, relative growth index, soluble sugar and starch contents appeared to be important determinants of phenotypic diversity among the landraces. Phenotypic coefficient of variance was higher than genotypic coefficient of variance for all the traits and all showed high heritability(90.38%–99.54%). Five rice landraces(Samudrabali, Basnamundi, Gadaba, Surudaka and Dokarakuji) were the most tolerant to submergence. When submerged for up to 14 d, Samudrabali, Basnamundi and Godoba were notable for having greater survival rates than a standard submergence tolerant variety FR13 A, and also notable for elongating more vigorously and accumulating more biomass. These three landraces may therefore be especially useful in lowland rice growing areas that are affected by both moderate stagnant water and flash flooding. Molecular genotyping revealed that the submergence tolerance of Samudrabali, Basnamundi and Godoba is linked to the presence of one or more different Sub1 loci and it may well prove useful for breeding improved submergence tolerant rice varieties, thereby assising to improve yield stability in the rainfed lowland agro-ecosystem.     

Physiological and molecular responses of seedlings of an upland rice (‘Tung Lu 3’) to total submergence compared to those of a submergence-tolerant lowland rice (‘FR13A’)

Background

Understanding the responses of rice to environmental stresses such as unscheduled submergence is of pressing important owing to increasing severity of weather thought to arise from global climate change. When rice is completely submerged, different types adopt either a quiescence survival strategy (i.e., minimal shoot elongation) or an escape strategy (i.e., enhanced shoot elongation). Each strategy can prolong survival depending on the circumstances. While submergence responses have been studied in rice typical of lowland and flood-prone areas, few studies have explored the physiological and molecular properties of upland rice under submergence. Here, we use seedlings of the upland rice ‘Tung Lu 3’ (‘TL3’) to analyze physiological and molecular responses to submergence. We compare them with those of ‘FR13A’, a lowland rice that tolerates submergence by adopting the quiescence strategy.

Results

Plant height and distance between leaf sheaths, increased rapidly in ‘TL3’ under submergence. Although this indicated a strong escape strategy the seedlings remained totally underwater for the duration of the experiments. In contrast, ‘FR13A’ elongated much less. Consequently, after 4 days complete submergence followed by drainage, ‘TL3’ lodged much more severely than ‘FR13A’. After 10 d complete submergence, 55% of ‘TL3’ seedlings survived compared to 100% in ‘FR13A’. Chlorophyll a, b and total chlorophyll concentrations of the 2^nd oldest leaves of ‘TL3’ were also significantly above those of ‘FR13A’ (but were lower than ‘FR13A’ in the 3^rd oldest leaves) and less hydrogen peroxide accumulated in ‘TL3’. Peroxidase activity in submerged ‘TL3’ was also greater than in ‘FR13A’ 1 day after submergence. Quantitative RT–PCR showed increased expression of sucrose synthase 1 and alcohol dehydrogenases 1 after 2 days complete submergence with significantly higher levels in ‘TL3’ compared to ‘FR13A’. Expression was also higher in ‘TL3’ under non-submerged conditions.

Conclusions

The upland rice line ‘TL3’ gave a stronger elongation response than ‘FR13A’ to complete submergence. This escape strategy is widely considered to prejudice survival when the plant remains totally submerged. However, contrary to expectations, ‘TL3’ survival rates were substantial although below those for ‘FR13A’ while physiological, biochemical and molecular parameters linked to adaptation differed in detail but appeared to be broadly comparable. These findings highlight that submergence tolerance is determine not only by the adoption of quiescence or escape strategies but maybe by metabolic and physiological properties unrelated to the underwater elongation rate.

     

淹水与汕优63白叶枯病发生的关系

采用人工接种法研究了淹水对汕优６３白叶枯病发生的影响。结果表明,稻株发病程度与淹水持续时间的长短有关。淹水２ｄ病情显著加重,当淹水延长到６ｄ以上后,病害反而明显变轻。淹水期间病斑扩展减慢和长时间淹水对汕优６３抗病性的诱导,可能是长时间受淹减轻白叶枯病对汕优６３危害的主要原因。     

杂交稻与常规稻对涝渍环境适应能力的比较研究

利用形态和产量性状指标,比较分析了杂交稻和常规稻在分蘖期和孕穗期对淹涝胁迫环境适应能力的差异性。在深水涝渍条件下,杂交稻生长发育普遍快于常规稻,单蔸苗数显著高于常规稻,有效穗相对受害率低于常规稻,因而单蔸产量显著高于常规稻。分蘖期遭受淹涝胁迫杂交稻的忍耐力优于常规稻,淹涝后的活苗率显著高于常规稻;而且,受淹涝后的杂交稻比常规稻能更快地恢复生长,成熟时主要农艺性状表现是成穗率极显著高于常规稻,每穗实粒数和结实率的相对受害率极显著低于常规稻,单蔸产量的受害程度低于常规稻。孕穗期淹涝胁迫后,杂交稻和常规稻之间产量及相关经济性状的差异均未达到显著水平。     

Saline-Alkali Tolerance in Rice: Physiological Response,Molecular Mechanism,and QTL Identification and Application to Breeding

Salinity-alkalinity is incipient abiotic stress that impairs plant growth and development. Rice (Oryza sativa) is a major food crop greatly affected by soil salinity and alkalinity, requiring tolerant varieties in the saline-alkali prone areas. Understanding the molecular and physiological mechanisms of saline-alkali tolerance paves the base for improving saline-alkali tolerance in rice and leads to progress in breeding. This review illustrated the physiological consequences, and molecular mechanisms especially signaling and function of regulating genes for saline-alkali tolerance in rice plants. We also discussed QTLs regarding saline-alkali tolerance accordingly and ways of deployment for improvement. More efforts are needed to identify and utilize the identified QTLs for saline-alkali tolerance in rice.     

不同淹涝胁迫强度对杂交稻和常规稻农艺性状和生化特性的影响

在分蘖期对目前湖南省普遍栽培的16个杂交稻和常规稻品种进行不同淹涝强度处理,测定了淹涝胁迫处理对杂交稻和常规稻的农艺性状、相对电导率、丙二醛和脯氨酸含量的影响。结果表明： 1）叶片相对受害率的高低表明杂交稻的耐淹涝能力明显强于常规稻。2）随着淹涝天数的增加,杂交稻和常规稻的株高都呈现出低 高 低变化规律,杂交稻出现最高株高的天数在处理4 d后,常规稻在处理2 d后。 3）随着淹涝天数的增加,杂交稻和常规稻的始穗期推迟的天数都增加,杂交稻始穗期推迟的天数幅度小于常规稻。 4）随着淹涝天数的增加,有效穗、实粒数、千粒重、单株产量都降低,杂交稻下降的幅度小于常规稻。 5）随着淹涝天数的增加,杂交稻相对电导率上升的幅度小于常规稻;在杂交稻中,丙二醛含量逐步上升,常规稻表现为先升高后急剧降低的变化趋势;杂交稻脯氨酸含量上升的趋势大于常规稻。 杂交稻耐淹涝胁迫的能力强于常规稻。     

早稻灌浆期淹水对剑叶理化特性及产量和品质的影响

以天优998和桂农占为试验材料,盆栽条件下在灌浆期进行2/3淹水和没顶淹水处理(淹水历时0 d、1 d、3 d、5 d和7 d,0 d为对照),对淹水后早稻剑叶理化特性以及产量和品质进行分析。 结果表明,灌浆期水稻在1 d~3 d短期2/3和没顶淹水后产量和品质显著下降,淹水5 d~7 d产量下降最为严重。有效穗数下降是淹水导致产量下降的主要因素。相同淹水条件下,两个水稻材料间产量和品质变化差异不显著。灌浆期水稻淹水后水稻剑叶的游离脯氨酸和MDA含量升高,SPAD值和SOD酶活性下降,随淹水深度和持续时间的延长变幅增大。灌浆期淹水后水稻剑叶SPAD值和MDA含量与产量和品质呈显著或极显著相关,是反映淹水后水稻产量和品质变化生理指标。     

Tolerance of longer-term partial stagnant flooding is independent of the SUB1 locus in rice

Longer-term partial stagnant flooding, particularly when it occurs following transient complete submergence causes severe damage to modern rice varieties. Progress was made in developing varieties tolerant of complete submergence through transfer of the Submergence-1 (SUB1) gene into popular varieties. However, SUB1 may not be effective under partial stagnant flooding (SF), as the new varieties may not elongate and continue growth when fully or partially submerged because of the SUB1-mediated suppression of elongation. We tested a set of rice genotypes, including a pair of near-isogenic lines (NILs), Swarna and Swarna-Sub1, under either SF or SF following complete submergence of 12 d. Swarna-Sub1 had higher survival and yield than Swarna following 12 d of submergence, but survival and grain yield of all lines decreased substantially when SF of 15-30 cm followed complete submergence, with the sensitive lines experiencing greater reductions in growth and yield. This suggests the importance of combining SUB1 with tolerance of SF in areas where both stresses are expected during the season. Swarna and Swarna-Sub1 are more sensitive to long-term partial SF than IR49830 and IR42 because of their short stature, and Swarna-Sub1 showed slightly higher reduction in tillering than did Swarna when subjected to deeper SF alone, possibly because of further inhibition of elongation by SUB1 if induced in submerged tissue. The results suggest that tolerance of these genotypes to SF depends less on SUB1 introgression and more so on the genetic background of the recipient genotype, with better performance of the genotypes that are inherently taller, such as IR42 and IR49830. The SUB1 donor landrace FR13A and its derivative breeding line IR49830 had better survival and relatively less reduction in grain yield under SF following complete submergence and under longer-term partial SF, indicating that these genotypes may have genes other than SUB1 for submergence and SF tolerance. For better adaptation to prolonged SF, SUB1 should be introgressed into genotypes that tolerate partial SF through better tillering ability and taller shoots, because SUB1 may not be effective in shorter genotypes, as it promotes survival of submerged plants by hindering shoot elongation to conserve energy reserves. Varieties combining tolerance of prolonged SF with SUB1 will have broader adaptation in flood-prone areas and greater impacts on yield stability.     

亚洲地区大豆育成品种幼苗期耐淹性鉴定和优选

以亚洲大豆育成品种为对象,评价其幼苗期耐淹性,揭示其遗传变异特点,从而为耐涝育种提供种质基础。采用我国黄淮、南方及亚洲其它15国的350份大豆育成品种,以相对死苗率为主要鉴定指标,结合叶片相对失绿率与相对萎蔫率,在苗期进行大豆耐淹性盆栽鉴定。结果表明:以相对死苗率为主的指标体系可以有效鉴定大豆品种的苗期耐涝性。亚洲品种群体存在丰富的耐淹性遗传变异,相对死苗率变幅为4.8%~212.0%。中国黄淮、中国南方、东亚、东南亚和南亚5个区域的品种均呈现中间多、两头少的单峰态分布,遗传变异系数均高于21.24%,耐淹性变异丰富,尤其中国黄淮地区覆盖了全群体相对死苗率变幅。各地区均存在耐淹品种,山东、江苏相对较多;从5个区域中依次优选出7、4、1、1、2,共15份耐淹性种质;系谱追踪发现莒选23、南农493-1、黔豆2号的耐淹性可能传递给后代;4份国外耐淹性品种兼具有抗病性可作为亲本拓宽中国耐涝育种的种质基础。     

一个水稻铜锌SOD酶基因在应答亚砷酸盐胁迫中的作用

【目的】水稻Os08g44770.1基因编码一个铜锌SOD酶,但其在响应亚砷酸盐[As(Ⅲ)]胁迫中的生物学功能未知。本研究旨在深入揭示由该基因调控水稻砷耐性改变的分子机理并为水稻抗逆育种提供理论参考。【方法】以野生型日本晴(WT)和2个Os08g44770.1过表达转基因株系为试材,通过胁迫处理、生理指标测定和基因表达分析等,系统探究了转基因植株对As(Ⅲ)的耐受性表现,并初步揭示了其调控水稻砷耐性的生理和分子机理。【结果】与WT相比,过表达转基因株系对As(Ⅲ)更加敏感;转基因植株在砷胁迫下的根系相对伸长量、生物量(干质量)、叶绿素含量、根系细胞质膜完整性、叶片抗氧化程度等均显著低于WT;Os08g44770.1在砷处理后的WT和转基因植株叶片中的表达模式略有不同,但均表现为处理24 h时被显著诱导表达。【结论】过度表达Os08g44770.1基因可导致水稻的砷耐受性极显著下降。     

返青期没顶淹水对粳稻生长及产量的影响与对策

采用系统调查方法,探讨了水稻返青期没顶淹水持续时间对粳稻生长发育及产量的影响,同时进行了灾后补救机插秧和水直播栽培试验。结果表明,随没顶淹水时间的延长,水稻株高变矮,始穗期推迟,有效穗数、每穗粒数变少,千粒重变小,产量下降,且没顶淹水时间持续越久,受害程度越深,但没顶淹水5 d内未死亡的水稻植株仍有利用价值;对于灾后秧苗生长点2/3以上死亡的田块,选择生育期短的粳稻品种进行机插秧补栽或水直播仍能取得一定的经济产量,是灾后重要的技术补救措施。     

Drought Tolerance in Rice: Focus on Recent Mechanisms and Approaches

Drought stress is a serious limiting factor to rice production,which results in huge economic losses.It is becoming a more serious issue with respect to the global climate change.Keeping in view of the current and forecasted global food demand,it has become essential to enhance the crop productivity on the drought-prone rainfed lands with priority.In order to achieve the production target from rainfed areas,there is a requirement of rice varieties with drought tolerance,and genetic improvement for drought tolerant should be a high priority theme of research in the future.Breeding for drought tolerant rice varieties is a thought-provoking task because of the complex nature and multigenic control of drought tolerant traits would be a major bottleneck for the current research.A great progress has been made during last two decades in our understanding of the mechanisms involved in adaptation and tolerance to drought stress in rice.In this review,we highlighted the recent progresses in physiological,biochemical and molecular adaptation of rice to drought tolerance.A brief discussion on the molecular genetics and breeding approaches for drought tolerance in rice will be focused for the future crop improvement program for development of drought tolerant rice varieties.     

水稻灌浆期耐热性的品种间差异及其与剑叶光合特性和内源多胺的关系

对65个不同来源的早籼稻品种进行了灌浆期耐热性的鉴定研究,并比较了耐热性相差很大的品种灌浆期高温胁迫前后的生理反应。结果表明：秕粒率、实粒重、整精米率、垩白度、蛋白质含量的胁迫指数可作为水稻品种灌浆期耐热性田间直接鉴定的 5个指标,可采用隶属函数值法对各品种的耐热性进行综合评价;不同品种的耐热性存在相当大的差异,筛选出了几个耐热性很强的品种;高温胁迫严重影响水稻的光合能力,但耐热性强的品种剑叶的光合速率高温胁迫后下降幅度明显较小,胁迫解除后恢复的程度也更高,叶绿素含量、RuBPc 活性及内源多胺含量的变化趋势与光合速率相一致,是水稻耐高温逼熟的重要生理特征。     

水稻灌浆期耐热性的品种间差异及其与剑叶光合特性和内源多胺的关系

 对65个不同来源的早籼稻品种进行了灌浆期耐热性的鉴定研究,并比较了耐热性相差很大的品种灌浆期高温胁迫前后的生理反应。结果表明：秕粒率、实粒重、整精米率、垩白度、蛋白质含量的胁迫指数可作为水稻品种灌浆期耐热性田间直接鉴定的 5个指标,可采用隶属函数值法对各品种的耐热性进行综合评价;不同品种的耐热性存在相当大的差异,筛选出了几个耐热性很强的品种;高温胁迫严重影响水稻的光合能力,但耐热性强的品种剑叶的光合速率高温胁迫后下降幅度明显较小,胁迫解除后恢复的程度也更高,叶绿素含量、RuBPc 活性及内源多胺含量的变化趋势与光合速率相一致,是水稻耐高温逼熟的重要生理特征。