孕穗期低温对黑龙江省主栽水稻品种空壳率的影响

障碍型冷害对黑龙江省水稻生产影响巨大,明确主栽水稻品种耐冷性及障碍型冷害的量化指标,可为当地水稻安全生产提供科学依据。本文对黑龙江省4个主栽水稻品种(垦稻12、龙稻3号、龙稻7号和空育131)在孕穗期进行不同低温处理,分析了各处理对水稻空壳率的影响。结果表明:在平均温度为15℃时,孕穗期低温的持续天数是水稻形成障碍型冷害的关键因素;在低温持续时间相同的条件下,昼夜恒温15℃使各品种水稻受低温影响最严重;在不同低温处理条件下,不同品种水稻发生一般障碍型冷害的临界时长为1～4d或5～8d,发生严重障碍型冷害的临界时长为5～8d或8d以上,品种间临界时长有所差异;供试品种中,垦稻12和龙稻3号耐冷性较弱,空育131耐冷性较强,龙稻7号耐冷性居中。     

基于引物扩增受阻突变技术开发水稻耐冷基因CTB4a特异性分子标记

水稻(Oryza sativa)作为热带与亚热带起源的作物对低温敏感.对水稻种质进行耐冷性鉴定,能筛选出耐冷性强的种质,发展耐冷基因分子标记,能够有效鉴别种质中耐冷基因的基因型.本研究使用芽期4℃低温处理10d对41份水稻材料进行芽期耐冷鉴定,对品种的芽期耐冷能力进行评价,获得了参试材料中除了'昆明小白谷'之外的芽期耐冷性最强的品种'南特号'.对已克隆的耐冷基因CTB4a开发分子标记,能够辅助选择水稻的耐冷育种.水稻孕穗期耐冷基因CTB4a来源于'昆明小白谷',能够影响水稻抵抗低温的能力.参照公布的CTB4a序列信息,从中挑选出序列中的作用位点SNP(单核苷酸多态性,single nucleotide polymorphism),结合引物扩增受阻突变技术(Penta-primer amplification refractory mutation system,PARMS),用Primer 6.0设计引物,建立CTB4a基因荧光分子标记GM-CTB4a,使用荧光分子标记GM-CTB4a对41份水稻品种进行鉴定,使用酶标仪在'昆明小白谷'中检测到利用标记扩增产物中包含'昆明小白谷'特异SNP、T碱基引物携带的FAM荧光信号,在另外40份品种的扩增产物中检测到包含作用位点的C碱基引物携带的HEX荧光信号.本研究利用设计的分子标记,鉴定了 41份水稻品种的耐冷性和基因型.比对分析耐冷性和基因型鉴定结果,说明我们开发的分子标记GM-CTB4a特异性较强,具有实际应用价值.研究结果为利用水稻孕穗期耐冷基因CTB4a培育强耐冷水稻品种奠定坚实基础.     

黑龙江省水稻空壳率与孕穗期低温的关系

对黑龙江省6个主要水稻品种(龙稻3号、垦稻12号、空育131、龙稻7号、龙粳16号和松粳6号)进行孕穗期低温(处理温度分别为15℃、17℃、19℃,低温持续时间分别为2、4、6和8d)处理,采用线性内插和统计回归方法,分析了水稻单穗空壳率与孕穗期低温的关系.结果表明:研究区敏感性水稻品种和耐冷性较强水稻品种的障碍型冷害临界温度分别为17℃和16℃;孕穗期水稻对低温最敏感的时期为抽穗前14～18d.15℃低温处理8d时,松粳6号、垦稻12号的空壳率明显增加,空育131空壳率小幅升高,表明松粳6号和垦稻12号对低温反应较敏感、耐冷性较弱,而空育131对低温反应迟钝,耐冷性较强;垦稻12号、龙粳16号、空育131的冷积温与空壳率存在显著的相关关系(P0.01),随着冷积温的增加,水稻空壳率明显升高,但品种间的增幅不同.     

高产水稻幼苗耐冷性

1998年早季在广东省农业科学院水稻研究所的人工气候箱内对5个不同类型的高产水稻幼苗作耐冷性比较,结果表明两系法杂交稻培矮64s/E32的耐冷性最强,培矮64s/9311次之;两系法杂交稻组合粤杂122和常规水稻品种粤香占、特三矮2号耐冷性稍差。     

中国粳稻地方品种孕穗期耐冷性评价及聚类分析

用原产于中国18个省的329份粳稻地方品种为材料,分析了自然低温和冷水胁迫下不同省份粳稻地方品种孕穗期耐冷性及主要农艺性状表型差异和聚类特点。结果表明,在自然低温和冷水胁迫下各省份粳稻地方品种的孕穗期耐冷性状及主要农艺性状有明显的差异。在自然低温和冷水胁迫下,天津、四川和台湾品种的结实率及冷水反应指数均较高,表现较强的孕穗期耐冷性和迟钝的冷水反应。云南品种在自然低温下表现为较强的孕穗期耐冷性（结实率）,而在冷水胁迫下播种至抽穗天数和株高的冷水反应指数较高,表现为迟钝的冷水反应。从总体趋势上看,自然低温和冷水胁迫下,除个别省份外,纬度相对较高的北方省份品种的孕穗期耐冷性（结实率）强于纬度相对较低的南方省份品种。此外,在自然低温和冷水胁迫下,各省粳稻地方品种的聚类结果总体上与各省品种的地理位置及其耐冷性有密切的联系,而在冷水胁迫下品种的聚类结果与品种地理位置的关系比自然低温下更为密切。     

超高产水稻剑叶的高效光合特性

以多年来大面积推广的杂交水稻汕优63为对照。研究了超高产杂交水稻两优培九的光合生理特性。结果表明：在生殖生长期两优培九剑叶具有较高的叶绿素含量,Fv/Fo,Fv/Fm,qP,φi和Rubisco含量,表明它有相对较高的光能吸收,转化和利用的能力;且两优培九的qN较汕优63大,1-qP/qN比它小,说明它比对照品种更耐光抑制;两个品种在剑叶衰老过程中都发生了光碳失衡,但两优培九光碳失衡状态较轻;这些可能是超高产水稻两优培九高产的重要原因。     

低温胁迫下粳稻选育品种耐冷性状的鉴定评价

选取来源于中国11个省份和其他9个国家的347份粳稻选育品种作为试验材料,分析了自然低温和冷水胁迫下,不同来源粳稻选育品种孕穗期的耐冷性及主要农艺性状的表型差异和聚类特点。研究表明,在自然低温和冷水胁迫下各省份或国家粳稻选育品种主要农艺性状及其冷水反应指数有明显的差异。在自然低温和冷水胁迫下,云南和日本品种的孕穗期结实率及其冷水反应指数均较高,表现出较强的孕穗期耐冷性。从总体趋势上看,在自然低温下,除个别省份外,我国纬度相对较高的北方省份品种的孕穗期耐冷性强于纬度相对较低的南方省份品种;而在冷水胁迫下,品种的耐冷性与其来源地的关系并不密切,没有呈现出一定的规律性。此外,聚类结果表明,不同省份或国家粳稻选育品种的聚类结果与其品种的地理来源均有一定的相关性,而与自然条件相比,冷水胁迫下粳稻选育品种的聚类结果与其品种的地理来源的相关性更为密切。     

中国水稻微核心种质不同生育时期耐冷性鉴定及其相关分析

以204份中国水稻微核心种质为试验材料,进行了水稻发芽期、芽期、幼苗期、孕穗期等耐冷性鉴定及其相关性分析。结果表明,水稻各生育时期耐冷性在籼粳亚种间、各种质之间存在明显的差异。粳稻种质的耐冷性明显强于籼稻种质,但籼稻种质中也存在耐冷性较强的种质。高阳淀稻大红芒、肥东塘稻、木樨球、卫国、兴国、山酒谷、中花8号等粳稻种质和包选21号、红米三担白、寸谷糯、红谷等籼稻种质在水稻各生育时期均表现较强的耐冷性,在水稻耐冷性育种及耐冷基因发掘研究中应加以利用。自然低温和冷水胁迫下水稻结实率与低温下发芽率呈显著或极显著正相关,而与死苗率呈显著负相关,即低温下发芽期耐冷性和芽期耐冷性强的水稻种质一般表现为较强的孕穗期耐冷性。认为低温下发芽率和芽期低温处理后的死苗率可以作为孕穗期耐冷性早期鉴定的间接指标。     

中国水稻微核心种质不同生育时期耐冷性鉴定及其相关分析

以204份中国水稻微核心种质为试验材料,进行了水稻发芽期、芽期、幼苗期、孕穗期等耐冷性鉴定及其相关性分析。结果表明,水稻各生育时期耐冷性在籼粳亚种间、各种质之间存在明显的差异。粳稻种质的耐冷性明显强于籼稻种质,但籼稻种质中也存在耐冷性较强的种质。高阳淀稻大红芒、肥东塘稻、木樨球、卫国、兴国、山酒谷、中花8号等粳稻种质和包选21号、红米三担白、寸谷糯、红谷等籼稻种质在水稻各生育时期均表现较强的耐冷性,在水稻耐冷性育种及耐冷基因发掘研究中应加以利用。自然低温和冷水胁迫下水稻结实率与低温下发芽率呈显著或极显著正相关,而与死苗率呈显著负相关,即低温下发芽期耐冷性和芽期耐冷性强的水稻种质一般表现为较强的孕穗期耐冷性。认为低温下发芽率和芽期低温处理后的死苗率可以作为孕穗期耐冷性早期鉴定的间接指标。     

广西水稻地方品种耐冷性鉴定及相关分析

对419份广西水稻地方品种初级核心种质进行芽期、苗期的耐冷性鉴定及相关分析,结果表明:广西水稻地方品种芽期、苗期耐冷性主要集中在7级和9级,总体耐冷性较弱。芽期、苗期极强耐冷种质(1级)分别为24份和27份,占参试总数的5.73%和6.44%,其中10份种质芽期和苗期均表现极强耐冷(1级)。芽期、苗期耐冷性呈极显著正相关(r=0.66)。粳稻芽期、苗期耐冷性均显著高于籼稻;粘糯稻之间耐冷性差异是由籼粳稻类型的耐冷差异引起的;来自高寒山区稻作区的品种芽期和苗期平均耐冷表现最强。利用34个SSR标记与芽期、苗期耐冷性进行Pearson相关分析,在第7和第9染色体上,各鉴定出1个同时与芽期和苗期耐冷性相关联的位点。本研究为水稻芽期、苗期耐冷育种提供新的抗源材料,并为水稻耐冷基因定位及机理研究奠定基础。     

Wheat flag leaf epicuticular wax morphology and composition in response to moderate drought stress are revealed by SEM,FTIR‐ATR and synchrotron X‐ray spectroscopy

Wheat (Triticum aestivum L.) is the largest cereal crop grown in Western Canada where drought during late vegetative and seed filling stages affects plant development and yield. To identify new physiochemical markers associated with drought tolerance, epidermal characteristics of the flag leaf of two wheat cultivars with contrasting drought tolerance were investigated. The drought resistant ‘Stettler’ had a lower drought susceptibility index, greater harvest index and water‐use efficiency than the susceptible ‘Superb’. Furthermore, flag leaf width, relative water content and leaf roll were significantly greater in Stettler than in Superb at moderate drought stress (MdS). Visible differences in epicuticular wax density on the adaxial flag leaf surfaces and larger bulliform cells were identified in Stettler as opposed to Superb. Mid‐infrared attenuated total internal reflectance spectra revealed that Stettler flag leaves had increased asymmetric and symmetric CH₂ but reduced carbonyl esters on its adaxial leaf surface compared to Superb under MdS. X‐ray fluorescence spectra revealed a significant increase in total flag leaf Zn concentrations in Stettler in response to MdS. Such information on the microstructural and chemical features of flag leaf may have potential as markers for drought tolerance and thereby accelerate the selection and release of more drought‐resistant cultivars.     

Boron accumulation and partitioning in wheat cultivars with contrasting tolerance to boron deficiency

Two pot experiments at the Plant Environment Laboratory (PEL), Reading, UK investigated sterility, boron (B) accumulation and B partitioning of wheat cultivars grown with limited B in the growing medium. The first experiment evaluated nine cultivars of spring wheat with diverse field responses to low available soil B, supplied with or without 20 μM B. A second experiment examined the response of a susceptible (SW-41) and a tolerant (Fang-60) cultivar to B-deficiency. These cultivars were supplied with either 20 μM B from sowing to flag leaf emergence and no added B thereafter, or 20 μM B from sowing to maturity. When B was not supplied in the nutrient solution, the number of grains ranged from 4 per ear (cv. BL-1135) to 32 per ear (cv. BL-1249) and sterility of competent florets ranged from 39% to 93%. Boron concentration in the flag leaf at anthesis did not differ greatly when the growing medium contained limited B, but differences between cultivars were evident when B was unlimited. Tolerance of B-deficiency was not related to the B concentration in the flag leaf. Some cultivars produced viable pollen and set grains while others failed to do so at similar B concentrations in the flag leaf. The two contrasting cultivars did not differ much in their pattern of B partitioning when B supply was restricted from flag leaf emergence onwards. Similarly, little evidence was found that the tolerant cultivars translocated B from their leaves, roots or stems when the supply in the growing medium was restricted. The proportion of total B partitioned in different organs was the same irrespective of B supply and cultivar. On average, leaves contained 68% of the total B content in the whole plant compared to 16% in the roots, 10% in the ears and only 6% in the stems. Tolerant or susceptible cultivars of wheat could not be distinguished based on the B concentration and B content of the flag leaf. This revised version was published online in June 2006 with corrections to the Cover Date.     

Physiological Responses of <i>Dendrobium officinale</i> under Exposure to Cold Stress with Two Cultivars

This study aimed to explore the cold tolerance of two cultivars of Dendrobium officinale (MG1, MG2) grown in different regions of China. Under -2°C incubation, cultivar MG1 remained active after 3 d, and continued to grow after returning to room temperature. However, MG2 could only maintain its activity after 2 d treatment at −2°C, and the seedlings died with the low temperature treatment time. Investigation of the characteristics of the plants grown in the south (Hangzhou) or north (Zhengzhou) of China indicated that the leaves of MG1 also had reduced stomatal density, the highest thickness, and a compact microstructure. The contents of proline and soluble sugars were higher in MG1 than those in MG2. The cultivar MG1 had higher SOD enzyme activity than MG2, while CAT and POD activities in samples from Zhengzhou were higher than those from Hangzhou. The contents of polysaccharides and alkaloids in stems of in MG1 were higher than those in MG2, while the content of flavonoids in the Zhengzhou samples was higher than that in the Hangzhou samples. In addition, plant heights, stem diameters, and chlorophyll content were higher in MG1. Overall, MG1 had better cold resistance than MG2. MG1 is a cold tolerant cultivar with thick leaves and reduced stomatal density, higher contents of soluble sugars, proline, CAT, POD, polysaccharides, flavonoids and alkaloids, which together make it more adaptable to low temperatures. Thus, the cultivar MG1, with its demonstrated cold tolerance, can accordingly be grown on a large scale in cold regions, thereby expanding the available planting area for this important traditional medicinal plant to meet the increasing commercial demand for it.     

Saccharide Content and Growth Parameters in Relation with Flooding Tolerance in Rice

Pre-submergence reserve saccharides was found adequate to substantiate the survival of tolerant cultivar under flooding. Survival percentage declined in both tolerant and susceptible cultivars with less saccharide content. However, it was more apparent in susceptible cultivar. Plant height, fresh and dry mass of shoots, leaf mass/area ratio and starch content per plant before flooding showed significant positive association with submergence tolerance. Hence, the improved seedling vigour could be used to increase submergence tolerance.     

盾叶秋海棠叶表皮气孔簇的发育及分布格局

气孔是植物控制气体交换和调节水分散失的门户。大部分高等植物气孔的分布格局是相邻气孔之间被一至多个表皮细胞所间隔。而在有限分布的几个科属的植物种中发现气孔成簇分布的现象 ,即由 2至多个紧密相邻的气孔器组成相对独立的单元 ,称为气孔簇 (stomatalcluster)。以中国原产的盾叶秋海棠 (BegoniapeltatifoliaLi)为研究对象 ,探讨了叶表皮气孔簇的发育机制及其分布格局。结果表明 :气孔发育初期 ,气孔拟分生组织的成簇 (相邻紧密 )排列可能是气孔簇形成的主要机制 ;气孔副卫细胞恢复分裂形成的卫星拟分生组织也对气孔簇的形成起一定的作用。把气孔簇和单个气孔视为一个气孔单元发现 ,盾叶秋海棠气孔单元密度 (单位面积中气孔单元数 )和气孔单元大小 (气孔单元所包含气孔数 )在叶片上呈有规律的分布 :前者由叶片中部向叶尖、叶缘逐圈增多 ,而后者逐圈减少。对这种分布格局的成因进行了讨论     

Selection of RAPD marker for growth of seedlings at low temperature in rice.

We have developed a polymerase chain reaction (PCR)-based assay that could effectively reduce the time period required to screen and select the cold tolerance gene of rice seedlings under field conditions. The two specific random amplified polymorphic DNA (RAPD) fragments for the assay were identified on the basis of quantitative trait loci (QTL) analysis which were found to be tightly linked to cold sensitivity. The two RAPD fragments, OPT8(600) in the cold sensitivity rice cultivar 'Dular (indica)' and OPU20(1200) in the resistance rice cultivar 'Toyohatamochi (japonica)', were identified after screening 11 RAPD fragments using 2 random primers on the genomic DNAs of 'Dular' and 'Toyohatamochi'. These primers, when used in a multiplexed PCR, specifically amplified a 0.6 kb and a 1.2 kb fragment in the sensitive and resistant rice cultivars, respectively. When this assay was performed on the genomic DNAs of 16 japonica, 3 Tongil (indica/ japonica), and 2 indica rice cultivars, the primers amplified a 0.6 kb fragment in all of the cold sensitivity rice cultivars or 1.2 kb fragment in all of the resistance ones. These markers can be of potential use in the marker-assisted selection (MAS) for cold tolerance in rice seedling. As screening for resistance can now be conducted independent of the availability of low temperature, the breeding of cold tolerance cultivars can be hastened.     

High ethylene production slackens seed filling in compact panicled rice cultivar

Change of plant type in rice resulting in increased compactness of the panicle, allows space for accommodation of a larger number of spikelets, but grain yield does not increase proportionately because of limitations in grain filling. The objective of this study was to evaluate potential causes of poor filling of spikelets by comparing the physiological processes that influence source and sink activities between a compact- (OR-1920-7) and a loose-panicled (Lalat) rice cultivars growing in the open field conditions in the farm of Regional Research and Technology Transfer Station, Orissa University of Agriculture and Technology, Chiplima, India during dry season of 2007. Although grain number per unit length of the branches was higher in the compact-panicled cultivar than the loose-panicled cultivar, average grain weight was lower on the primary and secondary branches at top, middle and basal positions of the panicle in the former compared to the corresponding positions of the panicle in the latter. Compared to Lalat, ethylene production rate was considerably higher in the boot of the flag leaf sheath of OR-1920-7 during the pre-anthesis period. Ethylene evolution rate correlated negatively with growth and cell division rates and starch concentration of the juvenile endosperm. Because spikelet growth was slower in OR-1920-7 than in Lalat, unused carbohydrates accumulated in the endosperm. The stomatal conductance of the flag leaf during this period was also lower in the former than that of the latter and it correlated negatively with ethylene evolution rate of the boot. It is concluded that high ethylene production slackened grain filling of compact-panicled rice cultivar OR-1920-7 because of its adverse influence on both source and sink activities.     

A comparative screening of hybrid,modern varieties and local rice cultivar for brown leaf spot disease susceptibility and yield performance

Five rice cultivars, one hybrid (WR96), three modern (BR16, BR26, and BRRI Dhan27) and one local (Pari) were screened for reaction to brown leaf spot disease caused by Cochliobolus miyabeanus and performance of yield-related characters. The severity of brown leaf spot varied with growth stages of rice plant as well as different cultivars tested under field condition. Low disease severity was observed at maximum tillering stage compared to moderate to high at dough stage, with hybrid cultivar WR96 showing highest disease, while local cultivar Pari had the lowest. Brown spot disease severity in different cultivars under induced epiphytic condition also followed the similar trend. The results also revealed that most of the yield-contributing characters examined showed wide variations among the cultivars. Modern cultivar BR16 produced the highest panicle length, number of grain per panicle and grain yield per hectare. At the same time as local cultivar Pari generated the lowest number of tiller per plant, panicle length, grain number per panicle and grain yield per hectare. Moreover, hybrid cultivar WR96 produced the highest percentage of spotted grain per panicle and seed yielding C. miyabeanus, and also the lower percentage of seed germination, while the reverse was observed in local cultivar Pari. These findings may allow producers and breeders to select rice cultivar, resistant or tolerant to brown leaf spot disease and to avoid significant reductions in grain yields.     

High day–night transition temperature alters nocturnal starch metabolism in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Transitory starch plays a vital role in maintenance respiration as its degradation products provide substrate for the night respiration. A study was conducted with two contrasting rice cultivars: Vandana (high night temperature susceptible) and Nagina 22 (high night temperature tolerant) by subjecting them to increase in transition temperature from anthesis to physiological maturity. Night respiration on plant area basis increased by 35% in Vandana at 5 days after anthesis but was unaffected in tolerant cultivar. A simultaneous 18% decrease in starch content was observed in the susceptible cultivar. An analysis of the starch-metabolizing enzymes showed that activity of β-amylase increased markedly in Vandana whereas both β and α-amylase decreased in Nagina 22 following high day to night transition temperature exposure. The level of starch breakdown product, maltose, increased in the susceptible cultivar but glucose levels declined in both the cultivars. Concurrently, expression of chloroplastic isoforms α-amylase OsAMY1, OsAMY2 and β-amylase OsBAM2 increased in Vandana. A lower accumulation of dry matter was recorded in the susceptible than the tolerant cultivar. Our study elucidated the regulatory role of transitory starch in supporting the high day to night transition temperature-induced night-time respiration which is mediated by the increased activity of β-amylase through enhanced expression of OsBAM2 in flag leaves of susceptible cultivar.     

Phytochrome B control of total leaf area and stomatal density affects drought tolerance in rice

We report that phytochrome B (phyB) mutants exhibit improved drought tolerance compared to wild type (WT) rice (Oryza sativa L. cv. Nipponbare). To understand the underlying mechanism by which phyB regulates drought tolerance, we analyzed root growth and water loss from the leaves of phyB mutants. The root system showed no significant difference between the phyB mutants and WT, suggesting that improved drought tolerance has little relation to root growth. However, phyB mutants exhibited reduced total leaf area per plant, which was probably due to a reduction in the total number of cells per leaf caused by enhanced expression of Orysa;KRP1 and Orysa;KRP4 (encoding inhibitors of cyclin-dependent kinase complex activity) in the phyB mutants. In addition, the developed leaves of phyB mutants displayed larger epidermal cells than WT leaves, resulting in reduced stomatal density. phyB deficiency promoted the expression of both putative ERECTA family genes and EXPANSIN family genes involved in cell expansion in leaves, thus causing greater epidermal cell expansion in the phyB mutants. Reduced stomatal density resulted in reduced transpiration per unit leaf area in the phyB mutants. Considering all these findings, we propose that phyB deficiency causes both reduced total leaf area and reduced transpiration per unit leaf area, which explains the reduced water loss and improved drought tolerance of phyB mutants.