用渗透剂胁迫鉴定谷子芽期耐旱性的方法研究

采用PEG-6000、甘露醇2种渗透剂7种渗透势模拟水分胁迫,以谷子芽期发芽率、芽长、根长的相对值作为鉴定评价指标,研究谷子芽期耐旱性鉴定的水分胁迫条件.结果表明在胁迫强度较弱时,40%谷子品种萌发、80%谷子品种胚芽、胚根的生长表现促进作用;在胁迫强度较强时,表现出抑制作用.在PEG-6000、甘露醇胁迫下,萌发耐旱指数与种子千粒重呈负相关,与相对发芽势主要表现为中度正相关,与相对根/芽比主要表现为负相关(PEG-6000胁迫),与相对芽长、相对根长相关系数很小;相对芽长与相对根长的相关关系主要表现为中度正相关.种子萌发耐旱指数与相对根长两个指标宜作为谷子芽期耐旱性鉴定指标,-0.75MPa PEG-6000、-1.00MPa甘露醇处理可以作为谷子芽期耐旱性鉴定的水分胁迫条件.     

用渗透剂胁迫鉴定谷子芽期耐旱性的方法研究

采用PEG-6000、甘露醇2种渗透剂7种渗透势模拟水分胁迫,以谷子芽期发芽率、芽长、根长的相对值作为鉴定评价指标,研究谷子芽期耐旱性鉴定的水分胁迫条件。结果表明：在胁迫强度较弱时,40％谷子品种萌发、80％谷子品种胚芽、胚根的生长表现促进作用;在胁迫强度较强时,表现出抑制作用。在PEG-6000、甘露醇胁迫下,萌发耐旱指数与种子千粒重呈负相关。与相对发芽势主要表现为中度正相关,与相对根／芽比主要表现为负相关（PEG-6000胁迫）,与相对芽长、相对根长相关系数很小;相对芽长与相对根长的相关关系主要表现为中度正相关。种子萌发耐旱指数与相对根长两个指标宜作为谷子芽期耐旱性鉴定指标,-0.75MPa PEG-6000、-1.00MPa甘露醇处理可以作为谷子芽期耐旱性鉴定的水分胁迫条件。     

渗透胁迫下水稻种子萌发特性及抗旱性鉴定指标研究

用聚乙二醇（PEG）-6000作为渗透剂模拟干旱胁迫,探讨在4种不同浓度的渗透胁迫下水稻种子的萌发特性,并确立间接评价水稻苗期抗旱性的萌发期鉴定指标。结果表明,高浓度渗透液对种子萌发的抑制作用明显大于低浓度,萌发率的干旱胁迫反应指数随渗透液浓度的降低和萌发进程而增加。在不同浓度的渗透胁迫处理中,20％浓度下萌发6d后的萌发率表现较大的变异幅度和变异系数以及较均衡的品种频率分布,较好地反映了水稻种质对渗透胁迫的不同反应,认为20％／6d条件较适合作为萌发率鉴定的渗透液模拟干旱胁迫;经反复干旱后的幼苗存活率与萌发胁迫指数和20％胁迫浓度下萌发8d后芽鞘长的干旱胁迫反应指数（DRI）表现极显著或显著正相关,认为萌发胁迫指数和芽鞘长的DRI可作为评价水稻苗期抗旱性的间接鉴定指标。     

干旱胁迫对3种狼尾草种子萌发和幼苗生长的影响

采用聚乙二醇(PEG-6000)模拟干旱胁迫和盆栽控水方法,研究了干旱胁迫对3种狼尾草种子萌发及苗期生长的影响.结果表明:低浓度的PEG(5%)胁迫会提高狼尾草种子的发芽率和发芽指数,当PEG体积分数大于10%时,3种狼尾草的种子发芽率随PEG浓度的增加显著下降(P<0.05),但根冠比增加;在高浓度PEG胁迫下,小穗狼尾草种子相对发芽指数大于羽绒狼尾草和巨人狼尾草,其抗旱半致死浓度和极限浓度高于巨人狼尾草;苗期盆栽控水8 d后,巨人狼尾草叶片的旱害级别高于羽绒狼尾草和小穗狼尾草,小穗狼尾草的叶片相对含水量、脯氨酸含量均高于巨人狼尾草,丙二醛含量低于巨人狼尾草.研究发现,提高苗期狼尾草叶片含水量和脯氨酸积累量有利于增强其抗旱性;小穗狼尾草的苗期抗旱性结果和种子的抗渗透胁迫表现一致,并证实其抗旱性最强.     

用渗透胁迫鉴定小麦种子萌发期抗旱性的方法分析

本以聚乙二醇(PEG)-6000、甘露醇和蔗糖作为渗透剂模拟水分胁迫,胁迫溶液渗透势范围在-0．25MPa到-1．50MPa,分析适于进行小麦种子水分胁迫萌发试验的条件,以鉴定小麦萌发期的抗旱性。结果表明,蔗糖溶液易诱发霉茵,胚芽不能正常生长。渗透势为-0．25MPa的PEG-6000及-0．50MPa的甘露醇胁迫已经显抑制了胚芽伸长;-0．50MPa的PEG-6000及-1．00MPa的甘露醇显抑制种子萌发,随着胁迫强度增加,种子相对发芽率及胚芽长度减小,主要是因为渗透胁迫降低了种子吸水速度,胚芽的相对含水量和渗透势均低。在渗透势相同的胁迫条件下,PEG-6000对小麦种子萌发各项检测值的抑制作用均大于甘露醇。如果目的是通过鉴定小麦种子在高渗溶液中的萌发情况,评价萌发期的抗旱性。选用-0．50MPa的PEG-6000或-1．00MPa的甘露醇较为理想,若同时考虑降低试验成本,则应首选-0．50MPa的PEG-6000。     

谷子全生育期抗旱性鉴定及抗旱指标筛选

作物全生育期抗旱性对发掘和利用抗旱品种和抗旱基因至关重要,但谷子全生育期抗旱鉴定至今未有报道,抗旱鉴定缺乏鉴定指标。本试验在干旱池模拟干旱条件下,对苗期抗旱性表现不同的谷子品种进行了全生育期抗旱性研究,调查分析了根干重等形态和生理性状在干旱胁迫条件下的变化;采用相关和灰色关联度等方法,分析这些指标与抗旱性(DRI)的关系。结果表明,相对根冠比、相对单穗粒重和灌浆期光合速率、蒸腾速率同抗旱性表现极显著相关,可以作为谷子全生育期抗旱性鉴定的指标;而相对根干重、相对单穗重、相对株高和气孔导度则可以作为谷子全生育期抗旱性鉴定的参考指标;在供试的品种中,红根谷和大齐头白表现了良好的综合抗旱性。本文还讨论了抗旱性的复杂性以及不同性状对干旱胁迫的反应,所建立的指标对谷子全生育期抗旱鉴定具有指导意义。     

研究水稻种子萌发特性和抗旱性关系的高渗溶液法

鉴定农作物抗旱的方法大致可分为田间鉴定法、干旱棚或人工模拟气候箱法以及实验室法。在实验室法中根据高渗溶液中种子萌发百分率评价品种苗期的抗旱性是常用的一种方法,例如Ashraf等的模拟不同水分张力的方法以及陈培元等对采用甘露醇溶液模拟水分胁迫条件测定小麦种子萌发特性等。但由于标准掌握不一,因而对实验室法尚有不同的看法。有人认为,高渗溶液下的发芽率不能代表出苗期的抗旱性,二者之间的相     

不同花生品种(系)萌发期抗旱性鉴定评价

以发芽势、发芽率、发芽指数、胚根长、胚轴长、幼芽长、幼苗鲜/干重的相对值为指标,通过PEG6000模拟干旱处理,对15份花生品种(系)进行萌发期抗旱性鉴定。结果显示,胁迫处理初期,低浓度处理对种子萌发有促进作用,随着胁迫处理时间的延长及胁迫处理浓度的升高,种子萌发受抑制程度增强。除相对幼芽长以外,其他相对指标都和品种综合抗旱能力呈极显著正相关。通过隶属函数法结合抗旱分级标准筛选出泰花4号、徐花13号、泰0125、泰0005等4份抗旱品种,泰花5号、濮花28、中花16等3份中抗材料,表明该方法可以作为一种快速、简便的鉴定花生萌发期抗旱性的方法。     

DCPTA对干旱胁迫下玉米幼苗生长和抗氧化酶系统的影响

以玉米自交系‘昌7-2’幼苗为材料,采用水培方式研究了模拟不同干旱胁迫程度(10%、12.5%、15%、17.5%、20%、22.5%、25%PEG-6000)及15%PEG-6000干旱胁迫下不同浓度(5、10、15、20、25、30mg/L)植物生长调节剂2-(3,4-二氯苯氧基)三乙胺(DCPTA)对玉米幼苗生长和抗氧化酶系统的影响,以筛选出玉米苗期抗旱性鉴定的适宜PEG-6000浓度,为玉米自交系苗期的抗旱性鉴定提供依据。结果表明:不同浓度PEG-6000处理后,玉米幼苗地上部和根部的干重、鲜重、叶片相对含水量及叶绿素(SPAD)含量均下降,叶片抗氧化酶SOD、POD、CAT的活性增强,丙二醛(MDA)含量升高,渗透调节物质可溶性蛋白、脯氨酸的积累量增加。且当PEG-6000浓度达15%时,以上各指标变化均与清水对照差异显著;在15%PEG-6000浓度模拟干旱胁迫下,不同浓度DCPTA处理均使玉米幼苗上述抗氧化酶活性增强,渗透调节物质含量增加,叶片相对含水量、叶绿素(SPAD)含量和生物量提高,而MDA含量降低,并以15和20mg/L浓度效果较佳。研究认为,室内水培条件下采用PEG-6000模拟干旱鉴定玉米苗期抗旱性的适宜浓度可初步确定为15%;DCPTA处理可促进干旱胁迫下玉米幼苗的生长,并通过提高抗氧化酶活性和渗透调节物质含量来增强其抗旱性,其适宜浓度为15和20mg/L。     

不同水分胁迫条件下高粱种子萌发及吸水规律的研究

通过对抗旱性不同的高粱品种在不同水分胁迫条件下种子萌动、萌发及吸水过程的研究表明：高粱种子在萌动、萌发两个生理过程中对环境水分条件的敏感性不同,种子在萌动时比萌发时更适应低水环境。不同的高粱品种在萌动、萌发时所忍耐的临界环境水势也存在明显差异。种子胚和胚乳两部分的吸水过程具有不同的特点。胚部的干重含水量在吸水后一直急剧增加,直到萌动时达到最大,而胚乳的含水量除在前期快速增加外,随后缓慢增加,保持在相对稳定的水平。在种子吸水萌动过程中,种子胚与胚乳间,以及它们与环境间始终存在着水势梯度。     

不同生态区主要育成谷子品种芽期耐旱性鉴定

以-0.5 MPa的PEG6000作渗透介质模拟干旱条件,对不同生态区的谷子(Setaria italica(L.)Beauv.)品种(系)进行种子萌发耐旱鉴定。结果表明:在PEG6000胁迫下,萌发耐旱指数与相对根芽比、芽生长抑制率呈极显著负相关;与根生长抑制率呈正相关,但相关系数小,相关不显著;与相对发芽势呈极显著正相关,且相关系数达0.939,可以反映谷子芽期耐旱性。根据萌发耐旱指数,将201份谷子品种(系)划分为极抗旱、抗旱、中度抗旱、不抗旱和极不抗旱5个等级。     

抗拿捕净晋谷21突变体的筛选和分子鉴定

谷子(Setaria italica(L.)P.Beauv.)是我国重要的杂粮作物,具有抗旱耐贫瘠、水分利用率高、适应性广、营养丰富等特点,但谷子田间除草一直制约着谷子的集约化栽培和有机旱作产业规模化的推广与发展。为快速选育抗除草剂谷子品种,本试验以晋谷21突变体M2群体为试验材料,通过喷施0.33%拿捕净除草剂对晋谷21突变群体进行初次筛选和再次筛选,进而快速获得抗拿捕净除草剂突变体植株并对其进行分子鉴定。结果显示,在大田苗期喷施0.33%拿捕净除草剂的初次筛选中,筛选出抗拿捕净除草剂的晋谷21突变体共39个株系;对这39个突变体株系再次喷施0.33%拿捕净除草剂,筛选获得9个有抗拿捕净除草剂特性的株系。对筛选获得的抗拿捕净突变体株系的其中3个株系共15个植株进行分子鉴定,发现有4个突变体植株的ACCase基因编码的第1780个氨基酸-异亮氨酸突变为亮氨酸。该结果可为今后利用分子生物学手段改良名优谷子品种晋谷21、加速抗除草剂谷子品种的选育提供理论和材料基础。     

糜子育成品种苗期抗旱性评价与鉴定指标筛选

在年降雨量不足40 mm的敦煌市,对我国不同地区育成的56份糜子品种,采用反复干旱法进行了苗期抗旱性鉴定,利用反复干旱存活率和抗旱性综合评价值D的聚类结果筛选出一级抗旱品种4份,分别是陇糜5号、吉3、蒙粳糜1号和蒙粳糜7号;配对t测验显示:反复干旱胁迫后糜子苗高、植株含水量、单株叶面积、生物学产量分别降低了16.097 cm、0.393 g/株、10.358 cm2/株、0.075 g/株,差异达到了极显著水平,而根长、相对生长率反向增加了0.555 cm、3.213%;主成分分析中,植株含水量、生物学产量、单株叶面积3个指标在第1主成分中起决定作用(系数均≥0.881),且与两种抗旱评价参数值相关性均达到了极显著水平,因此,确定植株含水量、生物学产量、单株叶面积作为糜子苗期抗旱性鉴定1级指标。     

Association of an allele-specific marker with dehydration stress tolerance in foxtail millet suggests SiDREB2 to be an important QTL

Dehydration-responsive element binding (DREB) genes assist in improving stress tolerance of plants by activating the expression of several stress-responsive genes. Therefore, development of functional markers for useful alleles utilizing DREB genes is crucial for crop improvement strategies. Earlier we reported a synonymous single nucleotide polymorphism (SNP) associated with dehydration tolerance at 558^th bp (an A/G transition) in the SiDREB2 gene of foxtail millet (Setaria italica L.) and developed an allele-specific marker (ASM) for SiDREB2. In the present study, we validated this ASM using a set of 122 foxtail accessions, of which 45 were investigated in an earlier study. The QTL associated with SiDREB2 contributed to ~20 % of the total phenotypic variation (PV) for relative water content (RWC) and this signified the importance of this QTL for dehydration tolerance in foxtail millet.     

Over-expression of Osmotin Induces Proline Accumulation and Confers Tolerance to Osmotic Stress in Transgenic Tobacco

Osmotin has been implicated in conferring tolerance to drought and salt stress in plants. We have over-expressed the osmotin gene under the control of constitutive CaMV 35S promoter in transgenic tobacco, and studied involvement of the protein in imparting tolerance to salinity and drought stress. The transgenic plants exhibited retarded leaf senescence and improved germination on a medium containing 200mM NaCl. Further, the transgenics maintained higher leaf relative water content (RWC), leaf photosynthesis and free proline content than the wild type plants during water stress and after recovery from stress. When subjected to salt stress (200mM NaCl), the transgenic plants accumulated significantly more proline than the wild type plants. These results suggest the involvement of the osmotin-induced increase in proline in imparting tolerance to salinity and drought stress in transgenic plants over-expressing the osmotin gene.     

Analysis of Natural Variation in Bermudagrass (Cynodon dactylon) Reveals Physiological Responses Underlying Drought Tolerance

Bermudagrass (Cynodon dactylon) is a widely used warm-season turfgrass and one of the most drought tolerant species. Dissecting the natural variation in drought tolerance and physiological responses will bring us powerful basis and novel insight for plant breeding. In the present study, we evaluated the natural variation of drought tolerance among nine bermudagrass varieties by measuring physiological responses after drought stress treatment through withholding water. Three groups differing in drought tolerance were identified, including two tolerant, five moderately tolerant and two susceptible varieties. Under drought stress condition, drought sensitive variety (Yukon) showed relative higher water loss, more severe cell membrane damage (EL), and more accumulation of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), while drought tolerant variety (Tifgreen) exhibited significantly higher antioxidant enzymes activities. Further results indicated that drought induced cell injury in different varieties (Yukon, SR9554 and Tifgreen) exhibited liner correlation with leaf water content (LWC), H₂O₂ content, MDA content and antioxidant enzyme activities. Additionally, Tifgreen plants had significantly higher levels of osmolytes (proline level and soluble sugars) when compared with Yukon and SR9554 under drought stress condition. Taken together, our results indicated that natural variation of drought stress tolerance in bermudagrass varieties might be largely related to the induced changes of water status, osmolyte accumulation and antioxidant defense system.     

Effect of water stress on germination of some Hungarian wheat landraces varieties

In order to examine germination characters, seedling parameters, water relative content, tolerance index and enzyme activities of seven Hungarian wheat landraces varieties (Tiszadadai, Riscsei, Komloi, Leweucei, Mateteleki, Mikebudai and Nyiradi) under five concentrations of water stress (0, 6, 12, 18, and 24%) of polyethylene glycol (PEG-6000). A laboratory experiment has been conducted through Factorial Experiment in Randomized Complete Block Design (RCBD) with four repetitions at Research Institute of Nyiregyhaza, Hungary. From the obtained results, Leweucei variety was surpassed other studied verities under study and recorded the highest values of all studied characters followed by Mateteleki, Komloi, Nyiradi, Riscsei, Tiszadadai and Mikebudai. Increasing water stress (PEG-6000) from 0 to 6, 12, 18 and 24% significantly reduced germination characters, seedlings parameters, water relative content (WRC), tolerance index and α and β-amylases activities. Generally, under water stress condition, Leweucei and Mateteleki varieties were recorded the highest values of water relative content (WRC), tolerance index (TI) and α and β-amylases activities as well as able to prompt better drought tolerance and could be suggested as a good resource for breeding programs and cultivation under drought stress conditions compared with other wheat landraces varieties.     

Functional Genetic Diversity Analysis and Identification of Associated Simple Sequence Repeats and Amplified Fragment Length Polymorphism Markers to Drought Tolerance in Lentil (<Emphasis Type="Italic">Lens culinaris</Emphasis> ssp. <Emphasis Type="Italic">culinaris</Emphasis> Medicus) Landraces

Genetic diversity of 70 Mediterranean lentil (Lens culinaris ssp. culinaris Medicus) landraces was assessed using simple sequence repeats (SSRs) and amplified fragment length polymorphisms (AFLPs). These landraces were also assessed for variation in root and shoot traits and drought tolerance as estimated by relative water content (RWC), water losing rate (WLR) and wilting score (WS). Genetic diversity and clear differentiation of Moroccan landraces from those from northern Mediterranean regions (Italy, Turkey and Greece) were found. High genetic variation in root and shoot traits and traits related to drought tolerance was also observed. No relationship was found between drought tolerance of landraces and their geographic origin. Landraces with higher dry root biomass, chlorophyll content and root–shoot ratio were drought tolerant as evidenced by higher RWC and lower WLR and wilting severity. Kruskal–Wallis non-parametric test (K-W) was used to find SSRs and AFLPs associated with RWC, WLR and WS. Regression analysis showed six SSR and AFLP alleles explaining the highest phenotypic variation of RWC, WLR and WS (ranging from 21 to 50 % for SSRs and from 14 to 33 % for AFLPs). Functional genetic diversity analysis showed relationships between drought response of landraces and linked SSR and AFLP alleles to RWC, WLR and WS according to K-W test using canonical discriminant analysis. Our results confirm the feasibility of using association mapping to find DNA markers associated with drought tolerance in larger numbers of lentil landraces.