水稻分蘖期耐盐性鉴定评价方法确立及种质筛选

分蘖期是水稻由秧田生长向本田生长过渡的营养生长关键时期。在盐渍化土壤上种植水稻,分蘖期耐盐性对水稻能否正常生长至关重要。合适的耐盐性鉴定方法是水稻耐盐种质筛选的前提。本研究目的在于通过水稻分蘖期盐浓度梯度筛选试验,明确水稻分蘖期耐盐性鉴定最适盐胁迫浓度和调查时间;利用确立的鉴定方法,筛选出水稻分蘖期耐盐种质。本研究选取具有不同程度耐盐性的26份水稻品种,于2015年和2016年分别在10个和7个盐浓度梯度下,以盐害等级为分蘖期耐盐评价指标,开展水稻分蘖期耐盐性鉴定评价试验。结果表明,在0.5%盐浓度下,处理4～6周后供试种质的盐害等级差异表现为最大,因此认为0.5%盐浓度是水稻分蘖期耐盐性鉴定的最适盐胁迫浓度,盐处理后4～6周是水稻分蘖期盐害等级调查的最佳调查时间。参照国际水稻所提出的水稻分蘖期耐盐性评价标准,本研究对其进行了改进,提出以单株为单位进行水稻分蘖期耐盐性评价方法,利用平均盐害等级评估分蘖期耐盐性。该方法能够方便、准确地评价水稻耐盐性强弱。依据上述确立的水稻分蘖期耐盐性鉴定评价方法,本研究于2017-2019年期间对2886份来自不同生态区域的水稻种质进行分蘖期耐盐性鉴定评价,鉴定筛选出137份耐盐种质,为水稻耐盐遗传机制和育种研究提供资源支撑。     

干旱胁迫对烟草叶片丙二醛含量和细胞膜透性的影响

对干旱胁迫下5个烟草品种(系)丙二醛含量和细胞膜透性进行测定表明,随着干旱胁迫的不断加重,烟草叶片丙二醛含量呈现先升后降的趋势,而细胞膜透性则表现为持续升高;复水后细胞膜透性能很快恢复正常,而丙二醛含量需要较长时间才略有恢复。细胞膜透性反应了烟草受干旱胁迫的程度,而丙二醛含量的稳定对烟草的抗旱性有重要意义。     

水稻全生育期耐盐性鉴定评价方法研究北大核心CSCD

土壤盐渍化是危害水稻生产的重要非生物胁迫因素,而遗传改良是提高水稻耐盐性的有效途径之一。全生育期耐盐性是对水稻各生育时期耐盐性的综合反映。科学、准确、高效的水稻全生育期耐盐性鉴定评价方法是水稻耐盐遗传改良必要条件,也是正确判别水稻种质耐盐真实性的关键所在。本研究挑选19份不同耐盐性水稻种质作为研究材料,在正常环境和0.2%、0.3%、0.4%、0.5%、0.6%、0.7%盐处理浓度下,调查11个农艺性状并计算其耐盐系数,运用品种间四分位差法分析,明确水稻全生育期耐盐性鉴定最适浓度。品种间四分位差最大的盐浓度被认为是盐处理最佳浓度;综合多种多元统计分析方法,包括主成分分析、隶属函数分析、回归分析、聚类分析,对水稻全生育期耐盐性鉴定合理评价方法进行探索。结果表明,0.3%盐胁迫浓度下多数性状耐盐系数品种间四分位差最大,0.3%盐胁迫浓度是水稻全生育期耐盐性鉴定最适浓度。主成分分析结果表明,11个农艺性状的耐盐系数可简化为3个主成分。利用主成分贡献率和隶属函数分析,可进一步将3个主成分值简化为水稻耐盐性综合评价指标D值。D值能够简便、准确的评价水稻种质的耐盐性。本研究还利用逐步回归分析,建立D值与11个农艺性状耐盐系数最优线性回归方程:D=-0.365+0.647PL+0.152GP+0.274TW。从该方程可知穗长、穗粒数和总干物重耐盐系数是影响D值的关键指标。利用回归分析建立的模型,可准确完成对D值预测。本研究利用聚类分析,将19份水稻种质耐盐性划分为5个等级,对应于水稻5个耐盐等级划分,即极强、强、中、弱、极弱,可作为其他水稻种质耐盐性评价重要参考。     

水稻全生育期耐盐性鉴定评价方法研究

土壤盐渍化是危害水稻生产的重要非生物胁迫因素,而遗传改良是提高水稻耐盐性的有效途径之一。全生育期耐盐性是对水稻各生育时期耐盐性的综合反映。科学、准确、高效的水稻全生育期耐盐性鉴定评价方法是水稻耐盐遗传改良必要条件,也是正确判别水稻种质耐盐真实性的关键所在。本研究挑选19份不同耐盐性水稻种质作为研究材料,在正常环境和0.2%、0.3%、0.4%、0.5%、0.6%、0.7%盐处理浓度下,调查11个农艺性状并计算其耐盐系数,运用品种间四分位差法分析,明确水稻全生育期耐盐性鉴定最适浓度。品种间四分位差最大的盐浓度被认为是盐处理最佳浓度;综合多种多元统计分析方法,包括主成分分析、隶属函数分析、回归分析、聚类分析,对水稻全生育期耐盐性鉴定合理评价方法进行探索。结果表明,0.3%盐胁迫浓度下多数性状耐盐系数品种间四分位差最大,0.3%盐胁迫浓度是水稻全生育期耐盐性鉴定最适浓度。主成分分析结果表明,11个农艺性状的耐盐系数可简化为3个主成分。利用主成分贡献率和隶属函数分析,可进一步将3个主成分值简化为水稻耐盐性综合评价指标D值。D值能够简便、准确的评价水稻种质的耐盐性。本研究还利用逐步回归分析,建立D值与11个农艺性状耐盐系数最优线性回归方程:D=-0.365+0.647PL+0.152GP+0.274TW。从该方程可知穗长、穗粒数和总干物重耐盐系数是影响D值的关键指标。利用回归分析建立的模型,可准确完成对D值预测。本研究利用聚类分析,将19份水稻种质耐盐性划分为5个等级,对应于水稻5个耐盐等级划分,即极强、强、中、弱、极弱,可作为其他水稻种质耐盐性评价重要参考。     

He-Ne激光对盐胁迫下水稻幼苗抗氧化活性的影响

为减轻盐胁迫对植物造成的伤害,本研究采用He-Ne激光对盐胁迫下的水稻进行辐照处理,选用水稻9311作为对照、耐盐海稻86作为研究对象,以0.5%的氯化钠进行盐胁迫,He-Ne激光(辐照计量5 m W·mm-2,波长632.8 nm)进行照射。设置了对照组(CK),盐胁迫组、盐胁迫和激光复合处理组(分别为L、BL组),进行了水稻抗氧化活性方面的研究。结果表明:与对照组(CK)比较,He-Ne激光对水稻的盐胁迫有一定的缓解作用,其中对水稻9311的作用最明显,表现为激光处理提高了水稻幼苗中过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)的活性和减缓了丙二醛(MDA)含量的增速;同时也说明新选育的海稻86耐盐性高于水稻9311。因此,一定剂量的He-Ne激光可以提高了水稻的耐盐性,这为抗盐胁迫及耐盐植物的育种提供了途径和理论依据。     

盐胁迫下芙蓉菊与4种菊属植物生理响应特征及其耐盐机理分析

以耐盐优异种质芙蓉菊和2种菊属野生种质野菊(天堂寨)、野菊(神农架),以及2种菊属栽培品种‘繁花似锦’和‘寒露红’为材料,用200mmol·L~(-1) NaCl的1/2Hoagland营养液进行盐胁迫处理,在盐胁迫第0、5、10、15天分别测定各材料的相关生理指标,比较各材料随盐胁迫时间增加而产生的生理响应特征,探讨芙蓉菊的耐盐生理生化机制。结果显示:随着盐胁迫时间的增加,5个材料的叶绿素含量(Chl)、净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)、过氧化物酶(POD)活性均呈下降趋势,但芙蓉菊下降不显著或变化趋势与其他4个材料有明显区别;同期各材料的丙二醛(MDA)含量、脯氨酸含量、超氧化物歧化酶(SOD)活性均呈上升趋势,且芙蓉菊的丙二醛含量上升幅度最小;同期胞间CO_2浓度在各种质中的变化趋势各异。研究发现,芙蓉菊在盐胁迫下能够保持叶绿素含量和膜系统的相对稳定,从而维持正常水平的净光合速率,这可能是芙蓉菊耐盐性强于其他菊属植物的主要原因。     

外源硝酸钙对黄瓜幼苗盐胁迫伤害的缓解作用

采用营养液水培法,以较耐盐黄瓜品种'新泰密刺'为试材,研究了叶面喷施硝酸钙对盐胁迫(NaCl 65 mmol·L-1)下黄瓜幼苗生长、叶绿素含量、膜脂过氧化产物丙二醛(MDA)、脯氨酸及不同部位离子含量的影响.结果表明,叶面喷施硝酸钙能够显著提高盐胁迫下黄瓜幼苗的干鲜重、相对含水量和叶片叶绿素含量,显著减少MDA及渗透调节物质脯氨酸的积累;同时可显著降低盐胁迫下黄瓜幼苗体内Na+和Cl-含量,提高K+、Ca2+含量和 K+/Na+、Ca2+/Na+.可见,外源硝酸钙能缓解盐胁迫下黄瓜幼苗的失水程度和光合色素的下降幅度,保护膜的完整性,调节离子选择性吸收,从而减轻盐胁迫伤害,促进黄瓜植株生长.     

盐胁迫对黄独脱毒苗生长和若干生理生化指标的影响

通过在培养基中添加不同浓度NaCl,探讨盐胁迫对黄独脱毒苗生长及若干生理生化指标的影响。结果表明,在盐胁迫条件下,黄独脱毒苗的生长受到明显抑制,叶片中总叶绿素含量、SOD活性下降,丙二醛含量增加,脯氨酸大量积累;随盐胁迫强度的加大,对试管苗生长及生理生化指标的影响相应加剧;在盐胁迫下,黄独脱毒苗叶片脯氨酸含量与丙二醛含量呈极显著正相关,而与叶绿素含量和SOD活性呈极显著负相关。因此,盐胁迫下叶片中脯氨酸含量的变化可作为黄独脱毒苗受害程度的主要生理鉴定指标。     

外源GSH对盐胁迫下水稻叶绿体活性氧清除系统的影响

研究了外源GSH对盐胁迫下耐盐性不同的水稻品种Pokkali(耐盐)和Peta(盐敏感)叶绿体中抗氧化酶活性和抗氧化剂含量的影响.结果表明:盐胁迫下,外源GSH可以提高水稻叶绿体中活性氧清除系统中SOD、APX、GR的活性以及AsA、GSH的含量,降低叶绿体中H2O2和MDA的含量,从而降低了叶绿体膜脂过氧化的水平,缓解盐胁迫对叶绿体膜的伤害.外源GSH对盐胁迫下盐敏感品种Peta叶绿体中上述指标增加或减少的幅度大于耐盐品种Pokkali.     

油菜3个栽培种发芽期耐盐性评价

对油菜种质资源进行耐盐性评价是培育耐盐油菜品种的基础性工作。本研究在室内分别采用3种盐(NaCl)浓度(86 mmol/L、170 mmol/L、256 mmol/L)对芥菜型油菜(Brassica juncea)、白菜型油菜(B.rapa)和甘蓝型油菜(B.napus)等3个栽培种的203份种质资源进行盐胁迫,结果表明盐胁迫对各栽培种的发芽率有不同程度抑制作用,白菜型油菜表现最好,甘蓝型油菜次之,芥菜型油菜最差。基于发芽率筛选出14份优异种质。进一步利用梯度浓度盐(NaCl)溶液对其进行胁迫,发现各栽培种发芽率均随着盐浓度的升高呈下降趋势,符合Boltzmann曲线,但白菜型油菜下降最为缓慢。通过比较盐胁迫下各栽培种6个性状值(胚轴长、根长、总鲜重、地上部分鲜重、总叶绿素含量和电导率)后发现,白菜型油菜发芽期耐盐性优于甘蓝型油菜和芥菜型油菜。对170 mmol/L NaCl胁迫下14份种质各性状值的主成分分析表明,白菜型油菜Br2、甘蓝型油菜Bn1和Bn3为最耐盐种质,可用于耐盐油菜品种的培育。     

Comparative lipid peroxidation,antioxidant defense systems and proline content in roots of two rice cultivars differing in salt tolerance

The changes in the activity of antioxidant enzymes such as superoxide dismutase (SOD: EC 1.15.1.1), catalase (CAT: EC 1.11.1.6), peroxidase (POX: EC 1.11.1.7), ascorbate peroxidase (APOX: EC 1.11.1.11) and glutathione reductase (GR: EC 1.6.4.2), free proline content, and the rate of lipid peroxidation level in terms of malondialdehyde (MDA) in roots of two rice cultivars (cvs.) differing in salt tolerance were investigated. Plants were subjected to three salt treatments, 0, 60, and 120 mol m⁻³ NaCl for 7 days. The results showed that activated oxygen species may play a role in cellular toxicity of NaCl and indicated differences in activation of antioxidant defense systems between the two cvs. The roots of both cultivars showed a decrease in GR activity with increase in salinity. CAT and APOX activities increased with increasing salt stress in roots of salt-tolerant cultivar Pokkali but decreased and showed no change, respectively, in roots of IR-28 cultivar. POX activity decreased with increasing NaCl concentrations in salt-tolerant Pokkali but increased in IR-28. SOD activity showed no change in roots of both cultivars under increasing salinity. MDA level in the roots increased under salt stress in sensitive IR-28 but showed no change in Pokkali. IR-28 produced higher amount of proline under salt stress than in Pokkali. Increasing NaCl concentration caused a reduction in root fresh weight of Pokkali and root dry weight of IR-28. The results indicate that improved tolerance to salt stress in root tissues of rice plants may be accomplished by increased capacity of antioxidative system.     

Physiological and Biochemical Characteristics and Response Patterns of Salinity Stress Responsive Genes (SSRGs) in Wild Quinoa (<i>Chenopodium quinoa</i> L.)

Cultivating salt-tolerant crops is a feasible way to effectively utilize saline-alkali land and solve the problem of underutilization of saline soils. Quinoa, a protein-comprehensive cereal in the plant kingdom, is an exceptional crop in terms of salt stress tolerance level. It seems an excellent model for the exploration of salt-tolerance mechanisms and cultivation of salt-tolerant germplasms. In this study, the seeds and seedlings of the quinoa cultivar Shelly were treated with different concentrations of NaCl solution. The physiological, biochemical characteristics and agronomic traits were investigated, and the response patterns of three salt stress-responsive genes (SSRGs) in quinoa were determined by real-time PCR. The optimum level of stress tolerance of quinoa cultivar Shelly was found in the range of 250–350 mM concentration of NaCl. Salt stress significantly induced expression of superoxide dismutase (SOD), peroxidase (POD), and particularly betaine aldehyde dehydrogenase (BADH). BADH was discovered to be more sensitive to salt stress and played an important role in the salt stress tolerance of quinoa seedlings, particularly at high NaCl concentrations, as it displayed upregulation until 24 h under 100 mM salt treatment. Moreover, it showed upregulation until 12 h under 250 mM salt stress. Taken together, these results suggest that BADH played an essential role in the salt-tolerance mechanism of quinoa. Based on the expression level and prompt response induced by NaCl, we suggest that the BADH can be considered as a molecular marker for screening salt-tolerant quinoa germplasm at the early stages of crop development. Salt treatment at different plant ontogeny or at different concentrations had a significant impact on quinoa growth. Therefore, an appropriate treatment approach needs to be chosen rationally in the process of screening salt-tolerant quinoa germplasm, which is useful to the utilization of saline soils. Our study provides a fundamental information to deepen knowledge of the salt tolerance mechanism of quinoa for the development of salt-tolerant germplasm in crop breeding programs.     

Differential antioxidative responses of indica rice cultivars to drought stress

The present study investigated the linkages between drought stress, oxidative damages and variations in antioxidants in the three rice varieties IR-29 (salt-sensitive), Pokkali (salt-tolerant) and aromatic Pusa Basmati (PB), to elucidate the antioxidative protective mechanism governing differential drought tolerance. Water deficit, induced by 20% (w/v) polyethylene glycol (PEG-6000), provoked severe damages in IR-29 and PB in the form of huge chlorophyll degradation and elevated H₂O₂, malondialdehyde and lipoxygenase (LOX, EC 1.13.11.12) levels as compared to Pokkali. The protein oxidation was more conspicuous in IR-29. Increment in antioxidants, particularly flavonoids and phenolics was several folds higher over control in Pokkali, while much lesser in IR-29 and PB. The activity of catalase (CAT, EC 1.11.1.6) and superoxide dismutase (SOD, EC 1.15.1.1) were decreased in IR-29 and PB, but unaltered in Pokkali. However, marked drought-induced increase in guaiacol peroxidase (GPX, EC 1.11.1.7) activity was noted in both IR-29 and PB. Induction in radical scavenging activity, being the maximum in IR-29, and increased reducing power ability in all the cultivars, accompanied with drought stress, were observed as a defense mechanism. The novelty of our work is that it showed the aromatic rice PB behaving more closely to IR-29 in greater susceptibility to dehydration stress, while the salt-tolerant Pokkali also showed effective drought tolerance properties.     

Improving salinity tolerance in crop plants: a biotechnological view

Salinity limits the production capabilities of agricultural soils in large areas of the world. Both breeding and screening germplasm for salt tolerance encounter the following limitations: (a) different phenotypic responses of plants at different growth stages, (b) different physiological mechanisms, (c) complicated genotype × environment interactions, and (d) variability of the salt-affected field in its chemical and physical soil composition. Plant molecular and physiological traits provide the bases for efficient germplasm screening procedures through traditional breeding, molecular breeding, and transgenic approaches. However, the quantitative nature of salinity stress tolerance and the problems associated with developing appropriate and replicable testing environments make it difficult to distinguish salt-tolerant lines from sensitive lines. In order to develop more efficient screening procedures for germplasm evaluation and improvement of salt tolerance, implementation of a rapid and reliable screening procedure is essential. Field selection for salinity tolerance is a laborious task; therefore, plant breeders are seeking reliable ways to assess the salt tolerance of plant germplasm. Salt tolerance in several plant species may operate at the cellular level, and glycophytes are believed to have special cellular mechanisms for salt tolerance. Ion exclusion, ion sequestration, osmotic adjustment, macromolecule protection, and membrane transport system adaptation to saline environments are important strategies that may confer salt tolerance to plants. Cell and tissue culture techniques have been used to obtain salt tolerant plants employing two in vitro culture approaches. The first approach is selection of mutant cell lines from cultured cells and plant regeneration from such cells (somaclones). In vitro screening of plant germplasm for salt tolerance is the second approach, and a successful employment of this method in durum wheat is presented here. Doubled haploid lines derived from pollen culture of F₁ hybrids of salt-tolerant parents are promising tools to further improve salt tolerance of plant cultivars. Enhancement of resistance against both hyper-osmotic stress and ion toxicity may also be achieved via molecular breeding of salt-tolerant plants using either molecular markers or genetic engineering.     

Salt Tolerant and Sensitive Rice Varieties Display Differential Methylome Flexibility under Salt Stress

DNA methylation has been referred as an important player in plant genomic responses to environmental stresses but correlations between the methylome plasticity and specific traits of interest are still far from being understood. In this study, we inspected global DNA methylation levels in salt tolerant and sensitive rice varieties upon salt stress imposition. Global DNA methylation was quantified using the 5-methylcytosine (5mC) antibody and an ELISA-based technique, which is an affordable and quite pioneer assay in plants, and in situ imaging of methylation sites in interphase nuclei of tissue sections. Variations of global DNA methylation levels in response to salt stress were tissue- and genotype-dependent. We show a connection between a higher ability of DNA methylation adjustment levels and salt stress tolerance. The salt-tolerant rice variety Pokkali was remarkable in its ability to quickly relax DNA methylation in response to salt stress. In spite of the same tendency for reduction of global methylation under salinity, in the salt-sensitive rice variety IR29 such reduction was not statistically supported. In ‘Pokkali’, the salt stress-induced demethylation may be linked to active demethylation due to increased expression of DNA demethylases under salt stress. In ‘IR29’, the induction of both DNA demethylases and methyltransferases may explain the lower plasticity of DNA methylation. We further show that mutations for epigenetic regulators affected specific phenotypic parameters related to salinity tolerance, such as the root length and biomass. This work emphasizes the role of differential methylome flexibility between salt tolerant and salt sensitive rice varieties as an important player in salt stress tolerance, reinforcing the need to better understand the connection between epigenetic networks and plant responses to environmental stresses.     

Does exogenous glycinebetaine affect antioxidative system of rice seedlings under NaCl treatment?

The effect of exogenously applied glycinebetaine (GB) on the alleviation of damaging effects of NaCl treatment was studied in view of relative water content (RWC), malondialdehyde content, and the activity of some antioxidant enzymes in two rice (Oryza sativa L.) cultivars differing in salt tolerance (salt-tolerant Pokkali and--sensitive IR-28), comparatively. Both cultivars took up exogenously applied GB through their roots and accumulated it to considerable levels. Leaf RWC of both cultivars under salt treatment showed an increase with GB application. The activities of superoxide dismutase (SOD), ascorbate peroxidase (AP), catalase (CAT), and glutathione reductase (GR) increased in leaves of Pokkali, but peroxidase (POX) activity decreased under salinity. In IR-28, the activities of SOD, AP and POX increased, whereas CAT and GR decreased upon exposure to salt treatment. When compared to the salt-treated group alone, GB application decreased the activities of SOD, AP, CAT, and GR in Pokkali, whereas it increased the activities of CAT and AP in IR-28 under salinity. However, the activity of POX in IR-28 under salinity showed a decrease with GB application compared to the NaCl group. In addition, lipid peroxidation levels of both cvs. under salt treatment showed a decrease with GB treatment. Therefore, we conclude that GB protects both rice seedlings from salinity-induced oxidative stress.     

Redox homeostasis, antioxidant defense, and methylglyoxal detoxification as markers for salt tolerance in Pokkali rice

To identify biochemical markers for salt tolerance, two contrasting cultivars of rice (Oryza sativa L.) differing in salt tolerance were analyzed for various parameters. Pokkali, a salt-tolerant cultivar, showed considerably lower level of H₂O₂ as compared to IR64, a sensitive cultivar, and such a physiology may be ascribed to the higher activity of enzymes in Pokkali, which either directly or indirectly are involved in the detoxification of H₂O₂. Enzyme activities and the isoenzyme pattern of antioxidant enzymes also showed higher activity of different types and forms in Pokkali as compared to IR64, suggesting that Pokkali possesses a more efficient antioxidant defense system to cope up with salt-induced oxidative stress. Further, Pokkali exhibited a higher GSH/GSSG ratio along with a higher ratio of reduced ascorbate/oxidized ascorbate as compared to IR64 under NaCl stress. In addition, the activity of methylglyoxal detoxification system (glyoxalase I and II) was significantly higher in Pokkali as compared to IR64. As reduced glutathione is involved in the ascorbate–glutathione pathway as well as in the methylglyoxal detoxification pathway, it may be a point of interaction between these two. Our results suggest that both ascorbate and glutathione homeostasis, modulated also via glyoxalase enzymes, can be considered as biomarkers for salt tolerance in Pokkali rice. In addition, status of reactive oxygen species and oxidative DNA damage can serve as a quick and sensitive biomarker for screening against salt and other abiotic stresses in crop plants.