Ectopic overexpression of a mungbean vacuolar Na+/H+ antiporter gene (VrNHX1) leads to increased salinity stress tolerance in transgenic Vigna unguiculata L. Walp

Salinity is a major threat to sustainable agriculture worldwide. Plant NHX exchangers play an important role in conferring salt tolerance under salinity stress. In this study, a vacuolar Na+/H+ antiporter gene VrNHX1 (Genbank Accession No. JN656211.1) from mungbean (Vigna radiata) was introduced into cowpea (Vigna unguiculata) by the Agrobacterium tumefaciens-mediated transformation method. Polymerase chain reaction and Southern blot hybridization confirmed the stable integration of VrNHX1 into the cowpea genome. Comparative expression analysis by semi-quantitative RT-PCR revealed higher expression of VrNHX1 in transgenic cowpea plants than wild-type. Under salt stress conditions, T2 transgenic 35S:VrNHX1 cowpea lines exhibited higher tolerance to 200 mM NaCl treatment than wild-type. Furthermore, T2 transgenic 35S:VrNHX1 lines maintained a higher K+/Na+ ratio in the aerial parts under salt stress and accumulated higher [Na+] in roots than wild-type. Physiological analysis revealed lower levels of lipid peroxidation, hydrogen peroxide and oxygen radical production but higher levels of relative water content and proline, ascorbate and chlorophyll contents in T2 transgenic 35S:VrNHX1 lines.

Tree species’ tolerance to water stress, salinity and fire

According to climate change predictions, water availability might change dramatically in Europe and adjacent regions. This change will undoubtedly have an adverse effect on existing tree species and affect their ability to cope with a lack or an excess of water, changes in annual precipitation patterns, soil salinity and fire disturbance. The following chapter will describe tree species and proven-ances used in European forestry practice which are the most suitable to deal with water stress, salinity and fire. Each subchapter starts with a brief description of each of the stress factors and discusses the predictions of the likelihood of their occurrence in the near future according to the climate change scenarios. Tree spe-cies and their genotypes able to cope with particular stress factor, together with indication of their use by forest managers are then introduced in greater detail.

Measurement of the salinity and freezing tolerance of Crataegus genotypes using chlorophyll fluorescence

The effect of increasing salinity and freezing stress singly and in combination on a range of chlorophyll fluorescence parameters in foliar tissue of six Crataegus genotypes was examined. In general, increased stress reduced fluorescence values and absorption, trapping and electron transport energy fluxes per leaf reaction center and cross section, with decreased sigmoidicity of OJIP curves as a measure of the plastoquinone pool, reflecting decreased energy fluxes. Based on percentage reduction in a performance index from controls compared to stress-treated values, plants were ranked in order of tolerant > intermediate > sensitive. Use of this PIp ranking criteria enabled the distinguishing of marked differences in foliar salt/freezing hardiness between the Crataegus species used. Interpretation of the photochemical data showed that salinity and freezing affects both the acceptor and donor side of Photosystem II, while OJIP observations provided information regarding structural and functional changes in the leaf photosynthetic apparatus of the test species. It is concluded that chlorophyll fluorescence offers a rapid screening technique for assessing foliar salinity and freezing tolerance of woody perennials

Physiological basis of salt stress tolerance in rice expressing the antiapoptotic gene SfIAP

Programmed cell death-associated genes, especially antiapoptosis-related genes have been reported to confer tolerance to a wide range of biotic and abiotic stresses in dicotyledonous plants such as tobacco (Nicotiana tabacum L.) and tomato (Solanum lycopersicum L.). This is the first time the antiapoptotic gene SfIAP was transformed into a monocotyledonous representative: rice (Oryza sativa L.). Transgenic rice strains expressing SfIAP were generated by the Agrobacterium-mediated transformation method and rice embryogenic calli, and assessed for their ability to confer tolerance to salt stress at both the seedling and reproductive stages using a combination of molecular, agronomical, physiological and biochemical techniques. The results show that plants expressing SfIAP have higher salt tolerance levels in comparison to the wild-type and vector controls. By preventing cell death at the onset of salt stress and maintaining the cell membrane’s integrity, SfIAP transgenic rice plants can retain plant water status, ion homeostasis, photosynthetic efficiency and growth to combat salinity successfully.

Total peroxidase activity and peroxidase isoforms as modified by salt stress in two cultivars of fox-tail millet with differential salt tolerance

The effect of NaCl on total peroxidase activity, induction of isoperoxidases and lipid peroxidation in 5-day-old seedlings of two contrasting genotypes of Setaria italica L. (Prasad, a salt tolerant cultivar and Lepakshi, a salt susceptible cultivar), was studied. Total peroxidase activity increased under NaCl salinity and the degree of elevation in the activity was salt concentration dependent. Nevertheless, a greater activity was recorded in the tolerant cultivar (cv Prasad) compared to the susceptible (cv Lepakshi) one in all days of sampling. Further, the pattern of isoperoxidases was modified during stress conditions as evident from the electrophoregrams. Although, five acidic isoforms were detected in both cultivars, differences were found between the cultivars. Furthermore, it was observed that acidic isoperoxidases were strongly expressed and an acidic isoperoxidase, A(3p) (27 kDa) is specifically found in the tolerant cultivar (cv Prasad) under NaCl stress. This isoform was partially purified and found to be thermostable with pr 5.5 and the optimum pH 7.4. A close correlation exists between the rate of lipid peroxidation in terms of malonaldehyde (MDA) content and total peroxidase activity per gram fresh weight with salt tolerance of the two cultivars. The tolerant cultivar (cv Prasad) had low MDA content and high total peroxidase activity than the susceptible variety (cv Lepakshi) during salinity stress. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights reserved.

Heterologous expression of P5CS gene in chickpea enhances salt tolerance without affecting yield

Vigna Delta(1)-pyrroline-5-carboxylate synthetase (P5CS) cDNA was transferred to chickpea (Cicer arietinum L.) cultivar Annigeri via Agrobacterium tumefaciens mediated transformation. Following selection on hygromycin and regeneration, 60 hygromycin-resistant plants were recovered. Southern blot analysis of five fertile independent lines of T0 and T1 generation revealed single and multiple insertions of the transgene. RT-PCR and Western blot analysis of T0 and T1 progeny demonstrated that the P5CS gene is expressed and produced functional protein in chickpea. T1 transgenic lines accumulated higher amount of proline under 250 mM NaCl compared to untransformed controls. Higher accumulation of Na(+) was noticed in the older leaves but negligible accumulation in seeds of T1 transgenic lines as compared to the controls. Chlorophyll stability and electrolyte leakage indicated that proline overproduction helps in alleviating salt stress in transgenic chickpea plants. The T1 transgenics lines were grown to maturity and set normal viable seeds under continuous salinity stress (250 mM) without any reduction in plant yield in terms of seed mass.

Salt-tolerance in mangrove soil bacteria

A total of sixteen bacterial species were isolated from mangrove soils of Karachi, Pakistan. Twelve of the isolates were gram positive while four were gram negative. All sixteen species showed resistance to high concentration of streptomycin, however, resistance to chloramphenicol and tetracycline was variable. The isolates tolerated up to 110‰ salinity and accumulated sodium form the media.

Salinity and survival of Martesia striata (Linn) in Cochin harbour

The effects of salinity variations on the survival of Martesia striata from Cochin harbour are presented. It is observed that at least a few of the animals survive the low saline conditions during monsoon. Laboratory experiments showed the lethal salinity as 6‰ when animals acclimatised in 34‰ were subjected to abrupt changes in salinity. But acclimatisation to 17‰ salinity showed a downward shift in the lethal salinity to 4‰. The present observations indicate that M. striata is euryhaline arid the extent of tolerance to lower salinities depends on the degree of acclimatisation.

SHORT-TERM EFFECTS OF SALINITY ON SOME PHYSIOLOGICAL PARAMETERS OF YOUNG OLIVE TREES OF ARBEQUINA, COBRANÇOSA AND GALEGA VARIETIES

SHORT-TERM EFFECTS OF SALINITY ON SOME PHYSIOLOGICAL PARAMETERS OF YOUNG OLIVE TREES OF ARBEQUINA, COBRANÇOSA AND GALEGA VARIETIES Ana Elisa Rato1,4, Renato Coelho1, Margarida Vaz1, Teresa Carola2, Dália Barbosa2, Nádia Silva1, José dos Santos2, Lourenço Machado2, João Godinho2, Luzia Ruas2, Margarida Barradas2, Hernani Pereira2, Sara Porfírio4 1 ICAAM, Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal 2 Master students, Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal 3 Ph.D. student, Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal 4 aerato@uevora.pt Due to the desertification in some regions, the interest in plant’s tolerance to salinity has been increasing, as this response is determining for plant survival in stress conditions. This work reports the investigation of tolerance to salt in two year-old olive trees (Olea europaea L.) of three varieties, Arbequina, Cobrançosa and Galega vulgar. Plants were grown in 10 L plastic pots containing approximately 9 Kg of a sandy granitic soil, on a greenhouse. For 3 months (from the beginning of February to the end of April 2012), they were subjected to three levels of salinity in the irrigation water, 0 mM, 80 mM and 200 mM NaCl (6 plants per salinity level in a total of 18 plants of each variety),. Stomatal conductance (gs) and relative leaf chlorophyll content were assessed on each plant in February, March and April. Mid-day leaf water potential () and soil salinity were measured at the end of the experiment (April). On average, concerning all treatments and dates of determination, stomatal conductance of Arbequina and Galega vulgar was quite similar, around 40 mmol m-2 s-1, but Cobrançosa had a value of gs 36% higher, almost 50% higher (61 mmol m-2 s-1) when compared with the controls (0 mM salt) of the other two varieties. In percentage of controls, there was little difference in gs between varieties and between salinities during February and March. In contrast, in April, after about 90 days of exposure to salt, there was a clear decrease in gs with salt irrigation, proportional to salt concentration. Compared with controls, plants irrigated with 200 mM salt showed around 80% (Arbequina) or 85% (Cobrançosa and Galega vulgar) decrease in gs. Chlorophyll content of leaves showed less than 5% difference between varieties on the average of all treatments and dates of determination. During the course of this experiment, the salinity levels used did not show any relevant effect on chlorophyll content. Overall, at the end of the experimental period (April), leaf water potential () at midday was significantly higher in Cobrançosa (-1,4 MPa) than in Galega vulgar (-1,7 MPa) or Arbequina (-1,8 MPa), and salt decreased  of control plants (-1,25 MPa) by an average 30% (with 80 mM) and 65% (with 200 mM). At the end of the experiment, salinity in the soil irrigated with 0 mM, 80 mM or 200 mM NaCl was, on average of all varieties, 0,2 mS, 1,0 mS or 2,0 mS, respectively. Soil salinity was quite similar in Arbequina and Galega vulgar but about 35% lower in the pots of Cobrançosa, on average of all salt-irrigation levels. Plants of Cobrançosa had higher stomatal conductance, however they showed higher water potential and lower salinity in the soil. These apparently contradictory results seem to suggest that Cobrançosa responds to salt differently from the other two varieties. This issue needs further investigation.

Tolerance of young (Ceratonia siliqua L.) carob rootstock to NaCl

One-year-old carob (Ceratonia siliqua L.) rootstock was grown in fertilised substrate to evaluate the effects of NaCl salinity stress. The experiment consisted of seven treatments with different concentrations of NaCl in the irrigation water: 0 (control), 15, 30, 40, 80, 120 and 240 (mmol L(-1)), equivalent to electrical conductivities of 0.0, 1.5, 2.9, 3.9, 7.5, 10.9 and 20.6 dS m(-1), respectively. Several growth parameters were measured throughout the experimental period. At the end of the experiment, pH, extractable P and K, and the electrical conductivity of the substrate were assessed in each salinity level. On the same date, the mineral composition of the leaves was compared. The carob rootstock tolerated 13.4 dS m(-1) for a period of 30 days but after 60 days the limit of tolerance was only 6.8 dS m(-1). Salt tolerance indexes were 12.8 and 4.5 for 30 and 60 days, respectively. This tolerance to salinity resulted from the ability to function with concentrations of Cl(-) and Na(+) in leaves up to 24.0 and 8.5 g kg(-1), respectively. Biomass allocation to shoots and roots was similar in all treatments, but after 40 days the number of leaves was reduced, particularly at the larger concentrations (120 and 240 mmol NaCl L(-1)). Leaves of plants irrigated with 240 mmol NaCl L(-1) became chlorotic after 30 days exposure. However, concentrations of N, P. Mg and Zn in leaves were not affected significantly (P > 0.05) by salinity. Apparently, K(+) and Ca(2+) were the key nutrients affected in the response of carob rootstocks to salinity. Plants grown with 80 and 120 mmol L(-1) of NaCl contained the greatest K. concentration. Na(+)/K(+) increased with salinity, due to an elevated Na(+) content but K(+) uptake was also enhanced, which alleviated some Na. stress. Ca(2+) concentration in leaves was not reduced under salinity. Salinization of irrigation water and subsequent impacts on agricultural soils are now common problems in the Mediterranean region. Under such conditions, carob seems to be a salt as well as a drought tolerant species. (C) 2010 Elsevier B.V. All rights reserved.

Generation of Variability for Salt Tolerance in Rice Using Tissue Culture Techniques

The study deals with the generation of variability for salt tolerance in rice using tissue culture techniques. Rice is the staple food of more than half of the world’s population. The management of drought, salinity and acidity in soils are all energy intensive agricultural practices. The Genetic variability is the basis of crop improvement. Somaclonal and androclonal variation can be effectively used for this purpose. In the present study, eight isozymes were studied and esterase and isocitric dehydrogenase was found to have varietal specific, developmental stage specific and stress specific banding pattern in rice. Under salt stress thickness of bands and enzyme activity showed changes. Pokkali, a moderately salt tolerant variety, had a specific band 7, which was present only in this variety and showed slight changes under stress. This band was faint in tillering and flowering stage .Based on the results obtained in the present study it is suggested that esterase could possibly be used as an isozyme marker for salt tolerance in rice. Varietal differences and stage specific variations could be detected using esterase and isocitric dehydrogenase . Moreover somaclonal and androclonal variation could be effectively detected using isozyme markers.

Paddy Field Cyanobacteria : Diversity and Pesticide Tolerance

School of Environmental Studies, Cochin University of Science and Technology

Ecophysiology of seed dormancy and salt tolerance of Grewia tenax (Forssk.) Fiori and Ziziphus spina-christi (L.) Willd.

Higher Education Commission (HEC) of Pakistan and German Academic Exchange Service (DAAD)

Genetic analysis of heat tolerance at anthesis in rice

Genetic analysis of heat tolerance will help breeders produce rice (Oryza sativa L.) varieties adapted to future climates. An F6 population of 181 recombinant inbred lines of Bala (tolerant) × Azucena (susceptible) was screened for heat tolerance at anthesis by measuring spikelet fertility at 30°C (control) and 38°C (high temperature) in experiments conducted in the Philippines and the United Kingdom. The parents varied significantly for absolute spikelet fertility under control (79–87%) and at high temperature (2.9–47.1%), and for relative spikelet fertility (high temperature/control) at high temperature (3.7–54.9%). There was no correlation between spikelet fertility in control and high-temperature conditions and no common quantitative trait loci (QTLs) were identified. Two QTLs for spikelet fertility under control conditions were identified on chromosomes 2 and 4. Eight QTLs for spikelet fertility under high-temperature conditions were identified on chromosomes 1, 2, 3, 8, 10, and 11. The most significant heat-responsive QTL, contributed by Bala and explaining up to 18% of the phenotypic variation, was identified on chromosome 1 (38.35 mega base pairs on the rice physical genome map). This QTL was also found to influence plant height, explaining 36.6% of the phenotypic variation. A comparison with other studies of abiotic (drought, cold, salinity) stresses showed QTLs at similar positions on chromosomes 1, 3, 8, and 10, suggesting common underlying stress-responsive regions of the genome.