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Kh. A. Okasha and R. M. Helal

Salt tolerance of four okra cutivars namely : white velvet ; Gold coast ; Balady and Eskandarani, were investigated during three different stages of plant development namely : seed germination, seedling and reproductive stages. At both first and second stages of plant development various concentrations of sea water (diluted with tap water) were used for irrigation while at the third stage, various saline water with different electronic conductivities were used for irrigation

Results of these studies revealed that salinity reduced and delayed seed germination At this stage, white velvet cv. appeared to be tolerant to salinity. At the seedling stage, salinity generally reduced hash weight of plant for all tested cuitivars and Gold coast was the lead affected one At the reproductive stage, salinity reduced plant growth and total yield/plant but with different degrees depending upon cultivar In this respect, yield of both Gold coast and Balady was not greatly reduced at the high level of salinity

The anatomical studies showed that salinity reduced xylem and phloem elements in okra roots depending upon both salinity level and cultivar

Generally, the obtained results suggest that both Gold coast and Balady okra cultivars can considered as tolerant genotypes to salinity and recommended for cultivation in both and and semi-arid lands where salinity is considered a potential problem

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Carolyn F. Scagel, David R. Bryla, and Jungmin Lee

the same salt treatment ( P ≤ 0.05). Discussion Response of basil to NaCl and CaCl 2 salinity Tolerance to salinity. ‘Siam Queen’ basil was moderately tolerant to NaCl and CaCl 2 salinity in the present study. Salinity levels reached as high as 8 dS

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Michael C. Shannon and Anne F. Wrona

A salt-tolerance selected F5 generation from a cross between the wild tomato species, Lycopersicon cheesmanii, ecotype LA 1401, and the cultivated species, L. esculentum Mill. (cv Heinz 1350) was compared to the wild parental line in a solution culture experiment to determine the effects of selection on salt tolerance, and ion discrimination and accumulation characteristics in the selected line. Seedlings were transplanted to nutrient solutions at the 3 to 4-leaf stage of growth and after a 1-week period of adjustment, were salinized at 25 mM NaCl day-1 (approximately -1 bar osmotic potential) to final salt concentrations of 0, 50, and 100 mM. Plasmalemma and tonoplast vesicles were isolated from fresh root samples, and ATPase and Na+/H+ antiport activity was determined using fluorescence assays. The selected line restricted Na uptake into the shoot and maintained higher shoot K+ than did the wild parent. Growth rate under salinity was greater in the selected line than in the wild species, but relative salt tolerance was higher in the wild parent. Interspecific hybridization appears to be a useful process for the transfer of salt tolerance characters from wild to cultivated tomato.

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C.M. Grieve, M.R. Guzy, J.A. Poss, and M.C. Shannon

Agroforestry plantations offer environmentally acceptable strategies for the reuse of saline drainage waters. Tree species suitable for use in such systems must be selected for survival and sustained growth under highly saline conditions. In this screening trial, four clones of Eucalyptus camaldulensis Dehn. (4543, 4544, 4573, and 4590) and one clone of E. rudis Endl. (4501) were grown in greenhouse sand cultures irrigated with sodium sulfate–dominated waters. Solution compositions were prepared to simulate saline drainage waters typically found in the San Joaquin Valley of California. Electrical conductivities of the solutions ranged from 2 to 28 dS·m–1. Treatments were replicated three times. All plants survived and were harvested after 7 weeks under saline treatment. Plant height was measured weekly and shoot biomass was determined at final harvest. The salinity levels that resulted in a 50% reduction in biomass production (C50) were 16.4 (4573), 17.1 (4543), 17.7 (4544), 29.0 (4590), and 30.0 dS·m–1 (4501). Over the range of salinities from 4 to 20 dS·m–1, clones 4501, 4590, and 4573 generally maintained higher relative growth rates (RGR) than did clones 4544 and 4543. However, at the highest salinity, RGRs of clones 4501, 4544, and 4573 were significantly greater than those of clones 4543 and 4590. Assessed on the basis of biomass production, clones 4501 (E. rudis) and 4590 (E. camaldulensis) showed exceptional potential for use in agroforestry systems where the saline drainage waters are sodium sulfate–dominated.

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M.R. Foolad

The effectiveness of directional phenotypic selection to improve tomato seed germination under salt-stress was investigated. Seed of F2 and F3 progeny of F1 hybrids between a salt-tolerant and a salt-sensitive tomato cultivar were evaluated for germination response at three stress levels of 100 (low), 150 (intermediate), and 200 mm (high) synthetic sea salt (SSS). At each salt-stress level, the most tolerant individuals were selected. Selected individuals (F2s or F3s) were grown to maturity and self-pollinated to produce F3 and F4 progeny families. The selected progeny from each experiment were evaluated for germination at four treatment levels of 0 (nonstress), 100, 150, and 200 mm SSS and compared with unselected populations. The results indicated that selections were equally effective at all three stress levels and in both F2 and F3 generations and significantly improved progeny seed germination under both salt-stress and nonstress treatments. Estimates of realized heritability for rapid germination under the various salt-stress levels ranged from 0.67 to 0.76. Analysis of response and correlated response to selection indicated a genetic correspondence of up to 100% between germination at different salt-stress levels. Genotypic family correlations between germination at the low, intermediate, and high salt-stress levels ranged from 0.67 to 0.89 and those between nonstress and salt-stress conditions ranged from 0.25 (between 0 and 200 mm) to 0.71 (between 0 and 100 mm salt). The results indicated that similar or identical genes contributed to rapid germination response of tomato seeds at different salt-stress levels. Thus, selection at one stress level resulted in progeny with improved germination at diverse salt-stress levels.

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Yueju Wang, Michael Wisniewski, Richard Meilan, Minggang Cui, Robert Webb, and Leslie Fuchigami

Ascorbate peroxidase (APX) plays an important role in the metabolism of hydrogen peroxide in higher plants, affording them protection against oxidative stress. We studied the effect of overexpressing a cytosolic ascorbate peroxidase (cAPX) gene—derived from pea (Pisum sativum L.)—in transgenic tomato plants (Lycopersicon esculentum L.). Transformants were selected in vitro using kanamycin resistance and confirmed by polymerase chain reaction (PCR) and northern analyses. An APX native-gel assay indicated that, in the absence of stress, APX activity in transgenic plants was several times greater than that measured in wild-type (WT) plants. Several independently transformed lines were propagated and evaluated for resistance to chilling and salt stress. After placing seeds at 9 °C for 5 weeks, percent germination was greater for seeds obtained from transgenic lines (26% to 37%) compared to the WT (3%). Plants from transgenic lines also had lower electrolyte leakage (20% to 23%) than WT (44%) after exposure to 4 °C. Visual assessment of transgenic and WT lines exposed to salinity stress (200 or 250 mm) confirmed that overexpression of APX minimized leaf damage. Moreover, APX activity was nearly 25- and 10-fold higher in the leaves of transgenic plants in response to chilling and salt stresses, respectively. Our results substantiate that increased levels of APX activity brought about by overexpression of a cytosolic APX gene may play an important role in ameliorating oxidative injury induced by chilling and salt stress.

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Y. Saranga, D. Zamir, A. Marani, and J. Rudich

Accessions of four tomato species, Lycopersicon esculentum Mill. (Le), L. pennellii (Corr.) O'Arey (Lpen), L. cheesmanii Riley (Lc), and L. peruvianum (L.) Mill., (Lper), and interspecific populations were irrigated with saline water under field conditions and concentrations of Na, K, Cl, Ca, and Mg in leaves and stems were determined. Potassium: sodium ratios in leaves and stems of salt-tolerant genotypes were higher under salinity and were moderately changed by salinity compared to the sensitive genotypes. In the tolerant wild accessions and F1(Le × Lpen), Cl concentrations in leaves and the ratio between Cl in leaves to Cl in stems were lower than in the sensitive Le cultivar. Regulation of the K: Na ratio was found in tolerant wild accessions and tolerant Le cultivars, while regulation of Cl concentration in leaves was found only in the wild germplasm. The effects of ion concentrations on dry matter of interspecific segregating populations, F2(Le × Lpen) and BC1(Le × (Le × Lpen)), were studied by regression analyses. Dry matter was positively correlated with the K: Na ratio in stems and negatively correlated with the Cl concentrations in leaves and stems, thus confirming the results obtained by comparison between the tolerant and sensitive accessions.

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M.R. Foolad

The effectiveness of directional phenotypic selection to improve tomato (Lycopersicon esculentum Mill.) seed germination under salt-stress was investigated. Seed of F2 and F3 progeny of F1 hybrids between a salt-tolerant (PI174263) and a salt-sensitive (UCT5) tomato cultivar were evaluated for germination response at three stress levels of 100 (low), 150 (intermediate), and 200 mm (high) synthetic sea salt (SSS). At each salt-stress level, the most tolerant individuals, as determined by the germination speed, were selected. Selected individuals (F2s or F3s) were grown to maturity and self-pollinated to produce F3 and F4 progeny families. The selected progeny from each experiment were evaluated for germination at four treatment levels of 0 (nonstress), 100, 150, and 200 mm SSS and were compared with unselected populations. The results indicated that selections were equally effective at all three salt-stress levels and in F2 and F3 generations and significantly improved seed germination of progeny under salt-stress and nonstress treatments. Estimates of realized heritability for rapid germination under the various salt-stress levels ranged from 0.67 to 0.76. Analysis of response and correlated response to selection indicated a genetic correspondence of up to 100% between germination at different salt-stress levels. Genotypic family correlations between germination at the low, intermediate, and high salt-stress levels ranged from 0.67 to 0.89, and those between nonstress and salt-stress conditions ranged from 0.25 (between 0 and 200 mm) to 0.71 (between 0 and 100 mm salt). The results indicated that similar or identical genes with additive genetic effects contributed to rapid germination response of tomato seeds at different salt-stress levels. Thus, selection at one stress level resulted in progeny with improved germination at diverse salt-stress levels. The results also indicated that to improve tomato seed germination, selection can be based on individual seed performance and early segregating generations.

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Lingdi Dong, Waltram Ravelombola, Yuejin Weng, Jun Qin, Wei Zhou, Gehendra Bhattarai, Bazgha Zia, Wei Yang, Linqi Shi, Beiquan Mou, and Ainong Shi

and create further improvements in cowpea cultivars. However, little has been accomplished regarding the study of the responses of cowpea accessions to abiotic stresses such as salt tolerance, which constrains breeders from using the rich genetic

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Adam Bolton and Philipp Simon

carrots. Screening for salt tolerance at the germination stage is the first step in identifying tolerant genotypes because it is a critical stage for plant development. A number of studies of several crop species, including alfalfa, barley, corn, red