Plant growth promoting rhizobacteria (PGPR) are beneficial microorganisms that can be utilized to improve plant responses against biotic and abiotic stresses. In this study, 74 halotolerant bacterial isolates were isolated from rhizosphere and endorhizosphere of durum wheat (Triticum turgidum subsp. durum) plants cultivated in saline environments in the Ghor region near the east of the Dead Sea. 16S rDNA partial sequences and phylogenetic analysis of 62 isolates showed clear clustering of the isolates into three phyla: Firmicutes (61.3%), Proteobacteria (29.0%), and Actinobacteria (9.7%). At the genus level, the majority of them were grouped within the Bacillus, Oceanobacillus, and Halomonas genera. The isolates, which possessed plant growth promoting traits including nitrogen fixation, ACC deaminase activity, auxin production, inorganic phosphate solubilization and siderophore production, were selected. The effect of the inoculation of selected PGPR strains on growth of salt sensitive and salt tolerant durum wheat genotypes under high salt stress conditions was evaluated. Six halotolerant PGPR strains were able to improve survival in inoculated plants under high salinity stress conditions as reflected in higher germination percentages and seedling root growth when compared with non-inoculated plants. Furthermore, three halotolerant PGPR strains were able to improve durum wheat tolerance to water deficit stress. In addition, antagonistic effect in four halotolerant PGPR strains against an aggressive pathogenic isolate of Fusarium culmorum that causes crown rot disease was observed in a dual culture assay. In conclusion, the halotolerant PGPR strains described in this study might have great potential to improve durum wheat productivity under different stress conditions.

Tasco-Forage an extract from the brown seaweed Ascophyllum nodosum, has increased antioxidant activity in both plants and animals. Turf and forage grasses exhibited increased amounts of α-tocopherol, ascorbic acid, β-carotene, and increased activities of superoxide dismutase, glutathione reductase, and ascorbate peroxidase in response to exogenous application of Tasco. Endophyte (Neotyphodium coenophialum [(Morgan-Jones and Gams) Glenn, Bacon, and Hanlin]-infected tall fescue (Festuca arundinacea Schreb.) can increase oxidative stress. Both high environmental temperatures and increased body temperatures increase respiratory rates, which increase free radical production. Steers that grazed infected fescue had diminished immune function and vitamin E, Cu, and Se status, indicating less ability to deal with oxidative stress. Two applications of Tasco-Forage (3.4 kg/ha in water solution) to infected fescue during the growing season improved steers' immune function, and the effect lasted through cross-country transportation and a 160-d feedlot finishing period. Grazing infected fescue reduced serum cholesterol, but the effect was reversed by Tasco, indicating effects on lipid metabolism. Applying Tasco to low-endophyte fescue seemed to have an immune-dampening effect on steers, at least during the grazing season. At slaughter, marbling was greater in retail cuts of meat and meat had a longer shelf-life if steers had grazed the Tasco-treated fescue, regardless of the endophyte. Direct supplementation to steers with Tasco-EX (extract) during the final 14 d in the feedyard also extended shelf-life of strip loins. Supplementation of Tasco-EX or Tasco-14 (meal) to porcine reproductive and respiratory syndrome-stressed pigs during the nursery phase improved weight gain and feed intake within 35 d. Supplementing Tasco-EX in drinking water failed to reduce morbidity and mortality in transported heifers stressed by Pasturella haemolytica. The mode of action of Tasco is not clear, but antioxidants and specific vitamins may be involved. Supplementation with certain antioxidants can have beneficial effects, but inappropriate use can have detrimental effects. Although positive effects on stress tolerance and carcass composition are apparent, further research is needed to elucidate these relationships and to provide predictable responses. Copyright © 2001. American Society of Animal Science . ©2001 American Society of Animal Science

Increasing cuticular wax accumulation in plants has been associated with improving drought tolerance in plants. In this study, a cDNA clone encoding the SlSHN1 transcription factor, the closest ortholog to WIN/SHN1 gene in Arabidopsis, was isolated from tomato plant. Expression analysis of SlSHN1 indicated that it is induced in response to drought conditions. The over-expression of SlSHN1 in tomato under the control of the constitutive CaMV 35S promoter produced plants that showed mild growth retardation phenotype with shiny and dark green leaves. Scanning electron microscopy showed that the over-expression of SlSHN1 in tomato resulted in higher cuticular wax deposition on leaf epidermial tissue when compared to non-transformed plants. Expression analysis in transgenic lines over-expressing SlSHN1 indicated that several wax-related synthesis genes were induced. Transgenic tomato plants over-expressing SlSHN1 showed higher drought tolerance when compared with wild type plants; this was reflected in delayed wilting of transgenic lines, improved water status and reduced water loss rate when compared with wild type plants. In conclusion, the SlSHN1 gene can modulate wax accumulation and could be utilized to enhance drought tolerance in tomato plant.

Soil and irrigation water salinity are major limiting factor to citrus industry in arid environments. The objective of this study was to assess the effects of different salt stress levels on growth and ion uptake of three-month-old citrus rootstocks; sour orange (Citrus aurantium) and Volkamer lemon (Citrus volkameriana). Six levels of NaCl-salinity were used, 0.7 (control), 2, 4, 8, 12 and 15 dS m^-1. Salinity increment from 2.0 to 15.0 dS m^-1 significantly reduced seedlings height, stem diameter, leaf area, root dry weight, leaf relative water content, chlorophyll content index and chlorophyll fluorescence by one to three folds. In addition, leaf and root N concentration reduced by 10%-50%, P 6%-50%, K 8%-47%, Ca⁺² 7%-51% and Mg⁺² 7%-50% when salt stress in the irrigation water increased from 2.0 to 15.0 dS m^-1. Conversely, salt stress increment (2.0-15.0 dS m^-1) increased leaf stomatal resistance (5 folds), proline concentration (1 fold), Na⁺ and Cl^- in the leaf (10 fold) and root (4 fold) when compared to control (0.7 dS m^-1). In term of rootstock, Volkamer had higher seedling height, stem diameter, and root constituents (length, fresh and dry weight) than sour orange. While sour orange had higher leaf Cl^-, Ca⁺² and Mg⁺², Volkamer lemon had higher N, Na⁺, K⁺, and P. However, root nutrient (N, Na⁺, Cl^-, P and Mg⁺²) from Volkamer had consistently higher concentration compared to sour orange at 4.0, 8.0, 12.0 and 15.0 dS m^-1. Therefore, we believe that the Volkamer rootstock is more tolerant to salt stress than sour orange.