Improved Wheat Growth Research Articles

Silicon Improves the Tolerance to Water-Deficit Stress Induced by Polyethylene Glycol in Wheat (Triticum aestivum L.) Seedlings

Drought stress usually causes a serious yield reduction in wheat production. Silicon (Si) has been reported to be able to alleviate drought stress damage; however, the mechanism is still poorly understood. In this article, the effects of Si (as sodium silicate) on some parameters related to oxidative damage, proline, soluble sugar, and inorganic ions in the leaves of wheat under 20% (w/v) polyethylene glycol (PEG-6000) simulative drought stress are investigated. PEG stress depressed the growth of shoot and root and decreased leaf water potential and chlorophyll concentration. Addition of 1.0 mM Si could partially improve the growth of shoot (but not root) and increase the leaf chlorophyll concentrations of stressed plants. Inclusion of Si in culture solution also maintained leaf water potential of stressed plants at the same level as that of the control plants. PEG stress induced significant accumulation of leaf hydrogen peroxide (H2O2) and malondialdehyde (MDA) as well as an increase in electrolyte leakage, which were all decreased by added silicon. These results suggest that stress-induced membrane lipid peroxidation could be partly alleviated by added silicon. Moreover, the results were also supported by the observation that PEG stress-induced decrease in glutathione concentration in the leaves was reversed by added silicon. The proline concentration in the leaves was markedly increased under PEG stress, whereas added silicon partially reversed this. PEG stress decreased the leaf soluble sugar concentration. There were significant negative regressions between proline concentration and both shoot dry weight and leaf chlorophyll concentrations, whereas there were positive regressions between the proline concentration and both H2O2 and MDA concentrations in the leaves, supporting the view that proline accumulation is a symptom of stress damage rather than stress tolerance. Addition of Si obviously increased Si accumulation in the shoot. Analyses of Na, Mg, K, and Ca showed no accumulation of these ions in the shoot (on the basis of per tissue dry weight) under water stress, and added Si even decreased their concentrations. These results suggest that under short-term PEG-induced water stress conditions (1 week), antioxidant defense, rather than osmotic adjustment, contributed to the improved wheat growth by Si.

Immobilization and phytotoxicity of Cd in contaminated soil amended with chicken manure compost

The experiment was conducted to evaluate the effect of compost application on the immobilization and biotoxicity of Cd in winter wheat ( Triticum aestivum L.) potted soils. Soils treated with various levels of Cd (0–50 mg Cd kg −1 soil) were amended with 0, 30, 60 and 120 g compost kg −1 soil. The fractions of Cd in soil were evaluated by a sequential extraction procedure. Compost application resulted in more than 70% lower soluble/exchangeable Cd (KNO 3) but increased the concentration of organic-bound (NaOH) and inorganic precipitates (EDTA) Cd in soils. Addition of compost was effective in reducing the phytotoxicity of Cd by decreasing more than 50% Cd uptake by wheat tissue and improving wheat growth. Alleviation of Cd phytotoxicity by compost was attributed primarily to the increase of soil pH, complexation of Cd by the organic matter and coprecipitation with P content. Compost was effective in the immobilization of Cd in soils and can be used to remediate Cd-contaminated soils.

Biocontrol of Alternaria triticina by plant growth promoting rhizobacteria on wheat

Eighteen isolates of fluorescent pseudomonads and Bacillus spp. were isolated from Alternaria triticina suppressive soils of wheat fields. These isolates were evaluated in the laboratory and greenhouse for the biocontrol of A. triticina. Six isolates were considered to have potential for the biocontrol of A. triticina on the basis of antibiotic sensitivity, fluorescence produced by Pseudomonas, inhibitory effect on A. triticina and root colonization of wheat roots by these isolates. These six isolates (Pa22, Pf27, Pa28, B25, B28, and B30) were further tested for their biocontrol potential against A. triticina on wheat in a pot test. Out of six isolates, isolate B28 was best in improving wheat growth of A. triticina inoculated plants. Isolate B28 also caused higher reduction in percentage infected leaf area caused by A. triticina while isolate Pa22 was found best in improving growth of plants without A. triticina.

Soil available phosphorus status determines indigenous mycorrhizal colonization of field and glasshouse-grown spring wheat from Argentina

Wheat production ( Triticum aestivum L.) has increased across the world during last century with the intensification of agriculture. Phosphorus (P) fertilization is a common practice to improve wheat growth in Argentina. We investigate whether indigenous arbuscular mycorrhizal colonization (AMC) of hard red spring wheat is controlled by shoot P content (SPc) or by available soil P in an agricultural soil from the southeastern Argentine Pampas. In the field, AMC was monitored four times during two growing seasons of a conventional wheat crop. Treatments were: without P supply, annual supply of 11 and 22 kg P ha −1 during the last 5 years, and 164 kg P ha −1 applied once 5 years before the experiment. In the glasshouse, AMC was assessed three times in wheat growing in pots filled with the soil from unfertilized plots; treatments were: P (0 and 20 mg P pot −1), and nitrogen (N) fertilization (0 and 150 mg N pot −1). A range of soil P between 6 and 60 mg P kg −1 was obtained and the AMC ranged from 1% to 67% of root length colonized under both field and glasshouse conditions. P supplied annually increased growth and SPc but decreased AMC. N fertilization did not affect growth or AMC. Variations in SPc did not account for AMC. Variability in AMC was best accounted for local current soil available P content ( r 2 = 0.59). A linear-plateau relationship between soil P and indigenous AMC was established in wheat plants growing under contrasting environmental and experimental (field and glasshouse) conditions. Indigenous AMC was depressed by available soil P in the range 0–27 mg P kg −1 (a decrease of 2.8% mg P −1 kg −1). Above 27 mg P kg soil −1, AMC was stabilized at about 10%. Grain yield increased with fertilization and the highest relative shoot dry matter in field was obtained at 15.5 mg P kg soil −1. The soil P range that ensures high wheat production without deterring indigenous AMC is discussed.

Rhizosphere colonization of wheat by selected soil bacteria over diverse environments

The ability to colonize the rhizosphere is essential for bacteria to function as biological control agents for soil-borne plant pathogens. Eight bacterial strains reported to colonize wheat roots, inhibit root pathogens, and (or) improve wheat growth and yield were applied to wheat seeds that were planted in fumigated and nonfumigated soil in the 1990 and 1991 growing seasons at two locations in Arkansas. Rhizosphere population sizes were highly correlated with population sizes on seeds. Bacillus subtilis strain D-39Sr colonized roots as well in nonfumigated as in fumigated soil, and the other seven strains had rhizosphere populations 0.3 to 1.1 log units higher in fumigated soil. Pseudomonas fluorescens strain 2-79R was one of the best colonizers, and Streptomyces strain D-185S was the poorest. The greatest difference among strains was for relative colonization ability of crown roots in the spring. All strains except Streptomyces strain D-185S appear to have broad adaptation to colonize wheat roots and are able to compete with soil microflora for colonization sites. This research indicates that it is possible to select bacteria in the genera Bacillus, Pseudomonas, or Xanthomonas that will colonize roots well over diverse environments. Rhizosphere colonization by these strains was not associated with disease suppression or enhanced plant growth or yield.Key words: biological control, rhizosphere competence, wheat, Triticum aestivum.

Salinity-induced calcium deficiencies in wheat and barley

Salinity-calcium interactions, which have been shown to be important in plants grown in dryland saline soils of the Canadian prairies, were studied in two species differing in salt tolerance. In solution culture, wheat showed a greater reduction in growth and a higher incidence of foliar Ca deficiency symptoms than barley when grown under MgSO4 or Na2SO4 plus MgSO4 salt stress. Amendment of the saline solution with Ca to increase the Ca/(Na+Mg) ratio ameliorated the effects of salt, but more so in wheat than in barley. At least part of the difference in salt tolerance between the two species must therefore relate to species differences in the interaction of salinity and Ca nutrition. The greater response of wheat to Ca was not due to a lower Ca status in leaf tissue; on the contrary, although Ca amendments improved tissue Ca/(Na+Mg) ratios in both species, salinized wheat had equivalent or higher Ca content, and higher Ca/(Na+Mg) ratios than did barley. The higher Ca requirement of wheat is apparently specific to a saline situation; at low salinity, wheat growth was not reduced as extensively as that of barley as Ca/(Na+Mg) ratio was decreased. High night-time humidity dramatically improved wheat growth under saline conditions, but increasing the Ca concentration of the saline solution had no effect on growth in the high humidity treatment. Membrane leakage from leaf tissue of wheat grown under saline conditions was increased compared to tissue from non-saline plants. Plants grown in Ca-amended saline solutions showed no increase in membrane leakage. These results confirm the importance of Ca interaction with salinity stress, and indicate differences in species response.