Tolerance Of Cv Research Articles

Balance between oxidative stress and the antioxidant system is associated with the level of cold tolerance in sweet potato roots

Abstract The balance between oxidative stress and antioxidant defense system was investigated in roots of the cold-sensitive (cvs. BRS Rubissol and BRS Cuia) and cold-tolerant (cv. Beauregard) sweet potato stored at 6 or 13 °C for 60 d. We hypothesized that the absence of chilling injury symptoms on cv. Beauregard stored at 6 °C depends on the induction capacity of enzymatic and non-enzymatic antioxidant systems. The manifestation of chilling injury symptoms on cvs. BRS Rubissol and BRS Cuia were associated with the loss of membrane integrity, increased lipid peroxidation, accumulation of hydrogen peroxide (H2O2), and low catalase (CAT) and ascorbate peroxidase (APX) activities. In these cold-sensitive cultivars, proline and total phenolics increased with the progression of chilling injury, acting as markers for cold sensitivity, and parallel increased activity of phenylalanine ammonia-lyase. In contrast, constitutive levels of enzymatic and non-enzymatic antioxidants, as well as stress-induced increased CAT and APX activity played an important role in the detoxification of H2O2 in the tolerant cv. Beauregard. Our results suggest that the balance between oxidative stress and antioxidant system is involved in the tolerance of cv. Beauregard to chilling injury.

Variation in shoot tolerance mechanisms not related to ion toxicity in barley.

Soil salinity can severely reduce crop growth and yield. Many studies have investigated salinity tolerance mechanisms in cereals using phenotypes that are relatively easy to measure. The majority of these studies measured the accumulation of shoot Na+ and the effect this has on plant growth. However, plant growth is reduced immediately after exposure to NaCl before Na+ accumulates to toxic concentrations in the shoot. In this study, nondestructive and destructive measurements are used to evaluate the responses of 24 predominately Australian barley (Hordeum vulgare L.) lines at 0, 150 and 250mM NaCl. Considerable variation for shoot tolerance mechanisms not related to ion toxicity (shoot ion-independent tolerance) was found, with some lines being able to maintain substantial growth rates under salt stress, whereas others stopped growing. Hordeum vulgare spp. spontaneum accessions and barley landraces predominantly had the best shoot ion independent tolerance, although two commercial cultivars, Fathom and Skiff, also had high tolerance. The tolerance of cv. Fathom may be caused by a recent introgression from H. vulgare L. spp. spontaneum. This study shows that the most salt-tolerant barley lines are those that contain both shoot ion-independent tolerance and the ability to exclude Na+ from the shoot (and thus maintain high K+:Na+ ratios).

Growth and physiological alterations in Niger cultivars under drought stress

Aim of the present study was to determine differential responses in growth and physiology of tolerant (cv. IGPN 2004) and sensitive (cv. GA 10) cultivars of Niger (Guizotia abyssinica Cass.) using in vitro grown calli under water deficit conditions. The calli were subjected to drought stress using PEG-8000 (–0.16,–0.45,–0.87,–1.42 bar) for 15 d and relative growth rate (RGR), percent tissue water content (% TWC), osmolytes (proline–Pro, glycine betaine—GB, total soluble sugars—TSS) accumulation, malondialehyde (MDA) content as well as antioxidant enzyme activities such as superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) were analysed. Our findings showed that RGR and percent TWC was decreased significantly with the intensity of drought stress in both cultivars, but the RGR reduction was least (five folds) in cv. IGPN 2004 than in cv. GA 10 (6.2 folds). In osmolyte accumulation such as Pro and GB, cv. IGPN 2004 was found superior (5.5 and ten folds higher, respectively) to tolerate drought stress than GA 10; however, no change was observed in TSS accumulation. Further, it was noted that cv. IGPN 2004 caused least oxidative damage to the membranes. It also exhibited better SOD, CAT and APX activities and had higher α-tocopherol content. The least reduction in growth and MDA content and higher osmolytes and antioxidant activities in cv. IGPN 2004 revealed more drought stress tolerance at cellular level. It was suggested that increased drought tolerance of cv. IGPN 2004 was coupled with its better maintenance of RGR, percent TWC, reduced lipid peroxidation, more accumulation of osmolytes and higher antioxidant enzymes.

Persistence traits in perennial pasture grasses: the case of phalaris (Phalaris aquatica L.)

Persistence is consistently claimed by Australian farmers as a high priority for perennial grasses in long-term pastures. Phalaris (Phalaris aquatica L.) is a productive perennial grass with proven persistence in south-eastern Australia. Nevertheless, factors that determine the persistence of pasture species in southern Australia related to climate (drought), soil (acidity), grazing pressure, and, importantly, their interaction can reduce persistence of phalaris and other species in various situations. These factors and their interactions are discussed in this review, and strategies to improve persistence with emphasis on plant breeding approaches are considered, with the most durable outcomes achieved when breeding and management options are employed concurrently. Two examples of breeding to improve persistence traits in phalaris are described. A program to improve acid-soil tolerance resulted first in the release of cv. Landmaster, and recently Advanced AT, which is the most aluminium (Al)-tolerant cultivar of phalaris to date. It was bred by recurrent selection on acid soils in a population containing genes from a related, more Al-tolerant species, P. arundinacea. The higher Al tolerance of cv. Advanced AT is of most benefit in more assured establishment on acid soils under variable moisture conditions and confers improved flexibility of sowing date. Cultivar Holdfast GT was bred to address complaints of poor persistence under heavy grazing by cultivars of the highly productive, winter-active type, since high grazing tolerance is needed to achieve profitable returns from developed pastureland. Evidence of good persistence under grazing for cv. Holdfast GT and possible tradeoffs with productivity are discussed. Maintaining high productivity under a predicted higher incidence of drought stress (climate change) and increasing areas of acid soils presents ongoing challenges for persistence in pastures.

Apoplastic antioxidative system responses to ozone stress in strawberry leaves

Cell wall polysaccharides, pectin composition, as well as apoplastic superoxide dismutase and peroxidase activities were investigated in strawberry (Fragaria x ananassa) cultivars (cvs) Korona and Elsanta differing in their ozone sensitivity. Plants were exposed to 140-170 microg m(-3) ozone either short-term for 7 days or long-term for 2 months in order to investigate whether differences in ozone sensitivity were due to differences in the apoplastic antioxidative systems. Cell wall polysaccharides were increased after 7 days and 2 months of ozone stress. While water-soluble pectins, low methoxy pectinates and NaOH-soluble pectinates were elevated after 7 days, their contents were unaffected (water-soluble pectins) or lower (low methoxy pectinates, NaOH-soluble pectinates) after 2 months. In cv. Elsanta, ozone treatment resulted in a significant reduction of superoxide dismutase activity after 7 days and 2 months, while it remained similar in cv. Korona. After 7 days, peroxidase activity was significantly higher in ozone-exposed leaves of cv. Korona, whereas after 2 months it was similar to or higher than in controls. Superoxide dismutase in cv. Korona detoxified ozone and its products in the apoplast, and the resulting elevated levels of H(2)O(2) were balanced within 7 days by an increase in peroxidase activity. Long-term peroxidase activity may not play a comparably significant role in ozone defence, but the increase in cell wall polysaccharides and cell wall thickness measured after 2 months, resulting in a decrease in specific leaf area, reflected structural modifications that limited activities of reactive oxygen species efficiently. In contrast, the reduction of superoxide dismutase activity in cv. Elsanta indicated a less efficient apoplastic radical scavenging system, at least during the first 7 days of ozone stress, which was accompanied by membrane leakage and contributed to accelerated leaf senescence. Long-term, the reduction of intercellular air space volume in leaves contributed to ozone tolerance of cv. Elsanta as in cv. Korona.

Interactive Effects of Salinity and Air Humidity on Two Tomato Cultivars Differing in Salt Tolerance

ABSTRACT An environmentally controlled experiment was conducted in growth chambers to investigate the interactive effects of salinity and air humidity on two cultivars of tomato (Lycopersicon esculentum Mill.), Daniela (relatively salt tolerant) and Naomi (relatively salt sensitive). One month after germination, the plants were exposed for 15 days to factorial combinations of two salinity levels, 0 (control) and 80 mM sodium chloride (NaCl), and two relative humidity (RH) levels, 30% and 70%. The NaCl treatment decreased the growth of cv. Naomi by 34% and 21% at 30% and 70% RH, respectively, while there was no decrease in the growth of cv. Daniela at 30% RH and only a slight decrease at 70% RH. Under NaCl treatment, cv Daniela had significantly lower Na+ concentrations in leaves and stems and a higher root-to-shoot ratio than cv. Naomi at both relative humidities. Salt tolerance of cv. Daniela may be related to its high root-to-shoot ratio and its ability to exclude Na+ from the shoot. NaCl-treated plants of cv. Daniela had a lower biomass at 70% than at 30% RH. Conversely, NaCl-treated plants of cv. Naomi had a greater biomass at 70% compared with 30% RH. The ameliorating effects of high RH on NaCl-induced growth reductions in cv. Naomi could be attributed to an increase in leaf area, root growth, photosynthetic rate, and stomatal conductance and a decrease in Cl− concentration in leaves. The overall findings of this study suggest that the growth of salt-sensitive tomato cultivars under saline conditions could be improved by increasing air humidity.

SALT TOLERANCE IN TWO SOYBEAN CULTIVARS

Experiments were conducted in an environmentally controlled growth chamber to evaluate the role of the root system in the salt tolerance of two soybean (Glycine max(L.) Merr.) cultivars, Tachiyutaka and Dare, that differ in salt tolerance. Young plants were submitted to 0 (control), 40, 80, and 120 mM NaCl treatments for 3, 23, and 30 days in three experiments, respectively. The most significant differences between the two cultivars were obtained in 40 mM NaCl. Under this condition, compared with salt sensitive cv. Tachiyutaka, tolerant cv. Dare showed a higher relative shoot and root growth (Dare: 70 and 63%, Tachiyutaka: 42 and 42%, respectively), water extraction ability (Dare: 0.18 g cm−2 d−1 for transpiration and 0.98 g m−1 d−1 for water uptake, Tachiyutaka: 0.13 g cm−2 d−1 and 0.81 g m−1 d−1 respectively), root pressure (Dare: 5.68 mg g−1 for root exudate, Tachiyutaka: 0.32 mg g−1), better root osmotic adjustment (Dare: −0.61 MPa for osmotic potential, Tachiyutaka: −0.59 MPa), and less sodium (Na+) accumulation in plant tissue (Dare: 0.1, 0.4, and 9.2 mg g−1 in leaf, stem, and root, respectively, Tachiyutaka: 1.4, 3.5, and 11.6 mg g−1). The difference in salt tolerance between the two cultivars is attributed to the root system. The salt tolerance of cv. Dare is associated with high water uptake, and Na+ and chloride (Cl−) exclusion of the roots.

CV 205–502

CV 205-502 (CV) is a long-acting dopamine agonist with potent D2 and weak D1 activity, which has not as yet been tested in patients with Parkinson's disease. We performed a dosage ranging and placebo crossover study in six patients to evaluate the efficacy and tolerance of CV when used as an adjunct to Sinemet in patients with Parkinson's disease. All patients had striking improvement. This effect was lost with placebo substitution and regained with reintroduction of CV. Benefits were sustained throughout the 6 month study. Single daily dosing could sustain the response in all but one patient. Adverse effects were mild and transient and resolved with dosage manipulation or a divided dosage regimen. CV is a promising drug for use in Parkinson's disease and further studies are indicated to test its long-term safety and efficacy.

Calmodulin Levels Are Not Responsible for Aluminium Tolerance in Wheat

Circumstantial evidence has suggested that the protein calmodulin may be the primary target of aluminium toxicity in plants. Experiments were carried out to test the hypothesis that genetic differences in aluminium tolerance in wheat (Triticum aestivum L.) are the consequence of different levels of calmodulin. The tolerant wheat, selection Waalt, differed from cv. Warigal by a single dominant gene for aluminium tolerance as indicated by analysis of the F2. The tolerance of cv. Carazinho also is reported to be genetically simple. Crosses between the two tolerant wheats, Carazinho and Waalt, showed that they have linked or allelic genes for aluminium tolerance. Calmodulin was extracted from the whole roots and from root tips alone, either after 3 days exposure to aluminium, or without aluminium treatment. Calmodulin levels were measured using a radioimmunoassay. No significant differences were observed between Carazinho (tolerant) and Sunstar (sensitive). Additionally the four genotypes (Waalt, Carazinho, Warigal and Sunstar) showed no consistent differences in sensitivity, as measured by seedling root growth, to three calmodulin antagonists, trifluoperazine, chlorpromazine and calmidizolium. Thus it appears that the different aluminium tolerances in these wheats are not due to different calmodulin levels.