Response of sugarcane (Saccharum sp.) varieties to embryogenic callus induction and in vitro salt stress

Response of three varieties of sugarcane (Saccharum sp.) to callus induction, embryogenic callus production and in vitro salt tolerance was studied. For callus induction and embryogenic callus production, leaf bases segments were subjected to in vitro culture on Murashige and Skoog (MS) medium supplemented with 3 mg 1-1 2,4 Dichlorophenoxyacetic acid for 4 weeks. To evaluate salt tolerance of the varieties, growing calli were exposed after two subsequent subcultures (4 weeks each) to different concentrations of NaCl (0, 17, 34, 68 and 102 mM) added to the culture medium for 4 weeks. Comparision of genotypes was based on callus induction percentage, embryogenic callus production percentage and relative fresh weight growth (RFWG). For salt tolerance, necrosis percentage and relative fresh weight growth of callus were used. The three varieties responded well to callus induction with a percentage of induction about 82, 84 and 100% for CP70-321, NCo310 and CP65-357, respectively. The high percentages of embryogenic callus obtained for the three varieties indicated that these varieties have a high capacity for embryogenic callus production. Relative fresh weight growth of callus was about 1.076, 1.282 and 0.925 for CP70-321, NCo310 and CP65-357, respectively. NaCl effect resulted in calli necrosis and a reduction of their growth. However, growing calli derived from varieties CP70-321 and NCo310 showed less necrosis percentages and less relative fresh weight growth reduction under salt stress. They appeared to be more salt tolerant in vitro than CP65-357.African Journal of Biotechnology Vol. 4 (4), pp. 350-354, 200

Free proline, soluble sugars and soluble proteins concentration as affected by salt stress in two sugarcane (Saccharum sp.) cultivars differing in their salt tolerance

Salt stress is one of the environmental stresses which affect negatively the agricultural production of the world. In this study, the effects of salt stress on free proline, soluble sugars and soluble proteins accumulation were investigated in two sugarcane (Saccharum sp.) cultivars: CP66-346 (salt- tolerant) and CP65-357 (salt-sensitive). Young plants of these cultivars were exposed, in a hydroponic system, to four concentrations of NaCl (0, 17, 34 and 68 mM). These concentrations correspond to an electric conductivity of 1; 2.83; 4.26 and 6.63 mS/cm, respectively. Free proline, soluble sugars and proteins accumulation were quantified after 2 weeks of stress. Proline and soluble sugars concentrations increased significantly in leaves and roots under salinity. Furthermore, NaCl caused an increase in soluble proteins concentration in leaves and roots of the tolerant cultivar CP66-346 and a decrease in leaves and roots of the sensitive CP65-357. Salttolerant CP66-346 plants accumulated more soluble sugars in leaves than CP65-357, while both cultivars accumulated similar quantities of proline in leaves. These results provided evidence that soluble sugars could contribute mainly to counteract the negative water potential of the outside medium and that protein synthesis stimulation was implicated in sugarcane salt tolerance. Proline appeared as a symptom in salt-stressed sugarcane plants rather than as an indicator of tolerance.Keywords: Sugarcane, Saccharum sp., proline, soluble sugars, soluble proteins, salt-toleranc

Growth, proline and ion accumulation in sugarcane callus cultures under drought-induced osmotic stress and its subsequent relief

Calli obtained from two sugarcane cultivars (R570 and CP59-73) were exposed to different osmotic stress intensities followed by a period of stress relief. Relative rate growth, callus water content and changes in organic and inorganic solutes were determined at the end of stress and relief periods. After the stress period, calli derived from both cultivars showed a decrease in RGR, but at lesser extent in R570 than CP59-73 cultivar. Same tendency was recorded in the callus water content under mannitolinduced osmotic stress. The inorganic solutes seemed to have no contribution in the osmotic adjustment in mannitol-stressed calli since K+ and Ca2+ concentrations decreased drastically while Na+ and Mg2+ concentrations were not affected. The accumulation of proline occurred in both cultivars and was more marked in CP59-73 than R570 cultivar. At the end of the relief period, we observed that all the considered parameters have recovered completely to reach the control levels. According to these results, we conclude that the drought stress-induced changes are reversible, at the least at the cellular level, in sugarcane cultivar

The Ciliate Protist Tetrahymena pyriformis as a Cellular Adhesion Model for the Pathogenic Bacterium Staphylococcus aureus

Staphylococcus aureus is one of the main pathogenic agents responsible for nosocomial and community-acquired bacterial infections. The pathogenicity of this Gram-positive bacterium is ensured by its different adhesion factors. Collagen and the extracellular glycoprotein adhesin are among the Staphylococcus most important virulence factors. It has been shown that most of the S. aureus strains carry the ica operon, responsible for biofilm production. However, the coexpression of the icaA and the icaD genes is necessary for complete biofilm synthesis. The aim of our study was to study a collection of 15 clinical strains of S. aureus from different sources for the presence of cna and icaD genes coding intercellular adhesion proteins. We also intended to estimate the strains¿ ability to form biofilms by the red Cong method and to test the adhesion ability of S. aureus to the ciliated protist Tetrahymena pyriformis, which we used as a novel cellular adhesion model. Finally, we checked the adhesion¿s inhibition capacity of some plants extracts. The molecular detection of adhesion genes revealed that 80% of strains are cna positive, and 73% are icaD positive. Qualitative biofilm production of S. aureus revealed that 66.6% of strains were slime producers. The adhesion test revealed that 20% of strains are strongly adhering to T. pyriformis and that the Clematis cirrhosa extract has an anti-adhering effect of S. aureus to the ciliate T. pyriformis.Peer Reviewe

In vitro culture techniques as a tool of sugarcane bud germination study under salt stress

Germination was the first stage confronted to soil salinity and it is important to determine salt effects on this stage. In this study, we reported an in vitro procedure for studying sugarcane bud germinationand shoot growth under salt stress with different NaCl concentrations (0, 17, 34, 68 and 102 mM) using cultivar NCo310. Germination percentage of control was about 92% after 8 days. Germination of buds,plant fresh and dry mass decreased with increasing salinity. Data indicated that in vitro culture techniques could be used to evaluate salt stress effects in sugarcane at the germination stage