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Physiological and biochemical evolution of peach leaf buds during dormancy course under two contrasted temperature patterns
15-19.Views:120Budbreak anomalies in temperate fruit trees grown under mild conditions have often been described. However, only few authors approached the physiological evolution of leaf buds all along the dormancy period according to the temperature pattern. The aim of this study was to characterize the evolution of peach leaf bud dormancy through some physiological and biochemical parameters under temperate winter conditions and under total cold deprivation after the endodormancy onset. Two treatments were applied in peach trees cv. Redhaven: (i) Regular Chilling Amounts — RCA and (ii) Total Chilling Deprivation — TCD. Buds were sampled periodically from different parts of the stem (terminal, medium and basal ones). We recorded the evolution of: carbohydrate concentrations (glucose, fructose, sucrose, sorbitol and starch), respiration rate, water contents and energy metabolism (ATP and ADP ratio). The dynamics of these parameters were compared and correlated with dormancy evolution ("one node cuttings" test) and budbreak patterns in plank:. The endodormancy intensity of terminal buds was significantly lower than those of median and basal buds in early October. Under RCA treatment, this gradient faded and the bud endodormancy release was completed at the same time in all positions along the stem. Thereafter, the "cuttings" test indicated that terminal buds grew slightly faster than median and basal buds, and, consistently, budbreak in planta started with the terminals buds, followed by the medians and then by the basal ones. The carbohydrate contents showed a transitory change only when the buds began to grow after the endodormancy was released under RCA. Respiration, water content and ATP/ADP changed dynamics only under RCA and only after the end of the endodormancy (their respective changes were very parallel). The dynamics of none of the tested parameters could be related with the endodormancy dynamics, but respiration, water content and ATP/ADP could be consistent markers of the actual bud growth before bud break (in this respect, ATP/ADP could not show differences between the terminal and axillary buds while respiration and water content could).
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Organogenesis in eggplant (Solanum melongena L. cv. Embu) as affected by antibiotics and growth regulators
76-82.Views:253The influence of antibiotics (cefotaxime, timentin, kanamycin and hygromycin) and growth regulators (indolacetic acid and 6-benzylaminopurine) was evaluated on eggplant organogenesis. Solanum melongena hypocotyl segments (6 to 10 mm length), taken from 16 to 20-days in vitro grown seedlings, were used as explants. The basic medium was composed by MS salts, Gamborg vitamins and 2% sucrose, solidified with agar 0.8% and pH adjusted to 5.7±0.2. Morphogenesis was impaired at 50 to 100 mg L-I kanamycin and 7.5 mg L-1 hygromycin. Both Timentin and cefotaxime reduced the frequency of regenerating explants meanwhile hyperhydricity was not affected. A decrease in root regeneration was observed with increasing cefotaxime concentrations, although, timentin had no effect on root regeneration, as compared to the control treatment. Interestingly, the number of adventitious roots was more noticeable at 0.25 mg L-I IAA plus 0.5 mg L-1 BAP. However, if just IAA was added led to higher number of regenerated roots compared to other treatments.
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Genetic engineering of apple (Malus domestica Borkh.) for resistance to fungal diseases using g2ps1 gene from Gerbera hybrida (Asteraceae)
15-12.Views:291In the present study, g2ps1 gene from Gerbera hybrida coding for 2-pyrone synthase which contribute for fungal and insect resistance was used. The aim was to work out an efficient approach of genetic transformation for apple cvs. ‘Golden Delicious’, ‘Royal Gala’ and ‘MM111’, ‘M26’ rootstocks for improving their fungal resistance using genetic engineering techniques. Adventitious shoot formation from leaf pieces of apples studied was achieved using middle leaf segments taken from the youngest leaves from in vitro-grown plants.
Optimum conditions for ‚direct’ shoot organogenesis resulted in high regeneration efficiency of 0%, 95%, 92%, 94% in the studied apples respectively. Putative transgenic shoots could be obtained on MS media with B5 Vitamins, 5.0 mg l-1 BAP, or 2.0 mg l-1 TDZ with 0.2 mg l-1 NAA in the presence of the selection agent “PPT” at 3.0-5.0 mgl-1. Shoot multiplication of transgenic shoots was achieved on: MS + B5 vitamins + 1.0 mg l-1 BAP + 0.3 mg l-1 IBA, 0.2 mg l-1 GA3+1.0 g/l MES+ 30 g/l sucrose + 7.0 g/l Agar, with the selection agent PPT at 5.0 mg l-1 and were subcultured every 4 weeks in order to get sufficient material to confirm transformation of the putative shoots obtained. Six, seven, one and six transgenic clones of the apples studied respectively have been obtained and confirmed by selection on the media containing the selection agent “PPT” and by PCR analysis using the suitable primers in all clones obtained for the presence of the selection” bar gene (447 bp) and the gene-of- interest “g2PS1” (1244 bp), with transformation efficiency of 0.4%, 0.6%, 0.1% and 0.3% respectively. These transgenic clones were multiplied further in vitro in the presence of the selection agent ‘PPT’ and rooted in vitro. Rooted transgenic plantlets were successfully acclimatized and are being kept under-containment conditions according to the biosafety by-law in Syria to evaluate their performance for fungal resistance .