The influence of exogenous gibberellic acid (GA3) and 24-epibrassinolide (24-EpiBL) on seed germination and the expression of genes involved in GA and BR synthesis/signalling in pepper (Capsicum annuum L.)

Gibberellins (GAs) and brassinosteroids (BRs) are the plant hormones involved in various physiological processes including seed germination. In this study, the effects of exogenous gibberellic acid (GA3) and 24-epibrassinolide (24-EpiBL) treatments on the expression of key genes involved in GA and BR syntheis/signalling during seed germination were investigated in pepper (Capsicum annuum L). The expressions of BES1 and BRI1 involved in BR synthesis/signalling pathway as well as GA3OX1 and GA20OX1 associated with gibberellic acid biosynthesis in plants were determined. Exogenous GA3 treatments increased BES1 expression and the highest increase was determined with 10⁻⁸ M BR + 100 µM GA3 (P<0.05). On the contrary, the expression of BRI1 gene was significantly decreased by 10-8 M BR + 100 µM GA3 (P<0.05). The expression of GA3OX1 gene was induced with BR and GA3 treatments (P<0.05). GA20OX1 gene expression was generally higher compared to the expression of GA3OX1 and significantly increased by the GA3 treatments. Our findings are expected to bring an insight to the influence of BRs during seed germination together with the expression of associated genes.

Rooting of healthy and CVC-affected 'Valência' sweet orange stem cuttings, through the use of plant regulators

Citrus variegated chlorosis (CVC) is a disease caused by Xylella fastidiosa. Using different concentrations of plant regulators, such as auxins (indole-3-butyric acid) and gibberellic acid biosynthesis-inhibitor (paclobutrazol), physiological rooting capacity of healthy and CVC-affected stem cuttings were evaluated in order to investigate the importance of plant hormone imbalance and xylem occlusion in plants with CVC. The percentages of dead, alive and rooted cuttings, cuttings with callus and mean number of roots per cuttings did not show statistical differences in response to the distinct concentrations of synthetic plant regulators. There were differences only between healthy and CVC-affected cuttings. This showed the importance of xylem occlusion and diffusive disturbances in diseased plants, in relation to root initiation capacity and hormonal translocation in the plant tissue.

Grass seed yields increased with plant growth regulators and fungicides

Seed yields of ryegrass and tall fescue have increased rapidly over the last seven years; the best farm yields are now reaching 3000 kg/ha, up from 2000 kg/ha. These increases are largely due to the adoption of technologies developed from research funded from grower crop levies and effective technology transfer programmes. The key technologies are (1) the adoption of trinexapac ethyl (TE), a plant growth regulator that blocks gibberellic acid biosynthesis and reduces lodging; and (2) new generation triazole and strobilurin fungicides that give improved disease control and extend the period that green leaf area is maintained on crops. Seed yield data from 10 ryegrass and 6 tall fescue trials with TE, and from 13 fungicide trials are presented. The average seed yield increase in tall fescue treated with 200 g TE/ha and ryegrass with 400 g TE/ha was 67% and 50% respectively. In fungicide trials, seed yields in forage perennial ryegrass were increased by 20% and in turf ryegrass by 42%. A survey of growers indicated 95% of ryegrass growers and 100% of tall fescue growers had adopted the use of TE three years after the commercial release of the product. Keywords: fungicides, plant growth regulators, ryegrass, seed yield, strobilurin, tall fescue, triazole, trinexapac