Under greenhouse and field conditions three antioxidants i.e. ascorbic acid, oxalic acid and salicylic acid at 5.0 mM as seed soaking followed by bioagents i.e. Bacillus megaterium, Bacillus subtilis, Serratia marcesens, Trichoderma harzianum, T. lignorum and T. viride as seed coating were applied to study their effect against damping-off disease incidence of snap bean plants in addition to biochemical response of treated plants. Results revealed that all tested treatments significantly reduced pre- and post-emergence damping-off diseases incidence in addition to inducing an increase in survived plants under greenhouse and field conditions. Complete protection of damping-off incidence was obtained in case of using salicylic acid as seed soaking and Serratia marcesens as seed coating compared to other treatments and control. All tested treatments significantly increased both fresh and dry weight of shoots and roots per plant. Moreover, under field conditions, the best integrated treatments were ascorbic acid, oxalic acid and salicylic acid as seed soaking with Serratia marcesens as seed coating where the lowest percentage of pre- and post- emergence damping-off were ranged between 3.88 and 7.4%. In addition to increasing the survival plants more than 88.5%, other treatments showed moderate effect. As for biochemical response of snap bean plants under greenhouse conditions results indicated that all tested treatments increased the flavonoids content and affected positively the activities of peroxidase, polyphenoloxidase and phenylalanine ammonia lyase, chitinase and β-1,3-glucanase enzymes in snap bean plants. As for chitinase activity, the most effective treatment was ascorbic acid with Serratia marcescens where recorded the highest activity with efficacy being 315.21%. On other hand, the highest increase of β-1,3-glucanase activity was recorded with the integration between oxalic acid and any of Serratia marcescens and Bacillus megaterium where the recorded efficacy were 382.50 and 316.88% respectively. |
