Chemical inducers from different groups were tested, as solution for dipping the roots of strawberry plant before transplanting in the soil infested with Rhizoctonia solani, R. fragariae and Sclerotium rolfsii, and foliar sprayed after 7 day to induction a systemic resistance. In vitro, mycelial growth of three tested fungi was mostly inhibited by SA, Rizolex-T and Ethephon, but not or little affected by another tested inducers. Under greenhouse conditions, CuSO4 completely prevented disease incidence (as % of dead plants) in the presence of R. fragariae and R. solani either after 21 or 45 days from infestation. The same effect was achieved by BA against R. fragariae. After 21 days MgSO4, Bion 50%, and Ethephon were almost equal with Rizolex-T 50%, but lowest effect was recorded by using Ascorbic acid after 21 and 45 days. Under field conditions, all abiotic inducers were declined the dead strawberry plants (%) than untreated control after 21 and 45 days in both seasons (2004 -2005). However, abiotic were more effective in the second season than the first, especially SA, CuSO4 then BA, AA and Bion 50%. Clear increase in the shoot and root lengths of strawberry plants as response to treatment with all tested abiotic inducers than untreated plants was observed. Ethephon exceeded the others for the induction of the resistance against root-rot pathogens, and enhanced the growth parameters of strawberry plants under greenhouse conditions. KH2PO4 and SA inducers increased the enzyme activities of peroxidase, polyphenoloxidase, chitinase and ,1-3-glucanase than other abiotics, while little activities were recorded with other treatments. Lignin content was increased in the treated plants in response to all inducers than untreated.
Keywords: Strawberry, abiotic inducers, root-rot, Rhizoctonia, Sclerotium, plant growth parameters, enzyme activities. |
