IN-VITRO INHIBITION OF SPOT BLOTCH DISEASE CAUSAL AGENT (BIPOLARIS SOROKINIANA) BY PLANT EXTRACTS

Abstract

The inhibitory effect of essential oil (EO) of flowering buds and potential extracts of Eucalyptus camaldulensis Dehn (leaf, Bark and Flowering Buds) was evaluated on colony growth of the most aggressive isolate of Bipolaris sorokiniana from wheat by agar well diffusion, food poison technique and macro-dilution assay. Effect on mycelial growth of test organism was evaluated at nine different concentrations of essential oils (0.5%; 01%; 2.5%; 05%; 7.5%; 10%; 15%; 50%; 100%) and 3 concentrations of aqueous, ethanolic and methanolic  extracts of E. camaldulensis (01%; 05% and 10%) with time interval of 3, 6, 9 and 30 days. EO produced a maximum inhibition zone of 90 mm dia. and mycelial growth 0.00±0.00 compared to control 40.00±0.00 after 9 days of incubation period at 50% and 100% concentrations. The ethanolic extracts of flowering buds showed strong inhibition zone of 29.10±0.92 mm dia. that is significant values (P < 0.05) compared with water extract (19.80±0.33). Ethanolic and methanolic flowering buds extracts showed highest minimum inhibitory concentration (08mg/mL) than water extracts (200mg/ml) against B. sorokiniana while, minimum fungicidal concentration values were observed for ethanolic and methanolic flowering buds extracts at 40 mg/mL and for aqueous  extract at 300 mg/mL. Hypae treated with EOand flowering buds ethanolic extract were collapsed, damaged or thinner compared to control. This Study revealed that, flowering buds extracts had the highest inhibitory effect on the growth of the pathogen. The EO and ethanolic extract of flowering buds were considered most effective that showed considerable inhibition (up to 97% in- vitro inhibition) than bark and leaf ethanolic and methanolic extracts, while no significant inhibitory effect on mycelia growth of the pathogen was recorded upon treatment with aqueous leaf and bark extracts.