IN-VITRO ANTIFUNGAL SCREENING OF RADISH (Raphanus sativus L.) EXTRACTS AS SAFE BOTANICAL FUNGICIDES AGAINST Alternaria alternata AND Sclerotium rolfsii

Abstract

Two lab experiments were conducted on radish (Raphanus sativus var. BARI Mula-1) extractions to analyze quantitative phytochemical compounds in methanolic radish root extract (MRRE) and screen antifungal activity of methanolic and aqueous radish extracts against Alternaria alternata and Sclerotium rolfsii in Agricultural Chemistry Laboratory and Plant Pathology Laboratory, Hajee Mohammad Danesh Science and Technology University (HSTU) Dinajpur, Bangladesh during September, 2015 – September, 2016. Methanolic solvent was used following maceration method, where 15.12 g (30.24%) brown pungent greaseless jelly-like crude phytochemical substance was extracted from 50 g radish root powder dissolved with 200ml methanol. TLC analysis of MRRE showed at 1:10 ethyl acetate hexane 6 spots recorded as Rf values, where the highest Rf value was 0.91 cm and the lowest Rf value 0.29 cm. The 6 spots indicated the presence of 6 different compounds representing R1-R6, where their polarities were ranked from most non-polar compound traveling longest distance to most polar compound travelling shortest distance as R1 (0.91 cm) < R2 (0.82 cm) < R3 (0.70 cm) < R4 (0.59 cm) < R5 (0.40 cm) < R6 (0.29 cm). From the nature of the TLC, R1 was probably waxy type hydrocarbon functioning as mimic in phytodefence. In-vitro inhibitory activity of the radish extracts against A. alternata and S. rolfsii was screened using poisoned food technique. Three poisoned media viz. methanolic radish root extract media (MRREM, T1), aqueous radish root extract media (ARREM, T2) and aqueous radish leaf extract media (ARLEM, T3), and non-poisoned control PDA media (Tc) were used as treatments. There were highly significance differences among the poisoned media in reduction of mycelial growth of the test fungi over non-poisoned control PDA media. MRREM inhibited the growth of A. alternata and S. rolfsii 94 % and 58.1 %, followed by ARREM 93 % and 40 % and by ARLEM 90 % and 20 %, respectively, over the control. It may be concluded that the radish extracts can be used as safe natural botanical fungicides to control A. alternata and S. rolfsii and methanolic radish root extracts have more intense antifungal activity than aqueous radish root and leaf extracts.