Isolation, Purification and Characterization of Phytotoxins Produced by Rhizoctonia solani AG-3, the Cause Agent of Potato Stem Canker

Abstract

Studies were conducted to isolate and characterize the phytotoxins extracted from culture filtrates of Rhizoctonia solani isolate anastomosis group 3 (AG-3) using preparative thin layer chromatography (TLC) method. The culture filtrates of R. solani contain a toxic substance that causes canker on potato stems. Eight toxin fractions were collected by column layer chromatography but only four spots were obtained in the TLC analysis. All the four toxin fractions (third, fourth, sixth and seventh fractions) were recognised to have phytotoxic activity. Fourier-transform infrared spectroscopy (FTIR), high performance liquid chromatography (HPLC) and 1H and 13C NMR spectral techniques were used to characterize the phytotoxin. The major functional groups identified from FTIR spectrum includes 2962.1 cm−1 (−CH3), 1465.6 cm−1 (−CH2−), 1727.9 cm−1 (C = O), 1729.8 cm−1 (−COOH) and 1124.3 cm−1 (−OH). Result from HPLC, 1H NMR and 13C NMR showed phytotoxic fractions of 3-methylthiopropionic acid (3-MTPA) and 3-methylthioacrylic acid (3-MTAA). The results of this investigation add to the body of evidence that multiple related compounds are involved in R. solani disease development.