ACCUMULATION OF PHYTOALEXINS AND THEIR ROLE IN RESISTANCE OR SUSCEPTIBILITY OF POTATO TUBER SLICES INOCULATED WITH FUSARIUM SOLANI INCUBATED AT TWO REGIMES OF TEMPERATURE

Abstract

The present investigation was aimed to study the role of phytoalexins accumulated in potato tuber slices inoculated with Fusarium solani caused the potato dry rot on disease resistance or susceptibility. Potato tuber slices inoculated with F. solani were incubated at two different regimes of temperature i.e., 16oC or 25oC. Disease severity on slices incubated at 25oC was very higher than that found on slices incubated at 16oC. This observation was opposite to phytoalexins accumulated at 16oC whereas the intensity of phytoalexin spots separated by TLC was very intensive than that accumulated at 25oC. The role of phytoalexins accumulated in potato tuber slices inoculated with F. solani incubated at 16oC was studied by inhibiting of biosynthesis of them in inoculated slices by HMG-CoA reductase (3-hydroxy-3-methylglutaryl-CoA reductase) inhibitor. This treatment led to increase disease severity of Fusarium infection accompanied by disappearance of phytoalexin spots on TLC and benzene extracts of such slices had no effect on spore germination and germ tube length when spores were germinated in it. These results strongly indicated the role of phytoalexins in disease resistance especially at 16oC