Pectic Enzyme Production by Fusarium oxysporum f. sp, ccpac: Induction by Cell Walls from Different Parts of Onion Bulbs at Different Growth Stages

Abstract

Abstract Fusarium oxysporum f. sp. cepae produced significantly different amounts of pectic enzymes when grown on cell walls from morphologically different parts of onion bulbs. Cell walls from stem plate tissue of both tolerant and susceptible onion genotypes allowed a rapid and high production of both exo‐polygalacturonase and endo‐pectin‐frans‐eliminase. Bulb scale cell walls from susceptible genotypes induced synthesis of these enzymes at much lower rates and levels, whereas bulb scale cell walls from tolerant genotypes gave poor induction of pectic enzyme synthesis. Leaf sheath cell walls from both susceptible and tolerant genotypes were poor inducers of enzyme synthesis. Enzyme induction by cell walls from leaf sheaths and bulb scales of tolerant genotypes increased dramatically during ageing. Differences in pectic enzyme accumulation on cell walls were not related to fungal growth. These patterns of enzyme induction could help to explain susceptibility or tolerance of bulb scale and leaf sheath tissue of the different genotypes.