Effect of Sclerotial Damage of Sclerotinia sclerotiorum on the Mycoparasitic Activity of Trichoderma hamatum

Abstract

Damaged sclerotia of Sclerotinia sclerotiorum buried in soil infested with Trichoderma hamatum isolate TMCS - 3 were degraded rapidly when the medulla of sclerotia was com pletely exposed by the feeding activity of larvae of the fungus gnat Bradysia coprophila. These heavily damaged sclerotia also enhanced , in vitro, the growth of TMCS - 3 . Growth of TMCS - 3 in liquid culture was studied using different carbon sources as substrates , including sclerotia of S. sclerotiorum. Significantly more biomass of TMCS - 3 was recovered using sclerotia as a substrate compared to other carbon sources tested . Exudates from sclerotia whose melanized rinds had been completely removed by feeding larvae accelerated the germination of conidia of TMCS - 3 . Concentrations of amino acids , carbohydrates and proteins in the sclerotial exudates were not increased as damage to sclerotia was increased . Exudation of electrolytes was higher in undamaged than damaged sclerotia . Glucanase activity of TMCS - 3 was slightly increased when the fungus was exposed to damaged sclerotia . However , chitinase activity was not increased by damaging the sclerotia . Larval damage altered the sclerotia not only physically but also chemically , thereby enhancing the activity of the fungus T. hamatum.