Cultural conditions on the production of extracellular enzymes by Trichoderma isolates from tobacco rhizosphere

Abstract

tTwelve isolates of Trichoderma spp. isolated from tobacco rhizosphere were evaluated fortheir ability to produce chitinase and -1,3-glucanase extracellular hydrolytic enzymes. Iso-lates ThJt1 and TvHt2, out of 12 isolates, produced maximum activities of chitinase and -1,3-glucanase, respectively. In vitro production of chitinase and -1,3-glucanase by iso-lates ThJt1 and TvHt2 was tested under different cultural conditions. The enzyme activitieswere significantly influenced by acidic pH and the optimum temperature was 30◦C. Thechitin and cell walls of Sclerotium rolfsii, as carbon sources, supported the maximum andsignificantly higher chitinase activity by both isolates. The chitinase activity of isolate ThJt1was suppressed significantly by fructose (80.28%), followed by glucose (77.42%), whereasthe -1,3-glucanase activity of ThJt1 and both enzymes of isolate TvHt2 were significantlysuppressed by fructose, followed by sucrose. Ammonium nitrate as nitrogen source sup-ported the maximum activity of chitinase in both isolates, whereas urea was a poor nitrogensource. Production of both enzymes by the isolates was significantly influenced by the cul-tural conditions. Thus, the isolates ThJt1 and TvHt2 showed higher levels of chitinase and -1,3-glucanase activities and were capable of hydrolyzing the mycelium of S. rolfsii infect-ing tobacco. These organisms can be used therefore for assessment of their synergism inbiomass production and biocontrol efficacy and for their field biocontrol ability against S.rolfsii and Pythium aphanidermatum infecting tobacco.