Improvement of antagonism and fungicides tolerance in Trichoderma harzianum and T.viride local isolates by Ultra-Violet irradiation

Abstract

Among 22 Iraqi Trichoderma harzianum  and T.viride isolates, T3,T5,D5,S1 and S6 related to T. harzianum  showed a higher antagonistic activity against the plant pathogenic fungi  Fusarium oxysporum and Rhizoctonia solani. These isolates were selected for improvement their biocontrol activity by usi

ng uv-irradiation. The optimum exposure time to ultraviolet irradiation is 30 min, in which, the percentage of kill was 98-99% .After UV-irradiation treatment (Quartz lamps 30W at 240-280 nm, peak 254nm, distance from the source was 20 cm), antagonistic capability against R. solani and F. oxysporum was improved in mutants MT3,MT5,MS1 and MS6, in which antagonistic reaction score were 3.6,3.9,3.2 and 3.6 against F. oxysporum and 3.7,4,3.4 and 4 against R. solani compared to 3.2, 2.8, 2.6 and 2.8 against F. oxysporum and 2.7, 2.9,3.1 and 3 against R. solani in the wild types T3, T5, S1 and S6,respectively. The growth of T. harzianum isolates (estimated as colony diameter) was significantly increased in all T. harzianum mutants except MT3 and MD5 mutants, CMCase activity was increased from 13.2, 16.2, 10 and 15.8 U/ml / mg protein in the wild isolates T3, T5, S1 and S6 to 18.6, 20.3, 17.7 and 22.5 U/ml / mg protein in the mutants MT3, MT5, MS1 and MS6, respectively. Chitinase activity was also increased in these mutants to 88.4,132.3,86.1 and 136.7 U/ml / mg protein, compared to 82.7, 93.2, 74.5 and 103.2 U/ml / mg protein in their wild, respectively. As comparison between wild types and mutants, the maximum growth was 5.2 and 4.8 cm (as colonies diameters) by MT5 in present of 25% of the recommended field rate of Topsin and Benomyl, compared to 3.3 and 2.2 cm in the wild type T5, respectively, followed by MS6,in which, the maximum growth in this mutant was 4.8 and 4.2 cm in the same concentration of these two fungicides, compared to 3.4 and 2.5 cm in the wild type S6, respectively. According to these results, the mutants MT5 and MS6 developed from UV-irradiation treatment, showed as promising T. harzianum mutants through their antagonistic activity (at mycoparasitism level) , fast growth, higher  CMCase and chitinase activity and growth in 25% of the recommended field rate of Elsa , 25 and 50% of the recommended field rate of Diathen and Mizab and all concentrations of Topsin and Benomyl with complete inhibition of pathogenic fungi F. oxysporum and R. solani.