| The potential of the biocontrol agent Trichoderma harzianum NF9 to trigger rice defense responses against blast (Magnaporthe grisea) and bacterial leaf blight (Xanthomonas oryzae pv. oryzae) diseases was investigated.In the dual culture test, T. harzianum NF9 inhibited the mycelial growth of M grisea strains SY1 and H16 by 40.71% and 41.63%, respectively, at 5 days after incubation. Likewise, T. harzianum NF9 easily grew over X. oryzae pv. oryzae strains CR1 and CR7, giving control of X. oryzae pv. oryzae growth by nearly 100%. The antagonism of T. harzianum NF9 against M. grisea in the filter culture test showed an inhibition of 89.5% for SY1 and 89.8% for H16. No difference in the inhibition effect of T. harzianum NF9 on X. oryzae pv oryzae strains CR1 and CR7 was detected as T. harziannm NF9 grew over CR1 and CR7 with almost 100% inhibition as compared to the control.In the greenhouse experiments, the severities of the blast and bacterial leaf blight diseases caused by M. grisea and X. oryzae pv. oryzae, respectively, in three-week-old rice seedlings of cultivar yuanfengzao grown from seeds coated with T. harzianum NF9 conidia were significantly reduced. Trichoderma-lreated rice seedlings exhibited a moderate resistance response against the blast and bacterial leaf blight diseases; whereas controls were susceptible response.After the rice seedlings were pretreated with T. harzianum NF9 and challenged inoculated with M. grisea and X. oryzae pv. oryzae separately, enzyme activities of PAL and POD increased in both experiments although the differences were not really significant over the controls in some cases. The analysis of the enzyme activities of tested rice plants grown in the greenhouseshowed the potential of T harzianum NF9 to induce rice resistance to Mgrisea and X oryzae pv OI7)zae. The further studies on the induced resistanceby 1kichoderma and mechanisms are in progress in our laboratory. |
