Abstract:
The total of 654 isolates of indigenous microorganisms including 379, 168 and 107 isolates of fungi, bacteria and yeasts, respectively were isolated from plant and soil samples, collected from forest and agricultural areas in Nakhon Si Thammarat province. All isolates were in vitro tested for their efficacy to inhibit mycelial growth of Sarocladium oryzae, a causal agent of sheath rot on rice. The results showed that 196 isolates could inhibit the mycelial growth of the pathogen by 2.5-59.0%, especially, isolate FR-NST-152 gave the highest efficacy with 59.0% of inhibition. Ten promising isolates were tested for survival ability on rice leaf and in planting soil under growth chamber conditions. All isolates survived on leaf and in planting soil for 60 days after inoculation. Under plastic house conditions, all isolates could control sheath rot on rice (Var. Chainat 1) by 34.3-70.0%. Particularly, two promising isolates, FR-NST-152 and FR-NST-092, provided 70.0 and 68.3% of disease control which were comparable to the carbendazim fungicide treatment. Moreover, isolate FR-NST-152 also increased markedly healthy seeds, number of panicles per pot, number of seeds per panicle and weight of 1,000 seeds. Only antagonistic fungi and bacteria survived on rice leaf and in planting soil for 120 days after inoculation. For root colonization detection, the results showed that isolate FR-NST-092 had high percentage (90.0%) of root colonization. According to morphological characteristics, FR-NST-092 and FR-NST-152 were identified as Trichoderma harzianum, while isolate BR-NST-098 was identified as Bacillus pumilus by using 16S rDNA sequencing method.
WALAILAK UNIVERSITY. CENTER FOR LIBRARY RESOURCES AND EDUCATIONAL MEDIA