Bioformulation Pseudomonas fluorescens SP007s against dirty panicle disease of rice

Two-different carrier formulations, kaolin and talc-based products were developed with Pseudomonas fluorescens SP007s biocontrol agent. SP007s viability in different carriers stored at room temperature (28 to 33°C) slowly declined to approximately 46.2 and 61.0% after 12-month-old shelf life. The decreased population was first found in five and month months of storage for kaolin and talc-based formulations, respectively. Field experiment with 6-foliar spray intervals (1 × 108 cfu/ml) of SP007s was conducted against naturally-occurred dirty panicle disease caused by a multiplex fungus at Suphanburi. The two bioformulations significantly reduced pathogen colonization on rice panicle and exhibited the greatest yield that correlated with increased defense-related enzyme accumulation in treated plants, compared to 4-fungicide spray intervals and nontreated control. Protection of seeds collected from colonized and noncolonized plants of dirty panicle treated with bioformulations (1 × 106 cfu/ml) and fungicides (copper hydroxide) was further determined for 12 months of storage at room temperature. The best results in reducing 6-causal fungi including Alternaria padwickii, Cercospora oryzae, Curvularia lunata, Fusarium semitectum, Helminthosporium oryzaeqe and Sarocladium oryzae; and induced seedling vigor (35%) were obtained from SP007s kaolin-based formulation evaluated at 8-month storage, but not at 12 months which indicated that these causal pathogens totally recovered their colonization except S. oryzae. In 8-month trials, control efficacy with dose of 1 × 106 cfu/ml SP007s seed treatment, the increase in SP007s populations relatively with the decreased colonization of pathogens could be found. SP007s in kaolin-based formulation increased GABA in SP007s treated seeds suggesting this plant bioactivator may involve plant’s defense against stress conditions also.   Key words: Biocontrol, multiplex fungus causes, induced systemic resistance, protective enzymes, reduced chemical application.