Plant growth-promoting rhizobacterial (PGPR) strains were isolated from different agroecosystems of Tamil Nadu, India, and were tested for their efficacy against the sheath rot pathogen Sarocladium oryzae under in vitro, glasshouse and field conditions. Vigour and a relative performance index (RPI) were used to assay the growth promotion and antagonistic activity of Pseudomonas strains against S. oryzae under in vitro conditions. The results revealed the significant performance by strains Pf1, TDK1 and PY15 compared to other strains. Further, the combination of Pseudomonas strains Pf1, TDK1 and PY15 was more effective in reducing sheath rot disease in rice plants compared to individual strains under glasshouse and field conditions. Quantitative and native polyacrylamide gel electrophoresis (PAGE) analysis of peroxidase (PO), polyphenol oxidase (PPO) and chitinase activity in rice plants showed an increased accumulation of defence enzymes in the treatment with a combination of Pf1, TDK1 and PY15 compared to the treatment with individual strains and untreated controls. The present study revealed the probable influence of antagonism, plant growth promotion and induced systemic resistance (ISR) by the mixture of Pseudomonas bioformulations in enhancing the disease resistance in rice plants against sheath rot disease.

Fluorescent pseudomonad strains Pf1, TDK1 and PY15 individually and in combination were evaluated against leaffolder, Cnaphalocrocis medinalis Guen., in rice under in vitro, glasshouse and field conditions. Among the various treatments used, a combination of Pf1, TDK1 and PY15 strains effectively reduced the incidence of leaffolder pest in rice plants to an extent comparable with chlorpyrifos-methyl. In addition, morphogenesis of the insect pest in all stages, larval, pupal and adult, was greatly affected by a combination of Pseudomonas Pf1, TDK1 and PY15 strains. Further, the induction of defence-related molecules was demonstrated. An increased accumulation of defence molecules such as chitinase and proteinase inhibitors was observed with a combined Pf1, TDK1 and PY15 treatment compared with all other treatments. Western blot analysis of chitinase revealed the extra induction of 18, 28 and 35 kDa isoforms in rice plants treated with a mixture of Pf1, TDK1 and PY15 strains against leaffolder pest. The study revealed that a combination of fluorescent pseudomonad strains affects the development of leaffolder pest by inducing defence molecules in rice plants which in turn enhance resistance to leaffolder attack.

Thirteen Beauveria strains were isolated from the soil and infected insects. Among the various isolates, B 2 isolate (Arachalore) showed a higher percentage of mortality against C. medinalis (73.3%) under in vitro conditions. Conidial concentration of 1 9 10 8 of the B2 strain registered maximum mortality of 76.7%. The least LT 50 value of 4.4 days was registered in B2 isolate with the spore concentration of 1 9 10 8 and the LC 50 value was 3.4 9 10 4 . Beauveria strains altered the feeding behavior of C. medinalis, reduced the pupal weight, prolonged the pupation period, malformed the pupa and adult under in vitro. The efficacy of the talc-based bioformulation of Beauveria (B2) strain was tested as seed treatment + seedling dip + soil application + foliar spray against rice leaffolder under in vitro and greenhouse conditions. The percentage damage was significantly less (5.5) in B2 as compared to untreated healthy control (25.8). In addition, the same treatment increased the activities of defenserelated enzymes, namely peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, chitinase, and phenolics in rice.