Novel Trichoderma strains isolated from tree barks as potential biocontrol agents and biofertilizers for direct seeded rice.

This study is the first time report of utilization of Trichoderma spp. isolated from different tree bark from Odisha state of India for rice crop health management and higher productivity. Six isolates of Trichoderma spp. were identified based on the morphological characteristics and species determination was performed by molecular assays. One of the isolated strains determined as Trichoderma erinaceum outperformed others. Trichoderma erinaceum controlled three soil borne plant pathogens i.e. Rhizoctonia solani, Sclerotium rolfsii and Sclerotium oryzae effectively under controlled condition and R. solani and Helminthosporium oryzae under filed condition. Seed treatments with the formulated isolates improved the germination rate of rice and enhanced vigour. These parameters along with higher chlorophyll content could be related to higher yield observed in two rice varieties; Karuna and Sahabhagidhan. Among the six isolates tested, Trichoderma erinaceum treatment recorded highest yield. Significantly higher expression of some stress related enzymes was observed in Trichoderma treated plants which helped in better crop growth both under biotic and abiotic stresses. These isolates helped both the varieties to accumulate more nutrients. This study proves that Trichoderma erinaceum obtained from tree bark may be incorporated in integrated rice crop management both as biocontrol agent and biofertilizer.

Optimization and characterization of chromium(VI) reduction in saline condition by moderately halophilic Vigribacillus sp. isolated from mangrove soil of Bhitarkanika, India.

A Gram-positive moderately halophilic Cr(VI) tolerant bacterial strain H4, isolated from saline mangrove soil, was identified as Vigribacillus sp. by biochemical characterization and 16S rRNA analysis. In LB medium, the strain could tolerate up to 1000 mg L(-1) Cr(VI) concentration and reduced 90.2 and 99.2% of 100 mg L(-1) Cr(VI) under optimized set of condition within 70 h in absence and presence of 6 wt.% NaCl, respectively. The fitting of time course reduction data to an exponential rate equation yielded the Cr(VI) reduction rate constants in the range (0.69-5.56)×10(-2)h(-1). Analyses of total chromium and bacterial cell associated with reduced product by AAS, SEM/EDS, TEM/SAED, FT-IR and UV-vis-DRS indicated the formation of about 35% of insoluble Cr(III) either as Cr(OH)(3) precipitate in nanometric size or immobilized on the bacterial cell surface while the remaining 65% of reduced chromium was present as soluble Cr(III) in the growth medium. Powder XRD analysis revealed the amorphous nature of the precipitated Cr(OH)(3). The high Cr(VI) reducing ability of the strain under saline condition suggests the Vigribacillus sp. as a new and efficient strain capable of remediating highly saline Cr(VI) polluted industrial effluents.

Diversity of Bacillus thuringiensis in the rice field soils of different ecologies in India.

Diversity of the Bacillus thuringiensis (Bt) in the rice field soils of different ecologies viz. the island (Port Blair), the Himalayan (Srinagar), brackish water (Mahe) and coastal mesophilic (Mangalore) habitats was analyzed by phenotypic characterization of 5, 66, 14 and 54 Bt isolates, respectively. The Bt isolates produced either monotypic (bipyramidal or spherical) or heterotypic (polymorphic-bipyramidal or bipyramidal-rhomboidal) crystals. The organisms were generally resistant to the penicillin group of antibiotics, tolerated 5-12% NaCl and 0.5M Na-acetate. The Bt isolates contained 1-5 plasmids of 0.89-58.61 kbp sizes. The plasmid profiles had no correlation with crystal morphology or salt tolerance of different bacteria. Each soil was inhabited by different types of Bt. Two Bt strains of Mangalore and one strain each of the other places were phenotypically similar. One Bt strain each of Port Blair and Srinagar was different from all other strains.

Pseudomonas aeruginosa, a facultative pathogen of red palm weevil, Rhynchophorus ferrugineus.

Pseudomonas aeruginosa was identified as a facultative pathogen of red palm weevil. Intra-haemocoelic injection of the pathogen within larvae and pre-pupae was more effective at killing the insects [with a median lethal dose (LD50) of 9×10(2) to 2×10(3) bacteria/insect] than inoculation by force feeding (LD50 of 10(5) to 4×10(5) bacteria/insect) or by wading the insects in a suspension of the pathogen (LD50 of 10(5) to 2×10(5) bacteria/insect). Injection of 3×10(3) bacteria/insect killed 69% of larvae; small larvae were more susceptible (LD50 of 9×10(5) bacteria/larva) than either larger larvae (LD50 of 10(3) bacteria/larva) or pre-pupa. The median time to death of the small larvae following injection of P. aeruginosa was about 6 days but that following force feeding or wading was about 8 days. A secondary invader, Serratia marcescens, had no effect on the pathogenicity of P. aeruginosa but hastened death of larvae by about 3 days.