Genetic polymorphism and plant growth promotion traits of potent fungal entomopathogens of rice leaf folder.

Entomopathogenic fungal biocides are preferred for environment friendly sustainable management of insect pests due to their host specificity and harmlessness to non-target insects. Plant growth promotion (PGP) functions of the entomofungi are also important attributes but hitherto insignificantly explored. Therefore, virulence of 17 natural fungal entomocides (Cordyceps, Beauveria, Metarhizium, Nomuraea, Fusarium, Verticillium, Trichoderma and Paecilomyces spp.) were evaluated for pathogenicity against five rice pests (brown plant hopper (Nilaparvata lugens) and green leaf hopper (Nephotettix virescens) nymphs, leaf folder (Cnaphalocrosis medinalis) and yellow stem borer (Scirpophaga incertulas) larvae and swarming caterpillar (Spodoptera mauritia), respectively), and PGP traits of the potent leaf folder pathogens. Among the fungi, only the leaf folder pathogens (3 isolates each of Beauveria and Metarhizium spp.) infected > 50% (80-90%) larvae but other fungi were ineffective as infected < 50% (0-47%) insects. Besides, the leaf folder pathogens exhibited diverse PGP traits such as organic/inorganic phosphate solubilization (104.7-236.4 µg/ml), and siderophore, ammonia, hydrogen cyanide (HCN), indole production etc. Restriction fragment length polymorphism (RFLP), random amplified polymorphic DNA (RAPD), simple sequences repeat (SSR) and internal transcribed spacers (ITS) analysis ascertained strain identity and genetic (inter and intra-specific) diversity among the potent biocides Beauveria and Metarhizium spp. The virulent natural fungal pathogens of rice pests with polyvalent PGP traits may be prospected for rice growth promotion and biocontrol of leaf folder.

Microbial Dynamics and Diversity of Bacillus thuringiensis in Textile Effluent Polluted and Non-polluted Rice Field Soils of Orissa, India.

Microbial diversity was assessed in the soils of non-polluted rice fields of Central Rice Research Institute and Choudwar, and textile effluent contaminated (about 30 years) rice fields of Choudwar about 4 years after cessation of pollution. The soils contained 0.62-1.01 % organic C and 0.07-0.12 % total N, and measured 6.18-8.24 pH and 0.6-2.68 mS/cm Eh which were more in the polluted Choudwar soil. The microbial populations (×10(6) cfu/g soil) in the soils were: heterotrophs 1.21-10.9, spore formers 0.9-2.43, Gram (-)ve bacteria 4.11-8.0, nitrifiers 0.72-1.5, denitrifiers 0.72-2.43, phosphate solubilizers 0.14-0.9, asymbiotic nitrogen fixers 0.34-0.59, actinomycetes 0.07-0.11, fungi 0-0.5 and Bacillus thuringiensis (Bt) 0.4-0.61 which predominated in the polluted soil of Choudwar. The fungi were scarce in the polluted rice fields. The Bt isolates belonged to three motile and one non-motile group. Two motile Bt isolates were phenotyped as Bt subsp. sotto and israelensis, whereas, the non-motile isolate was Bt subsp. wahuensis. All Bt isolates produced extracellular protease, lipase and amylase enzymes. The microbial guilds had positive correlation among themselves, as well as, with soil physico-chemical characters but the fungi had negative relation and the nitrogen fixers were unrelated with the biotic and abiotic components.

Shade tolerance in Swarnaprabha rice is associated with higher rate of panicle emergence and positively regulated by genes of ethylene and cytokinin pathway.

This study identifies characteristics of seedling, mature plant phenotypes, changes at genetic and genomic level associated with Swarnaprabha (SP) rice grown under prolonged shade and compared with Nagina 22 (N22). Coleoptile length under low red/far-red was intermediate between that in dark and red light in a 7-days growth frame. Whereas, highest rootlet number was discriminating in seedlings grown for 28 days in hydroponics. In shade, SP and N22 both showed several tolerant mature plant phenotypes, except the panicle length, yield per plant and % grain filling, which were higher in SP. Percentage decrease in yield / plant in shade showed significant positive correlation with increase in NDVI, decrease in panicle length and % grain filling (p ≤ 0.01). Rate of panicle emergence in shade was higher in SP than N22. Expression patterns of PHYTOCHROME INTERACTING FACTOR LIKE-13 and PHYTOCHROME B were contrasting in SP and N22 seedlings under continuous red or red/far-red. Microarray analysis revealed the up-regulation of most of the ethylene and cytokinin pathway genes in shade grown panicles of SP. Significant up-regulation of ETHYLENE RESPONSE ELEMENT BINDING PROTEIN-2, MOTHER OF FLOWERING TIME 1, and SHORT PANICLE1 genes in shade grown panicles of SP could explain its sustainable higher yield in shade.

Reduction of selenite to red elemental selenium by moderately halotolerant Bacillus megaterium strains isolated from Bhitarkanika mangrove soil and characterization of reduced product.

Two Gram (+) bacterial strains, BSB6 and BSB12, showing resistance and potential for Se(IV) reduction among 26 moderately halotolerant isolates from the Bhitarkanika mangrove soil were characterized by biochemical and 16S rDNA sequence analyses. Both of them were strictly aerobic and able to grow in a wide range of pH (4-11), temperature (4-40°C) and salt concentration (4-12%) having an optimum growth at 37°C, pH ∼7.5 and 7% salt (NaCl). The biochemical characteristics and 16S rDNA sequence analysis of BSB6 and BSB12 showed the closest phylogenetic similarity with the species Bacillus megaterium. Both the strains effectively reduced Se(IV) and complete reduction of selenite (up to 0.25 mM) was achieved within 40 h. SEM with energy dispersive X-ray and TEM analyses revealed the formation of nano size spherical selenium particles in and around the bacterial cells which were also supported by the confocal micrograph study. The UV-Vis diffuse reflectance spectra and XRD of selenium precipitates revealed that the selenium particles are in the nanometric range and crystalline in nature. These bacterial strains may be exploited further for bioremediation process of Se(IV) at relatively high salt concentrations and green synthesis of selenium nanoparticles.