Biomanagement of rice root-knot nematode Meloidogyne graminicola using five indigenous microbial isolates under pot and field trials.

AIMS: To ascertain the effectiveness of Aspergillus niger, Trichoderma harzianum, Pochonia chlamydosporia, Bacillus subtilis and Pseudomonas fluorescens against rice root-knot nematode, Meloidogyne graminicola, and to optimize their application methods. METHODS AND RESULTS: The relative effectiveness of five indigenous biocontrol agents (BCA) against M. graminicola on rice cv. PS-5 was tested initially in pot culture. The BCAs, A. niger, P. chlamydosporia and P. fluorescens proved more effective, and significantly reduced the nematode disease. It is hypothesized that success of a biocontrol module may vary with the BCA and application methods. Hence, the effectiveness of the above three BCAs as well as seven different treatment schemes were evaluated in naturally infested farmer's fields during 2 consecutive years. In nematode-infested plots without any BCA treatments, terminal galls formed on the roots, and plants suffered a 19-31% decrease in the growth and yield. The treatments with P. chlamydosporia or A. niger through root-dip (RD) plus one soil application (SA) at 15 days after planting were found to be highly effective against the nematode. CONCLUSIONS: Relatively greater nematode control was achieved with RD plus two SAs (15 + 30 DAP) but statistically the effect was on par with RD + one SA at 15 DAP. These treatments significantly reduced galling (22-25%), egg mass production (21-29%) and reproduction factor (63-70%) of M. graminicola, and subsequently increased the grain yield (11-21%). SIGNIFICANCE AND IMPACT OF THE STUDY: Application methods enhanced the effectiveness of BCAs against M. graminicola. The RD plus one SA at 15 DAP proved to be most effective treatment to control root-knot disease in rice. Use of multiple treatments (root dip and SA) appears cumbersome, but in view of effectiveness and limitation of chemical control in rice paddies, farmers may adopt the above module that may lead to 11-21% yield improvement.

Theoretical study of the alkoxyls groups effect on PPV-ether excited states, a relationship with femtosecond decay.

Based on Density Functional Theory (DFT), the effect of alkoxyl substituents groups on the excited states of new PPV derivative (PPV-ether) are studied. Thus differences on the relaxation energy, the atomic charge distribution and the conjugation length at their excited state are interpreted on the pathways of the nature on the emissive species. Photoluminescence and optical spectra of the corresponding modeling structures are carried out. Furthermore, the life time at the excited state are emphasized either theoretically from oscillator strength or experimentally from time resolved photoluminescence.

Effects of organic compounds on the degradation of p-nitrophenol in lake and industrial wastewater by inoculated bacteria.

Many microorganisms fail to degrade pollutants when introduced in different natural environments. This is a problem in selecting inocula for bioremediation of polluted sites. Thus, a study was conducted to determine the success of four inoculants to degrade p-nitrophenol (PNP) in lake and industrial wastewater and the effects of organic compounds on the degradation of high and low concentrations of PNP in these environments. Corynebacterium strain Z4 when inoculated into the lake and wastewater samples containing 20 micrograms/ml of PNP degraded 90% of PNP in one day. Addition of 100 micrograms/ml of glucose as a second substrate did not enhance the degradation of PNP and the bacterium utilized the two substrates simultaneously. Glucose used at the same concentration (100 micrograms/ml), inhibited degradation of 20 micrograms of PNP in wastewater by Pseudomonas strain MS. However, glucose increased the extent of degradation of PNP by Pseudomonas strain GR. Phenol also enhanced the degradation of PNP in wastewater by Pseudomonas strain GR, but had no effect on the degradation of PNP by Corynebacterium strain Z4. Addition of 100 micrograms/ml of glucose as a second substrate into the lake water samples containing low concentration of PNP (26 ng/ml) enhanced the degradation of PNP and the growth of Corynebacterium strain Z4. In the presence of glucose, it grew from 2 x 10(4) to 4 x 10(4) cells/ml in 3 days and degraded 70% of PNP as compared to samples without glucose in which the bacterium declined in cell number from 2 x 10(4) to 8 x 10(3) cells/ml and degraded only 30% PNP. The results suggest that in inoculation to enhance biodegradation, depending on the inoculant, second organic substrate many play an important role in controlling the rate and extent of biodegradation of organic compounds.

Microbial specificity of metallic surfaces exposed to ambient seawater.

High-molecular-weight materials associated with the extracellular matrix and film found on titanium and aluminum surfaces after exposure to flowing coastal seawater were isolated. This material was purified by hydroxylapatite chromatography and subsequently employed to produce antibodies in the toad, Bufo marinus. The antibodies were immobilized on a solid support and employed to isolate adhesion-enhancing, high-molecular-weight materials from the laboratory culture media of bacterial strains recovered from the respective metallic surfaces during the course of their exposure to seawater. The adhesion-enhancing materials produced by the surface-associated bacterial strains were immunologically related to the extracellular biofouling matrix material found on the surfaces from which these bacteria were isolated. The surface selectivity of these bacterial strains appeared to be based on the specificity of the interaction between adhesion-enhancing macromolecules produced by these bacteria and the surfaces in question.