Influence of leaffolder feeding on chlorophyll, PS II activity and plant–water relations, effect of larval density on leaf damage and time course studies on larval feeding behaviour on altered physiological changes in TN1 rice culture were studied. Quantification of yield losses in the field caused by leaffolder was also assessed. Leaffolder damage resulted in 57% reduction in chlorophyll content, 23% reduction in PS II activity and 23% reduction in relative water content in comparison with control. Rice leaffolder larva folds the leaf and scrapes the green tissue from within the fold resulting in scorching and drying of the leaves. Larval density had differentially influenced effective leaf area of rice crop. Larval densities of more than 3 larvae per hill at maximum tillering stage resulted up to 20% unfilled grains, 28–57% reduction in PS II activity and 23% reduction in relative water content in comparison with the control. At flowering stage, flag leaf area damage of above 25% resulted in more than 50% unfilled grains over control, indicating direct effect of yield reduction in rice. Thus, a cumulative effect of loss in chlorophyll, reduced photosynthate availability and altered water relations caused by the leaffolder injury to flag leaf lead to greater yield loss in rice.
Field experiments were conducted at DRR farm located at ICRISAT, Patancheru, in sandy clay loam soils during four seasons, Kharif 2008, Rabi 2008-09, Kharif 2009 and Rabi 2009, to investigate plant growth parameters, water-saving potential, plant root characteristics, chemical, biological and microbial properties of the rhizosphere soil, and grain yield of rice (Oryza sativa L.) by comparing the plants grown with system of rice intensification (SRI) methods, with organic fertilization only or organic + inorganic fertilization, compared with currently recommended best management practices (BMP).All of the growth parameters including plant height, effective tillers, panicle length, dry matter, root dry weight, and root volume were found to be significantly higher with the SRI-organic + inorganic treatments over BMP.With SRI-organic fertilization only, growth parameters showed inconsistent results; however, root dry weight and root volume were found to be significantly greater compared to BMP.Grain yield was found significantly higher in the SRI-organic + inorganic treatments (12−23% and 4−35% in the Kharif and Rabi seasons, respectively), while with SRI-organic management only, yield was found higher (4−34%) only in the Rabi seasons compared to BMP. On average, 31% and 37% of irrigation water were saved during Kharif and Rabi seasons, respectively, with both SRI methods of rice cultivation compared to BMP. Further, total nitrogen, %organic carbon, soil dehydrogenase, microbial biomass carbon, and total bacteria, fungi and actinomycetes were found higher in both sets of SRI trials in comparison to BMP. It is concluded that SRI practices create more favorable conditions for beneficial soil microbes to prosper, save irrigation water, and increase grain yield.
Studies on the effect of saturated hydrocarbons on parasitization by the egg parasitoid Trichogramma chilonis Ishii were carried out in the laboratory and net house. Bioassay of 11 hydrocarbons, viz. pentadecane, heptadecane, ecosane, heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, octacosane and hexatriacontane, were carried out under controlled conditions in the laboratory. These were also tested on potted maize plants in a net house. Among the saturated hydrocarbons, octacosane recorded the highest parasitoid activity index followed by docosane and tricosane. However, tricosane caused the highest percentage of parasitization, which was at par with octacosane and docosane. A positive correlation was found between concentration and kairomonal activity only in case of tricosane. In the net house, tricosane recorded the highest parasitization. Response of the parasitoid to egg cards treated with hydrocarbons decreased with increase in distance between the release point and host eggs. No parasitization was observed in host eggs placed at 8 m and 10 m away from the point of release except in the case of tricosane and pentacosane.
Temperature driven development of rice brown planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) population (biotype 4) was examined at seven constant temperatures (15, 18, 20, 25, 30, 32 and 35°C). Complete development of BPH from egg to adult was observed at constant temperatures ranging from 15 to 32°C with linear development observed till 30°C. Total immaturedevelopmental duration decreased from 74.4 days at 15°C to 22.4 days at 30°C. Linear and non-linear models fitted to describe developmental rates of life stages as a function of temperature, gave estimates of bioclimatic thresholds (lower, optimum and upper temperature thresholds). Thermal constants estimated from Campbell linear model for egg, nymph and cumulative immature development to adult were, 198.8, 275.5 and 473.9 degree days, respectively. Among empirical non-linear models, Lactin 2 model was selected for estimates of upper temperature threshold at 35°C based on higher coefficient of determination. Application of thermodynamic SSI model explained the observed nonlinear relationship of development of BPH life stages at temperatures higher than 30°C. The estimated thermal constants and bioclimatic thresholds were used in developing temperature dependent phenology model based on Campbell equation. Phenology model predicted closely the occurrence of different life stages of BPH with those observed under field conditions.
Plants are the important sources for several drugs. In recent years many drug formulations are based on plant products. The present study was carried out with an objective to investigate the antibacterial and antifungal potentials of leaves of Artabotrys hexapetalus Linn. belonging to the family Annonaceae. It is widely distributed throughout the southern part of the Asia and china. In the present study, methanolic extracts of leaves of Artabotrys hexapetalus Linn was evaluated for potential antimicrobial activity against medically important bacterial and fungal strains. The antimicrobial activity was determined in the extracts using agar well diffusion method. The antibacterial and antifungal activities of extracts (25, 50, 75 and 100 μg/ml) of Artabotrys hexapetalus were tested against ten human pathogenic bacteria; and four fungal strains. The results revealed that the remarkable inhibition of the microbial growth was shown against the tested organisms. Phytochemical analysis of the plant was also carried out. The microbial activity of the Artabotrys hexapetalus was due to the presence of various secondary metabolites. Hence, this plant can be further studied to discover bioactive natural products that may serve as lead molecules in the development of new pharmaceutically important compounds
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