Antimicrobial activity of Memecylon malabaricum leaves

The petroleum ether, chloroform and methanol extracts of Memecylon malabaricum leaves were tested for antimicrobial activity. Only methanol extract has shown activity against bacteria both Gram (+) and Gram (-), and fungi.     

Changes in enzyme activities,soluble sugars and phenols during in vitro adventitious shoot regeneration from leaflet explants of <Emphasis Type="Italic">Albizia procera</Emphasis> (Roxb.) Benth

Changes in nitrate reductase, i.e. NR (E.C. 1.7.1.1) activity, peroxidase (E.C. 1.11.1.14) activity, soluble sugars and phenols were monitored at various time intervals from day 0 to 60 during in vitro adventitious shoot regeneration from leaflet explants of Albizia procera (Roxb.) Benth. The explants were incubated on semi-solid Murashige and Skoog medium supplemented with 2.6 g l^?1 Phytagel^®, 2.5% sucrose, 10 μM BAP, 1 μM NAA and 15 μM AgNO₃. NR activity, soluble sugars and phenols exhibited initial sharp rise on around day 20 followed by steep decline on day 25, whereas peroxidase activity peaked on day 50, highlighting significance of early input of nitrogen and energy and late emergence of lignification process for cellular differentiation and organization into adventitious shoot primordia. Morpho-anatomical changes in leaflets at various stages of in vitro adventitious shoot formation also followed the endogenous biochemical pattern.     

Large cardamom (Amomum subulatum Roxb.) plantation — An age old agroforestry system in Eastern Himalayas

Large cardamom (Amomum subulatum Roxb.) is a shade loving plant grown in the Indian hill states of Sikkim and Dargeeling district of West Bengal. About 30 important tree species are used to provide shade to the cardamom plants. Alnus nepalensis, a deciduous, nitrogen fixing and fast growing tree, is the species most commonly underplanted with cardamom. In addition to providing shade, it is also used for fuelwood. The old trees are cut and young plants coming up are allowed to grow in cyclic order. The quick decomposing leaf litter of A. nepalensis also fertilises the cardamom plants. The nitrogen added to the soil in this way has been found to be as high as 249 kg/ha. Large cardamom thrives well in a moist soil, which is maintained by water diverted from seasonal springs on the upper slopes. The system is well suited to conserving soil, water and tree cover of the characteristically steep slopes of the region. Moreover, the management inputs required for growing cardamom are low but the crop gives a higher financial return than rice or maize. The shade trees used in the system are also a major source of fuel, fodder and timber, especially as access to state owned forests is restricted by legislation. However, increasing incidence of viral chirkey and foorkey disease, panicle rot and capsule borer are reducing the cardamom productivity. It has been observed that integrating dairying and apiculture will further augment profitability from large cardamom agroforestry system.     

Seasonal dynamics of mineral N pools and N-mineralization in soils under homegarden trees in South Andaman,India

Agroforestry trees are now well known to play a central role in the build up of nutrients pools and their transformations similar to that of forest ecosystem, however, information on the potential of homegarden trees accumulating and releasing nitrogen (mineralization) is lacking. The present study reports seasonal variations in pool sizes of mineral N (NH₄⁺-N and NO₃⁻-N), and net N-mineralization rate in relation to rainfall and temperature under coconut (Cocos nucifera L.), clove (Eugenia caryophyllata Thunb) and nutmeg (Myristica fragrans Houtt. Nees) trees in a coconut-spice trees plantation for two annual cycles in the equatorial humid climate of South Andaman Island of India. Concentration of NH₄⁺-N was the highest during wet season (May–October) and the lowest during post-wet season (November–January) under all the tree species. On the contrary, concentration of NO₃⁻-N was the lowest in the wet season and the highest during the post-wet season. However, concentrations of the mineral N were the highest under the nutmeg and the lowest under the coconut trees. Like the pool sizes, mean annual mineralization was the highest under the nutmeg (561 mg kg⁻¹ yr⁻¹) and the lowest under the coconut trees (393 mg kg⁻¹ yr⁻¹). Rate of mineralization was the highest during the post-wet season and the lowest during the dry season (February–April) under all the tree species. High rainfall during the wet season, however, reduced the rate of nitrification under all the tree species. The mean annual mineralization was logarithmically related with rainfall amount and mean monthly temperature.     

Identification of a diverse mini‐core panel of Indian rice germplasm based on genotyping using microsatellite markers

Identification of a small core germplasm set representing the available genetic diversity is essential for its proper evaluation and subsequent utilization in rice improvement programmes. For constituting a small diverse mini‐core panel of Indian rice germplasm, a representative set of 6912 accessions drawn based on their geographic origin from the whole rice germplasm collection available in the National Gene Bank was genotyped using 36 microsatellite markers. Automated fragment analysis of amplicons yielded a total of 435 alleles, with an average 12.4 and range of 3–29 alleles per locus. Polymorphism information content (PIC) ranged from 0.08 (RGNMS190) to 0.86 (RM552) with an average of 0.528. Based on genotyping data, a mini‐core consisting of 98 genotypes was identified. Ninety‐four per cent of the alleles present in the core set were present in the mini‐core. The identified small but diverse panel will be useful for further intensive trait‐specific evaluation and utilization in allele mining.     

Prospects of breeding biofortified pearl millet with high grain iron and zinc content

Development of crop cultivars with elevated levels of micronutrients is being increasingly recognized as one of the approaches to provide sustainable solutions to various health problems associated with micronutrient malnutrition, especially in developing countries. To assess the prospects of this approach in pearl millet (Pennisetum glaucum), a diverse range of genetic materials, consisting of 40 hybrid parents, 30 each of population progenies and improved populations, and 20 germplasm accessions, was analysed for grain iron (Fe) and zinc (Zn) content, deficiencies of which adversely affect human health. Based on the mean performance in two seasons at ICRISAT, Patancheru, India, large variability among the entries was found, both for Fe (30.1–75.7 mg/kg on dry weight basis) and Zn (24.5–64.8 mg/kg). The highest levels of grain Fe and Zn were observed in well‐adapted commercial varieties and their progenies, and in the parental lines of hybrids, which were either entirely based on iniari germplasm, or had large components of it in their parentage. There were indications of large within‐population genetic variability for both Fe and Zn. The correlation between Fe and Zn content was positive and highly significant (r = 0.84; P < 0.01). These results indicate that there are good prospects of simultaneous selection for both micronutrients, and that selection within populations, especially those with the predominantly iniari germplasm, is likely to provide good opportunities for developing pearl millet varieties and hybrid parents with significantly improved grain Fe and Zn content in pearl millet.     

Potential of Eisenia foetida for Sustainable and Efficient Vermicomposting of Fly Ash

Vermicomposting of fly ash has been attempted, using red earthworm, Eisenia foetida. Fly ash, which was obtained from thermal power station, was mixed with cowdung in different proportions (20, 40, 60 and 80%). These mixtures were used as feed for earthworms, and after 30 days, vermicast recovery, worm zoomass and numbers of juveniles produced were recorded. A total of six runs each of 30 days were conducted during the whole study. Concentrations of heavy metals in different mixtures of fly ash–cowdung, before and after vermicomposting and in the earthworms used in the study were also estimated. Results show maximum output of vermicasts and maximum number of juveniles produced was in reactors with 40% fly ash while maximum weight gain by earthworm was in 20% fly ash vermireactors. Performance of vermireactors up to 60% fly ash was more or less similar but at 80% fly ash, there is a marked reduction in overall performance of the reactors. Chemical analysis of different samples of fly ash–cowdung mixtures prior to vermicomposting revealed high concentrations of zinc, chromium, lead, nickel and copper. Chemical analysis of vermicomposted samples showed 30–50% reduction in heavy metals up to 60% fly ash and 10–30% reduction in 80% fly ash. Metal analysis of earthworms revealed considerable bioaccumulation of heavy metals in their body. The Present study indicates the feasibility of E. foetida for mitigating the toxicity of metals and up to 60% fly ash–cowdung mixtures can be used for sustainable and efficient vermicomposting.     

Effects of long-term 2,4-D application on microbial populations and biochemical processes in cultivated soil

Summary The effects of 15 years of field applications of 2,4-dichlorophenoxy acetate (2,4-D) on soil microbial population and biochemical processes were studied in a field cropped with maize followed by potatoes. Amine or ester formulations at the rate of 0.95 kg 2,4-D per hectare applied in May and October every year. Fungal, bacterial, and actinomycete populations, and microbial biomass C and N were reduced by the 2,4-D treatment, the reduction being more marked where the ester was used. N mineralization, nitrification, and potentially mineralizable N were reduced by the 2,4-D ester only, while urease activity was depressed by both formulations. Dehydrogenase activity and soil microbial respiration tended to be temporarily increased by the amine, but were reduced substantially by the ester, indicating that the ester probably interfered with nutrient cycling.     

土壤中黑碳对农药敌草隆的吸附-解吸迟滞行为研究

采用批处理振荡法和连续稀释法分别测定了敌草隆在人工添加黑碳土壤和自然形成的不同有机质和黑碳含量的土壤中的吸附一解吸行为。吸附结果表明，人工添加黑碳的土壤对敌草隆的吸附强度和吸附容量以及吸附等温线的非线性均随土壤黑碳添加浓度的增加而逐步增大；自然土壤的吸附容量和吸附强度随土壤总有机质含量增加而增加，但吸附等温线的非线性则与土壤中黑碳对有机质的相对含量有关，黑碳比例越高，等温线非线性越大。解吸实验结果表明，无论是人工添加黑碳的土壤还是自然土壤，对敌草隆的解吸迟滞作用均随土壤黑碳含量增高而愈明显。