Ontogeny of in vitro shoot organogenesis from axillary meristem explants in chickpea (Cicer arietinum L.)

Chickpea (Cicer arietinum L.) is a major food legume crops for the tropics and sub-tropical regions and is the main dietary protein source for vegetarians in developing countries. Besides several abiotic factors, its production is constrained by insect pests, as well as many fungal diseases. The success of any attempt to produce resistant varieties through genetic engineering to a large extent depends on the availability of efficient and reproducible regeneration and transformation procedures. Further, the transformation techniques can be more successfully applied if the ontogeny of shoot development is well understood. Ontogeny of shoot development from axillary meristem explants (AME) in chickpea has been studied with the optimization of conditions for high-frequency multiple shoot induction. Preculture of seeds in TDZ significantly enhances the frequency of multiple shoot induction from the explants. Ontogeny and early events of multiple shoot induction revealed direct adventitious origin of the shoots. The understanding of the regeneration process could be further utilized in the designing of efficient transformation methods.     

Changes in Certain Antioxidative Enzymes and Growth Parameters as a Result of Complete Submergence and Subsequent Re-aeration of Rice Cultivars Differing in Submergence Tolerance

An experiment was conducted on the three indica rice ( Oryza sativa L.) cultivars IR 42, CR 383-10 and FR 13A, which are susceptible to submergence, submergence-avoiding and tolerant to submergence, respectively. A deleterious effect of submergence was noted as both above-ground dry matter accumulation and chlorophyll content decreased during submergence and subsequent re-aeration. However, the rate of reduction was lower in the tolerant cultivar. The tolerant cultivar FR 13A maintained higher dry weight during submergence and subsequent re-aeration and accumulated lower proline and malondialdehyde contents than the other cultivars. The activities of the enzymes catalase, peroxidase and superoxide dismutase, expressed on a per g fresh weight of leaves basis, were higher in FR 13A than in the other cultivars, both under water and 24 h after the initiation of re-aeration. However, ascorbic acid oxidase activity was lower in FR 13A. The cultivar CR 383-10, which has the capacity to accumulate more above-ground dry matter under normal conditions, showed a greater elongation ability under submergence and was similar to the susceptible cultivar IR 42 in terms of enzyme activities and the other parameters investigated during submergence and subsequent re-aeration.     

Pyramiding of four resistance genes of bacterial blight in Tapaswini, an elite rice cultivar, through marker-assisted selection

Breeding for resistance against Bacterial blight (BB), a destructive disease in rice, is a major challenge because of the rich diversity of the pathogen, Xanthomonas oryzae pv. oryzae. Three resistance genes i.e. xa5, xa13 and Xa21 were transferred from IRBB 60 through marker-assisted backcross breeding to supplement the Xa4 gene present in Tapaswini, an elite cultivar having a wide coverage. The precise transfer was aided through effective foreground selection using STS markers RG 556, RG 136 and pTA248 linked to the three target genes, respectively. In the screening assays, the gene pyramids having four genes exhibited higher level of resistance against the disease. Background selection based on morphological and grain quality traits and SSR markers led to the recovery of 85–96 % of the recurrent parent genome in the gene pyramids. Multi location evaluation conducted over a two year period at several hotspot locations of bacterial blight in India has resulted in identification and release of CRMAS 2622-7-6 (IT-6), a promising gene pyramid as improved Tapaswini. The high levels of resistance exhibited in the improved genotype without any yield penalty and its similarity to the recurrent parent provides a successful demonstration of the potential of MAS in pyramiding genes as well as the recovery of the parental genome with high accuracy.     

Induction of mutations for heat tolerance in potato by using in vitro culture and radiation

Heat tolerant mutants were obtained in two commercial potato cultivars, `Kufri Jyoti' and `Kufri Chandramukhi' through in vitro mutagenesis of in vitro propagated plantlets. Gamma-irradiated (20 and 40 Gy) shoots were micropropagated for three cycles (M₁V₃). A large number of the micropropagated shoots produced microtubers at 28 ^°C. Microtubers induced at high temperature had distorted shape but showed normal germination in field. Under stress conditions of high temperature, the frequency of chlorophyll variants increased in the gamma irradiation-derived material, however, nearly 40% of the plants had normal leaf tissue, whereas control plants showed completely damaged leaves. This revised version was published online in July 2006 with corrections to the Cover Date.     

An avenue for replacement of chemical fertilization under rice-rice cropping pattern: Sustaining soil health and organic C pool via MSW-based vermicomposts

ABSTRACT

The impacts of Municipal solid wastes (MSW) vermicompost (VC) on soil-crop interface have rarely been studied. Hence, the influence of vermicompost on soil health and soil organic C (SOC) dynamics was assessed under intensive rice–rice cropping system. A 20–40% of the recommended N-fertilization was substituted by MSW-vermicompost for the crop. SOC storage, degree of humification, humic acid C, and fulvic acid C in soil gradually increased by 55–60% under NPK₆₀ + VC and NPK₈₀ + VC treatments in 2 years. The improvement in N-mineralization was spectacular in NPK₆₀ + VC (2.79 folds) and NPK₈₀ + VC (2.25 folds) treated soil. The carbon pool management index in soil was greatest under NPK₆₀ + VC (2.1) treatment followed by NPK₁₀₀ + VC (1.96) and NPK₈₀ + VC (1.87) treatments. Moreover, the crop biomass and grain yield increased under VC treatments. The correlation and regression statistics revealed that rice production was enhanced due to improvement of SOC pool and humified carbon fractions in soil. Finally, we recorded highest benefit-cost ratio under NPK₆₀ + VC (benefit/cost 5.55) followed by NPK₈₀ + VC (benefit/cost 5.44). The study indicated that MSW-vermicompost sustained soil microbial health and SOC balance, which significantly correlated with rice production.     

Influence of arbuscular mycorrhizae on growth, leaf yield and phosphorus uptake in mulberry (Morus alba L.) under rainfed, lateritic soil conditions

 A field experiment was conducted to study the effect of arbuscular mycorrhizal association in mulberry saplings var. S₁, together with two levels of phosphate, on growth characters, leaf yield and phosphorus uptake. The experiment was conducted in the period 1995 to 1997 at the Technical Service Centre, Kashipur, Purulia (West Bengal) under rainfed, lateritic soil conditions. Pooled data analysis revealed that there was no significant variation among the treatments in most of the characters except height of plant and leaf moisture percentage. Plant height in both treatments with Glomus mosseae was significantly less than in the others, while there was significant reduction in moisture percentage in G. fasciculatum with 25 kg of phosphate and G. mosseae with 10 kg of phosphate ha^–1 year^–1 than in other treatments. There was no significant season–treatment effect on any of the parameters. Considering all the quantitative and qualitative characters, G. fasciculatum together with the most economic dose of phosphate showed more promising performance than G. etunicatum and G. mosseae with different doses of phosphate fertilizer. At 80% of the recommended dose of inorganic phosphate fertilizer, Rs 534.0 were earned as net profit. Received: 11 February 1998     

Rapid detection of Mycobacterium bovis on its lipid profile by thin layer chromatography

Sixteen Mycobacterium bovis (M. bovis) strains isolated from bovine tissues and one standard reference strain of M. bovis AN5 alongwith other species of mycobacteria for comparison were investigated for the presence of phenolic glycolipid (PGL) and phthiocerol dimycocerosate (PDIM) for rapid identification of M. bovis by thin-layer chromatography (TLC). The study indicated presence of PGL with an Rf value of 0.75 in chloroform-methanol solvent in all 17 M. bovis strains. The dimycocerostate A corresponding to spot A was the major constituent among all the three spots in M. bovis strains. TLC appeared to be a promising alternative to conventional biochemical methods for identification of M. bovis taking into consideration both PGL and PDIM lipids.