Bipul K. Biswas

Diversity and genetic resources of wild Vigna species in India

Diversity in morphological characters of 206 accessions of 14 wild Vigna species from India was assessed. Of these, 12 species belonged to Asian Vigna in the subgenus Ceratotropis and two were V. vexillata and V. pilosa belonging to subgenus Plectotropis and Dolichovigna, respectively. Data on 71 morphological traits, both qualitative and quantitative, were recorded. Data on 45 qualitative and quantitative traits exhibiting higher variation were subjected to multivariate analysis for establishing species relationships and assessing the pattern of intraspecific variation. Of the three easily distinguishable groups in the subgenus Ceratotropis, all the species in mungo-radiata group, except V. khandalensis, viz. V. radiata var. sublobata, V. radiata var. setulosa, V. mungo var. silvestris and V. hainiana showed greater homology in vegetative morphology and growth habit. The species, however, differed in other plant, flower, pod and seed characteristics. Within species variation was higher in V. mungo var. silvestris populations and three distinct clusters could be identified in multivariate analysis. V. umbellata showed more similarity to V. dalzelliana than V. bourneae and V. minima in the angularis-umbellata (azuki bean) group. Within species variations was higher in V. umbellata than other species in the group. In the aconitifolia-trilobata (mothbean), V. trilobata populations, were more diverse than V. aconitifolia. The cultigens of the conspecific wild species were more robust in growth, with large vegetative parts and often of erect growth with three- to five-fold increase in seed size and seed weight, except V. aconitifolia, which has still retained the wild type morphology to a greater extent. More intensive collection, characterisation and conservation of species diversity and intraspecific variations, particularly of the close wild relatives of Asian Vigna with valuable characters such as resistance to biotic/abiotic stresses, more number of pod bearing clusters per plant etc. assumes great priority in crop improvement programmes.

Antimicrobial Activities of Leaf Extracts of Guava (Psidium guajava L.) on Two Gram-Negative and Gram-Positive Bacteria

Aim. To determine the antimicrobial potential of guava (Psidium guajava) leaf extracts against two gram-negative bacteria (Escherichia coli and Salmonella enteritidis) and two gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) which are some of foodborne and spoilage bacteria. The guava leaves were extracted in four different solvents of increasing polarities (hexane, methanol, ethanol, and water). The efficacy of these extracts was tested against those bacteria through a well-diffusion method employing 50 μL leaf-extract solution per well. According to the findings of the antibacterial assay, the methanol and ethanol extracts of the guava leaves showed inhibitory activity against gram-positive bacteria, whereas the gram-negative bacteria were resistant to all the solvent extracts. The methanol extract had an antibacterial activity with mean zones of inhibition of 8.27 and 12.3 mm, and the ethanol extract had a mean zone of inhibition of 6.11 and 11.0 mm against B. cereus and S. aureus, respectively. On the basis of the present finding, guava leaf-extract might be a good candidate in the search for a natural antimicrobial agent. This study provides scientific understanding to further determine the antimicrobial values and investigate other pharmacological properties.

In vitro organogenesis of elephant apple (Feronia limonia)

Elephant apple (Feronia limonia L.). was micropropagated on MS medium containing 4.4 μM benzyladenine and 4.6 μM kinetin using cotyledon explants taken from in vitro-grown seedlings. Adventitious buds formed on the cotyledon developed into shoots that were rooted in half-strength MS medium containing 0.57 μM indoleacetic acid and 0.49 μM indolebutyric acid. Plants were successfully established in soil.

Regeneration of plantlets from in vitro cultured cotyledons of Aegle marmelos Corr. (Rutaceae)

Abstract Cotyledons from seedlings of various ages of Aegle marmelos were cultured on Murashige and Skoog (MS) medium supplemented with different combinations of phytohormones. The optimum seedling age was 10 days for shoot induction response and benzyladenine (BA) was superior to either kinetin, isopentenyladenine or zeatin. The optimum cytokinin (BA) concentration for bud induction was 2 mg l−1. The addition of indole-3-acetic acid (IAA; 0.2 mg l−1) improved shoot regeneration efficiency. The proximal part of the cotyledon had the highest regeneration potential. Adventitious shoots were elongated on MS medium containing 0.5 mg l−1 kinetin and 0.1 mg l−1 gibberellic acid. Approximately 25% of regenerated shoots were induced to differentiate roots on half-strength MS medium with 0.5 mg l−1 indole-3-butyric acid. The rooted plantlets were successfully transplanted to soil.

Broadening the genetic base of sesame ( Sesamum indicum L.) through germplasm enhancement

Sesame ( Sesamum indicum L.) is one of the worlds oldest oil crops and has been cultivated in Asia from ancient times. India has a rich diversity of this crop and a landrace collection is maintained at the National Genebank at the National Bureau of Plant Genetic Resources (NBPGR). The breeding potential of this germplasm has been hardly exploited to date. The major hindrance for the utilization of these resources is the transfer of diversity into a form that can be easily used by breeders and farmers. As part of a core collection strategy, a selection was made of 24 of the most diverse and unadapted parental lines, including one accession of the wild species S. mulayanum , and these were intercrossed in various combinations to maximize genetic diversity and to develop locally adapted pools of genetic resources. A weak and decentralized selection regime was maintained at four selected target sites on the progeny of 103 crosses. The range of variation in the selected F 4 progenies was assessed, and promising types with desired plant characteristics and high seed yield were selected. Realized genetic gains, especially for yield-related traits, were also assessed. Only a limited fraction of the existing diversity held in the genebank was used in the present study and there is much more diversity available for large-scale genetic enhancement of sesame in the future.

A Comparison of Diffusion-Conductimetric and Distillation-Titration Methods in Analyzing Ammonium- and Nitrate-Nitrogen in the KCl-Extracts of Georgia Soils

ABSTRACT Soil mineral (or inorganic) nitrogen (SMN), which primarily exists as exchangeable and soluble ammonium (NH4+) and the nitrate (NO3−) ions, represents readily available nitrogen for plant growth. Over the years a 2M potassium chloride (KCl) solution has become the extraction solution of choice for extracting SMN. In the research and service laboratories, either distillation-titration method (DTM) or colorimetric method (CM) is virtually the standard to measure NH4+- and NO3−-N in the 2M KCl soil extracts. However, being a time-consuming and labor intensive method, DTM generally has a very low throughput. Likewise, CM is affected by interferences from pH variation, color, turbidity, presence of organic species, and some other constituents in the extracts. In contrast, diffusion conductivity method (DCM) is a less expensive and high throughput one, which is also relatively free from common interferences. In this study, we, therefore, compared the extraction efficiency of various KCl concentrations and performance of diffusion conductivity method (DCM) with DTM in measuring NH4+-N and NO3−-N in KCl extracts of 32 agricultural soils of Georgia. A 0.2M KCl solution extracted statistically similar amounts of NH4+-N and NO3−-N as did 2M KCl, suggesting that a 10-fold dilute KCl solution than the standard 2M KCl might be good enough to extract and estimate the most of SMN. For the analyses of NH4+- and NO3−-N in the KCl extracts, the DCM produced results statistically similar to those produced by DTM. The deviation between the results given by DCM and DTM was no more than ±10%. Thus, DCM appears to be an attractive alternative to the labor intensive and time-consuming DTM for measuring NH4+- and NO3−-N in the KCl extract of soils in the research and service laboratories.