Metabolism of Na2 75SeO4 in Astragalus bisulcatus Lima Bean, and Wheat: a Comparative Study

A comparative study of the metabolism of Na₂ ⁷⁵SeO₄ in Astragalusbisulcatus, luma bean, and wheat has been carried out. The resultsindicate that all three plants metabolize selenium extensively.Important differences were observed in the distribution of radioactivitybetween the various fractions isolated from the plants. Comparedto the protein fraction, the free amino acid fraction from A.bisulcatus contained a higher percentage of radioactivity. Theconverse was true for wheat and lima bean. As A. bisulcatusproteins contained a significant percentage of radioactivity,it is suggested, that the differences in the toxicity of seleniumtowards wheat, lime bean, and A. bisulcatus are difficult toexplain in terms of the differences in its incorporation intothe protein of the three species.     

The impacts of larval density and protease inhibition on feeding in medicinal larvae of the greenbottle fly Lucilia sericata

Larval therapy, the therapeutic use of blowfly larvae to treat chronic wounds, is primarily used in debridement. There are, however, gaps in current knowledge of the optimal clinical application of the therapy and mechanisms of action in the debridement process. Using an artificial assay, two studies were undertaken to investigate these aspects of larval debridement by Lucilia sericata Meigen (Diptera: Calliphoridae); the first studied the effects of the density of larvae on tissue digestion and larval mass, and the second considered the effects on the same parameters of incorporating protease inhibitors into the feeding substrate. The total mass of tissue digested increased with larval density until saturation was observed at 5.0–7.5 larvae/cm². This range was considered optimal as lower doses resulted in the removal of less tissue and higher doses offered no additional tissue removal and appeared to exacerbate competition for feeding. In the second study, increased protease inhibitor concentration led to significant decreases in tissue digestion and larval mass, suggesting that serine proteases, particularly trypsin, may play major roles in larval digestion. Such information is important in elucidating the main constituents that make up larval digestive products and may be significant in the development of new therapies.     

Selection index for identifying high-yielding groundnut genotypes in irrigated and rainfed environments

Selection of high yielding genotypes to be carried over to subsequent selection cycles in a breeding programme can sometimes be accomplished using a suitable index of secondary traits that may be relatively less sensitive to genotype‐by‐environment interactions than yield. We used the concept of correlated response to selection to measure the relative efficiency of nine selection indices. The results showed that the selection index, based on median and semi inter‐quartile range, which was actually used in identifying high yielding genotypes, had an efficiency that is comparable to the best index, the latter being a modification of the Elston index.     

The host range of Tobacco streak virus in India and transmission by thrips

Tobacco streak virus (TSV) recently caused an epidemic in peanut (= groundnut, Arachis hypogaea) crops in Andhra Pradesh, India. In the epidemic area TSV occurred in many widely distributed weeds of which Parthenium hysterophorus probably plays a major role in its spread by thrips. Three thrips species, Megalurothrips usitatus, Frankliniella schultzei and Scirtothrips dorsalis were vectors in the presence of infected pollen. Of crop species, Helianthus annuus (sunflower) and Tagetes patula (marigold) could act as sources of inoculum. In limited tests, the virus was not seed‐transmitted in the peanut cultivar JL‐24 or in the sunflower hybrids KBSH‐41, ‐42, ‐44, and ‐50, MSFH‐17 and ZSH‐976. Strategies adopted to reduce the incidence of TSV are discussed.     

The effect of male sandfly pheromone and host factors as attractants for female Lutzomyia longipalpis (Diptera: Psychodidae)

Abstract Male Lutzomyia longipalpis (Lutz & Neiva) pheromone extracted from tergal glands combined with heat, carbon dioxide gas and hamster urine was found to be attractive to virgin female sandflies. The host factors if offered in the absence of pheromone or a heat source were, however, unattractive to female flies. Pheromone stored for 6 days and then combined with the same host components remained attractive to female flies but storage failed to enhance its attractiveness. The effects of carbon dioxide gas, hamster urine, chicken uropygial gland extract and octenol plus acetone on the responses of females were inconsistent. A ceramic battery powered heat source was tested with pheromone and host attractants and showed potential for field application in developing a pheromone trap.     

Efficiency of physiological trait-based and empirical selection approaches for drought tolerance in groundnut

Drought is the major abiotic constraint affecting groundnut productivity and quality worldwide. Most breeding programmes in groundnut follow an empirical approach to drought resistance breeding, largely based on kernel yield and traits of local adaptation, resulting in slow progress. Recent advances in the use of easily measurable surrogates for complex physiological traits associated with drought tolerance encouraged breeders to integrate these in their selection schemes. However, there has been no direct comparison of the relative efficiency of a physiological trait‐based selection approach (Tr) vis‐à‐vis an empirical approach (E) to ascertain the benefits of the former. The genetic material used in the present study originated from three common crosses and one institute‐specific cross from four collaborating institutes in India (total seven crosses). Each institute contributed six genotypes and each followed both the Tr and E selection approaches in each cross. The field trial of all selections, consisting of 192 genotypes (96 each Tr and E selections), was grown in 2000/2001 in a 4 × 48 alpha design in 12 season × location environments in India. The selection efficiency of Tr relative to E, RE_Tr, was estimated using the genetic concept of response to selection. Based on all the 12 environments, the two selection methods performed more or less similarly (RE_Tr= 1.045). When the 12 environments were grouped into rainy season and post‐rainy season, the relative response to selection in Tr method was higher in the rainy than in the post‐rainy season (RE_Tr= 1.220 vs 0.657) due to a higher genetic variance, lower G × E, and high h². When the 12 environments were classified into four clusters based on plant extractable soil‐water availability, the selection method Tr was superior to E in three of the four clusters (RE_Tr= 1.495, 0.612, 1.308, and 1.144) due to an increase in genetic variance and h² under Tr in clustered environments. Although the crosses exhibited significant differences for kernel yield, the two methods of selection did not interact significantly with crosses. Both methods contributed more or less equally to the 10 highest‐yielding selections (six for E and four for Tr). The six E selections had a higher kernel yield, higher transpiration (T), and nearly equal transpiration efficiency (TE) and harvest index (HI) relative to four Tr selections. The yield advantage in E selections came largely from greater T, which would likely not be an advantage in water‐deficient environments. From the results of these multi‐environment studies, it is evident that Tr method did not show a consistent superiority over E method of drought resistance breeding in producing a higher kernel yield in groundnut. Nonetheless, the integration of physiological traits (or their surrogates) in the selection scheme would be advantageous in selecting genotypes which are more efficient water utilisers or partitioners of photosynthates into economic yield. New biotechnological tools are being explored to increase efficiency of physiological trait‐based drought resistance breeding in groundnut.