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Abstract  

The nature and composition of complexes formed by the reaction of Fe(III), Cr(III), Zn(II), and Co(II) with potassium pentacyanonitrosyl manganate K3 [Mn(CN)5NO] has been investigated by radiometric method. The metals form 1∶1 complexes with K3 [Mn(CN)5NO], the optimum pH for maximum precipitation being 3.6 for Fe(III), 7.3 for Cr(III), 5.4 for Zn(II), and 8.3 for Co(II). The solubility of the complexes as computed from activity at maximum precipitation point follows the order: chromium complex > iron complex > cobalt complex > zinc complex. The radiometric titration curves also show the formation of colloidal precipitates with dilute Zn(II) solutions.

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A study was undertaken to determine the genetics of corn leaf aphid (CLA) resistance in barley under controlled conditions with artificial inoculation at adult plant stage. Inheritance of CLA resistance was investigated in five resistant barley genotypes (EB921, EB2507, Manjula, DL529 and K144) in crosses with susceptible parent Alfa93 in F1, F2, F3 and backcross (BCF1) generations. The aphid inoculation was done using the brush method as well as the detached leaf method. Individual plants were classified in resistant, moderately resistant, susceptible and highly susceptible categories base on number per shoot as well as multiplication of CLA on any of the fresh, young leaf. The plants scored as resistant or moderately resistant were observed twice more at 10 days interval to confirm their reaction. Resistance was governed by a single dominant gene in EB921, DL529 and K144, while it was monogenic recessive in Manjula and EB2507. These diverse sources may be used in breeding for CLA resistance in barley improvement programme.

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Apart from the issue of sustainability and resource drain, the yield plateau in the rice-wheat cropping system of south-east Asia is the major area of concern. Realizing that genetic gain is a remote possibility, efforts are directed to management options for yield improvement. Adequate crop nutrition in general and nitrogen (N) in particular figure at the top among various management issues. A survey was conducted covering the rice-wheat belt of Haryana state, India representing Trans-Gangetic plains to know about on-farm practices related to N management in wheat crop and how far it deviates from the blanket recommendations given by State Agricultural Universities. The survey revealed that about 42.7 per cent farmers used either recommended dose of N (150 kg/ha) or less and others used higher dose of N. Positive correlation between the size of the farm and extent of N used was established. Whenever the farmers tended to use higher dose of N, they also tended to partition it in more number of splits (up to 3 splits, excluding basal application) staggering upto 54 days after sowing (DAS) as against the recommended practice of two splits (including basal application) within 35 DAS. The study confirmed deviation from the recommended practices of N management but major revelation came about reverse gap holding that the practice of N management in wheat crop being followed by the farmers is better in terms of grain yield. The NPhysical optimum and NEconomic optimum exceeded the current use (165.7 kg/ha) and recommended levels. This study suggests a fit case for the upward revision of recommended dose of N in wheat crop involving no element of risk as arising from aggravated problem of insect pest and disease complex. Nearly half of the farmers use either recommended dose of N or less than that and it is here, where opportunity lies in augmenting the wheat productivity by enhancing the existing level of N use.

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Toxic metals such as cadmium (Cd) are detrimental for growth of the crops. The differential sensitivity of maize and rice, the two vital cereals, which also belong to C4 and C3 plant types, respectively, to a similar degree of Cd stress is not known that comprised the objective of this study. Maize and rice genotypes were grown hydroponically in the presence of 5 and 10 μM cadmium (Cd) concentrations to examine their relative sensitivity to this metal at growth and metabolic levels. The shoots of maize genotypes accumulated relatively greater cadmium than those of rice while the roots of both the plant types did not differ significantly in cadmium accumulation. The shoots and roots of maize genotypes showed higher growth than rice genotypes under both Cd levels. At similar Cd level, the rice shoots showed greater damage to membranes and chlorophyll than maize shoots. The activities of RUBP carboxylase and phosphoenolpyruvate carboxylase were significantly greater in maize than in rice under Cd stress. Maize genotypes also possessed greater sucrose content and sucrose phosphate synthase activity in their shoots than rice genotypes. The oxidative damage as malondialdehyde and hydrogen peroxide was higher in rice genotypes. The rice genotypes showed greater induction of antioxidants such as superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and ascorbic acid than maize genotypes. On the other hand, glutathione, proline, metallothioneins, total thiols content and glutathione-s-transferase activity were significantly higher in maize genotypes under Cd stress suggesting their superior capacity to deal with Cd toxicity. The observations indicated that the maize genotypes representing C4 plant type appear to have greater Cd tolerance than the rice genotypes representing C3 plant type. The findings speculate that C4 plant species may adapt to toxic metals such as Cd in a better way than C3 ones but further study involving several representatives of these plant types need to be carried out to corroborate it.

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European Journal of Microbiology and Immunology
Authors: Andreas E. Zautner, A. Malik Tareen, U. Groß and R. Lugert

Abstract

Chemotaxis is the common way of flagellated bacteria to direct their locomotion to sites of most favourable living conditions, that are sites with the highest concentrations of energy sources and the lowest amounts of bacteriotoxic substances. The general prerequisites for chemotaxis are chemoreceptors, a chemosensory signal-transduction system and the flagellar apparatus.

Epsilonproteobacteria like Campylobacter sp. show specific variations of the common chemotaxis components. CheV, a CheWlike linking-protein with an additional response regulator (RR) domain, was identified as commonly used coupling scaffold protein of Campylobacter jejuni. It attaches the histidine autokinase (CheAY), which also has an additional RR-domain, to the chemoreceptors signalling domains. Theses additional RR-domains seem to play an important role in the regulation of the CheAY-phosphorylation state and thereby in sensory adaptation.

The Campylobacter-chemoreceptors are arranged into the three groups A, B, and C. Group A contains membrane-anchored receptors sensing periplasmic signals, group B consists only of one receptor with two cytoplasmic ligand-proteins representing a bipartite energy taxis system that senses pyruvate and fumarate, and group C receptors are cytoplasmic signalling domains with mostly unknown cytoplasmic ligand-binding proteins as sensory constituents. Recent findings demonstrating different alleles of the TLP7 chemoreceptor, specific for formic acid, led to an amendment of this grouping.

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Cereal Research Communications
Authors: B. Kumar, K.S. Hooda, R. Gogoi, V. Kumar, S. Kumar, A. Abhishek, P. Bhati, J.C. Sekhar, K.R. Yathish, V. Singh, A. Das, G. Mukri, E. Varghese, H. Kaur, V. Malik and O.P. Yadav

Maydis leaf blight (MLB), a serious foliar fungal disease of maize, may cause up to 40% losses in yield. The present studies were undertaken to identify the stable sources of MLB resistance, its inheritance study, and testing of MLB resistance linked markers from diverse background in the Indian adapted tropical maize genotypes. A set of 112 inbred lines were screened under artificially created epiphytotics conditions at three hotspot locations. Analysis across multi-locations revealed significant effects of genotypes and environments, and non-significant effects due to genotypes × environment interaction on disease incidence. A total of 25 inbred lines with stable resistance were identified across multi-locations. Inheritance of resistance was studied in six F1s and two F2s of resistant and susceptible parents. The null hypothesis of segregation of resistance and susceptible for mono and digenic ratios in two F2 populations was rejected by Chi-square test. The non-significant differences among the reciprocal crosses depicted the complete control of nuclear genome for MLB resistance. Partial dominance in F1s and normal distribution pattern in F2s of resistant and susceptible parents suggested polygenic nature of MLB resistance. Correlation studies in F2 populations exhibited significant negative correlation between disease score and days to flowering. Five simple sequence repeats (SSRs) markers, found associated to MLB resistance in different studies were unable to differentiate amongst MLB resistance and susceptible parents in our study. This emphasizes the need of fine mapping for MLB resistance in Indian germplasm. The identified stable sources of resistance and information on inheritance study can be used further in strengthening of resistance breeding against MLB.

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