Assam Agricultural University

About: Assam Agricultural University is a education organization based out in Jorhāt, India. It is known for research contribution in the topics: Population & Nutrient management. The organization has 1436 authors who have published 1056 publications receiving 8361 citations.

Insect pests of tea and their management.

Abstract: Globally, 1031 species of arthropods are associated with the intensively managed tea Camellia sinensis (L.) O. Kuntze monoculture. All parts of the plant, leaf, stem, root, flower, and seed, are fed upon by at least one pest species, resulting in an 11%-55% loss in yield if left unchecked. There has been heavy use of organosynthetic pesticides since the 1950s to defend the plant against these pests, leading to rapid conversion of innocuous species into pests, development of resistance, and undesirable pesticide residues in made tea. As a result of importer and consumer concerns, pesticide residues have become a major problem for the tea industry. Integrated pest management (IPM) may help to overcome the overuse of pesticides and subsequent residues. We review the advances made in our understanding of the biology and ecology of major insect and mite pests of tea, host plant resistance, cultural practices, biocontrol measures, and need-based application of botanicals and safer pesticides to understand the present status of IPM and to identify future challenges to improvement.

Endophytes: exploitation as a tool in plant protection

Abstract: Endophytes are symptomless fungal or bacterial microorganisms found in almost all living plant species reported so far. They are the plant-associated microbes that form symbiotic association with their host plants by colonizing the internal tissues, which has made them valuable for agriculture as a tool in improving crop performance. Many fungal endophytes produce secondary metabolites such as auxin, gibberellin etc that helps in growth and development of the host plant. Some of these compounds are antibiotics having antifungal, antibacterial and insecticidal properties, which strongly inhibit the growth of other microorganisms, including plant pathogens. This article reviews the endophyte isolated from different plants, mode of endophytic infection and benefits derived by the host plant as a result of endophytism.

Distribution of virulence genes in Salmonella serovars isolated from man & animals.

Abstract: Background & objectives: Pathogenesis of Salmonellosis depends upon a large number of factors controlled by an array of genes that synergise into the actual virulence of Salmonella. A study was undertaken to observe the distribution of three such genes, namely, Salmonella enterotoxin (stn), Salmonella Enteritidis fimbrial (sef) and plasmid encoded fimbrial (pef) genes, among different serovars of Salmonella enterica isolated from man and animals. Methods: A total of 95 isolates belonging to S. Typhimurium (51), S. Enteritidis (36), S. Bareilly (3), and S. Paratyphi B (5) serovars were subjected to polymerase chain reaction (PCR) assay for the detection of stn, sef and pef genes using their specific primers and the PCR products were analysed by 1 per cent agarose gel electrophoresis for the presence of the respective genes. Results: Varying distribution pattern of these genes was observed amongst the isolates. While, stn was found in all the 95 strains, sef was found only among the S. Enteritidis isolates. The pef gene was found to be absent in 10 isolates including the three S. Bareilly isolates. Interpretation & conclusion : Findings indicated that the stn gene is widely distributed among Salmonella irrespective of the serovars and source of isolation. However, the sef gene appears to be serovar specific. Since the stn gene is found in all the isolates, it can be a viable target gene to explore the possibility of direct detection of Salmonella from samples from biological sources. Epidemiology and pathogenic process in salmonellosis are dictated by an array of factors that act in tandem and ultimately manifest in the typical symptoms of salmonellosis. Virulence genes encode products that assist the organisms in expressing its virulence in the host cells. Some genes are known to be involved in adhesion and invasion viz., sef 1 , pef 2 , spv 3 or inv 4 ; others are associated with the survival in the host system- mgtC5 or in the actual manifestation of pathogenic processes viz., sop 6 , stn 7 , pip A, B, D 8 . Nucleic acid based diagnostic techniques are being employed for the detection of various gene -encoded virulence factors viz., Salmonella enterotoxin (stn) 9,10 , Salmonella Enteritidis fimbriae (sef) and plasmid encoded fimbriae (pef) 11 genes. However, the distribution of these genes among the various isolates obtained from biological source is yet to be elucidated. The present study reports on the distribution of these genes among the Salmonella strains isolated from clinical cases of infections in man and animals.