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J Environ Biol ; 2020 Mar; 41(2): 261-265
Article | IMSEAR | ID: sea-214504


Aim: The aim of the present study was to understand the basic pathogen dynamics of Colletotrichum species infecting chilli crop in the Andaman and Nicobar Islands for disease management practices. Methodology: Twenty fungal isolates associated with chilli (Capsicum annuum) anthracnose disease from diverse locations of tropical Andaman, India were characterized using polyphasic approaches. Results: Upon morphological studies, out of twenty isolates, fourteen isolates were found chromogenic and eleven showed concentric ring pattern of mycelial growth. Based on conidial morphology, the isolates were grouped into two species (C. capsici and C. gloesporioides). The pathogenicity tests on three chilli varieties revealed difference in the pathogenic potential among the collected isolates. The sequence analysis using internal transcriber spacer (ITS) region revealed the presence of two other species C. siamense and C. plurivorum, in addition to C. gloesporioides and C. capsici. Interpretation: The present study revealed the presence of high level of genetic and pathogenic variability among the Colletotrichum isolates infecting chilli in Andaman Islands.

J Environ Biol ; 2019 Nov; 40(6): 1137-1144
Article | IMSEAR | ID: sea-214449


Aim: Alternaria blight caused by Alternaria lini is one of the major diseases of linseed which severely affects the yield and productivity. Here, we utilizes F2 mapping population derived from a resistant (JRF-4) and a susceptible (Chambal) genotypes of linseed and SSRs to identify the markers associated with Alternaria blight resistance using bulk segregant analysis approach. Methodology: A population consisting of 154 F2 individuals was developed from the cross between JRF-4 (resistant) and Chambal (susceptible). All 154 F2 individuals were screened with 100 polymorphic SSRs to identify extreme phenotype. Two bulk of extremes phenotypes (disease resistant and disease susceptible) from F2 mapping population were used for the bulked segregant analysis. The SSR primers that distinguished the parental lines were used to amplify the DNA from two bulks and banding pattern was observed to identify the SSRs that can differentiate the resistant and susceptible phenotypes bulk for Alternaria blight. Markers validation was carried out by amplifying DNA from individual plants of each bulk. Results: Out of 100, only 10 markers showed polymorphism among the bulks and of which only three markers viz., LUSc 898_3_12, Lu 2472 and Lu 3078 were able to differentiate the disease resistant and susceptible individuals from F2 population. Further, single marker linear regression approach was used to validate the association of selected polymorphic markers with the disease. The markers LUSc 898_3_12 and Lu 2472 showed significant regression which confirmed their linkage with Alternaria blight resistance. Interpretation: The two markers having significant regression can be used for diseases resistance breeding during marker assisted selection.

Article | IMSEAR | ID: sea-195848


Background & objectives: To support recent political commitments to end tuberculosis (TB) in the World Health Organization South-East Asian Region (SEAR), there is a need to understand by what measures, and with what investment, these goals could be reached. These questions were addressed by using mathematical models of TB transmission by doing the analysis on a country-by-country basis in SEAR. Methods: A dynamical model of TB transmission was developed, in consultation with each of the 11 countries in the SEAR. Three intervention scenarios were examined: (i) strengthening basic TB services (including private sector engagement), (ii) accelerating TB case-finding and notification, and (iii) deployment of a prognostic biomarker test by 2025, to guide mass preventive therapy of latent TB infection. Each scenario was built on the preceding ones, in successive combination. Results: Comprehensive improvements in basic TB services by 2020, in combination with accelerated case-finding to increase TB detection by at least two-fold by 2020, could lead to a reduction in TB incidence rates in SEAR by 67.3 per cent [95% credible intervals (CrI) 65.3-69.8] and TB deaths by 80.9 per cent (95% CrI 77.9-84.7) in 2035, relative to 2015. These interventions alone would require an additional investment of at least US$ 25 billion. However, their combined effect is insufficient to reach the end TB targets of 80 per cent by 2030 and 90 per cent by 2035. Model projections show how additionally, deployment of a biomarker test by 2025 could end TB in the region by 2035. Targeting specific risk groups, such as slum dwellers, could mitigate the coverage needed in the general population, to end TB in the Region. Interpretation & conclusions: While the scale-up of currently available strategies may play an important role in averting TB cases and deaths in the Region, there will ultimately be a need for novel, mass preventive measures, to meet the end TB goals. Achieving these impacts will require a substantial escalation in funding for TB control in the Region.

Indian J Exp Biol ; 2019 Feb; 57(2): 138-144
Article | IMSEAR | ID: sea-191434


Bacillus spp. isolated from different soils of Andaman Islands was characterized for antimicrobial potential by different methods. Among 65 strains tested, six Bacillus strains showed best in vitro antagonistic potential against solanaceous bacterial wilt pathogen Ralstonia solanacearum. The identity of the Bacillus strains were confirmed using 16S rRNA gene sequencing and biolog based phenotypic fingerprinting. The functional analysis revealed that most of the strains were positive for the production of IAA, siderophore and phosphate solubilization. In glass house and field studies, Bacillus amyloliquifaceans strain (Bs_Abi) showed significant biocontrol efficacy (92.1 and 73.7%, respectively) against brinjal bacterial wilt disease. The antimicrobial potential of Bs_Abi were further ascertained by presence of nine antimicrobial peptide (AMP) gene biosynthesis in PCR amplifications which confirmed the presence of peptide genes for six antibiotics (iturin, bacillomycin D, mycosubtilin, surfactin, bacilysin and subtilin). Our study revealed that the utilization of such antagonistic Bacillus spp. with multi antimicrobial peptide genes and more functional traits from tropical/ extreme soils would play a vital role in management of eggplant bacterial wilt disease and in formulation of new bioinoculants for improving the cropping system in Andaman and Nicobar Islands

Indian J Exp Biol ; 2018 Mar; 56(3): 202-206
Article | IMSEAR | ID: sea-190928


High temperature stress during grain filling period in wheat (Triticum aestivum L.) has pronounced effects on yield in major wheat growing agro-ecological zones. The fast chlorophyll fluorescence transients expose the damage to leaf photosynthetic activity under high temperatures. The method relies on the functioning of photosynthetic apparatus of plants under stress; however, these transients have been studied in detached leaves under controlled conditions. Still no reports are available on the potential usefulness of chlorophyll a fluorescence kinetics on intact wheat leaves for screening heat stress tolerant genotypes under field conditions. Hence, we conducted a study with the hypothesis that chlorophyll a fluorescence parameters and kinetics of plant-attached leaves under field conditions can be useful for screening of heat tolerant genotypes. The experimental population for testing the hypothesis consisted of 20 diverse wheat genotypes grown under timely and late sown environments (terminal heat stress) for two years. The results showed influence of high temperature on the expression of parameters Fo, Fv/Fo, Fv/Fm, and performance index. Analysis of the fast OJIP fluorescence transients indicated that the relative variable fluorescence between steps O and K and between steps O and J were related to high temperature stress tolerance. Five genotypes with consistent performance for better photosynthetic efficiency under thermal stress were observed. The inferences drawn from the present study supported our hypothesis that the analysis of chlorophyll a fluorescence transient parameters of plant attached leaves under field conditions can be used as a tool in the selection of wheat cultivars with better thermostability and functioning of photochemical reactions that could sustain photoassimilation and grain dry matter accumulation.