Gunjan Sharma

The ApMat marker can resolve Colletotrichum species: a case study with Mangifera indica

Anthracnose disease caused by the Colletotrichum gloeosporioides species complex is a major problem worldwide. In this study, we investigated the phylogenetic diversity of 207 Indian Colletotrichum isolates, associated with symptomatic and asymptomatic tissues of mango, belonging to this species complex. Phylogenetic analyses were performed based on a 6-gene dataset (act, cal, chs1, gapdh, ITS and tub2), followed by ApMat sequence-analysis. The ApMat-based phylogeny was found to be superior as it provided finer resolution in most of the species-level clades. Importantly, the ApMat marker identified seven lineages within C. siamense sensu lato, including C. jasmini-sambac, C. hymenocallidis, C. melanocaulon, C. siamense sensu stricto and three undesignated, potentially novel lineages. In this study, C. fragariae sensu stricto, C. fructicola, C. jasmini-sambac, C. melanocaulon and five undesignated, potentially novel lineages were found to be associated with mango tissues. There is a need to develop a consensus among mycologists as to which genes should be used to define and delimit a Colletotrichum species and in the mean time mycologists should voluntarily restrain from describing new species based on inadequate datasets.

Resolving the Colletotrichum siamense species complex using ApMat marker

Colletotrichum gloeosporioides sensu lato has been associated with anthracnose in diverse commercial crops. It is now established that C. gloeosporioides sensu lato comprises 33 phylogenetic species and C. gloeosporioides sensu stricto is not a common pathogen of tropical fruits. In this study, we investigated the phylogenetic relationships of 85 Colletotrichum isolates associated with select tropical fruits and flowering plants from India. In the ApMat marker analysis, the 85 isolates clustered with 7 known Colletotrichum species (C. aotearoa, C. dianesei, C. endomangiferae, C. musae, C. siamense, C. theobromicola, Glomerella cingulata f. sp. camelliae) and six novel lineages. One of the novel lineages is described and illustrated in this paper as Colletotrichum communis sp. nov., while new-host pathogen associations for C. aotearoa, C. endomangiferae, C. dianesei and C. theobromicola are reported from India. Out of the 85 isolates analysed in this paper, 73 isolates clustered within the C. siamense species complex, indicating that C. siamense species complex, not C. gloeosporioides sensu stricto, is common on tropical fruits. In comparison with act, cal, gapdh, ITS and tub2 gene markers, we recommend the use of the ApMat marker for accurate identification of cryptic species within the C. siamense species complex. We believe that the ApMat marker, in combination with one or two similar ‘phylogenetically superior’ gene markers, is a better candidate for species-level classification of fungi that were traditionally identified as ‘Colletotrichum gloeosporioides’.

Colletotrichum fructicola and C. siamense are involved in chilli anthracnose in India

Chilli anthracnose is a major problem in India and worldwide. In this study, we investigated the phylogenetic relationships of 52 fungal isolates associated with chilli anthracnose in southern India. All the 52 isolates were sequenced for partial ITS/5.8S rRNA and glyceraldehyde-3-phosphate dehydrogenase (gapdh) genes and showed affinities with Colletotrichum siamense and C. fructicola within Colletotrichum. gloeosporioides species complex. Further, a reduced subset of 17 selected isolates was made and in a maximum parsimony analysis of a multigene data-set including partial ITS/5.8S rRNA, actin (act), calmodulin (cal), chitin synthase (chs1), gapdh and β-tubulin (tub2) gene sequence data, these fungal isolates clustered with the type strain of C. fructicola, except for strain MTCC 3439 that showed phylogenetic affinities with C. siamense. The pathogenicity tests involving two representative isolates: UASB-Cg-14 and MTCC 3439, confirmed the involvement of C. fructicola and C. siamense in the development of disease symptoms on fresh chilli fruits. This is the first report of the association of C. fructicola and C. siamense in causing chilli anthracnose in India.

Infra-specific diversity of Colletotrichum truncatum associated with chilli anthracnose in India based on microsatellite marker analysis

Colletotrichum truncatum is a fungal species associated with anthracnose disease in many economically important crops within the plant families Fabaceae and Solanaceae. Understanding the degree of genetic diversity within C. truncatum population will provide insights into the ability of this species to evolve in response to environmental conditions, and thus be helpful in designing effective control strategies for this pathogen. In this study, microsatellite markers from 27 loci were used to investigate the genetic diversity and population structure among 99 isolates of C. truncatum from India. All the loci (100%) were polymorphic and a total of 140 different alleles were amplified. Six distinct groups were obtained based on unweighted pair group method with arithmetical average cluster analysis. The isolates belonging to Group V showed the highest level of genetic diversity and a broad host range. Analysis of molecular variance analysis showed that the variation occurs mostly within groups. Microsatellite markers-based genetic diversity estimation revealed high diversity among C. truncatum isolates from India.

Xanthomarina gelatinilytica gen. nov., sp. nov., isolated from seawater.

A novel Gram-stain-negative, rod-shaped, yellow-pigmented, non-sporulating, non-motile bacterium, designated strain AK20T, was isolated from seawater collected from Kochi city, Kerala state, India. Colonies on marine agar were circular, yellow, shiny, translucent, 2-3 mm in diameter, convex and with entire margin. Flexirubin-type pigment was present. The fatty acids were dominated by iso-branched units with a high abundance of iso-C15:0, iso-C15:1 G, iso-C17:0 3-OH, summed feature 3 (C16:1ω7c and/or iso-C15:0 2-OH) and iso-C15:0 3-OH. Polar lipids included phosphatidylethanolamine, two unidentified aminophospholipids, two unidentified phospholipids and four unidentified lipids. Menaquinone 6 (MK-6) was the predominant respiratory quinone. The DNA G+C content of strain AK20T was 38.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain AK20T was closely related to Formosa spongicola A2T and Bizionia paragorgiae KMM 6029T (pair-wise sequence similarities of 95.9 and 95.7%, respectively), forming a distinct branch within the family Flavobacteriaceae and clustering with the clade comprising species of the genus Bizionia. Based on phenotypic and chemotaxonomic characteristics and phylogenetic analysis, strain AK20T is different from the existing genera in the family Flavobacteriaceae, and is therefore considered to represent a novel species of a new genus, for which the name Xanthomarina gelatinilytica gen. nov., sp. nov. is proposed. The type strain of Xanthomarina gelatinilytica is AK20T ( = MTCC 11705T = JCM 18821T).

Effect of sublimation on performance of CuPc: PTCDA bilayer organic solar cell

Silicon photovoltaic is the most commonly used commercial technology. However it has limitation in terms of efficiency and cost effectiveness. As such there is a need to search for alternate technologies for conversion of solar energy into electricity. Organic photovoltaic (OPV) is one of the emerging R&D areas in this direction. In OPV two approaches are being used for fabrication of solar cells i.e. using small molecule and polymers, respectively. In both the cases donor:acceptor (D/A) concept is being used for the fabrication of the device. For example in small molecule approach bilayer devices having D/A layer is used whereas in polymer solar cells D/A interpenetrating bulk hetrojunction is being used. Both the type of devices need improvement in their performance in terms of efficiency, stability, life time etc. Global efforts are being made to improve the performance of these devices by using new hetrojunction materials, interface layers, thermal treatments, purification/sublimation etc. The present work is also an attempt in this direction wherein we have improved the performance of small molecules based solar cell by the process of sublimation of the material used in device fabrication. The configuration of the device used in the present work was prepared as follows. Thin film of PEDOT: PSS was deposited on ITO substrate by spin casting. Subsequently copper(ll)phthalocyanine (CuPc) film (~45nm) (both without sublimation as well as with sublimation) was vacuum deposited in a vacuum ~ 10-6. Then on top of CuPc layer Perylen-3, 4,9,10-tetracarbonsaure-dianhydrid 3,4,9,10- Perylenetetracarboxylic dianhydride dianidride perilen-3,4:9,10-tetracarbossilico (PTCDA) film (~40 nm) was also vacuum deposited. Finally LiF and Al electrodes were vacuum deposited resulting in to a bilayer device having the configuration ITO/PEDOT: PSS/CuPc: PTCDA/LiF/AI. The device without sublimation of CuPc shows the solar cell parameters i.e. open circuit voltage (Voc),short circuit current density (Jsc), fill factor ( FF) and power conversion efficiency( eta) as 0.20 V, 2.8 times10- 6A/cm2, 0.32, and 2.2 times 10- 4% .respectively. However when the device is made in same configuration by sublimation of CuPc prior to its deposition a considerable improvement in the Jsc and eta of the device has been observed. In fact new electrical parameter obtained in the second case (sublimated/purified CuPc) being 0.12V, 52.6times 10- 6A/cm2, 0.25 and 13.2 times 10- 4% respectively. The improvement in the Jsc and overall eta of CuPc: PTCDA bilayer device has been attributed to the reduction in the defects/impurities in CuPc on sublimation.