Browsing by Author "R. Thava Prakasa Pandian"

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    Colletotrichum kahawae subsp. cigarro causing leaf spot disease on arecanut, Areca catechu L. in India: A first report
    (2024) R. Thava Prakasa Pandian; Shivaji Hausrao Thube; Bhavishya; Merin babu; H. Rajashekara; T.N. Madhu; Diwakar, Y.; P. Santhoshkumar; B.J. Nirmalkumar; Balanagouda Patil; V. Hegde
    Arecanut is a prominent cash crop in India, known for its potential to significantly boost per capita income. The presence of fungal diseases poses a significant constraint to arecanut cultivation. In October 2019, a severe outbreak of leaf spot disease with 90°% disease incidence was recorded in the farmer's arecanut gardens from Kalasa hobli, Chikkamangaluru, Karnataka, India. Leaf spot symptoms started as small, irregular, light-dark brown spots (3–10 mm in diameter) with a yellow halo on the leaf lamina, which later coalesced to form larger necrotic lesions and a blighted appearance. The symptoms were also observed on leaf sheaths and nuts. In the present study, we identified and characterized the pathogen causing leaf spot disease using cultural, morphological, molecular characterization using multi-gene phylogeny, and pathogenicity assays. Microscopic, and molecular identification of CPCRICkc7G isolate retrieved from the leaf spot infected sample established the association of Colletotrichum kahawae subsp. cigarro as the causal agent. Pathogenicity assays confirmed the Koch's postulate by reproducing the field observed symptoms. To best of our knowledge, this confirms the first report of C. kahawae subsp. cigarro causing leaf spot disease on arecanut in India. The findings from this current study play a pivotal role in enhancing the knowledge of arecanut diseases in India, and lay an essential foundation for devising effective disease management approaches to curtail the disease spread.
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    Field detection, molecular characterization and biology of the tea tortrix, Homona coffearia Neitner (Lepidoptera: Tortricidae) on Cocoa (Theobroma cacao. L) from India
    (2024) Madhu T. N.; Saneera E. K; R. Thava Prakasa Pandian; Bhavishya; Nagaraja N. R; M. Chaithra; S. Elain Apshara; B. J. Nirmal Kumar; Diwakar Y; Suchithra M; Rajesh M. K; Vinayaka Hegde
    Cocoa (Theobroma cacao. L) is an important commercial crop widely cultivated in humid tropical regions; however, its production faces various constraints including insect pests. The survey conducted in 2022–2023 found significant damage to cocoa nurseries and fields caused by the larvae of H. coffearia. The caterpillars web the young leaves, feeds within the sheltered nests and affects the crop canopy. The percent incidence was 27.55 ± 1.81% in the nursery and 43.77 ± 3.42% in open fields. A detailed morphological examination and molecular characterization using the mitochondrial cytochrome c oxidase I (COI) gene confirmed the identity of the pest as H. coffearia. The study also documented the key biological parameters of H. coffearia on cocoa under laboratory conditions. The life cycle from egg to adult was completed in about 49 ± 2.32 days. Female moths laid an average of 106 ± 3.48 eggs, which hatched into larvae that underwent five instars before pupation. Both the larval and pupal stages lasted around 27.69 ± 0.72 and 7.72 ± 0.17 days respectively. To our knowledge, this is the first report of the tea tortrix, H. coffearia infesting cocoa in India. As a polyphagous pest, the ability of H. coffearia to adapt and feed on new host plants like cocoa poses a significant threat to cocoa production. The findings of this work highlight the need for further research on the population dynamics, damage potential and management strategies for this emerging pest in cocoa ecosystems.
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    From the discovery of a novel arepavirus in diseased arecanut palms (Areca catechu L.) in India to the identification of known and novel arepaviruses in bee and plant transcriptomes through data-mining
    (2024) R. Thava Prakasa Pandian; Bhavishya; V. Kavi Sidharthan; M.K. Rajesh; Merin Babu; Susheel Kumar Sharma; B.J. Nirmal Kumar; M. Chaithra; Vinayaka Hegde
    Arecanut palm is a commercially important plantation crop valued for its nut. In this investigation, we report the discovery of a putative novel arepavirus, named areca palm necrotic ringspot virus 2 (ANRSV2), in necrotic ringspot diseased areca palms in Bantwal, Dakshina Kannada, Karnataka, India through RNA-sequencing and transmission electron microscopy. Further, the presence of ANRSV2 in the diseased samples was confirmed through reverse transcriptase-polymerase chain reaction assays. In addition, by mining public domain transcriptome data for arepaviral sequences, we identified a putative novel arepavirus in Psychotria rubra, a non-palm host. We recovered the genome sequences of the areca palm necrotic ringspot virus in honey bees, tomato, Onobrychis viciifolia, and Rhamnus heterophylla. These findings broaden our comprehension of arepaviral diversity and host range, and suggest an intriguing possibility of pollen-mediated arepaviral transmission that necessitates empirical validation. Further studies are needed to understand the biology of identified putative novel arepaviruses.
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    Laboratory rearing of tea mosquito bug, Helopeltis theivora Waterhouse (Hemiptera: Miridae) on cocoa (Theobroma cacao L.)
    (2024) T. N. Madhu; E. K. Saneera; R. Thava Prakasa Pandian; Bhavishya; M. Chaithra; M. Sujithra; N. R. Nagaraja; B. J. Nirmal Kumar; S. Elain Apshara
    Tea mosquito bug (TMB), Helopeltis theivora is a most serious pest on cocoa worldwide that inflicts huge economic losses under epidemic situations. Laboratory colonies are necessary to perform year-round research to develop suitable management strategies for this pest. This study aimed to establish a population of TMB on suitable cocoa-feeding substrates under laboratory conditions. We used green cocoa pods and tender shoots as a food substrate and compared the biological parameters of H. theivora between them. The adult females preferred to lay more eggs on pods (32.20 ± 1.86 eggs/female) either singly or in a small group, and low fecundity was observed on shoots (20.75 ± 1.16 eggs/female). Meanwhile, egg hatching was highest on pods (92.48 ± 2.91%) than on shoots (74.08 ± 3.73%). This pest consists of five nymphal instars and the total nymphal duration was 13.53 ± 1.26 and 14.73 ± 0.85 days on pods and shoots, respectively. In addition, the per cent survival of H. theivora was highest on pods (78.66 ± 3.46) and lowest on shoots (51.85 ± 2.33). Significant differences were recorded in adult longevity and the mean life span of males and females were 13.17 ± 1.58 and 16.63 ± 1.64 days on pods; 11.10 ± 1.41 and 14.36 ± 1.53 days on shoots, respectively. Further, females lived longer than males in both substrates. Although, TMB will survive both on pods and tender shoots; rearing on pods could be more suitable and reliable to establish a sizable population of H. theivora under laboratory conditions.
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    Xylosandrus crassiusculus (Motschulsky) on Cocoa Pods (Theobroma cacao L.): Matter of Bugs and Fungi
    (2022) Shivaji Hausrao Thube; R. Thava Prakasa Pandian; Josephrajkumar, A.; Bhavishya; Nirmal Kumar, B.J.; Dnyaneshwar M. Firake; Vivek Shah; T. N. Madhu; Enrico Ruzzier