Arecanut (Areca catechu L.) is an important plantation crop cultivated predominantly in the India... more Arecanut (Areca catechu L.) is an important plantation crop cultivated predominantly in the Indian states of Karnataka, Kerala, Assam, West Bengal, and Maharashtra in an area of 5.19 lakh ha, with Karnataka State alone accounting for about 68.41% of the area and 79.97% of production. Arecanut production has recently been hampered due to environmental and disease pressures, especially the escalating incidence of Yellow Leaf Disease (YLD). The involvement of phytoplasma as the etiological agent of YLD has been reported. Symptoms include yellowing at the tip of leaflets of two or three fronds of the outer most whorl which gradually spreads to the inner whorl of leaves. As the disease progresses, the entire crown becomes yellow leaving only the spear leaf green. In severe cases, the affected leaves often show necrosis from their tips. In advanced stages, the leaves are reduced in size and become stiff and pointed and the crown ultimately falls off. Degeneration of cortex is commonly observed in the diseased roots. The kernel of affected nuts shows discolouration and later turns blackish. The reduction in yield over a period of three years, immediately after the incidence of the disease, has been estimated to be around 50%. Harnessing the arecanut–microbiome interactions to address the biotic and abiotic stresses of the host plant offers immense opportunity to increase arecanut production sustainably. Here, we report a comprehensive analysis of the structural composition of the arecanut rhizosphere bacterial diversity utilizing next-generation sequencing (NGS) technology. We have used amplicon sequencing (V3-V4 regions of the 16S rRNA gene) of bulk soil and rhizosphere samples collected from YLD endemic regions of Aranthodu, Sullia Taluk, Dakshina Kannada District, Karnataka State, India, to assess the microbial diversity. The results revealed that while there is a great diversity of bacterial communities, relatively few bacterial phyla predominate with higher relative abundance. The phyla viz., Proteobacteria, Bacteroidetes, Firmicutes, Acidobacteria, Planctomycetes, Patescibacteria, Chloroflexi, Actinobacteria, Fusobacteria, and Verrucomicrobia were found to be dominant in the rhizosphere of the arecanut.
Lethal wilt disease of coconut, reported as a disease of unknown etiology as early as 2007, was f... more Lethal wilt disease of coconut, reported as a disease of unknown etiology as early as 2007, was for the first time found consistently in association with a phytoplasma in diseased coconut trees in Thanjavur, Thiruvarur and Pudukkottai districts in Tamil Nadu on the southeastern coast of India. Nested PCR with phytoplasma-specific universal primers and in silico restriction analysis of 16S rDNA sequences revealed the association of ‘ Candidatus Phytoplasma asteris’ (16SrI-B) group phytoplasma, which was confirmed by sequence analysis of translation elongation factor ( tuf ) and ribosomal protein ( rp ) genes. Because this disease kills affected palms within 5 months, recommendations are given to arrest the spread of the pathogen to other coconut-growing regions in the country.
All through the occurrence of Rugose spiraling whitefly ( Aleurodicus rugioperculatus Martin) inf... more All through the occurrence of Rugose spiraling whitefly ( Aleurodicus rugioperculatus Martin) infestation in coconut gardens from ICAR-CPCRI, Kayamkulam Regional station, Kerala that commenced during late 2017, a close association of a sooty mould fungus, with the insect feeding was found that was responsible for the cosmetic damage on palm leaflets as well as intercrops grown within the coconut gardens. The fungus was isolated and studied the morphological and molecular character for identification. The vegetative hyphae consist of cylindrical shaped cells having constrictions at the septum and a thick mucilaginous layer covering the cells. The long synnemata originates from the vegetative hyphae which has a bulbous base and funnel-shaped conidiomata at the apex. Conidiomata contains innumerous single celled round to oval shaped conidia. Based on the morphological studies and molecular characterization of the internal transcribed spacer (ITS) region of rDNA, the fungus was identified as Leptoxyphium sp., a sooty mold not previously reported from coconut gardens. A classical association of a Leiochrinid beetle devouring sooty mold fungus from palm leaflets was also observed.
ABSTRACT Phytoplasma belonging to subgroup 16SrII-A and identified as “Candidatus Phytoplasma aus... more ABSTRACT Phytoplasma belonging to subgroup 16SrII-A and identified as “Candidatus Phytoplasma australasiae”- was found constantly associated with phyllody of Pedalium murex, a common medicinal cum succulent weed in coconut ecosystem prevalent in South India. Infected P. murex showed stunted growth with reduced leaf size, shortened internodes and the characteristic transformation of floral parts into leafy structures typical to that of phytoplasma disease. This weed could possibly serve as a reservoir of sesamum phyllody in this region but no link with root (wilt) disease in coconut could be established based on molecular characterization studies. This is the first report of the association of 16SrII-A group phytoplasma with pedalium phyllody from the world.
Areca triandra Roxb. ex Buch.-Ham., a wild relative of cultivated arecanut ( Areca catechu L.) is... more Areca triandra Roxb. ex Buch.-Ham., a wild relative of cultivated arecanut ( Areca catechu L.) is known as a resistant source for fruit rot caused by Phytophthora meadii Mc Rae. However, during monsoon 2019–20, a heavy shedding of immature nuts with whitish mycelial growth was observed from A. triandra plantations in Dakshina Kannada district, Karnataka, India. Pure culture of the associated oomycete was isolated from the symptomatic nuts and pathogenicity was confirmed. Based on morphological characteristics and internal transcribed spacer (ITS) sequences the pathogen was identified as P. palmivora E. J. Butler. To the best of our knowledge, this is the first report of Phytophthora palmivora infecting Areca triandra in the world.
Current Journal of Applied Science and Technology, 2020
Aims: To determine the chemical composition of secondary metabolite of cocoa endophytic fungi L. ... more Aims: To determine the chemical composition of secondary metabolite of cocoa endophytic fungi L. pseudotheobromae PAK-7, L. theobromae TN-R-3 and their anti-oomycete activities. Statistical Design: Multivariate analysis. Place and Duration of Study: Department of Plant Pathology, TNAU, Coimbatore, Tamil Nadu from April 2018 to December 2019. Methodology: Lipophilic extracellular secondary metabolites were extracted using ethyl acetate as a solvent and their chemical composition was detected by Gas Chromatography-Mass Spectrometry (GC-MS) and identified by NIST library and Pub Chem databases. Results: Metabolic profiling of cocoa endophytic fungi L. pseudotheobromae PAK-7 and L. theobromae TN-R-3 showed the presence of eleven peaks representing nine compounds. The most abundant compound observed were Acetic acid, 3-methyl-6-oxo-9oxabicyclo[3.3.1]non-2-yl ester, 2H-Pyran-2-one, tetrahydro-4-hydroxy-6-pentyl-, Melezitose, Ethyl à-d-glucopyranoside collectively representing 58.01% ...
Abstract An infestation of the ambrosia beetle, Euplatypus parallelus (F.) (Coleoptera: Curculion... more Abstract An infestation of the ambrosia beetle, Euplatypus parallelus (F.) (Coleoptera: Curculionidae: Platypodinae) on arecanut, Areca catechu L., is reported from the state of Karnataka in southwestern India for the first time. The visible symptoms on healthy and younger palms include oozing of a yellowish brown resinous exudation from infested stems. Small, pinheadsize holes were visible after removal of the resinous exudation. Symptoms on older, stressed, and diseased palms appear as extrusion of sawdust frass in the form of loose, cylindrical strings. Fronds of infested palms lose vigor and turn yellow. The size of the larval galleries varied 1.40–1.46 mm in diameter. Large numbers of larvae, pupae, and adults were found in the galleries of affected palms. Adult beetles are slender, 4.0–4.2mmlong, and brownish with yellowish hairs. Male and female specimens were distinguished based on the elytral declivity. The taxonomic identity of the species was confirmed by amplification of 649 base pairs of the mitochondrial cytochrome oxidase I gene. In a climate change scenario, this beetle may become a serious threat to arecanut production in India and elsewhere.
Phytophthora diseases are serious and often fatal in arecanut causing huge losses to farmers (50–... more Phytophthora diseases are serious and often fatal in arecanut causing huge losses to farmers (50–100%) if timely and proper management measures aren’t adopted. Among Phytophthora diseases, fruit rot disease predominantly exists in all the arecanut growing regions receiving heavy rainfall during the south-west monsoon season. The extended manifestation of pathogen causes crown and bud rot disease which prevails till November–December due to prolonged rains and congenial weather factors. The role of Phytophthora in causing these diseases of arecanut was established in the early 1900’s and later the Phytophthora meadii was identified as a causal agent. Though the diseases are sporadic, their management in the field situation is a challenging task due to intense rainfall and the variability in the pathogen. The continuous heavy rainfall during the tender arecanut developmental stage, non-availability of professional climbers coupled with the absence of machinery for powerful spraying, occurrence of aggressive pathotypes and lack of Phytophthora resistant/tolerant arecanut varieties are the major hindrance for taking up effective disease management measures. The present review has attempted to compile the earlier findings, present status of this century-old disease, and discusses future strategies for the development of effective remedies for this serious malady of the areca palm.
Ganoderma wilt or Thanjavur wilt disease is the most lethal one, is caused by the fungus Ganoderm... more Ganoderma wilt or Thanjavur wilt disease is the most lethal one, is caused by the fungus Ganoderma lucidum (leys) Karst and it is of major limiting factor in coconut production in nine coastal districts of Tamil Nadu. The high alarming of the disease alerted the government to launch the Ganoderma wilt research in the state in the yesteryear. Subsequently, more than five decadal researches done on this disease that provides preliminary, applied and advanced results and outcomes that are crucial and fruitful in the disease management. The endemic nature of the disease is evident and it has been witnessed with the severe spread of the disease in the east coast region of Tamil Nadu after the attack of Gaja cyclone urges the research efforts to contain the disease. The disease incidence ranges from 6.5 % to 50% in Thanjavur district followed by Nagapattinam and Thiruvarur districts is continuously reminds the threat of the disease to the coconut farmers in this region. In this juncture,...
IOP Conference Series: Earth and Environmental Science
Exotic pests upset biotic balance, threaten biodiversity and distort the livelihood security of t... more Exotic pests upset biotic balance, threaten biodiversity and distort the livelihood security of the nation. In coconut, five exotic whiteflies viz., spiralling whitefly, Aleurodicus dispersus Russell, rugose spiralling whitefly, Aleurodicus rugioperculatus Martin, Bondar’s nesting whitefly, Paraleyrodes bondari Peracchi, non-native nesting whitefly, Paraleyrodes minei Iaccarino and palm whitefly, Aleurotrachelus atratus Hempel were reported from India. Morphological and molecular identification of these invasive whiteflies were established by puparium and (or) adult taxonomy and cytochrome c oxidase subunit 1 (COI) gene, respectively. Co-existence of nesting whiteflies with other exotic whiteflies regulated population explosion and warranted correct diagnosis of whiteflies in coconut system. Weather parameters viz., precipitation, temperature and humidity play an important role in the gradient outbreak of exotic whiteflies. The aphelinid parasitoids (Encarsia guadeloupae Viggiani, E...
During 2018 summer season (April–May), several young (1–3-year-old) arecanut seedlings exhibited ... more During 2018 summer season (April–May), several young (1–3-year-old) arecanut seedlings exhibited yellowing, drying, drooping and wilting symptoms in farmer’s gardens located in Dakshina Kannada district of Karnataka, India. The longitudinal section of the infected seedlings showed extensive decaying of fibrous roots which extended up to the collar region and ultimately resulted in the death of young seedlings. A series of cultural, morphological, molecular characterization using multi-gene phylogeny and pathogenicity assays with Koch’s postulates confirmed the association of Fusarium falciforme (FSSC 3 + 4) as the causal organism of arecanut root decay disease. To the best of our knowledge, the present study confirms the first report of root decay disease caused by F. falciforme in arecanut.
Arecanut (Areca catechu L.) is an important plantation crop cultivated predominantly in the India... more Arecanut (Areca catechu L.) is an important plantation crop cultivated predominantly in the Indian states of Karnataka, Kerala, Assam, West Bengal, and Maharashtra in an area of 5.19 lakh ha, with Karnataka State alone accounting for about 68.41% of the area and 79.97% of production. Arecanut production has recently been hampered due to environmental and disease pressures, especially the escalating incidence of Yellow Leaf Disease (YLD). The involvement of phytoplasma as the etiological agent of YLD has been reported. Symptoms include yellowing at the tip of leaflets of two or three fronds of the outer most whorl which gradually spreads to the inner whorl of leaves. As the disease progresses, the entire crown becomes yellow leaving only the spear leaf green. In severe cases, the affected leaves often show necrosis from their tips. In advanced stages, the leaves are reduced in size and become stiff and pointed and the crown ultimately falls off. Degeneration of cortex is commonly observed in the diseased roots. The kernel of affected nuts shows discolouration and later turns blackish. The reduction in yield over a period of three years, immediately after the incidence of the disease, has been estimated to be around 50%. Harnessing the arecanut–microbiome interactions to address the biotic and abiotic stresses of the host plant offers immense opportunity to increase arecanut production sustainably. Here, we report a comprehensive analysis of the structural composition of the arecanut rhizosphere bacterial diversity utilizing next-generation sequencing (NGS) technology. We have used amplicon sequencing (V3-V4 regions of the 16S rRNA gene) of bulk soil and rhizosphere samples collected from YLD endemic regions of Aranthodu, Sullia Taluk, Dakshina Kannada District, Karnataka State, India, to assess the microbial diversity. The results revealed that while there is a great diversity of bacterial communities, relatively few bacterial phyla predominate with higher relative abundance. The phyla viz., Proteobacteria, Bacteroidetes, Firmicutes, Acidobacteria, Planctomycetes, Patescibacteria, Chloroflexi, Actinobacteria, Fusobacteria, and Verrucomicrobia were found to be dominant in the rhizosphere of the arecanut.
Lethal wilt disease of coconut, reported as a disease of unknown etiology as early as 2007, was f... more Lethal wilt disease of coconut, reported as a disease of unknown etiology as early as 2007, was for the first time found consistently in association with a phytoplasma in diseased coconut trees in Thanjavur, Thiruvarur and Pudukkottai districts in Tamil Nadu on the southeastern coast of India. Nested PCR with phytoplasma-specific universal primers and in silico restriction analysis of 16S rDNA sequences revealed the association of ‘ Candidatus Phytoplasma asteris’ (16SrI-B) group phytoplasma, which was confirmed by sequence analysis of translation elongation factor ( tuf ) and ribosomal protein ( rp ) genes. Because this disease kills affected palms within 5 months, recommendations are given to arrest the spread of the pathogen to other coconut-growing regions in the country.
All through the occurrence of Rugose spiraling whitefly ( Aleurodicus rugioperculatus Martin) inf... more All through the occurrence of Rugose spiraling whitefly ( Aleurodicus rugioperculatus Martin) infestation in coconut gardens from ICAR-CPCRI, Kayamkulam Regional station, Kerala that commenced during late 2017, a close association of a sooty mould fungus, with the insect feeding was found that was responsible for the cosmetic damage on palm leaflets as well as intercrops grown within the coconut gardens. The fungus was isolated and studied the morphological and molecular character for identification. The vegetative hyphae consist of cylindrical shaped cells having constrictions at the septum and a thick mucilaginous layer covering the cells. The long synnemata originates from the vegetative hyphae which has a bulbous base and funnel-shaped conidiomata at the apex. Conidiomata contains innumerous single celled round to oval shaped conidia. Based on the morphological studies and molecular characterization of the internal transcribed spacer (ITS) region of rDNA, the fungus was identified as Leptoxyphium sp., a sooty mold not previously reported from coconut gardens. A classical association of a Leiochrinid beetle devouring sooty mold fungus from palm leaflets was also observed.
ABSTRACT Phytoplasma belonging to subgroup 16SrII-A and identified as “Candidatus Phytoplasma aus... more ABSTRACT Phytoplasma belonging to subgroup 16SrII-A and identified as “Candidatus Phytoplasma australasiae”- was found constantly associated with phyllody of Pedalium murex, a common medicinal cum succulent weed in coconut ecosystem prevalent in South India. Infected P. murex showed stunted growth with reduced leaf size, shortened internodes and the characteristic transformation of floral parts into leafy structures typical to that of phytoplasma disease. This weed could possibly serve as a reservoir of sesamum phyllody in this region but no link with root (wilt) disease in coconut could be established based on molecular characterization studies. This is the first report of the association of 16SrII-A group phytoplasma with pedalium phyllody from the world.
Areca triandra Roxb. ex Buch.-Ham., a wild relative of cultivated arecanut ( Areca catechu L.) is... more Areca triandra Roxb. ex Buch.-Ham., a wild relative of cultivated arecanut ( Areca catechu L.) is known as a resistant source for fruit rot caused by Phytophthora meadii Mc Rae. However, during monsoon 2019–20, a heavy shedding of immature nuts with whitish mycelial growth was observed from A. triandra plantations in Dakshina Kannada district, Karnataka, India. Pure culture of the associated oomycete was isolated from the symptomatic nuts and pathogenicity was confirmed. Based on morphological characteristics and internal transcribed spacer (ITS) sequences the pathogen was identified as P. palmivora E. J. Butler. To the best of our knowledge, this is the first report of Phytophthora palmivora infecting Areca triandra in the world.
Current Journal of Applied Science and Technology, 2020
Aims: To determine the chemical composition of secondary metabolite of cocoa endophytic fungi L. ... more Aims: To determine the chemical composition of secondary metabolite of cocoa endophytic fungi L. pseudotheobromae PAK-7, L. theobromae TN-R-3 and their anti-oomycete activities. Statistical Design: Multivariate analysis. Place and Duration of Study: Department of Plant Pathology, TNAU, Coimbatore, Tamil Nadu from April 2018 to December 2019. Methodology: Lipophilic extracellular secondary metabolites were extracted using ethyl acetate as a solvent and their chemical composition was detected by Gas Chromatography-Mass Spectrometry (GC-MS) and identified by NIST library and Pub Chem databases. Results: Metabolic profiling of cocoa endophytic fungi L. pseudotheobromae PAK-7 and L. theobromae TN-R-3 showed the presence of eleven peaks representing nine compounds. The most abundant compound observed were Acetic acid, 3-methyl-6-oxo-9oxabicyclo[3.3.1]non-2-yl ester, 2H-Pyran-2-one, tetrahydro-4-hydroxy-6-pentyl-, Melezitose, Ethyl à-d-glucopyranoside collectively representing 58.01% ...
Abstract An infestation of the ambrosia beetle, Euplatypus parallelus (F.) (Coleoptera: Curculion... more Abstract An infestation of the ambrosia beetle, Euplatypus parallelus (F.) (Coleoptera: Curculionidae: Platypodinae) on arecanut, Areca catechu L., is reported from the state of Karnataka in southwestern India for the first time. The visible symptoms on healthy and younger palms include oozing of a yellowish brown resinous exudation from infested stems. Small, pinheadsize holes were visible after removal of the resinous exudation. Symptoms on older, stressed, and diseased palms appear as extrusion of sawdust frass in the form of loose, cylindrical strings. Fronds of infested palms lose vigor and turn yellow. The size of the larval galleries varied 1.40–1.46 mm in diameter. Large numbers of larvae, pupae, and adults were found in the galleries of affected palms. Adult beetles are slender, 4.0–4.2mmlong, and brownish with yellowish hairs. Male and female specimens were distinguished based on the elytral declivity. The taxonomic identity of the species was confirmed by amplification of 649 base pairs of the mitochondrial cytochrome oxidase I gene. In a climate change scenario, this beetle may become a serious threat to arecanut production in India and elsewhere.
Phytophthora diseases are serious and often fatal in arecanut causing huge losses to farmers (50–... more Phytophthora diseases are serious and often fatal in arecanut causing huge losses to farmers (50–100%) if timely and proper management measures aren’t adopted. Among Phytophthora diseases, fruit rot disease predominantly exists in all the arecanut growing regions receiving heavy rainfall during the south-west monsoon season. The extended manifestation of pathogen causes crown and bud rot disease which prevails till November–December due to prolonged rains and congenial weather factors. The role of Phytophthora in causing these diseases of arecanut was established in the early 1900’s and later the Phytophthora meadii was identified as a causal agent. Though the diseases are sporadic, their management in the field situation is a challenging task due to intense rainfall and the variability in the pathogen. The continuous heavy rainfall during the tender arecanut developmental stage, non-availability of professional climbers coupled with the absence of machinery for powerful spraying, occurrence of aggressive pathotypes and lack of Phytophthora resistant/tolerant arecanut varieties are the major hindrance for taking up effective disease management measures. The present review has attempted to compile the earlier findings, present status of this century-old disease, and discusses future strategies for the development of effective remedies for this serious malady of the areca palm.
Ganoderma wilt or Thanjavur wilt disease is the most lethal one, is caused by the fungus Ganoderm... more Ganoderma wilt or Thanjavur wilt disease is the most lethal one, is caused by the fungus Ganoderma lucidum (leys) Karst and it is of major limiting factor in coconut production in nine coastal districts of Tamil Nadu. The high alarming of the disease alerted the government to launch the Ganoderma wilt research in the state in the yesteryear. Subsequently, more than five decadal researches done on this disease that provides preliminary, applied and advanced results and outcomes that are crucial and fruitful in the disease management. The endemic nature of the disease is evident and it has been witnessed with the severe spread of the disease in the east coast region of Tamil Nadu after the attack of Gaja cyclone urges the research efforts to contain the disease. The disease incidence ranges from 6.5 % to 50% in Thanjavur district followed by Nagapattinam and Thiruvarur districts is continuously reminds the threat of the disease to the coconut farmers in this region. In this juncture,...
IOP Conference Series: Earth and Environmental Science
Exotic pests upset biotic balance, threaten biodiversity and distort the livelihood security of t... more Exotic pests upset biotic balance, threaten biodiversity and distort the livelihood security of the nation. In coconut, five exotic whiteflies viz., spiralling whitefly, Aleurodicus dispersus Russell, rugose spiralling whitefly, Aleurodicus rugioperculatus Martin, Bondar’s nesting whitefly, Paraleyrodes bondari Peracchi, non-native nesting whitefly, Paraleyrodes minei Iaccarino and palm whitefly, Aleurotrachelus atratus Hempel were reported from India. Morphological and molecular identification of these invasive whiteflies were established by puparium and (or) adult taxonomy and cytochrome c oxidase subunit 1 (COI) gene, respectively. Co-existence of nesting whiteflies with other exotic whiteflies regulated population explosion and warranted correct diagnosis of whiteflies in coconut system. Weather parameters viz., precipitation, temperature and humidity play an important role in the gradient outbreak of exotic whiteflies. The aphelinid parasitoids (Encarsia guadeloupae Viggiani, E...
During 2018 summer season (April–May), several young (1–3-year-old) arecanut seedlings exhibited ... more During 2018 summer season (April–May), several young (1–3-year-old) arecanut seedlings exhibited yellowing, drying, drooping and wilting symptoms in farmer’s gardens located in Dakshina Kannada district of Karnataka, India. The longitudinal section of the infected seedlings showed extensive decaying of fibrous roots which extended up to the collar region and ultimately resulted in the death of young seedlings. A series of cultural, morphological, molecular characterization using multi-gene phylogeny and pathogenicity assays with Koch’s postulates confirmed the association of Fusarium falciforme (FSSC 3 + 4) as the causal organism of arecanut root decay disease. To the best of our knowledge, the present study confirms the first report of root decay disease caused by F. falciforme in arecanut.
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Papers by Vinayaka Hegde