Silpa, P
Characterization of viruses associated with mosaic disease of ivy gourd :Coccinia grandis(L.) voigt - Vellanikkara Department of Plant Pathology 2023 - 83,xvii,p.
MSC
MSc
Ivy gourd (Coccinia grandis (L.) Voigt) is an important vegetable and medicinal plant from the cucurbitaceae family. The fruits are used as a green vegetable, while different parts of the plants are utilized in traditional medicine. However, its production is hampered by many fungal and viral diseases. Kerala is one of the major ivy gourd producing states in India. Viral disease is one of the major constraints faced in cultivation of ivy gourd in Kerala. But no study has been conducted in Kerala to identify and characterize viruses of ivy gourd. Hence, in an endeavor to get the information on the viruses causing mosaic disease on ivy gourd in Kerala, the present study was conducted to identify and characterize the viruses causing mosaic disease of ivy gourd in Kerala.
Purposive sampling survey was conducted in ivy gourd growing areas of Palakkad, Malappuram and Thrissur district of Kerala. Highest Percent Disease Incidence (PDI) of mosaic in ivy gourd was recorded from the fields of Kizhakkanchery (100%) in Palakkad district. Lowest PDI was recorded from Valayar (1%) in Palakkad district. Disease severity assessment revealed that the disease is severe in Kizhakkanchery field with Percent Disease Severity (PDS) of 76-80. The lowest PDS was recorded in Kaippini (1.4%) of Malappuram district.
Symptoms recorded during the survey include mottling, mosaic, reduced leaf size, puckering, curling, distortion of leaf, cupping, stunted growth, vein thickening and chlorotic spot. The virus culture established from infected cuttings also expressed similar symptoms.
Electron microscopic study revealed the presence of typical flexuous rod shaped particles of size 780-820 × 12 nm and geminate particle of size 15 × 30 nm. This indicates the possibility of association of geminivirus and potyvirus with mosaic disease of ivy gourd. ELISA was also conducted using antisera specific to CMV and potyvirus, which confirmed presence of potyvirus in four samples and none of them tested positive for CMV.
PCR analysis of all the samples were done using begomovirus specific degenerate primer (DengA/DengB). The results revealed that all the samples were
infected with begomovirus. The PCR reaction yielded an amplicon of size approximately 500 bp. Four representative isolates were sequenced and in silico analysis was carried out. Isolate IVG M1B showed maximum nucleotide identity to the Tomato leaf curl New Delhi virus isolate ToLCNDV-A RG segment DNA-A, complete sequence (MH520664.1) reported from Pakistan (96.50%) in homology analysis using BLAST. The two samples from Malappuram namely IVG AB and IVG KaB showed per cent identity of 98.34 and 97.72 respectively to the Tomato leaf curl New Delhi virus clone ToLCNDV/C11 segment DNA-A, complete sequence (MW620977.1) reported from Tamil Nadu on bitter gourd. Isolate IVG K1B showed 96.67 per cent identity to the Coccinia mosaic Tamil Nadu virus isolate TN TDV Coc 1 segment DNA A, complete sequence (NC024810.1). Dendrogram constructed with begomovirus isolates reported from other parts confirmed the results of homology analysis as the isolates IVG M1B, IVG AB and IVG KaB clustered together with ToLCNDV and isolate IVG K1B clustered with Coccinia mosaic virus.
RT-PCR with species specific primer revealed the presence of PRSV in four samples. Amplicon of RT-PCR (one from each district) were sequenced and homology analysed. Both the isolates showed maximum nucleotide identity with different PRSV isolates reported from different parts of the world. Isolate from Palakkad district (IVG K1PRSV) showed 84 per cent similarity to Papaya ringspot virus isolate H1K coat protein gene, partial cds (AF196839.1) reported from USA. It has an identity per cent of
83.32 with Papaya ringspot virus isolate TN UDU RG1 polyprotein gene, partial cds (KP161499.1) reported from Tamil Nadu with highest query coverage of 88%. Isolate from Malappuram district (IVG APRSV) showed 82.90 per cent similarity to Papaya ringspot virus isolate W polyprotein gene, partial cds (AF063221.1) reported from India on papaya. Phylogenetic analysis with other reported potyviruses revealed that the isolate IVG APRSV is closely related to other PRSV isolates as it clustered with other PRSV isolates. While IVG K1PRSV isolate is forming a separate cluster without grouping with existing strains of PRSV. This suggests the possibility of isolate K1PRSV to be a new strain PRSV.
Transmission studies of begomovirus revealed that whitefly could transmit the virus with 70 per cent transmission rate. The symptoms developed 18-20 days after inoculation which included chlorotic spot, mild mottling puckering and curling.
Mechanical as well as vector transmission was studied for PRSV. 100 per cent transmission was recorded in mechanical inoculation where the symptoms developed 21 days after inoculation on young leaves as chlorotic spots and mild chlorosis. Vector transmission of potyvirus using Aphis gossypii confirmed that the virus could be transmitted by aphids in non-persistent manner with a transmission percentage of 57. Symptoms observed under aphid transmission includes chlorotic spot and mild chlorosis. Initial symptom was observed 14 days after inoculation.
Host range studies were carried out for potyvirus and begomovirus infecting ivy gourd. Seven crop species belong to family cucurbitaceae, solanaceae and malvaceae and also four weed plants were tested. Among the crop plants ash gourd, cucumber, tomato and weeds such as Alternanthera sessilis and Synedrella nodiflora were found to be host for begomovirus when inoculated by viruliferous whiteflies. The results were confirmed by PCR. Only snake gourd was found to be host for potyvirus from ivy gourd. Though symptoms were expressed through mechanical inoculation in all the cucurbit hosts tested, ELISA could confirm the presence of potyvirus only in snake gourd.
To conclude, mosaic disease incidence on ivy gourd in survey fields varied from 1 to 100 per cent. Highest severity recorded was 80 per cent and the lowest was 1.4 per cent. ToLCNDV and PRSV were the predominant viruses associated with mosaic disease in ivy gourd in Kerala. Begomovirus causing mosaic disease in ivy gourd was whitefly transmissible to cucumber, ash gourd, tomato and weeds such as Synedrella nodiflora and Alternanthera sessilis. PRSV was transmitted by mechanical inoculation as well as by aphid vector (Aphis gossypii). Host range studies could confirm only snake gourd as a host for PRSV from ivy gourd.
English
Plant Pathology
Mosaic disease
Ivy gourd
632.3 / SIL/CH PG
Characterization of viruses associated with mosaic disease of ivy gourd :Coccinia grandis(L.) voigt - Vellanikkara Department of Plant Pathology 2023 - 83,xvii,p.
MSC
MSc
Ivy gourd (Coccinia grandis (L.) Voigt) is an important vegetable and medicinal plant from the cucurbitaceae family. The fruits are used as a green vegetable, while different parts of the plants are utilized in traditional medicine. However, its production is hampered by many fungal and viral diseases. Kerala is one of the major ivy gourd producing states in India. Viral disease is one of the major constraints faced in cultivation of ivy gourd in Kerala. But no study has been conducted in Kerala to identify and characterize viruses of ivy gourd. Hence, in an endeavor to get the information on the viruses causing mosaic disease on ivy gourd in Kerala, the present study was conducted to identify and characterize the viruses causing mosaic disease of ivy gourd in Kerala.
Purposive sampling survey was conducted in ivy gourd growing areas of Palakkad, Malappuram and Thrissur district of Kerala. Highest Percent Disease Incidence (PDI) of mosaic in ivy gourd was recorded from the fields of Kizhakkanchery (100%) in Palakkad district. Lowest PDI was recorded from Valayar (1%) in Palakkad district. Disease severity assessment revealed that the disease is severe in Kizhakkanchery field with Percent Disease Severity (PDS) of 76-80. The lowest PDS was recorded in Kaippini (1.4%) of Malappuram district.
Symptoms recorded during the survey include mottling, mosaic, reduced leaf size, puckering, curling, distortion of leaf, cupping, stunted growth, vein thickening and chlorotic spot. The virus culture established from infected cuttings also expressed similar symptoms.
Electron microscopic study revealed the presence of typical flexuous rod shaped particles of size 780-820 × 12 nm and geminate particle of size 15 × 30 nm. This indicates the possibility of association of geminivirus and potyvirus with mosaic disease of ivy gourd. ELISA was also conducted using antisera specific to CMV and potyvirus, which confirmed presence of potyvirus in four samples and none of them tested positive for CMV.
PCR analysis of all the samples were done using begomovirus specific degenerate primer (DengA/DengB). The results revealed that all the samples were
infected with begomovirus. The PCR reaction yielded an amplicon of size approximately 500 bp. Four representative isolates were sequenced and in silico analysis was carried out. Isolate IVG M1B showed maximum nucleotide identity to the Tomato leaf curl New Delhi virus isolate ToLCNDV-A RG segment DNA-A, complete sequence (MH520664.1) reported from Pakistan (96.50%) in homology analysis using BLAST. The two samples from Malappuram namely IVG AB and IVG KaB showed per cent identity of 98.34 and 97.72 respectively to the Tomato leaf curl New Delhi virus clone ToLCNDV/C11 segment DNA-A, complete sequence (MW620977.1) reported from Tamil Nadu on bitter gourd. Isolate IVG K1B showed 96.67 per cent identity to the Coccinia mosaic Tamil Nadu virus isolate TN TDV Coc 1 segment DNA A, complete sequence (NC024810.1). Dendrogram constructed with begomovirus isolates reported from other parts confirmed the results of homology analysis as the isolates IVG M1B, IVG AB and IVG KaB clustered together with ToLCNDV and isolate IVG K1B clustered with Coccinia mosaic virus.
RT-PCR with species specific primer revealed the presence of PRSV in four samples. Amplicon of RT-PCR (one from each district) were sequenced and homology analysed. Both the isolates showed maximum nucleotide identity with different PRSV isolates reported from different parts of the world. Isolate from Palakkad district (IVG K1PRSV) showed 84 per cent similarity to Papaya ringspot virus isolate H1K coat protein gene, partial cds (AF196839.1) reported from USA. It has an identity per cent of
83.32 with Papaya ringspot virus isolate TN UDU RG1 polyprotein gene, partial cds (KP161499.1) reported from Tamil Nadu with highest query coverage of 88%. Isolate from Malappuram district (IVG APRSV) showed 82.90 per cent similarity to Papaya ringspot virus isolate W polyprotein gene, partial cds (AF063221.1) reported from India on papaya. Phylogenetic analysis with other reported potyviruses revealed that the isolate IVG APRSV is closely related to other PRSV isolates as it clustered with other PRSV isolates. While IVG K1PRSV isolate is forming a separate cluster without grouping with existing strains of PRSV. This suggests the possibility of isolate K1PRSV to be a new strain PRSV.
Transmission studies of begomovirus revealed that whitefly could transmit the virus with 70 per cent transmission rate. The symptoms developed 18-20 days after inoculation which included chlorotic spot, mild mottling puckering and curling.
Mechanical as well as vector transmission was studied for PRSV. 100 per cent transmission was recorded in mechanical inoculation where the symptoms developed 21 days after inoculation on young leaves as chlorotic spots and mild chlorosis. Vector transmission of potyvirus using Aphis gossypii confirmed that the virus could be transmitted by aphids in non-persistent manner with a transmission percentage of 57. Symptoms observed under aphid transmission includes chlorotic spot and mild chlorosis. Initial symptom was observed 14 days after inoculation.
Host range studies were carried out for potyvirus and begomovirus infecting ivy gourd. Seven crop species belong to family cucurbitaceae, solanaceae and malvaceae and also four weed plants were tested. Among the crop plants ash gourd, cucumber, tomato and weeds such as Alternanthera sessilis and Synedrella nodiflora were found to be host for begomovirus when inoculated by viruliferous whiteflies. The results were confirmed by PCR. Only snake gourd was found to be host for potyvirus from ivy gourd. Though symptoms were expressed through mechanical inoculation in all the cucurbit hosts tested, ELISA could confirm the presence of potyvirus only in snake gourd.
To conclude, mosaic disease incidence on ivy gourd in survey fields varied from 1 to 100 per cent. Highest severity recorded was 80 per cent and the lowest was 1.4 per cent. ToLCNDV and PRSV were the predominant viruses associated with mosaic disease in ivy gourd in Kerala. Begomovirus causing mosaic disease in ivy gourd was whitefly transmissible to cucumber, ash gourd, tomato and weeds such as Synedrella nodiflora and Alternanthera sessilis. PRSV was transmitted by mechanical inoculation as well as by aphid vector (Aphis gossypii). Host range studies could confirm only snake gourd as a host for PRSV from ivy gourd.
English
Plant Pathology
Mosaic disease
Ivy gourd
632.3 / SIL/CH PG