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Characterization, Host Range and Management of Sweet Potato Feathery Mottle Virus
A survey revealed that sweet potato feathery mottle is widely prevalent in the farmers' fields of sweet potato at Thiruvananthapuram district of Kerala and the types and intensity of symptoms varied between varieties. Chlorotic leaf spot, pink spot, ring spot and feathering are the major sym...
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| Aineistotyyppi: | Ph.D Thesis |
| Kieli: | Undetermined |
| Julkaistu: |
Vellayani
Department of Plant Pathology, College of Agriculture
2001
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| 100 | |a Jeeva M L | ||
| 245 | |a Characterization, Host Range and Management of Sweet Potato Feathery Mottle Virus | ||
| 260 | |a Vellayani |b Department of Plant Pathology, College of Agriculture |c 2001 | ||
| 502 | |b PhD | ||
| 520 | 3 | |a A survey revealed that sweet potato feathery mottle is widely prevalent in the farmers' fields of sweet potato at Thiruvananthapuram district of Kerala and the types and intensity of symptoms varied between varieties. Chlorotic leaf spot, pink spot, ring spot and feathering are the major symptoms observed. No vectors were present and no tuber symptoms were found except tuber constrictions in one variety, Vavvathooki. In symptomatology studies also; similar types of symptoms with various combinations were observed. Initial symptom was found after 15 days and the highest intensity between 30 to 60 days after planting in pots. The intensity of symptoms got reduced as the intensity of shade was increased. The virus was readily transmitted through single node, double node and triple node vine cuttings, tubers and three types of graftings, viz., approach grafting, side grafting and wedge grafting. It was non- persistently transmitted by Aphis craccivora, A. gossypii and through sap from infected 1. nil to 1. batatas. However, sap transmission from 1. batatas to 1. batatas was not achieved. There was no transmission either through seed or through Pentalonia nigronervosa and Bemisia tabaci. Photosynthesis was reduced only in the susceptible variety Sree Rethna due to leaf infection but respiration and transpiration were not affected in both the susceptible and tolerant varieties. The infection caused a reduction in the content of total carbohydrates, starch, total chlorophyll, chlorophyll'a' and chlorophyll'b' and polyphenoloxidase activity in leaves of susceptible varieties, Sree Rethna and Vavvathooki. In leaves, total sugars, total phenolics, protein, peroxidase and phenylalanine ammonia lyase activities were not affected by the infection. There was no significant change in number of vines, length of vine, number of leaves, leaf area, total biomass and drymatter caused by SPFMV - infection except an increase in internode length. There was no colour change in tubers. Tubers of Vavvathooki plants infected with SPFMV showed constrictions , increase in length and reduction in girth. In tubers, quantities of total carbohydrates, starch and drymatter were reduced while protein and sugars were not affected due to infection. The virus was purified and infectivity was tested. The antiserum produced was confirmed by agar double diffusion test for the presence of antibodies. Detection of SPFMV in samples was done through DAC-ELISA and NCM-ELISA. The dilution end point (DEP) of SPFMV was found to be between 10-3 and 10-4, thermal inactivation point (TIP) between 60 and 65°C and longevity in vitro between 6 and 8 h at room temperature (28± 4°C) and 10 and 12 h at 8°C. The petiole sample was ideal in electron microscopy for quick detection of SPFMV. The particles were long flexuous rods measuring approximately 748 nm in length. In host range studies, among 25 plant species from nine families, eight species, three from Convolvulaceae, four from Solanaceae and one weed species fro!ll Asteraceae were found to act as collateral hosts of the virus. Hot water treatment between 34 to 42°C for 5, 10 and 15 min and dry heat incubation of cuttings at 37° and 39°C for different periods were not effective in inhibiting the virus. In the induction of resistance, the chemical barium chloride (0.015%) showed highest per cent inhibition of infection in 1. nil plants followed by manganese chloride and the least by salicylic acid. Through meristem culture 85 and 96 per cent of virus free sweet potato plants were produced from the two varieties, Sree Rethna and Vavvathooki. Storage of vine cuttings for disease management was unsuccessful. | |
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