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Snake gourd mosaic virus disease commonly occurring in Kerala was investigated.
The symptoms appeared as typical mosaic mottling with dark green and light green patches. The leaves were much reduced in size, variously crinkled and deformed. Diseased plants were severely stunted and produced only a few flowers and fruits.
Transmission studies showed that the virus could be transmitted through mechanical means, grafting and by aphid vectors. The virus was found to be transmitted by the aphids, Aphis gossypii Glov., Aphis malvae Koch. and Aphis craccivora Koch. Among the three species of aphids, A. gossypii was found to be the most efficient vector.
Investigations on the physical properties of the virus revealed that the virus had a thermal inactivation point between 70-750C, Dilution end point between 1:10000-1:50000, longevity in vitro between 96-120 h at room temperature (28-300C), and between 144-168 h at 100C.
The minimum acquisition feeding and inoculation feeding period were found to be 30 s and 1 min respectively. But the percentage of transmission was maximum when an acquisition feeding of 20 min and inoculation feeding of 1 h were given.
Influence of starvation before acquisition and inoculation feeding proved that pre-acquisition starvation for 1 h produced maximum infection but post-acquisition starvation decreased the per cent infection. The vector was found to retain the virus for 1 ½ h. A single aphid could transmit the virus to healthy test plants, but maximum percentage of transmission was obtained with 10 aphids.
Host range studies showed that the virus was restricted to the members of the family chenopodiaceae, compositae, cucurbitaceae and solanaceae.
Serological studies showed that snake gourd mosaic virus is related to cucumber mosaic virus and pumpkin mosaic virus.
Varietal screening trial with seven varieties of snake gourd revealed that all the varieties were susceptible to snake gourd mosaic virus infection.
Studies on estimation of loss revealed that early infection reduced significantly the length of vine, number of leaves, number of flowers, number of fruits and yield, whereas late infection did not produce significant effect, on both the varieties tested. There was significant reduction on leaf area and internodal length on plants inoculated at all stages of growth. |
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