STUDIES ON SUNFLOWER NECROSIS DISEASE
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Date
2001-08-04
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK BANGALORE
Abstract
Sunflower necrosis disease, causing considerable damage to the
crops, is a serious disease and present in almost all parts of Northern
Kamataka wherever sunflower in grown.
Affected plants were characterised by production of mosaic and
chlorotic ringspots. In extreme cases the affected leaves developed
marginal necrosis with reduction in leaf size. In later stage of disease
development, affected plants produced malformed head and seeds of poor
quality.
The virus causing necrosis disease in sunflower was sap
transmissible but not with ease. It was not transmitted through seeds and
dodder. The virus was transmitted by thrips (Thrips tabad) vector from
sunflower to sunflower and to tomato. But not by aphids, jassids and
whiteflies.
The virus had a narrow host range and infected only 3 plant species
among 15 different hosts tested belonging to 6 families. The virus had
DEP between 10-3 to 10-4, TIP between 35° to 40°C and retained infectivity
upto 2 hours at room temperature.
Based on symptoms, host range, transmission and physical
properties, it was concluded that the sunflower necrosis disease in this
area, is probably caused by member of Tomato spotted wilt virus
(Tospovirus) group.
In early infected crop (15 days after sowing) the disease had a severe
effect on yield and yield parameters. The disease reduced yield of
sunflower to a tune of 90.86 per cent when app)eared in early stage of the
crop growth as compared to 31.69 per cent when appeared late. Field
trials indicated that the spread of the disease could be minimised by
spraying Imidacloprid (0.025%) insecticide.
None of the 56 sunflower hybrids screened were resistant to virus
infection, but hybrid UH-32 and 7 others exhibited some tolerant
properties.
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