Diseases of Fruit Plantation Medicinal and Aromatic Crops

Fan leaf of grapes

Causal organism: Grapevine fan leaf virus ( GFLV ). ( Syn. Grapevine infectious degeneration virus). In India, fan-leaf disease was first reported in 1965.
Symptoms

• Infected young leaves show variegated mottling.
• The malformed leaves have open petiolar sinuses. Widening of the petiolar sinuses and reduction of areas between the veins give the impression of a half-closed fan.
• Affected leaves stand upright along the axis of young shoots and become cup-like.
• The dark green areas in the mottled leaf bulge upward and leaf surface become rough.
• The characteristic symptom of the disease is the underdeveloped leaves.
• The infected leaves turn light yellow and show cupping.
• The distance between internodes is reduced and nodes and internodes become thin and weak. Growth becomes zig-zag at the nodes.
• Few lateral branches are produced and axillary branches proliferate to produce small, thin and weak, secondary branches.
• Infected plants do not produce flowers and fruits even at the age of three years.
• Plants become stunted and produce very few and weak rootlets.
• Virus – virus particles are isometric, SS DNA virus and 25-30nm in diameter.


Physical properties of the virus

• Thermal inactivation point is 60-650 C.
• Longevity in vitro is 15-30days at 200C
• Dilution end point is between 103 and 104.
Transmission

• The vectors are Nematodes like Xiphinema index and X. italiae are the vectors
• The virus is mechanically transmissible to Cucumis sativus, Chenopodium amaranticolor, Gomphrena globosa, Nicotiana tabacum cv. ‘White Burley’, Phaseolus vulgaris cv. prince.
• The disease has been transmitted by grafting or budding of the diseased scion onto the healthy rootstock of variety Emperor. It is not transmitted through pollen.
Management

• Soil application with nematicide controls the nematode vectors and reduce spread of the disease.