Virus Diseases of Black Pepper in Thailand

Abstract

Symptoms of two different diseases of black pepper are widely observed in Thailand. The first disease is characterised by a yellowing of the leaves and roughening of the leaf surfaces, with leaf curling. the leaves are also reduced in size and there is a shortening of internodes and stunting of stem growth. Sometimes many small leaves develope from a bud where normally there would be a single leaf. The internal strcuture of the diseased leaves showed the leaf cells were shrunken and aggreagated, with the nuclei also being abnormal. the causal agent of this disease was detected using an electron microscope and leaf-dip method. Flexuous rod virus particless about 15 x 500 - 1000 nm. long were isolated from teh yellowing portions of the leaves.
The second disease is characterised by mosaic symptoms with the size of teh leaves remanining normal, Electron microscope examination black pepper leaves and wild betal leafbush leaves with the symptoms, showed isometric virus particles 53 - 57 nm. in diameter.
Both diseases can be transmitted by grafting but not by sap transmission.