SCREENING SOME MEDICINAL PLANTS AGAINST MOROCCAN WATERMELON MOSAIC VIRUS (MWMV. A RESEARCH PROJECT MATERIAL ON BIOCHEMISTRY
ABSTRACT
The antiviral activities of plant leaves extract of four species, were investigated. The extract were tested for antiviral activities on the host plant (Cocumba) against Moroccan watermelon mosaic virus. Results showed that two plants (Phyllanthus amerus and Mirabiles jalapa) presented inhibitory activities against the virus. While Ficus exaspirata and Citrus spp were unable to inhibit the virus.
Moroccan watermelon mosaic virus is still a major problem on the cucubite cultivation in Africa.
CHAPTER ONE
INTRODUCTION
1.1 Background of study
Plant viruses are responsible for huge economic losses in many countries around the world.
A virus is an infection agent that typically consists of nuclei and molecule in a protein coat, it is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host. (Holmes, 1939). Viruses can be spread by direct transfer of sap by contact of a wounded plant with a healthy one, such contact may occur during agricultural practices, as by damage caused by tools or hands, or naturally as by animal feeding on the plant. Most of the viruses infecting plants rely on insects to move from one host to another, some remain associated with the mouth parts and can be inoculated within seconds or minutes. (Martinus, 1898). This work those not cover insect transmission but basically mechanical inoculation.
1.2 Methods employed to control plant viruses
Plant viruses and virus diseases have been studied for more than 100 years and much attention has been given to their control. However, this has been difficult to achieve because of the lack of any effective means of curing virus-infected plants. Chemotherapy, thermotherapy and Meristem-tip culture can be successful but they cannot be used on a large scale. (Brook, 1964). The main approach has been to prevent or delay virus infection or to minimize its effect. Various means have been used to achieve these objectives, including phyto-sanitation. (Involving quarantine measures, crop hygiene use of virus-free plant materials and eradication) changes in crop practices, use of pesticide for control of vectors, mild strain protection and the employment of resistant or tolerant varieties. (Sarkar, 1995). Some viruses can be eliminated from infected plant by heat or meristem-tip therapy or by the use of chemicals (Faccioli and Marami, 1998) these methods are used widely to develop virus-free plants of vegetatively-propagated crops for further propagation. It prevents plants from becoming infected, delay infection to such a life stage of crop impaired and decrease the effects of infection. (Mink et al, 1998).