Alkaloids and Virus Resistance

Resistance to a virus in a certain plant may be caused by two major factors (1) the cell medium of the plant is capable of providing no suitable material for replication of the viral nucleic acids and protein, and (2) the plant is avoided by the vector, usually an insect, because of certain chemical or mechanical properties. We shall deal with the first possibility. The host specificity of most plant viruses is known still there is a broad spectrum of species and genera that may be attacked by the same virus. Very often the species and genera belong to a single family, but exceptions 

Evidence of activities of alkaloids in the DNA reproduction mechanism is impressive. Some alkaloids are used as drugs for inhibiting the development, e.g., of animal cancerous tumors, including humans (Kup-chan and By, 1968 Kupchan, 1975), some are known for hallucinogenic properties (Schultes, 1975 Wall, 1975 Hoffman et al., 1975), antimicrobial effects (Mitscher, 1975), neurotoxins (Kessler, 1975), and teratogenic (Kuc, 1975) and allergenic behavior (Mitchell, 1975), and some are used in folk medicine (Duke, 1975). 

The other aspects of resistance, the unpalatability of the plant for the vector, will be dealt with in the next section of this chapter, together with further evidence for plant-insect coevolution. 

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