Host pests and pathogens (REF). Cultivars that

Host plant resistance. Both agriculturalists and horticulturalists aim to manipulate the genetic diversity that is present in all plant species in order to maximise crop productivity and to minimize the harmful effect caused by pests and pathogens (REF).

Cultivars that are resistant genotypes against biotic and abiotic factors are selected, however, one must bear in mind the negative and positive impact of such genotypes, states (REF). Negative selection is whereby a cultivar is discarded due to its inability of resisting the virus and produce milder symptoms or no symptoms at all, and its poor productivity (REF). Positive selection is whereby a cultivar is selected because of it resistance against a virus that it has been purposely exposed to (RF). Thus, positive selection demands more scientific input and expertise, as opposed to negative selection. This technique has made a noticeable contribution towards virus disease control by decreasing the incidence (REF).

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