Explain variants or mutation as a method of disease resistance.

(N/A) Mutation is the process by which genetic variations are created through changes in the base sequence within genes,resulting in the creation of a new character or trait not found in the parental type.
It is possible to induce mutations artificially through the use of chemicals or radiations (like $\gamma$ radiations) and selecting and using the plants that have the desirable character as a source in breeding; this process is called mutation breeding.
Several wild relatives of different cultivated species of plants have been shown to have certain resistant characters but have very low yield.
Hence,there is a need to introduce the resistant genes into the high-yielding cultivated varieties. Resistance to yellow mosaic virus in bhindi $(Abelmoschus esculentus)$ was transferred from a wild species and resulted in a new variety of $A. esculentus$ called Parbhani Kranti.
All the above examples involve sources of resistance genes that are in the same crop species,which has to be bred for disease resistance,or in a related wild species.
Transfer of resistance genes is achieved by sexual hybridisation between the target and the source plant followed by selection.