Clones are genetically identical individuals. If a species or individual has desirable traits, then it may be advantageous to clone that species or individual. One reason that a farmer would clone a specific plant within a crop is because that plant may demonstrate resistance towards a particular pest or infection. Another reason that a farmer may want to clone a particular plant within a crop is because of a high yield in fruit or other desirable or profitable resource.
Plants can be cloned either artificially or through natural means. Cloning crops artificially using tissue cultures. Plants may be cloned naturally via the use of plant cuttings or runners. Using plant cuttings to clone plants is advantageous if the plant is difficult to grow from seed.
One disadvantage of cloning plants is that it reduces that variety within a crop. Therefore, all plants will respond the same way to a change in the environment. If none of the plants are resistant to the change, the farmer may lose his entire crop. If variety was maintained within the crop, then there is bound to be at least some plants that are resistant to the change and survive.