Plant breeding is the skillful use of different plant varieties to produce a desired plant type, thereby improving crop yield. But in most cases, crop production is affected by several crop diseases caused by pathogens such as fungi, bacteria and viruses. Blast of rice, red rot of sugarcane and late blight of potato are examples of fungal plant diseases while black rot of crucifers is a bacterial disease and tobacco mosaic virus and turnip mosaic virus are viral diseases.
In such cases, plant breeding can be used to develop crops possessing resistance to a particular pathogen provided the causative pathogen and its mode of transmission is known. Resistance can be defined as the crops’ ability to prevent a pathogen from attacking it and is determined by the genetic make-up of a particular crop. The genetic make-up of crops can be altered using plant breeding techniques like conventional breeding and mutation breeding. Conventional breeding involves hybridisation and artificial selection. It involves several steps that include collection of germplasm, selection of disease-resistant parents from germplasm, hybridisation of the disease-resistant parents, selection of disease-resistant hybrids and evaluation of the selected hybrids.
There are many disease-resistant hybrid varieties of different crops developed through conventional breeding. As the disease-resistant genes are available in the same crop species, the transfer of disease-resistance genes between the crops is done by sexual hybridisation. Although many disease-resistant hybrid varieties were produced through conventional breeding, the process is limited by the number of disease-resistant genes available in different crop varieties and their wild relatives.
As a result, another plant breeding technique called mutation breeding is widely employed. Mutation breeding involves the use of chemicals or gamma radiations to induce alterations in the genetic make-up of crops. The second generation of mutation-induced crops possess new characters that are absent in their parents. These plants are screened for disease-resistant genes and then artificially picked for breeding. Apart from pathogens, pests also reduce crop production. As a result, there is a need to develop crops that are resistant to pests as well by using plant-breeding methods.
These involve the same steps that are involved in the development of disease-resistant plants. Germplasm of cultivars or wild relatives are used as a source of pest-resistant genes. Insect-resistance in crop plants can be attributed to the morphological, biochemical or physiological features of a crop. There are quite a few insect-resistant hybrid varieties developed through plant breeding. In this manner, plant breeding techniques help improve crop production as well as prevent the use of bacteriocides and fungicides that can be harmful. They help develop crops that are resistant to pests and pathogens and can assist in boosting food production.