Question

Plants can be made disease resistant through?

Answer 1

Plant breeding means the purposive manipulation of plant species so that they are more crop-friendly, better yielding and disease-resistant. Plants that have higher qualities are selected and crossed to obtain plants with desired quality. This results in an improved plant population with desired character. Raising the crops with desired traits using plant breeding techniques helps increase the crop yield and develop disease resistant and stress tolerant crops.

Complete answer:
Plant breeding can be carried out by any of the following means- inbreeding, hybrid breeding, mutational breeding or via genetic engineering. Inbreeding involves self-fertilization which helps in improving the original traits. Two different breeds are crossed to produce a more efficient offspring than the parents in hybrid breeding. Mutation in plant genes might result in new varieties. They can be induced by exposing the plants with certain chemicals or radiation. Genetic engineering helps in producing crops with desirable traits by inserting the gene of interest within the crop DNA, ex. Bt crops.

Plant breeding technique is a step-by-step process-
1. Collection of variability: Variability forms the root of all breeding practices. This involves collection of plants or seeds for all possible diverse alleles for all genes in a given crop. This process is called the ‘germplasm collection’. It also involves the collection and preservation of the different wild varieties and species.
2. Evaluation and selection of parents: The germplasm is evaluated in order to determine seedlings of desired nature. Whenever needed, pure lines are created and the selected plants are multiplied and then hybridized.
3. Cross hybridization among selected parents: The two parents are hybridized crosswise to produce genetically modified hybrids. It is a very time consuming and tedious process. First the pollen from one parent is transferred to the stigma of another parent by the process of emasculation and bagging. Also, only one or two progenies in a few hundred show the desired combination of characteristics.
4. Selection and testing of superior recombinants: The hybrids with the desired are selected and this is a crucial process and requires careful scientific evaluation of the progeny obtained. The progeny that is superior to both of the parents is selected and are self-pollinated till they attain a state of homozygosity.
5. Testing, release and commercialisation of new cultivars: The new lines are grown in research fields where they are tested for their agronomic traits of quality, yield, resistance to diseases, etc. followed by the cultivation of these crops in different fields along with the different agroclimatic zones. When the results are achieved successfully the new progeny are released for commercial use.

Some crop varieties that are made disease resistant through conventional breeding techniques are:

Crop	Variety	Resistance to diseases
Wheat	Himgiri	Leaf and stripe rust, hill bunt
Brassica	Pusa swarnim(Karan rai)	White rust
Cauliflower	Pusa Shubhra,Pusa Snowball K-1	Black rot and CurlBlight black rot
Cowpea	Pusa Komal	Bacterial blight
Chilli	Pusa Sadabahar	Chilli mosaic virus,Tobacco mosaic virusAnd Leaf curl

Plants can be made disease resistant through plant breeding techniques.

Note:
In Mung bean, resistance to yellow mosaic virus and powdery mildew were induced by mutations. Bhindi (A. esculentus) was genetically transferred to a wild animal with resistance to yellow mosaic virus and resulted in a new type of A. esculentus known as 'Parbhani Kranti.'
Animal breeding techniques are also implemented, as is the case with plants, aimed at increasing animal yield and the desired product quality.