question_answer 7)

Briefly describe various steps involved in plant breeding. 

Answer:

Plant breeding is the purposeful manipulation of plant by crossing different varieties in order to create desired plant types that are better suited for cultivation, give better yields and are disease resistant. Plant breeding involves the following steps: (i) Collection of variability – Collections and preservation of all the different wild varieties, species and relatives of the cultivated species. The entire collection (of plant/seeds) having all the diverse alleles for all genes in a given crop is called germplasm collection. (ii) Evaluation and selection of parents – The germplasm is evaluated so as to identify plants with desirable combination of characters. (a) Selection in self-pollinated crops – The degree of cross pollination is less than 5%. There is repeated self-pollination of selected plants till superior homozygous genotypes are obtained. The best one is used as new variety. The self-pollinated progeny of homozygous plant constitutes a pure line. (b) Selection in cross-pollinated crops – The cross pollinated crop are heterozygous for most of their genes and their population contains plants of several different genotypes. Superior genotype plants are selected and are allowed to crossbreed (these plants are not allowed to self-breed) so that heterozygosity is also maintained. (ii) Cross hybridization among the selected parents – Hybridization is crossing of two or more types of plants for bringing their traits together in the progeny. The procedure of hybridization involves selection of parents with desired characters, selfing, emasculation, bagging, tagging and artificial pollination. (iv) Selection and testing of superior recombinants – This is the selection of the plants, from the progeny of hybrids, which have the desired combined character. The selected plants are then self-pollinated for several generation to get a uniformity i.e., homozygosity. (v) Testing, release and commercialisation of new cultivars – The newly selected lines are evaluated for their yield and other agronomic traits of quality, disease resistance etc. these selected cultivars are then tested with local best cultivar and then are released for commercialisation.