Write a note on heterosis.

Explanation

The superiority of the `F_(1)` hybrid in performance oveer its parents is called heterosis os hybrid vigour. Vigour refers to increase in growth, yield, greater adaptability of resistance to diseases, pest and drought. Vegetative propagation is the best suited measure for maintaining hybrid vigour, since the desired characters are not lost and can persist over a period of time. Many breeders believe that its magnitude of heterosis is directly related to the degree of genetic diversity between the two parents. Depending on the nature, origin, adaptability and reproducing ability heterosis can be classified as: (i) Euheterosis- This is the true heterosis can be classified as: (a)Mutational Euheterosis - Simplest type of euheterosis and result from the sheltering or eliminating of the deleterious, unfavourable often lethal, recessive, mutant genes by their adaptively superior dominant alleles in cross pollinated crops. (b)Balanced Euheterosis - Well balanced gene combinations which is more adaptive to environmental conditions and agricultural usefullness. Pseudoheterosis - Also termd as luxuriance. Progency possess superiority over parents in vegetative growth but not in yield and agricultural usefulness.