Hint: Heterosis, commonly known as an outbreeding enhancement, is one of the most commonly followed methods to improve the quality of any offspring over their parents. The offsprings which are enhanced using this technique are called heterotic.
Complete answer: In heterosis, the genes of the parents are mixed to produce superior offspring. The term ‘heterosis’ given by G. H. Shull replaced the term heterozygous which was used earlier. The physiological characteristics of an organism depend upon the degree of dissimilarities of the gametes united to produce the organism. Heterosis is the affinity to surpass the characters of both the parents. Selective breeding is the most common way to perform this function. If one of the parents has a unique quality and the other parent has some other quality which is absent in the first partner, and then combining the genes of these two parents could lead to the formation of a superior offspring. In plants, heterosis helps in increasing the yield of the crops by producing better quality and higher resistance to pests and diseases. It is accomplished by crossing different heterotic groups to produce a vigorous F1 hybrid progeny. Modern techniques are very beneficial to produce hybrids that are better adapted to the environment and respond more to the fertilizers. Major crops produced by heterosis to increase their yield are maize, rice, sunflower, sorghum, sugar beet, onion, etc.
Note: Heterosis is done to avoid inbreeding depression in which the biological species reduces its fitness due to repeated self-fertilization, and thus loses its ability to survive. Thus genetic variation is very important within a breeding population.