Q.Write a note on heterosis.

Step 1. Heterosis, or hybrid vigour, is defined as the superiority of an F1 hybrid in performance over both its parents — G. H. Shull first used the term in 1912. It shows up as increased growth, yield, and greater adaptability or resistance to disease, pests and drought.

Step 2. Because this vigour is not reliably passed on through seed to later generations, vegetative propagation is the best way to maintain it, and its magnitude is thought to depend on how genetically diverse the two parents are.

Step 3. Heterosis is classified into euheterosis — true, heritable heterosis — with two sub-types: mutational euheterosis, where superior dominant alleles mask deleterious recessive mutant genes in cross-pollinated crops, and balanced euheterosis, where well-balanced gene combinations are more adaptive and agriculturally useful. …

Summarise the definition, classification and practical implications of …

• Describing heterosis only as 'hybrid vigour' without covering its classification into euheterosis and pseudoheterosis. …