Question

A hybrid is generally more vigorous than either of the parents, this is due to
A. Homozygosity
B. Heterozygosity
C. Superior genes in hybrid
D. Mixing of cytoplasm

Answer 1

Hybrids are obtained when two genetically homozygous inbreeds are crossed together. The hybrids resulting from the cross are usually vigorous and more productive than the parents. Increased or superiority over the parents is known as heterosis or hybrid vigor. The superiority of the ${F_1}$ hybrid over both the parents in terms of yield can be defined as heterosis.

Complete answer: In order to create desired plant types, plant breeding is the purposeful manipulation of plant species that suits better for cultivation and gives better yields, and is disease resistant.
The technology of plant breeding has helped in increasing yields to a very large extent. Plant breeding for getting a new genetic variety of a crop consists of the following techniques firstly, selection and evaluation of parents then collecting variability, among the selected parents cross-hybridization is done, which is followed by testing and election of superior recombinants and finally release of new cultivars.
The presence of different alleles at one or more corresponding chromosomal loci is termed as heterozygosity. Zygosity is the degree of similarity alleles for a trait in an organism. Eukaryotes are diploid i.e. they are having two matching sets of chromosomes. When a diploid organism contains a gene locus with two different alleles of a gene it is called heterozygous.
If an offspring is produced after self-pollination for several generations, finally they reach a state of uniformity i.e. called homozygosity, and hence the characters do not segregate in the progeny. So, when a hybrid is produced homozygosity and mixing of cytoplasm can’t occur. The hybrids are more vigorous than either of the parents because of heterozygosity and not for expressing superior genes.

Thus, the correct answer is Option B, Heterozygosity.

Note:
Plant breeding may be used to create varieties, which are resistant to pathogens and to insect pests. Plant breeding has increased the yield up to huge content. Plant breeding is also successful in increasing the protein content of the plant foods and thereby enhancing the quality of food.
Several varieties of different crop plants have been produced in India by this method which finally enhanced the production of food.
Techniques like somatic hybridization and tissue culture are also very techniques for the production of new varieties of plants through in vitro methods.