Techniques of developing hybrid in vegetable crops/ J.C. Kumar and M.S. Dhaliwal.

The term heterosis was first coined by shull, signifies an increased or decreased vigour of F1 hybrids over the midparent or better parental vslues. Hybrid cultivar is used to designate F1 populations can be obtained by crossing clones, openpollinated varieties, inbred lines, pure lines or other populations that are genetically diverse exploiting different pollination mechanisms such as male-sterility, self-incompatibility, dioecy, monoecy, etc. The secret of success of F1 hybrids lines in the fact that all plants are exceptionally uniform in growth and development, resistant to insect-pest and disease, better adaptability to changing and adverse ecological conditions (homeostatic) andabove all give high early as well as total yields. Resistance to insects, pests and diseases when dominant over insects, pests and diseases when dominant over susceptibility can be directly availed in F1 hybrids thus eliminating the tedium of selecting resistant segregates in successive generations. In addition to superior performance by hybrids due to heterosis, intermediate state of gene expression in heterogygotes may be of potential value.