Question

Importance of heterosis to crop improvement

Answer 1

An effort has been made in the present paper to critically assess the level of success and future strategies in the development and adoption of hybrid technology in selected field crops under three categories: (i) extention of hybrid technology to new niches and situations (maize, sorghum and pearl millet); (ii) sustenance of hybrid technology in new crops of proven potential (rice, cotton and sunflower), and (iii) extending hybrid technology to new prospective crops (Brassica, wheat, pigeonpea and castor). Maize closely followed by sorghum and pearl millet have been the pioneer crops in India since mid fifties. However, lack of single cross short duration hybrids in maize; lack of higher yielding dual purpose hybrids suitable for rabi season in sorghum and narrow cytoplasmic base of CMS system in pearl millet are certain limitations which we need to overcome. Failure to produce and supply targeted quantity of hybrid seed, specially of public bred hybrids warrants urgent attention. High yielding cotton hybrids combining early maturity and resistance to leaf curl virus and boll worm complex for irrigated north and north-west regions having limited growing season are yet to be developed. Dissemination of transgenic Bt. cotton hybrids/varieties all over to effectively manage boll worm complex and thereby stabilise yield and reduce cost on plant protection is required. One of the major concerns in sunflower hybrids is slow pace of development of heterotic gene pools, exclusive dependence on a single CMS source (PET-1) and narrow genetic diversity for seed yield and oil content. Broadening of genetic base through enrichment of source nursery with germplasm for yield vigour is important keeping in view the fact that available genetic variability in Indian mustard is too inadequate to realize the desired level of yield heterosis; at the same time, it is worth searching for cytoplasmic-genetic male sterility source. First wheat hybrid “Pratham” is being commercialised. However, viable seed production technology either through CMS/chemical based system is yet to be perfected.

Answer 2

Heterosis or hybrid vigour is improved or increased function of any biological quality in a hybrid offspring. An offspring exhibit heterosis if its traits are enhanced as a result of mixing the genetic contribution of its parents. Heterosis increases the overall crop productivity. It results in increased yield, intercropping and crop rotation.