Hybrid varieties have been commercially exploited in most of the cross-pollinated crops. The greatest use of hybrid varieties has been made in maize. Other cross-pollinated crop species where hybrid varieties have been commercially exploited are jowar, bajra, sugarbeets (B.vulgaris), sunflower (H.annuus), broad bean (Vicia faba), onions (A. cepa), etc. Hybrid varieties have been successful in some self-pollinated crops as well, e.g., cotton (Gossypium sp.) in India, tomatoes in Europe and rice in China. Most of the self-pollinated crops do show heterosis, but hybrid varieties are not feasible due to the difficulties in hybrid seed production.

Hybrid varieties were the first to exploit heterosis in maize in this country. The first hybrid varieties in maize were released in 1961 when four hybrids, viz., Ganga 1, Ganga 101, Ranjit and Deccan, were released for cultivation. All these hybrids are double crosses. Subsequently, several other hybrids were released. At present, about a dozen double cross hybrid varieties are recommended for cultivation. These hybrids include Ganga 3, Ganga 4, Ganga 5, Ganga 7, Deccan 101, Hi-Starch and Ganga Safed 2. These hybrids give 25-40% higher yields than the local open-pollinated varieties. The hybrids have yielded up to 4 tonnes per hectare of given on the farmer’s fields. Hybrid varieties have been commercially used in bajra.

The first hybrid bajra was developed by the Punjab Agriculture University. Ludhiana, and was released in 1965 and HB1. Subsequently, two other hybrids, HB 3 and HB 5, were released. These hybrids give yields up to 7 tonnes per hectare. In addition to being higher yielding the T X D and D X T hybrids are earlier in first flowering (earlier by about 10-11 months) than the parents.

Several varieties of clonal crops have been developed either by bud selection or by clonal selection from heterogeneous clones. Kufri Red potato is a clonal selection from Darjeeling Red Round; it was developed from a single disease-free plant. Similarly, Kufri Safed is a clonal selection from the potato variety Phulwa. Bud selection has been done in several fruit trees. For example, Bombay Green banana is considered to be a bud selection from Dwarf Cavendish; Pidi Monthan from Monthan, and High Gate from Gross Michel.

A large number of varieties of clonal crops have been developed through hybridization. Some prominent potato varieties developed through hybridization are Kufri Alankar, Kufri Kuber, Kufri Sindhuri, Kufri Kundan, Kufri Chamatkar, Kufri Chandramukhi etc. Kufri Jyoti is late blight resistant and Kufri Sheetman is frost resistant. In case of sugarcane, all the varieties have been developed through interspecific hybridization. Some prominent varieties of sugarcane are CO 1148, CO 1158, COS 510, CO 975, COS 109, CO 541 etc.

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