The annual sunflower is a genetically and morphologically variable species belonging to the genus Helianthus. Sixty seven species are identified under the genus Helianthus and two of these, Helianthus annuus and Helianthus tuberoses, are known to be cultivated as food and several other species are grown as an ornamental plant. The principal ones being H. annuus, H. argophyllus T. & G. and H. debilis Nutt among the annuals and H. decapetalus L., H. X lactiflorus Pers., H. maximilians Schrad, H. X multiflorus L., and H. salisifolius A. Dietr. among perennial (Heiser, 1978). The genus is characterized by a basic chromosome number of x=17 and also there are diploid, tetraploid, and hexaploid species (Heiser 1978).
Cultivated sunflower (Helianthus annuus) deserves the second rank in the world in it's use as an oil crop next to soybeans. Seeds are used for human consumption for example as confectionery, raw material for oleochemistry and substitute for mineral oil in various applications as fuel, lubricant and oil for hydraulic systems.
Sunflower is a predominantly cross pollinated species, with a pollination behavior primarily accomplished by insects and to a limited extent by wind. A wide range of self fertility occurs among individuals in a breeding population, though low level of self incompatibility is realized in certain lines (Friedt et. al 1997). It is a primary objective in most breeding programs to develop hybrids although improved open pollinated and synthetic cultivars have value, especially in countries where hybrid seed production is not feasible for technical and economical reasons (Fick 1989).