Description

The cultivated sunflower scientifically is Helianthus annuus L. that belongs to family Asteraceae. It is a diploid specie (2n = 2x = 34) that belongs to the sub tribe Helianthinae, subfamily Asteroideae. The genus Helianthus includes 12 annual and 36 perennial species. Sunflower, in Pakistan is cultivated on 443.2 thousand hectares with the seed production of 643 thousand tones and oil production of 244 thousand tones.Sunflower is highly cross pollinated crop and is ideally suited for heterosis exploitation. In sunflower, heterosis breeding evolved successfully as the detection of cytoplasmic male sterility source. The line x tester analysis is an efficient method to assess the large number of inbreds and it provides the information on the relative importance of general and specific combining ability effects to understand the genetic basis of important plant characters viz., plant height, head diameter, stem diameter, achene weight, achene yield and oil contents etc. The general combining ability (GCA) of line means the average value of its performance in hybrids when crossed with other lines. The specific combining ability (SCA) means the performance of individual hybrids.