Heterosis and combining ability in sunflower (Helianthus annuus)

An experiment was conducted during 1995-96 to estimate the combining ability and heterosis for seed yield and certain yield components. Twenty four artificial hybrids were created using 6 CMS and 4 restorer lines in sunflower (Helianthus annu L.) The variances due to general and specific combining ability were highly significant for number of seeds head and seed yield. Specific combining ability variance was significant for head diameter, seed weight head and 1000-seed weight only. But general combining ability variance was significant for plant height. However, the ratio of the gca to sea variance showed the preponderance of non-additive type of gene action for all the characters except plant height. Two parents had significant positive gca effect for seed yield and some yield components. Most of hybrids having high heterosis involved parents with low gca x low gca or low gca x high gca effects.