Abstract
This study was carried out to estimate the extent of heterosis and inheritance of different morphological traits in 32 sunflower hybrids developed at the Department of Plant Breeding and Genetics, University of Agriculture Faisalabad from 2010 to 2011. The crosses were developed using North Carolina Mating Design (NCD-1). The experiment was arranged using randomized complete block design (RCBD) in three replications. Plant height, head diameter, 100-achene weight, percent filled achenes and achene yield per plant were recorded in spring and autumn seasons. Non-additive type of gene action was important in the inheritance of plant height, head diameter, 100-achene weight and percent filled achenes while in case of achene yield per plant additive effects were more important. High magnitude of heterosis was observed for all the traits under study. None of the crosses were consistent in heterosis for all the traits. However, for achene yield, the cross combinations G40 x L31 (60.42) and A12 x HBRS-5 (48.02) showed significantly higher values of heterosis over Hysun-33 which is the highest yielding hybrid being used commercially in Pakistan. Majority of the hybrids displayed very low to negative heterosis (H-t = -13.1 to 9.31 and H-b = -19.8 to 3.55) for plant height during autumn. Larger heads with bolder seeds and minimum number of unfilled achenes were recorded for majority of hybrids during spring season compared with autumn season.