ABSTRACT
Twenty-six genotypes of sunflower (16 F1-hybrids, four female lines, four restorer lines and two check varieties; Sakha 53 and Giza 102) were evaluated under two contrasting environments, i.e., loamy sand soil at A.R.C., Arab El-Awamer Res. Stn., and clay soil at Assiut Univ. Exper. Farm in season 2016. Genotypes mean squares of the studied traits was significant (P<0.01) either in the separate or in the combined analysis. The differences between the two environments were significant for all traits except head diameter (HD). The genotype x environment interaction was significant for all traits, indicating differential responses of genotypes to the two environments. The sixteen hybrids showed negative significant heterosis (P<0.01) for 50% flowering from the earlier check Giza 102 (standard heterosis; SH %), which ranged from -8.39 to -18.44% under loamy sand soil, and from -2.80 to -12.92% under clay soil. The heterotic effects were higher under loamy sand than under clay soil. The combined data showed that 4, 5 and 12 hybrids were significantly earlier than the mid-parent, better parent and the earlier check; respectively. The combined data over the two environments of plant height indicated that 15 hybrids showed negative significant standard heterosis ranged from -8.42 to -25.16%. This gives a good opportunity to select short sunflower hybrids. All the hybrids showed negative SH% for head diameter, and none of them exceeded the check variety in 100-SW. Otherwise, all the hybrids showed negative significant (P<0.01) heterosis in husk% from the better check Sakha 53 either at the two environments or at the combined data. Over environments the SH% in oil% was positive and significant (p≤ 0.01) for four hybrids (ranged from 4.47 to 9.83%), for three hybrids in kernel weight and for one hybrid in number of seeds/head. Mid-parent heterosis in seed yield/head was positive and significant (P<0.01) for 14 and 13 hybrids under loamy sand and clay soil; respectively, eight and three hybrids showed positive and significant BPH heterosis in seed yield/head under the respective environments. The positive and significant (P<0.01) BPH in seed yield/head ranged from 16.54 to 685.33% under loamy sand soil, and from 13.42 to 70.38% under clay soil. Otherwise, only one hybrid No. 1 (A7 x Rf1) gave positive significant (P<0.01) heterosis from the check hybrids Sakha 53 under clay soil and combined data. Mid-parent heterosis in oil yield/head was positive and significant (P<0.01) for 14 hybrids under both environments and ranged from 3.35 to 823.12% under loamy sand, and from 3.01 to 151.88% under clay soil. Eight and three hybrids gave positive significant (P<0.01) BPH under loamy sand and clay soil; respectively. The BPH in oil yield/head ranged from 9.48 to 708.95% and from 3.91 to 66.06% under the two respective environments. Standard heterosis in oil yield/head from the better check cultivar was positive and significant for five hybrids under loamy sand, one hybrid under clay soil and two hybrids in the combined data.
Key words: Heterosis, Helianthus annuus L., Standard heterosis