M. Drumeva

Abstract. The experimental research work encompassed the period 2007 – 2009 and was carried out at Dobrudzha Agricultural Institute, General Toshevo. Six highly productive commercial hybrids (Х1, Х2, Х3, Х4, Х5 and Х6) were used as initial material for production of sunflower fertility restorer lines by the method of gamma-induced parthenogenesis. Mixed pollen treated with dose 600 Gy was used for parthenogenetic induction. Thirty plants from each hybrid were pollinated with irradiated pollen. A total of 833 immature embryos were obtained from the six hybrids, which were further grown under in vitro conditions till formation of young plantlets. Normal growth and development were observed in 569 embryos. The obtained young plantlets were transferred to soil and grown till maturity in a greenhouse. Of these plants, 326 were fertile and were potential double haploid lines. After selfing under greenhouse conditions, a total of 6 016 P2 seeds were obtained from them. In 2008 the P2 progeny was reproduced to fertile plants under field conditions. One hundred ninety-eight double haploid R lines were selected. In 2009 the double haploid lines were investigated under field conditions, performing morphological, biometrical, phytopathological and phenological evaluation of the lines. The lines with origin from hybrids X3 and X1 possessed better developed vegetative mass, well formed and large heads on the side branches and powerful stems. One hundred fifty-nine lines were selected. Ninety-eight of them demonstrated full resistance to downy mildew race 731. The resistant lines originated from hybrids Х1, Х2, Х3, Х4 and Х6. The lines obtained from hybrid X5 did not carry genes for resistance to downy mildew race 731. Phytopathological evaluation was done also with regard to the diseases phoma, phomopsis and alternaria under field conditions. Ninety-five percent of the lines showed full resistance to phoma (rank 0) and high resistance to moderate susceptibility to phomopsis (rank 1 – 3). In 16 % of the lines full resistance to alternaria (rank 0) was found.