M. Ilchovska Maize Research Institute, 5835 Knezha, Bulgaria (Manuscript received 1 September 2018; accepted for publication 3 December 2018) Abstract. Ecological stability and plasticity of maize hybrids in different groups of ripeness – Knezha 307, Knezha 435, Knezha 509 and Knezha

G. Georgiev*, P. Peevska, E. Penchev Dobrudzha Agricultural Institute, 9520 General Toshevo, Bulgaria Abstract. Four new Bulgarian sunflower hybrids were investigated: Veleka and Vokil, which were officially registered in 2013 in Romania; Gaby, which will be registered in Romania in 2

I. Productivity and traits related to productivity G. Georgiev, P. Peevska, E. Penchev Abstract. The investigation was carried out at Dobrudzha Agricultural Institute, General Toshevo during 2011 – 2012. It was aimed at determining the production potential and the values of some of th