1. Department of Mathematical and Statistical Methods, Poznań University of Life Sciences, 60-637 Poznań, Poland
2. Polish Academy of Sciences, The Franciszek Górski Institute of Plant Physiology, Niezapominajek 21, 30-239 Kraków, Poland
3. Plant Breeding and Genetics Laboratory, Joint FAO/IAEA Centre of Nuclear Techniques in Food and Agriculture, IAEA Laboratories Seibersdorf, International Atomic Energy Agency, Vienna International Centre, P.O. Box 100, A-1400 Vienna, Austria