The present invention provides a method of producing hybrid F1 seed of an angiosperm plant, which contains the following steps:- a maternal line is prepared by inactivation of a gene involved in the synthesis of sporopollenin and by mutation of acetolactate synthase gene resulting in resistance to herbicides of the acetolactate synthase inhibitor group- a paternal line is prepared, which is a fertile line without resistance to herbicides of the acetolactate synthase inhibitor group- subsequently, hybrid F1 seeds are produced by mixing the seed of the sterile herbicide-tolerant maternal line and the fertile herbicide-sensitive paternal line in a 95:5 ratio and by subsequent sowing this mixture of seeds of the maternal line and paternal line and- after the flowering period of the vegetation of mixture of the maternal line and paternal line, the plants are treated with a herbicide of the acetolactate synthase inhibitor group, thereby killing the herbicide-sensitive paternal line plants and leaving the herbicide-resistant maternal line plants producing pure fertile hybrid F1 seed- whereas the sterile maternal line is maintained by spraying with 4-oxo-6-octadecane-pyran-2-olate in the phase in which pollen tetrads are formed.
