Embryological studies on Fragaria x ananassa Duch. after pollination by three species of Potentilla

Abstract

Embryological studies were carried out after pollinating four female varieties of Fragaria ananassa Duch. (Freja, Sonja, Mieze Schindler, Reine des Precoce) with three species of Poteiatilla (P. geoides, P. rupestris, P. fruticosa). The aim was to elucidate the manner in which matroclinous progeny arises after pollination of the strawberry with Potentilla pollen. In addition to meiotic, apo- and diplosporous embryo sacs were formed in the Freja variety. On the average, in the four studied varieties,, 49% of the ovules contained more than one embryo sac. At the most, five embryo sacs developed, but only two of them attained full maturity. Pollen from Potentilla germinated on the stigma of the strawberry and the pollen tubes grew through the style to the ovule. Symptoms of fertilization were not found in the strawberry ovules after pollination with Potentilla, however, after pollination with the Redgauntlet F. x ananassa variety, extra nucleoli or chromatin grains were found in the ovule. False polyembryony was found in the Mieze Schindler (16 cases), Sonja (2 cases) and Freja (1 case) varieties. The germination of two plants from one seed was observed, which shows the possibility of full development of twin embryos. The low germination ability of the seeds was caused by abnormalities in the development of the embryos.