Incompatibility in the cross-pollination of apple varieties and their hybrids

Abstract

A number of cross-pollination tests were carried out from 1959 to 1961 among 20 commercial apple varieties and 31 of their hybrids bred at our Station.Unfruitfulness was observed in the crosses between hybrids and their parents. The hybrid G. Y 44 or G. Y 53 (G. Y shows a hybrid obtained from the cross between Golden Delicious (_??_) and Yellow Newtown (_??_)) did not pollinize Yellow Newtown satisfactorily and the same was true of the reciprocal pollination. G. Y 44 also did not well pollinize G. Y 53. Pollination between either of these hybrids and Golden Delicious did not show unfruitfulness. Dr. KIKUCHI found in Japanese pear such an unfruitfulness in the cross-pollination between hybrids and their father. Most pear hybrids which were incompatible to their father were incompatible each other too. He called this phenomenon“patroclinal incompatibility”.Pollination was unsuccessful in the following pairs of the hybrids raised from the same parents: M. W 107 & M. W 30 (the cross between McIntosh and Worcester Pearmain); J. G 84 & J. G 51 (Jonathan× Golden Delicious); J. W 50 & J. W 32 (Jonathan× Worcester Pearmain) and R. D 329 & R. D 125 (Ralls× Delicious).Unfruitfulness was often observed in the crossing between certain hybrids having either same mother or father. Those pairs were as follows: Megumi (R. J) & J. G 51; Red Gold (G. D) & J. G 51. This phenomenon seems to be explained by the hypothesis of oppositional factors.Any cross between hybrids which descended from different parents is compatible each other, excepting a case in which R. J 259 (Ralls×Jonathan) pollinated with Red Gold bore only a few fruits for two successive years.Several hybrids and varieties poorly pollinized Early Red Bird variety. But this seemed to be caused by a certain mechanism other than cross- incompatibility, because in the reciprocal pollination high fruit set resulted.Pollen of any variety or hybrid employed in this work germinated well on artificial medium. Even the pollen of J. G 51 which failed to pollinize well Megumi and Red Gold, germinated normally. Yellow Newton pollinated by G. Y 44 and J. G 84 pollinated by J. G 51 set few fruits. But the seeds obtained from these fruits germinated well in sand bed and resulted in healthy seedlings.The hybrid seedlings obtained in this work had often three cotyledons. Frequency of such seedlings varied with cross-combinations. It was especially high in the crossing in which Orei was used as a female parent.