Abstract
Two types of unfruitfulness were found in our apple breeding programs; one was in the reciprocal cross between 'Kizashi' and 'Golden Delicious' and the other in the crosses of HCR6T132, a strain bred in Purdue university, U. S. A., with pollen of other culti-vars.The reciprocal cross between 'Kizashi' and 'Golden Delicious' resulted in very low rates of fruit set. Microscopic examinations revealed that pollen of both cultivars germi-nated normally on the stigma, but their tubes ceased growth in the upper part of the style; a number of pollen tubes formed swollen tips, indicating that the sterility was con-trolled by gametophytic incompatibility mechanisms.HCR6T132 yielded a high rate of fruit set when it was used as a pollen parent, where-as it failed as a seed parent. The unfruitfulness of the strain as a seed parent could not be ascribed to the incompatibility, because there was no difference in pollen tube be-havior, compared with the cross compatible combinations.It was found that the fruit set was reduced when HCR6T132 flowers were emascu-lated (petals and anthers were removed) just before pollination; the injured flowers evolved much more ethylene than the intact ones. On intact flowers, the strains retains its fruitfulness, as did the treatment with AVG (aminoethoxyvinyl glycine), an ethylene synthesis inhibitor, to the emasculated flowers. These results revealed that the strain is probably very sensitive to ethylene and/or produces much wound ethylene, and that the unfruitfulness is ascribed to ethylene induced by emasculation.
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call