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Embryo sac development in relation to pollen fertility and seed set in irradiated apple clones Barritt, Bruce Harold

Abstract

Investigations were made of the association among megagametogenesis, pollen morphology, and seed production in two irradiated apple varieties, Golden Delicious and McIntosh, and in two years, 1964 and 1965. In each year eight to ten clones of each variety were selected on the basis of low, medium, and high pollen abortion. Untreated and treated Golden Delicious and McIntosh clones with normal pollen production, approximately 90% and 50% respectively, had the highest proportion of embryo sacs at the differentiated 8-nucleate stage, and the smallest proportion of embryo sacs at the 2- and 4-nucleate stages. Irradiated clones with the least normal pollen had the highest proportion of immature 2- and 4-nucleate embryo sacs. With both varieties and in both years reduced pollen fertility was positively correlated with retarded embryo sac development. Check clones with high pollen fertility had the highest number of developed seeds per fruit and irradiated clones with reduced pollen fertility had the smallest number of developed seeds per fruit. The number of developed seeds per fruit was positively correlated with the proportion of mature 8-nucleate embryo sacs. The reduction in seed numbers in irradiated apple clones with reduced pollen fertility may be explained, in part, by retarded embryo sac development.

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