Date of Award

1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Gregory A. Lang

Second Advisor

Charles Johnson

Abstract

To study the physiological and biochemical effects of pollen sources on fruit growth and development of southern highbush blueberry (Vaccinium corymbosum hybrids), five-year old 'Sharpblue' plants were grown in a greenhouse for self- and cross-pollination experiments. Cross-pollination with 'Gulfcoast' and 'O'Neal' as pollen sources increased fruit weight by 58.2% and 54.9%, respectively, compared to self-pollination. Coincidentally, cross-pollination doubled the number of mature ovules, and increased their size by 14%. Ovule abortion occurred between 5 and 10 days after pollination (DAP) in both pollination treatments. More abortion occurred in self-pollination (35%), compared with cross-pollination (22% for 'Sharpblue' $\times$ 'O'Neal' and 29% for 'Sharpblue' $\times$ 'Gulfcoast'). More ovules (88.1%) developed poorly in selfed 'Sharpblue' than in crosses with 'O'Neal' (33.6%) and 'Gulfcoast' (50.8%). Cross-pollination resulted in significantly greater ovule area and fruit weight during early fruit development and at ripening. Ovule volume was maximum at 25 to 30 DAP for both pollination treatments, followed by an exponential fruit growth (phase II). Cross-pollination showed a greater fruit growth rate and a shorter phase II. At 5 DAP, ovules from cross-pollination were larger, suggesting that cross pollination initiated ovule growth immediately after fertilization. Compared to 'Sharpblue', 'O'Neal' and 'Gulfcoast' had greater pollen viability (reflected by higher percentages of fluorescing pollen tetrads), significantly higher in vitro germination percentages of pollen tetrads and higher incidences of multiple pollen tubes. Both soluble and ionically bound peroxidase activities were present throughout fruit development. Activities were very high during early development, with peaks at 10 and 20 days after self- and cross-pollination, respectively. Activity was much higher for cross-pollinations. During rapid fruit development, peroxidase activities were low. Soluble peroxidase activity increased, then declined during ripening for both treatments. Bound peroxidase activity increased during the color transition from blue to dark blue, with a greater increase in self-pollinated fruits. Banding patterns of both soluble and bound isoperoxidases varied with pollination treatments and fruit developmental stages. Pollen sources alter peroxidase isozymes and activities in developing fruits.

Pages

129

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