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Raquel Cano-Medrano and Rebecca L. Darnell

To determine if multiple applications of GA3 would increase size of parthenocarpic fruit, and to assess the interaction between GA3 applications and pollination, `Beckyblue' rabbiteye blueberry (Vaccinium ashei Reade) flowers were treated with single or multiple applications of GA3 alone or in combination with full or partial pollination. Single or multiple applications of GA3 resulted in similar or increased fruit set compared with pollination, and increased fruit set compared with no pollination. GA3 applications decreased fruit mass and increased the fruit development period in comparison with pollination alone. Multiple, late applications of GA3 were ineffective in overcoming these effects. Partial (nonsaturating) pollination resulted in an average fruit set of 60%, while set following GA3 treatment in combination with full or partial pollination averaged 85%. Fruit mass was greater in the full pollination ±GA3 treatments than in all other treatments. The number of large seeds and seed mass per fruit were greatest in the full pollination treatment, and were significantly decreased by all treatments in which GA3 and/or partial pollination were used; however, there were no concomitant effects of GA3 in delaying the fruit development period. Our results indicate that under optimal pollination conditions, no detrimental effects of GA3 applications on fruit set, fruit size, or fruit development period in blueberry are to be expected, even though GA3 reduces seed number and seed mass. Furthermore, GA3 applications appear to be beneficial in increasing fruit set under suboptimal pollination conditions, although smaller fruit are to be expected under such conditions. Chemical name used: gibberellic acid (GA3).

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Adriana Beatriz Sanchez-Urdaneta, Raquel Cano-Medrano, and Jorge Rodrl̀guez-Alcazar

The purpose of this research was to investigate the effect of 1% N foliar sprays (0, 2, and 4 sprays at weekly intervals) and girdling (G) on budbreak of three peach advanced selections CP95-1 °C, CP91-8, and CP91-17, and its relationship with both reduced nitrogen (RN) and polyamine contents. Foliar N was applied in July, before flower initiation was detected and girdling was performed 30 days after nitrogen sprays (DAT) The results indicate that 4N+G treatment had the highest content of (RN) with values between 232 and 1000 mg N/g of DW. CP 91-17 and CP95-1 °C selections showed higher RN content than that of CP91-8. Both 2N+G and 4 N+G showed the highest content of putrescine (Put) (908 and 1635 nmol·g-1 FW, respectively). Among peach selections CP91-8 was the one with the highest content of Put. Putrescine content went down as the flower differentiation process evolved. Four N+G treatment promoted budbreak in CP95-1 °C advancing it in 55 days as compared to the control. Budbreak began earlier in the three peach selections treated with 4N+G (11/12/98) followed by 2N+G treatment (7/001/99), and the control (4/02/99). Fruit set was 19%, 12%, and 11% for 4N+G, 2N+G, and control treatments, respectively.

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J. Arnulfo Marquez-Cervantes, Raquel Cano-Medrano, and Jorge Rodrl̀guez Alcazar

The effect of thidiazuron (TDZ) at 0, 150, 300, and 450 mg·L-1 in `Perlette' grape cuttings after chilling treatments (0, 150, 300, and 450 chill units, CU) on polyamine content and budbreak was studied. In addition, the treatment 300 CU + 300 mg·L-1 TDZ + 50 mg·L-1 GA3 was evaluated The results indicated that, from 0 to 6 days after treatment (DAT), putrescine (Put) content was low (50-80 nmol·g-1 FW regardless of treatment, but it reached an average of 600 nmol·g-1 FW in both 150 CU + 300 mg·L-1 TDZ and 300 CU + 300 mg·L-1 TDZ FW treatments, at 12 DAT These treatments had the highest bud fresh weight (BFW) (122 mg) and final budbreak (82%). Spermidine (Spd) content remained almost unchanged in the above mentioned treatments (20-30 nmol·g-1 FW) showing the highest value at 6 DAT. Spermine (Spm) content declined from 100 to 80 nmol·g-1 FW from 0 to 6 DAT remaining almost constant until the end. Neither Spm nor Spm showed clear relationship with either BFW or budbreak. Control treatments and treatments with GA3 included had an average of 100 nmol·g-1 FW of Put throughout the evaluation period and showed the lowest BFW (≈45 mg) and budbreak (≈30%) compared to the rest of the treatments.