ISHS Acta Horticulturae 527: International Symposium on Growth and Development of Fruit Crops
EFFECTS OF SEED NUMBER, FRUIT REMOVAL, BOURSE SHOOT LENGTH AND CROP DENSITY ON FLOWERING IN ‘SPENCER SEEDLESS’ APPLE |
| Authors: | John C. Neilsen, Frank G. Dennis Jr |
| Keywords: | Malus x domestica Borkh., alternate bearing, flower induction, flower formation, parthenocarpy, apetalous mutant |
| Abstract:
The objective of this study was to determine the effects of seed number, bourse shoot length, and crop density on flowering in ‘Spencer Seedless’ apple. ‘Spencer Seedless’ is an apetalous cultivar that is facultatively parthenocarpic; pollination results in seeded fruits. Individual spurs bearing either seedless or seeded fruits were tagged and the fruits were removed at various times between bloom and harvest in 1989–1992. The fruits were weighed, seeds counted and bourse shoots measured for each spur. Seventy to 100 % of the spurs bearing seedless fruits flowered the following year. The percentage flowering in spurs bearing seeded fruits decreased as defruiting was delayed; this reduction was variable among years, with 10 % to 70 % of the spurs flowering when fruits were left until harvest. In 1994 and 1996 spurs were tagged at harvest, and grouped into classes based on fruit weight, seed number, shoot length, and crop density. Flowering of each bourse shoot was recorded the following year. Percentage flowering decreased from 94 % to 38 % (1995) or 15 % (1997) as seed number increased from 0 to >15. Flowering increased with bourse shoot length; no bourse shoots less than 2 mm long flowered, whereas almost all bourse shoots longer than 16 mm flowered regardless of seed number. Seeds had the greatest inhibitory effect in shoots 2–4 mm long or when crop density was greater than four fruits per cm2 branch cross-sectional area. There was little inhibitory effect of fruit mass independent of seeds. | |
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