Fruit Set and Carbohydrate Status in Alternate and Nonalternate Bearing Citrus Cultivars

in Journal of the American Society for Horticultural Science
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  • 1 Department of Horticulture, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, Israel


A comparative study of fruit set of an alternate bearing cultivar of Citrus (‘Murcott’, a C. reticulata hybrid of unknown origin) and a nonalternating cultivar [C. sinensis (L.) Osbeck ‘Shamouti’] was conducted. ‘Murcott’ set a higher percentage of flowers (13.6%) than ‘Shamouti’ (3.8%), because of a higher abscission rate in ‘Shamouti’ throughout the fruit set period. Prebloom girdling increased fruit set significantly in ‘Shamouti’ but had a smaller effect in ‘Murcott’. The nonstructural carbohydrate balance of ‘Murcott’ and ‘Shamouti’ fruiting branches during fruit set as affected by girdling also were investigated. ‘Murcott’ generally had a higher starch content in the fruiting twigs and a higher starch and soluble sugars content in the mature, source leaves. Girdling increased the starch content in mature leaves and twigs of both ‘Murcott’ and ‘Shamouti’. This increase was observed in ‘Murcott’ 2 weeks after girdling, but only 4 and 8 weeks after girdling in ‘Shamouti’ leaves and twigs, respectively. ‘Shamouti’ mature leaves and twigs also had increased soluble sugars content because of girdling. In expanding new leaves, ‘Shamouti’ had similar or higher amounts of nonstructural carbohydrates than did ‘Murcott’, but during maturation, ‘Murcott’ young leaves developed a higher sugar starch content than ‘Shamouti’ young leaves, similar to the situation in mature one-year-old leaves. These results are discussed in terms of source-sink relationships and fruit set.

Contributor Notes

Lady Davis Postdoctoral Research Fellow.

Received for publication 19 July 1984. This research was supported by Grant No. 18380 from BARD, The United States-Israel Binational Agr. Res. and Development Fund. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.