Citrus is the main fruit tree crop in the world and therefore has a tremendous economical, social and cultural impact in our society. In recent years, our knowledge on plant reproductive biology has increased considerably mostly because of the work developed in model plants. However, the information generated in these species cannot always be applied to citrus, predominantly because citrus is a perennial tree crop that exhibits a very peculiar and unusual reproductive biology.
Weather and genetics have the strongest impact on reproductive response of citrus. Flowering is primarily determined by the amount of cool temperatures and/or drought as well as previous crop load and amount of year-old flush. Citrus in many locations in the Americas responds to both cool temperatures and drought in establishing the flowering level for the next season. Some major factors involved in regulation of fruit set are temperatures, evapotranspiration balance against available soil moisture, and competition with growth amongst fruit and vegetative flush.
Girdling increases carbohydrate availability and fruit-set in citrus cultivars irrespective of parthenocarpic ability
F. Rivas, M. Juan, V.Almela, M. Agusti
Departamento de Producción Vegetal, Cátedra de Citricultura, Universidad Politécnica de Valencia.
Departamento de Citricultura, Instituto Valenciano de Investigaciones Agrarias. Valencia, Spain
Department of Fruit Tree Sciences. Israel
The effects of girdling performed at various dates were evaluated during two consecutive years in high- and lowbearing commercial orchards of ‘Fortune’ mandarin and ‘Clausellina’ Satsuma mandarin. The time-dependent response was evaluated through fruitlet abscission, final fruit-set and yield as related to carbohydrate contents in developing fruitlets. A few days after treatment, girdling increased the soluble sugars content (SSC) in fruitlets, reduced the daily fruit drop, and thereby diminished abscission. Application of girdling to low-bearing ‘Fortune’ mandarin orchards was most effective 15 d before anthesis (DBA) and 35 d after anthesis (DAA). It increased yield by 125%. In high-bearing orchards, the best results were achieved by girdling 35 DAA, which increased yield by 28%.