The Valencia orange is a high quality fruit grown in Turkey; however, small fruit size resulting in poor packouts is common in Valencia oranges. Small fruit size is the main factor limiting the marketing of Valencia oranges; thus, synthetic auxins are commonly used to enhance the size of citrus fruit. The objective of the present study was to observe the effects of 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6-TPA) on fruit size, yield and quality of Valencia oranges from 29-year-old trees budded on sour orange rootstock in Adana, Turkey in 2006. The application of 3,5,6-TPA to the entire tree was from 8th to 11th week after anthesis during June drop (JD). Following 3,5,6-TPA treatments, different combinations were used in the experiment: T1 2 tablets per 100 litres applied just after the end of June drop (JD), T2 2 tablets per 100 litres applied 5-7 days after the end of JD, T3 3 tablets per 100 litres applied 5-7 days after the end of JD, T4 4 tablets per 100 litres applied 5-7 days after the end of JD, T5 3 tablets per 100 litres applied 10-14 days after the end of JD and control trees receiving no 3,5,6-TPA (T0).
Effects of NAA and GA3 Sprays on Fruit Size and the Incidence of Creasing of ‘Washington’ Navel Orange
‘Washington’ navel orange [Citrus sinensis (L.) Osb.] orchards in Israel suffer from creasing – a physiological disorder of the fruit, leaving the fruit unsuitable for the fresh fruit market. Many ‘Washington’ navel orchards tend to bear small size fruit with low market value. This paper presents two experiments, in which the effects of naphthaleneacetic acid (NAA, 300 mg·L-1) on yield, fruit size, fruit quality and the incidence of creasing of ‘Washington’ navel orange were examined. The NAA effects were compared to those of gibberellic acid (GA3, 20 mg·L-1) – the common treatment for creasing reduction. In the first experiment, 36% of the fruit of the control trees suffered from severe creasing. The NAA sprays in May (at 18-mm fruitlet diameter) and in June (at 30-mm fruitlet diameter) reduced the incidence of creasing to 9 and 6% respectively, while the GA3 spray at August reduced the incidence of creasing to 17% of the fruit.
Plant growth regulators (PGRs) are a tool used to manipulate vegetative and reproductive growth, flowering, and fruit growth and development. PGRs have been successfully used in agriculture for decades to amend plant growth characteristics and maximize yield and thus grower profit. Foliar-applied PGRs are routinely used in various fruit crops for flower and fruit thinning, improving fruit set, growth and development, controlling vegetative growth, and reducing fruit drop. Citrus is no exception to the use of PGRs, which can provide significant economic advantages to citrus growers when used appropriately.
According to the Florida state legislature, PGRs are defined “as any substance or mixture of substances intended, through physiological action, for accelerating or retarding the rate of growth or maturation or for otherwise altering the behavior of ornamental or crop plants or the produce thereof, but not including substances intended as plant nutrients, trace elements, nutritional chemicals, plant inoculants, or soil amendments.”
Harsimrat K. Bons, H.S. Rattanpal
Department of Fruit Science, Punjab Agricultural University, Ludhiana, Punjab, India.
Department of Botany, Punjab Agricultural University, Ludhiana, India.
Citrus is one of the most important fruit tree species in the world, as the fruits are a valuable source of nutrients, vitamins and other antioxidant compounds. The citrus productivity depends on various factors, among these the plant growth regulators holds a prime position. The use of plant growth regulators has become an important component in the field of citriculture because of the wide range of potential roles they play in increasing the productivity of crop per unit area. The plant growth regulating compounds actively regulate the growth and development by regulation of the endogenous processes and there exogenous applications have been exploited for modifying the growth response.
Paul J. R. Cronje
Citrus Research International | Department of Horticultural Science, Stellenbosch University
Ockert P. J. Stander and Karen I. Theron
Department of Horticultural Science, Stellenbosch University
Various citrus cultivars of ‘Navel’ and ‘Valencia’ orange [Citrus sinensis (L.) Osbeck], as well as mandarin and mandarin hybrids (Citrus reticulata Blanco) are prone to a preharvest physiological rind disorder, known as fruit splitting.
Similar disorders occur as fruit cracking and/or splitting in other commercially important horticultural crops, most notably in apple, apricot, cherry, grape, nectarine, prune, and tomato. Fruit splitting in citrus differs from other crops due to the unique morphology of a citrus fruit, consisting of the pulp and rind, which is made up of the spongy white internal layer, the albedo (mesocarp), and the external layer, the flavedo (exocarp).