22 Feb 2024
Citrus Fruit Variety

Increasing fruit size in Citrus. Thinning and stimulation of fruit growth

The importance of fruit size as a parameter of quality of citrus fruits has increased markedly in recent times. The consumer’s marked preference for large fruit causes huge differences in price between large and small fruit to the point that the income from the smaller fruit is often less than picking and hauling costs. Fruit size has become as important as yield in the determination of the profitability of citrus plantings, and an economic premium is usually obtained through the increase in fruit size even at the expense of a reduction in crop yield. This applies not only to the small fruited mandarins and hybrids but also to large fruit species such as lemons, oranges and grapefruit. To increase fruit size beyond the limits which may be obtained through the optimization of the standard cultural practices (fertilization, irrigation, pruning), several techniques have been tried such as hand thinning [80], chemical and hormone thinning [49, 77] and the hormonal  stimulation of fruit growth rate by synthetic auxins [69, 70, 71]. The earlier investigations on this subject were reviewed extensively by Coggins and Hield [12], Monselise [57] and Wilson
[78], which pointed out some drawbacks encountered with the use of these techniques in practice. Particularly, the application of synthetic auxins to increase fruit size often resulted in too erratic results to justify the use of these compounds by the growers [57].


29 Sep 2023
Hand thinning citrus

Reviewing the Commercial Potential of Hand Thinning in Citrus with a Cost-benefit Analysis of Summer Hand Thinning of ‘Nadorcott’ Mandarin

Hand thinning is not often applied as a commercial cultural practice in citriculture due to the practice’s reliance on costly manual labor. However, hand thinning could provide unique benefits such as treatment selectivity and easier control over thinning intensity, as opposed to foliar sprays of chemical thinning agents. In ‘‘on-year’’ ‘Nadorcott’ mandarin (Citrus reticulata) trees, summer (January) and autumn (April) hand-thinning treatments of removal of all fruit <20 and <40 mm diameter were evaluated for effects on leaf carbohydrates and fruit growth rate. Other factors assessed included treatments’ effects on tree total fruit yield, fruit quality, and fruit size distribution. In addition, two different summer hand-thinning treatments (removal of all fruit <20 and <25 mm) were evaluated for effects on fruit size distribution and fruit yield over two seasons to determine their potential financial implications.


21 Apr 2023
Citrus flower and leaves

Changes in carbohydrates and mineral elements in Citrus leaves during flowering and fruit set

Mineral elements and metabolizable carbohydrates in Citrus leaves [Citrus sinensis (L.) Osbeck cv. Washington navel] have been determined from bud sprouting until the end of the June drop and related to fruitlet growth and abscission. Mineral elements in old leaves decreased during the spring flush of growth and reached minimum values at flower opening, coinciding with a peak in abscission. This was followed by a rapid recovery in potassium and nitrogen to the initial values, with little change afterwards. Old leaves accumulate carbohydrates until flowering, and lose them during post-anthesis at a constant rate for more than 4 months; this rate of export is unaltered by the presence of a nearby growing fruit. Inflorescence leaves accumulate carbohydrates and mineral elements during post-anthesis; during the June drop there is an interruption in the accumulation of nitrogen and a net loss of phosphorus, potassium and carbohydrates from these leaves, coinciding with the attainment of the maximum growth rate of the fruit.


31 Jul 2019
Citrus Improvement

Quality and Quantity Improvement of Citrus: Role of Plant Growth Regulators

Harsimrat K. Bons, H.S. Rattanpal
Department of Fruit Science, Punjab Agricultural University, Ludhiana, Punjab, India.
Nirmaljit Kaur
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.