Granulation : A Major Threat in Citrus Production
Author: Rajni Sinha

Citrus is the world’s leading fruit crops. The major citrus producing countries are Spain, USA, Israel, Moracco, South Africa, Japan, Brazil, Turkey and Cuba. India ranks 6^th in the production of citrus fruit in the world and contributes its share in area is 1077.7 thousand hectares and total annual production of 11147.1 thousand tones with productivity 10.3 tone /ha of total fruit production in India. It keeps 3 ^rd position after mango and Banana. Citrus fruit have been originated in subtropical and tropical region of South East Asia mainly India and China. It is quite important as it has a great variety of beverage, industrial and medicinal

uses due to its attractive colour, distinctive flavour, refreshing juice and being rich source of vitamin ‘C’, vitamin ‘B’, β-carotene, calcium and phosphorous. Citrus comprises many species of economic importance. In India few species are commercially cultivated, which include grape fruit, lemons, limes, sweet oranges, and mandarins. Mandarin is one of the most important citrus crops covering 4.6 % of area and 3.9 % of production followed by sweet orange and then lime and lemon. It can be grown in wide range of soil and climate. In India this is particularly grown in Maharashtra, Andhra Pradesh, Punjab, Karnataka, Uttaranchal, Bihar, Assam, and Gujarat. Citrus fruits suffer from several physiological disorders, of which juice-sac granulation is of serious nature which drastically affect citrus production.Granulation is a serious pre-harvest disorder of juice sacs of citrus fruit, wherein they become hard, dry and enlarged, assume a greyish colour and have little free juice. It was first reported by Bartholomew et al. (1934) in California, and later by many researchers from different citrus growing countries. Granulation is known by different names, e.g. dryness, kaosan and crystallization, but the term granulation is commonly used throughout the world. Granulation affect severely the Pineapple, Washington Navel, Hamlin, Blood Red, Mosambi and Valencia Late cultivars of Sweet orange and mandarin cultivars like Kaula, Nagpur and Dancy but the disorder is less serious in other citrus fruits like, grapefruit, pummelo, lemons, limes, tangors and tangelos (Singh, 2001). However, the phenomenon of juicy sac granulation, which causes Citrus quality to decline in the process of postharvest storage, seriously affects the Citrus edible value and commodity value. Although the problem of granulation has been encountered in many citrus growing countries of the world, its exact cause are not yet fully understood. However, there are several factors, e.g. frequent irrigation, high application rates of nitrogenous fertilizers, luxuriant growth following heavy pruning or fertilization, and delayed harvesting, are reported to be associated with the disorder. It has been also investigated that problem is further complicated by climatic factors, tree aspect, fruit size and tree age. Granulation is associated with lower acid, sugar levels, total phenolics

content, antioxidants and phenyl ammonia lyase activity within the fruit and increased content of senescent related enzymes like lipoxigenase (LOX) and pectin methyl esterase (PME) activity and respiration or ethylene evolution rate. Many of the factors mentioned above relating to granulation also result in reduced internal sugar and/or acid content (e.g. late bloom fruit, large fruit, high temperatures, increased fruit water content through irrigation or rain, shaded conditions etc.).

Major cause related to granulation :

Delayed harvesting – The most common cause of dry citrus fruit is when the fruits are left too long on the tree after they are fully ripe. Fruit harvested later in the season will be more affected than fruit harvested earlier in the season. So, it is advisable to pluck fruits at proper maturity otherwise deteriorates quality.

Improper irrigation and nutrient management -- If the tree receives too little water while in fruit, this can cause dry oranges .Too much nitrogen can cause dry orange fruit. This is because nitrogen will encourage rapid growth of foliage at the expense of the fruit. In the areas with high incidence of granulation, the plant tissues contain high Ca and Mn, and low P and B. So, it is crucial to apply efficient dose of fertilizer according to standard fertilizer schedule.

Adverse atmospheric condition - If weather is unseasonably warm or persistent cold weather throughout the period of maturity while the fruit on tree, this can be a cause of dry fruit. When a tree suffer tension from weather conditions, the fruit will suffer while the tree works to survive the unexpected conditions.

Selection of Rootstock - Granulation was significantly influenced by different rootstocks, being high with vigorous rootstock, and low with dwarfing rootstock.

It has been also found that the incidence of granulation is relatively higher in large sized fruit compared with small fruit and the fruit of younger plants as compared to those in older plants.The incidence of granulation could be reduced to 50 per cent by applying two to three sprays of NAA (300 ppm) in the months of August, September and October. Spraying of GA 15 ppm followed by NAA 300 ppm in October and November also reduce granulation.

References:

1. Bartholomew, E.T., Sinclair, W.B., Raby, E.C., 1934. Granulation (crystallization) of Valencia oranges. Calif.Citrogr. 19, 88â€"89, 106, 108.

2. Singh, R., 2001. 65-year research on citrus granulation. Ind. J. Hort. 58 (1â€"2), 112â€"144.


About Author / Additional Info:
I am Ph.D research scholar in department of Horticultue (Fruit and Fruit Technology )at Bihar Agricultural University,Sabour,Bhagalpur