Most effecting Factors in Citrus Fruit Quality?

Most Effecting Factors in Citrus: Which are affecting the Fruit Quality?

Mehvish Sadique¹, Rashad Mukhtar Balal¹, Muhammad Adnan Shahid^1,3_, Muhammad Zubair¹ and Mujahid Ali²

1. Department of Horticulture, University College of Agriculture, University of Sargodha
2. Institute of Horticultural Sciences, University of Agriculture, Faisalabad
3. Horticultural Sciences Department, Institute of Food & Agricultural Sciences, University of Florida, Florida, USA.

Citrus is a main fruit in the world and it has a great economic, social and cultural impact in the society. It is cultivated all over the tropical and sub-tropical world (Sidana et al., 2013). Citrus fruit belongs to the family Rutaceae. A large number of citrus varieties found in the world such as Lime, Kinnow, Mandarin, Minneola, Grapefruit, Satsuma, Sweety and Pummelo but oranges and lemons are most famous among all varieties. Pakistan is at 10^th position in citrus production in the world (Anonymous, 2017). In Pakistan citrus fruit grown on an area of 192832 hectres with an annual production of 2395550 tones (Fruit, vegetables and condiments statistics of Pakistan 2016-17). The potential yield of citrus is 18-20 tons per hectare and average yield is 12.78 tons per hectare (Anonymous, 2006).

Citrus has an Indo-Chinese origin and in Chinese literature it was first mentioned in 2200 BC (Anonymous, 2006). Orange juice production and citrus processing mainly occur in Florida but California is the main producer for fresh consumption of citrus fruit (USDA, 2010). China produces more citrus in the world followed by Brazil, India, USA and Mexico (Anwar et al., 2008). After grapes citrus stands on 2nd rank contributing over 70 million tons per annum and occupy 1st position in terms of trade revenue of fresh fruits (FAO, 2012). Citriculture is commercially followed in more than 52countries of the world (Ahmad et al., 2006). Citrus is the leading fruit in terms of area, yield and export. The present status of citrus is defenseless due to many factors, which impede the yield and quality of fruit. Citrus is considered as evergreen trees and shrubs. Citrus fruit has great nutritional values. It contains vitamin A, B, minerals, ascorbic acid, phosphorus, iron and calcium which increase its nutritive properties (Niaz et al., 2004). Citrus is a good source of vitamin C. It also contains minerals and 3-4% sugar which are very important for proper health (Shah, 2007). Citrus fruit is good medicine to cure lungs infection, skin cancer, liver, birth defects and also good for heart diseases (Ghirdharilal, 2000).

Citrus produces in all four provinces of Pakistan but Punjab produces 95% of the fruit because of its suitable growing conditions, huge population and sufficient amount of water. Punjab’s distribution is biggest in Pakistan owing to its climate (Sharif, 2004). The most important citrus producing districts in Punjab are Sargodha, Sahiwal and Toba Tek Singh. In Sargodha, citrus grown on an area of 89,399 ha with the total production of 1,025,007 tonnes. This fruit is the major source of income for the small size traders and growers (Safdar et al., 2010). Citrus increases the economy of Pakistan because it is a source of foreign exchange (Ganwar and Lal, 1988). Due to extensive range of varieties, distribution and high nutritive values, sweet orange (Citrus sinensis Osbeck) is prominent in the world Citriculture. More than 60 percent world citrus production is contributed by the sweet orange. At this time USA Brazil and China are leading sweet orange producing countries with 24, 10 and 3 MMT production correspondingly (Anonymous, 2017).

Sweet orange is a small evergreen tree 7.5 m high and in some cases up to 15 m. This fruit originated from southern China but now a day grown commercially in tropical, sub-tropical and other temperate regions of the world (Ethler, 2011; Nicolosi et al., 2000). The pulp of citrus fruit is very sweet and juicy, containing 10 to 14 segments and color of fruit ranges from yellow to orange to red (Atta et al., 2012). Sweet orange contain, 9.35 g sugars, 197 KJ (47 kcal) energy, 2.4 g Dietary fibre, 0.12 g fats, 0.94 g proteins, 86.75 g water, 11 µg (1%) vitamin A, 0.18 mg (1%) vitamin E, 53.2 mg (64%) vitamin C, 0.087 mg (8%) vitamin B1, 0.06 mg (5%) vitamin B6, , 0.04 mg (3%) vitamin B2, 40 mg (4%) calcium, 0.1 mg (1%) Iron, 10 mg (3%) magnesium, 0.025 mg (1%) manganese, 181 mg (4%) potassium and 0.07 mg (1%) Zinc (USDA Nutrient Database, 2014).

Essential oils produced from orange peel are the most important and commonly used for flavoring in several beverages, toothpastes, foods and cosmetics (Orav and Kann, 2001). An orange fruit contains 60 calories. It is also a rich source of beta-carotene and bioflavonoid and all these components are very important in healthy diet (Lee and Kader, 2000). Jaffa was introduced to Florida from Palestine in 1883. The fruit of Jaffa is commercially seedless (0-6 seeds), small to medium with a smooth and thin peel. The peel color of fruit is yellow like its juice color. The flesh is of very high quality and melting in texture producing a thick, nectar-like juice. Pineapple orange is medium-large, sometime flattened on both ends, with a fairly thick and smooth peel. Under cool night conditions it develops good orange color. Juice quality and color are very good. It generally contains 15-25 seeds. In Florida it is the favorite mid-season orange.

Pineapple is also known as Pineapple-156, Hickory, Ridge seedling and Ridge Pineapple. Salustiana has medium-large fruit and almost seedless. The surface of fruit is moderately pebbled and rind is medium-thick. The flesh is very juicy and flavor is sweet and rich. Salustiana is a highly-regarded variety because of its seedlessness, early maturity and high quality (http://citruspages.free.fr/sweetoranges.html). Citrus cultivation has been flourished due to its ornamental value and fruit quality. Citrus is at top among other fruit crops in Pakistan. Pakistan is the sixth largest producer of oranges and kinnow, generating 95% of the world Kinnow production. Pakistan citrus industry is contributing 1% of fresh fruit from 2% area of cultivation yielding approximately 12.7 tons per hectare. Citrus is contributing 25% fruit production, of which Punjab’s share is 95% (Anonymous, 2010).

Fruit quality is defined both its pre and post harvest factors such as changes in flavor, texture and colour as fruits develop, grow and ripen, as well as its maintenance following harvest as the perishable tissues senesce (Ogundiwin et al., 2009). Fruit quality includes various internal and external factors on the basis of which, minimum standards of palatability and commercial acceptability have been established over the years (Davies and Albrigo, 1994). In citrus fruit, external factors like fruit colour, size and texture are very important to check the quality of the fruit, while internal characters include seediness, vitamin C contents, amount and quality of juice, TSS, TSS:TA ratio  and titratable acidity (TA) (Ahmad et al., 2006). The factors which are mostly affecting fruit quality are stage of maturity and type of cultivar. Many factors like EC of soil and pH badly affect the quality of citrus fruit (Avais et al., 2011).

Production of citrus depends on many biotic (rootstock, cultivar, insect pest & disease management) and abiotic (climate, site, soil, nutrition & irrigation and nutrition management) factors (Davies and Albrigo, 1994; Iglesias et al., 2007). Now a day’s in Pakistan Citrus orchards are facing many problems like fruit size, color, quality and premature fruit drop. These problems occur due to the deficiencies of essential nutrients (Ibrahim et al., 2007). The production of plant growth regulators disturbs due to the deficiency of nitrogen (Ibrahim et al., 2007; Ashraf et al., 2012; Razi et al., 2011). Maturity has a great effect on the quality of fresh produce, also on the storage potential and incidence of many storage disorders (Siddiqui and Dhua, 2010). Soils having salt concentration more than 1000ppm should be avoided for good quality citrus production (Singh et al., 2002). The yield of grape fruits, oranges and lemons decreases 10-20 percent at EC levels 3, 3.5 and 2.5 dS/m (Muhammad, 2005). Citrus grows better in well aerated, deep loose soils free of any hard pan layer of calcium carbonate in root zone. The pH of Sargodha soils is 8.0- 8.8 (Chaudhry, 2003).