ROLE OF PRUNING IN CITRUS, TIMING AND ITS IMPACT ON TREE AND FRUIT

*Muhammad Shafique Khalid, *Muhammad. Amin, *Omer Hafeez, **Muhammad Umar and **Faheem Haider

* PhD Scholar, Institute of Horticultural Sciences, University of Agriculture Faisalabad

** M.Sc Scholar Institute of Horticultural Sciences, University of Agriculture Faisalabad

Pruning fruit trees is a technique that is employed by gardeners to control growth, remove dead or diseased wood or stimulate the formation of flowers and fruit buds. Pruning of tree fruits and vines is a horticultural practice handed down from ancient time. It has in common the objectives of manipulating various aspects of vegetative and fruiting behaviour. Some of the benefits traditionally attributed to pruning and girdling in the practical culture of citrus have been called into question by field research in the past few decades.

Citrus is a perennial crop. As long as the trees remain healthy, they can flower and fruit for years on end, some times for as long as twenty or thirty years (Mazhar and Nawaz, 2006). However, if the trees are not maintained at a proper size, the height and canopy shape of mature trees in a citrus orchard will not be uniform and the branches will be too crowded. In a crowded orchard, disease and pests can spread quickly. Fruit quality tends to be poor, and trees may not bear fruit every year. A proper training and pruning program is essential for the maintenance of a healthy and productive orchard.

Benefits of pruning in citrus

The major benifits of pruning in citrus include:

1. The total effective leaf area is increased resulting in increased photosynthesis by exposing the leaves to light and air.
2. The water use efficiency and the conversion of available plant nutrients is increased.
3. By removing diseased or infested branches and exposing leaves to light and air, a good training and pruning program helps control pests and diseases in citrus orchard.
4. Proper pruning of the tree keeps it in the right size.
5. It also increases the vigor of the tree, enhances its tolerance of various stresses, and helps maintain the most efficient balance between vegetative growth and fruiting.

Pruning and skirting (removal of low-hanging limbs) affects on canopy temperature, relative humidity (RH), and fruit yield and quality of Orlando' tangelo trees (Citrus paradisi Macf. x Citrus reticulata Blanco). Pruning increased the percentage of large fruit and reduced the percentage of small fruit. (Morales et al., 2000).

The alternate tendency exists across all varieties of the citrus. To attenuate alternate bearing, pruning and fertilization are processes the only options which growers can exploit. For pruning to be effective, it must be done after the end of an “off” or light crop year, i.e., prior to the season of anticipated high production. It should not matter whether the pruning is conducted before or after the bloom, as the results should be about the same, reduction in production during the season following pruning (Mazhar and Nawaz, 2006).

Eissenstat and Duncan (1992) reported that total reducing and ketone sugars (free fructose, sucrose and fructans) in the fine roots were less in pruned than unpruned trees 20 days after pruning, but not thereafter. By 30 days after pruning, at least 20% of the roots of the pruned trees at a soil depth of 9 to 35 cm apparently died. By 63 days after pruning, root length density had recovered to that of the unpruned trees, although starch reserves were 18% less in the fine roots of pruned than unpruned trees at this time.

Growers should select the correct time for the pruning. Since citrus trees are evergreen, they do not have a period of true dormancy. However, the metabolism of the tree is less active in the period after fruit harvesting. This period of reduced metabolism activity is the time to prune. Light pruning can also be conducted at other seasons to remove unwanted and overcrowded shoots.

Tree age is another important factor that should be taken into account, because the tree’s response to pruning varies according to age (Mazhar and Nawaz, 2006). Therefore citrus growers have to recognize the characteristics of the different cultivars they are growing in order to select the best training and pruning system for their orchards.

References:

Eissenstat D.M and L.W Duncan.1992. Root growth and carbohydrate responses in bearing citrus trees following partial canopy removal. Tree Physiol. 10(3): 245-57.

Mazhar, M.S. and M.A. Nawaz. 2006. Pruning as a tool to improve yields in citrus. Pakistan Horticulture. 4(1): 23-25.

Morales, P., F.S. Davies and R.C Littell. 2000. Pruning and skirting affect canopy microclimate, yields, and fruit quality of 'Orlando' tangelo. Hort Science. 35: 30-35.

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KINNOW MANDARIN: THE PREMIER CITRUS OF PAKISTAN

*Muhammad Shafique Khalid,** Aman Ullah Malik,* Samina Khalid,* Omer Hafeez and *M. Amin

* PhD Scholar, Institute of Horticultural Sciences, University of Agriculture Faisalabad

**Professor, Institute of Horticultural Sciences, University of Agriculture Faisalabad

Kinnow mandarin (Citrus reticulata Blanco) is one of the major citrus cultivars and is extensively grown in Pakistan. It was developed by H.B. Frost at California as hybrid (F1 generation) between King and Willow leaf during 1915; released in 1935 and was introduced in sub continent during 1943-44. The first plantation in Pakistan was made at Experimental Fruit Garden of Punjab Agricultural College and Research Institute Lyallpur (now University of Agriculture, Faisalabad). Since its introduction, it has flourished well under the agro-ecological conditions of Punjab, Pakistan. According to an estimate approximately 95% of the world Kinnow is being produced in Pakistan (Anonymous, 2011). The Kinnow fruit of Pakistan possesses superior taste, flavor and aroma and competes well with other citrus cultivars in qualitative and nutritive attributes as under:

Ø Kinnow grown in Pakistan is naturally coloured, no chemical degreening is needed.

Ø The fruit peel off very easily unlike other citrus members.

Ø Kinnow mandarin fruits have higher juice contents i.e. 53% as compared to other citrus varieties e.g. Grapefruit (48.50%), Blood Red (37.7%). Even Kinnow is juicier than Clementine mandarin.

Ø Kinnow has 18.59% more vitamin C as compared to Blood Red orange, 9.9% than Musambi and 6.65% than Grapefruit. Vitamin C protects against cancer by scavenging their causing compounds.

Ø As far as minerals contents (calcium, iron, magnesium, potassium and sodium) are concerned, Kinnow possess 11.11% more calcium than Grape fruit, 14.50% than Blood Red and 16.27% than Musambi. Similarly Kinnow has 10.73% higher Magnesium contents than Grapefruit, 14.19% than Blood Red and 15.87% than Musambi. Iron contents are also 7.93% greater in Kinnow than Grapefruit, 11.47% than Blood Red and 28.30% than Musambi.

Ø Kinnow mandarin is also loaded with photochemicals like antioxidants and phenolic compounds. Almost 16.18% high phenolic compounds are present in Kinnow as compared to Blood Red.

Ø Kinnow has about 16.14%, 6.05% and 47.02% higher antioxidant activity than that of Blood Red, Hamlin and Lemon respectively. These compounds are very important due to their antiallergic, anti inflammatory, anticancer and antiviral properties

Ø Kinnow mandarin is good source of Folic acid, β-carotene etc. Folic acid is recommended before and early pregnancy for healthy babies (avoiding neural tube defects). While β-carotene is important in immune response and also acts as antioxidant.

Ø Consumption of Kinnow fruits can provide sufficient quantities of pectin in diet as juice sac walls and capillary membranes are effective source of pectin. Pectin affects several metabolic and digestive processes most important of them are its affect on glucose absorption and maintaining cholesterol levels. Dietary fiber also reduces the chances of colon cancer by absorbing carcinogen in gastrointestinal tract.

Table 1: Biochemical profile of Kinnow mandarin of Pakistan

1. Juice (%age)^* 51-54

2. TSS ^oBrix^* 09-10.3

3. Acidity (%age)^* 0.55-1.0

4. Ascorbic acid (mg/100ml)^* 41-53

5. Total Sugars (%age)^* 7.2-7.5

6. Total phenolics compound (ppm) ^* 852-1059

7. Antioxidant activity (I %)^* 65-73

8. Calcium (mg/100ml)⁺ 0.750

9. Iron (mg/100ml)⁺ 0.338

10. Magnesium (mg/100ml)⁺ 7.48

SOURCE: ^*Khalid and Malik (unpublished data); ⁺Rashid, (2007);

Variation exists for different maturity stages

Table 2: Biochemical profile of other citrus varieties grown in Pakistan.

Grape fruit Blood Red Musambi

1. Juice (%age)^{** *} 48.50 37.70 54.0

2. TSS ^oBrix⁺ 7.50 10.0 10.5

3. Acidity (%age) ⁺ 1.39 0.55 0.32

4. Ascorbic acid (mg/100ml)⁺ 46.39 36.38 43.45

5. Total Sugars (%age) ⁺ 5.3 5.55 8.51

6. Total phenolics compound (ppm) ---- 255.0^** ----

7. Antioxidant activity (I %) ---- 49.1⁺⁺ ----

8. Calcium (mg/100ml) ⁺ 0.602 0.562 0.542

9. Iron (mg/100ml)⁺ 0.287 0.268 0.188

10. Magnesium (mg/100ml)⁺ 6.03 5.62 5.42

SOURCE: ⁺ Rashid, (2007); ^** Tounsi et al. (2010); ⁺⁺Scalzo et al. (2004); ^{** *}Ikhtiar et al. (2010)

Variation exists for different maturity stages

Table 2: Biochemical profile of citrus varieties grown in USA.

	Tangerine	Clementine	Navel	Valencia	Grapefruit	Lemon
Energy Kcal	53	47	49	49	32	29
Total lipids (g)	0.31	0.15	0.15	0.30	0.10	0.30
Carbohydrates(g)	13.34	12.02	12.54	11.89	8.08	9.32
Dietary fiber (g)	1.8	1.7	2.2	2.5	1.6	0.4
β Carotene (mcg)	155	----	87	----	552	3
α Carotene(mcg)	101	----	7	----	4	1
β Crytoxanthin, (mcg)	407	----	116	----	6	20
Vitamin A IU(IU)	681	----	247	230	927	22
Vitamin E (mg)	0.20	0.20	0.15	----	0.13	0.15
Folate (mcg)	16	----	34	39	10	11

SOURCE: USDA National Nutrient database (2010)

It is clearly concluded from above facts and figures that Tangerine including Kinnow has higher energy, carbohydrates, carotenes, Vitamins, Minerals contents (Ca, Mg and Iron), Juice percentage, Phenolics compound and Antioxidant activity than other citrus varieties grown nationally and internationally. Its distinguished features like natural color, easy peel, aroma, size and good blend of TSS to acidity ratio is an asset and worth for consumer attraction and export of Kinnow from the country.

References:

Anonymous, 2010. U.S. Department of Agriculture, Agriculture research service data base for standard reference release 23. Available at: www.ars.usd.gov/ba/bhnrc/ndl. Date of retrieval: 25 Jan 2011.

Anonymous, 2011. All about Citrus. Available at: http://www.pakissan.com /english/allabout/ orchards/ citrus/index.shtml. Date of retrieval: 25 Jan 2011.

Khalid, S. and Malik, A.U. Fruit quality and storability of Kinnow mandarin (Citrus reticulata Blanco) in relation to tree age. (Unpublished data).

Khan, I., Shah, Z., Saeed, M. and Shah, H. 2010. Phytochemical analysis of Citrus sinensis, Citrus reticulata and Citrus paradise. J. Chem. Soc. Pak., Vol. 32(6). 774-780.

Rashid, A. 2007. Evaluation of organic acids and mineral contents in citrus juices. M.Sc (Hons) Thesis, National Institute of Food Science and Technology (NIFSAT), University of Agricutlure, Faisalabad, Pakistan.

Scalzoa, R.L., Iannoccari, T., Summa, C., Morelli, R. and Rapisarda, P. 2004. Effect of thermal treatments on antioxidant and antiradical activity of blood orange juice. Food Chem. 85, 41–47.

Tounsi, M. S., Wannes, W. A. Ouerghemmi, I. Jegham, S. Njima, Y. B., Hamdaoui, G. Zemnib, H. and Marzouka, B. 2011. Juice components and antioxidant capacity of four Tunisian Citrus varieties. J Sci Food Agric. 91: 142–151.

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Promoting Floriculture

By Dr S M Alam

FLORICULTURE is fast emerging as a profitable venture and the country is also earning a sizable foreign exchange by exporting roses to Middle East and European countries.
The local production of cut flowers is estimated at about 10,000-12,000 tons per annum. Roses are popular crop for both domestic and commercial cut flowers. They are harvested and cut when in bud and held in refrigerated conditions until ready for display at their point of sale.
Both local and grafted roses are grown in all the four provinces of the country, but Punjab has lion’s share in production of grafted roses and supply to all the cities of the country.
Roses may be grown in any well-drained soil with optimum sunlight. Most rose varieties are grown by budding on lower portion of a plant and propagated from seeds or cuttings. Clay soils, warm temperatures are always preferred, and the rose plants grow best when not set among other plants. Cow manure is the preferred fertilizer for rose cultivation, but other organic fertilisers, especially composts, are also used.
Rose plants usually require severe pruning, which must be adapted to the intended use of the flowers. Pattoki, a small town about 80-km south of Lahore, has emerged as a leading home for cut flower floriculture technology. More than one million pieces of cut flowers are sent daily from this town to all the major cities of the country. The availability of flowers and ornamental plants has recently increased with change in crop production priorities and rise in living standards. The availability of pick flowers of red rose in use since ages for garlands has increased manifold. Additionally, cut flowers for flowers arrangements have sprung up in market due to demand pull by the local consumers.
The demand for long stem roses, tube roses, gladioli has tremendously increased. In order to explain the cultivation of these plants, import of quality hybrid flower seeds and planting material may be allowed free of duty to promote production of quality leading to export. The small items of machinery and shading nets to be used by the flowers and ornamental plant nurseries should be exempted from the levy of duty.

Roses are best known as ornamental plants grown for their flowers in the garden and sometimes indoors. They have been also used for commercial perfumery and commercial cut flower crops. Some are used as landscape plants, for hedging and for other utilitarian purposes such as game cover. They also have minor medicinal uses. The majority of ornamental roses are selected hybrids. A few, mostly species roses are grown for scented foliage, ornamental thorns or for their ornamental fruit.
Rose perfumes are made from attar of roses or rose oil, which is a mixture of volatile essential oils obtained by steam distilling the crushed petals of roses. An associated product is rose water which is used for cooking, cosmetics, medicine and in religious practices. Rose water made as a byproduct of rose oil production, is widely used in Asian and Middle Eastern cuisine. The French are known for their rose syrup, most commonly made from an extract of rose petals.
By observing the rapid growth in cut flower export, this business can become Pakistan’s second largest export sector after textile if the government encourages the cut flower growers by facilitating them to provide better technology in the year round production, refrigerated transportation and exploring more foreign markets.
The world trade of cut flowers runs in billion of dollars and Holland serves as the centre of cut flower business.
The cut flowers trade is tremendously increasing due to its demand worldwide. The cut flowers importing countries are: Australia, Denmark, Dubai, France, Italy, Saudi Arabia, South Africa, Syria, Turkey, U.S.A. and United Kingdom and the major suppliers are Colombia, Ecuador, India, Israel, Kenya and Zimbabwe.
^{Courtesy: The DAWN}

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