Here is an essay on ‘Citrus’ for class 7, 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Citrus’ especially written for school and college students.
Essay on Citrus
- Essay on the Introduction to Citrus
- Essay on the Origin and History of Citrus
- Essay on the Area and Production of Citrus
- Essay on the Importance and Uses of Citrus
- Essay on the Choice of Varieties of Citrus
- Essay on the Raising of Rootstock of Citrus
- Essay on the Insects Pests in Citrus
- Essay on the Disorders Seen in Citrus
Essay # 1. Introduction to Citrus:
Citrus comprising of mandarins, sweet oranges, grapefruit, limes and lemons is most important fruit crop grown in India. Before partition of India, citrus industry has taken a strong foothold in the districts of Layallpur, Montgomery and Sargodha (now in Pakistan). In the present Punjab, then the plantings were restricted to the gardens of Maharajas, Princes, Nawabs and the rich people. To boost up citrus cultivation, the concept of garden colonies was introduced in the Punjab after 1947. Twenty- eight garden colonies were established throughout the State. In the early years of post-independence era, the cultivation of sweet orange to limited extent of local mandarin spread rapidly.
Citrus fruits are grown under varying agro-climatic conditions in all the States of the Indian Union, except in the high hilly temperate regions. The cultivation of citrus in the Northwestern States of Indian has steadily increased over the past few years due to its high productivity and adaptability to various agro- climatic regions. The area under citrus is likely to increase further if we try to match the production technology with the protection technology.
Essay # 2. Origin and History of Citrus:
Most of the citrus species are native to tropical and subtropical regions of South East Asia, particularly India and China and in the region between these two countries. The north-eastern region of India is considered as one of the natural home of few citrus species. Most of the taxonomists agree that the mandarin originated in Cochin China. However, Hodgson, a well-known American horticulturist, suspected that the mandarin is originated in eastern India. The existence of primitive forms like Citrus indica and several types of mandarin and mandarin like hybrids, growing wild in the forests of Assam lend support to this thinking.
Chinese literature written during 2200 BC showed evidence of citrus cultivation in China. Citrus was introduced in Greece between 250 and 200 BC. Bonnavia thought that Malaya is the home of lemon while pummelo is thought to be originated in the island east of Malaya archipelago, including Fiji and Friendly islands or in China. Citrus was probably introduced in Europe in 16th century by the Portuguese. It is believed that Columbus took orange and lemon seeds to America.
According to Bonnavia, the mandarin was introduced into Assam by Shan people who migrated westward from Yunan (China) and reached Southern Assam somewhere around the beginning of the Christian era. The spread of the mandarin from Assam to other parts of India particularly northern India seems to have taken place during the reign of Babar.
Kinnow, a hybrid between King mandarin and Willow leaf (Mediterranean mandarin), was developed by H.B. Frost in 1915 and released in 1935. A noble introduction of this cultivar made at Fruit Research Station, Layallpur (Now in Pakistan) inspired the growers to extend the cultivation in adjoining areas. In 1958 Dr. J.C. Bakhshi brought the virus-free bud wood of 25 different species of citrus-including Kinnow from California (USA).
The major citrus producing countries of the world are Brazil, USA, China, India, Mexico, Spain, Egypt, Italy, Indonesia, Turkey, Israel, Japan, Iran, Argentina, Morocco, Algeria, South Africa, Greece, Australia, Jamaica, etc.
Essay # 3. Area and Production of Citrus:
In India, citrus fruits (Mandarin, sweet orange and lime and lemons) are grown in 9.15 lakh hectares with total production of 79.22 lakh tonnes annually, accounts for 13.6 and 10.4 per cent of total area and production, respectively. Productivity of citrus varies from 4.4 to 21.9 tonnes per hectare depending agro- climatic regions which is much below the potential. Mandarin and sweet orange are grown mainly in Maharashtra, Andhra Pradesh, Punjab, Madhya Pradesh, Gujarat, Karnataka, Rajasthan, Assam, Odisha, Haryana and Uttarakhand.
Sweet orange (Mosambi) in India occupy an area of 1.62 lakh hectares, producing 12.32 lakh mt fruits accounting for 2.4 per cent and 1.6 per cent, respectively of total area and production under fruits. Major mosambi producing states are Maharashtra, Uttar Pradesh, Odisha, Punjab, Rajasthan, Madhya Pradesh, Kerala, Himachal Pradesh, Nagaland, Arunachal Pradesh, Assam, Meghalaya, Manipur, Tripura, Sikkim, Mizoram, Jammu and Kashmir, Haryana, Karnataka and Chhattisgarh.
Blood Red variety of sweet orange is mainly produced in Uttarakhand, Uttar Pradesh, Odisha, Punjab, Rajasthan, Madhya Pradesh, Maharashtra, Tamil Nadu, Chhattisgarh and Jharkhand. Sathgudi variety is mainly cultivated in Andhra Pradesh, Odisha, Tamil Nadu, Rajasthan and West Bengal. The average productivity of mosambi is 7.6 mt/ha. Andhra Pradesh is producing 46.8 per cent mosambi fruits among the states.
The total area under mandarin in India is 3.29 lakh hectares producing 31.29 lakhs mt fruits. The average productivity is 9.5 mt/ha. The area and production under mandarin is accounting for 4.9 per cent and 4.1 per cent, respectively of the total area and production under fruits. The highest production of mandarin i.e. 9.15 lakh mt is recorded in Punjab which is 29 per cent of total mandarin production in the country and productivity is 21.4 mt/ha. The other mandarin producing states are Madhya Pradesh, Andhra Pradesh, Maharashtra, Rajasthan, Assam, Karnataka, Manipur and Tripura.
Kinnow is the leading cultivated mandarin variety in Punjab, Rajasthan, Haryana and Uttar Pradesh. Nagpur mandarin is mainly growing in Maharashtra, Karnataka, Madhya Pradesh, Uttar Pradesh and Tamil Nadu. Khasi mandarin is grown commercially in Assam, Meghalaya, Manipur, Arunachal Pradesh etc. Coorg variety is cultivated mainly in Karnataka and Tamil Nadu.
Lime and Lemon are generally grown in Andhra Pradesh, Gujarat, Bihar, Karnataka, Maharashtra, Assam and Chhattisgarh. Total area under these is 2.34 lakh hectares and production is 22.7 lakh mt which is accounting for 3.5 per cent of area and 3.0 per cent of production in the country. The average productivity of lime and lemon is 9.7 mt in India. The area in Andhra Pradesh is 47.8 thousand hectares with annual production of 7.18 lakh metric tonnes with highest productivity of 15 mt/ha .
Among the citrus fruits, mandarin is placed at first position with respect to area and production which is followed by sweet oranges and limes. Other citrus fruits viz. grapefruit, pummelo and lemons are mostly grown as backyard plants.
In Punjab, the farmers took the lead and brought back the lost glory in citrus culture. Now kinnow has emerged number one fruit of the state, both from area and production point of view. The total area under citrus in Punjab is 49, 244 hectares out of which kinnow occupies major
share of 45, 851 hectares. The annual production of citrus fruits is 10.16 lakh tonnes, Kinnow alone produce 9.89 lakh tonnes. The districts of Fazilka, Ferozepur, Muktsar and Bathinda, occupy, 82% of the area under kinnow in the State. Sweet orange is grown particularly in the arid irrigated region of the Punjab i.e. the districts of Ferozepur, Muktsar, etc.
Kinnow cultivation has also become quite popular in Ganganagar, Bikaner and Jaipur districts of Rajasthan; Sirsa, Jind, Hissar,Ambala and Karnal districts of Haryana; Una, Sirmaur, Bilaspur, Mandi and Kangra districts of Himachal Pradesh and Jammu region of Jammu and Kashmir.
The oranges are exported from India to Bangladesh, Nepal, Sri Lanka, Cango P Republic, Oman, Singapore, Canada, Belgium, Saudi Arabia, Russia etc. Annual export of oranges is 34000 mt with value of Rs. 84.93 crores. Alone Bangladesh is importing 86.7 per cent of total export of oranges from India.
Kinnow is exported to Sri Lanka, Saudi Arabia and United Kingdom from Sri Ganganagar. Punjab Agro Industries Corporation exported Kinnow to United Kingdom, Dubai Mauritius and Sri Lanka.
Essay # 4. Importance and Uses of Citrus:
Citrus fruits are not only delicious and refreshing but also they provide vitamins, minerals and many other substances. Many of the vitamins contained in the citrus fruits are needed by the human body daily. Different species of citrus fruits have different chemical compositions. In sweet oranges, the chief constituents of the edible portions are sugars (glucose and sucrose), and acids (citric acid); the fruits of acid groups contain primarily the acids in the fruit juice. Citrus fruits contains considerable amount of vitamin C.
Kinnow contains 60 mg of vitamin C per 100 ml of juice. Lime is also a good source of vitamin C. Lemon has high medicinal value as it is a richer source of antiscorbutic vitamin C than the sour or acid lime. It is also good source of vitamins B, A, and P. Lemon is very useful in the case of the prevention of capillary bleeding and very useful in the case of teeth, hands and face and as a hair rinse. Grapefruit is a rich source of vitamin C and thiamine B1.
The mild bitterness in juice is due to the presence of glucoside called Naringin which is said to have a high medicinal value. Grapefruit is considered very well for prevention against malaria. The total soluble solid in the fruit juice in most of the sweet group of citrus varies from 8-12 per cent, while the titrable acidity usually ranges from 0.5 to 1.5 per cent. T.S.S. acid ratio of 30:1 in Musambi, 14 : 1 in pineapple, Jaffa and Blood Red, 10 : 1 in Valencia Late (sweet oranges), 12 : 1 to 14 : 1 in Kinnow (Mandarin) and 6 : 1 in Red Blush, Foster and Duncan and 7 : 1 in Marsh Seedless (Grapefruit) is considered to be optimum for marketable fruits.
Most of the citrus fruits such as sweet oranges, grapefruit and mandarins are taken as fresh fruits. The citrus fruits can, however, be utilized in a number of other ways as salads (orange salad, grapefruit-cheese salad, grapefruit-pineapple salad; grapefruit salad), juices, squashes (orange squash, lime and lemon squash), cocktails, syrup, concentrate, marmalades and pickles.
The peel of thick-rinded citrus fruits can also be made into delicious candy. Orange, lemon, lime and grapefruit juices are bottled and canned in large scale. Lemon-barely water is prepared from the common lemon. Grapefruit are mainly used as a dessert fruit after adding little sugar due to its slightly bitter taste. It is served in halves, in section or as juice.
The rind of citrus fruits is rich in pectin and certain essential oils. Lime and grapefruit peel is used as cattle feed. Dried lime feed powder and lime sediment obtained when lime juice is clarified are utilized for cleaning metal-ware. The lemon is used in many culinary purposes. Grapefruit is utilized in the preparation of dry and fortified wines and brandies. It is also used for flavour and in perfumery.
The following are the important citrus species of commercial importance:
A. Acid Members Group (Citron, Lemon, and Lime):
1. Citrus Medica L. – Citron:
A shrub or small tree of irregular habit of growth, twigs angled, glabrous. Stout, short spines in leaf axils. Leaves glabrous, elliptic-ovate, rounded at the tips, cuneate at the base, margins serrate. Petioles are wingless or narrowly margined and faintly joined with the blade. Fruit large, oblong or oval, blunt pointed, rough and lemon yellow. Rind is thick.
2. Citrus Limon (L) Burm – Lemon:
A small to medium tree of spreading growth habit and long shoots with small spines and strongly coloured new growth. Leaves medium large, light green, lanceolate and sharp pointed, with sub-serrate margins. Petioles medium, narrowly winged or margined; plainly joined with the blade. Flowers are medium sized and purple in the bud. Stamens are numerous. Fruit oval pointed commonly at both ends, light yellow. Rind is medium, juice abundant and acidic. Core is solid. Seeds are few, small, embryo white.
3. Citrus Jambhiri Lush- Rough Lemon (Jatti Khatti):
A medium to large trees are of spreading growth habit. Spines less than in lemon and colour of new growth is much paler. Leaves medium sized, pointed with notched tip and paler in colour. Leaf is margin serrate. Flowers smaller, faintly coloured in the bud. Fruits are lemon-brown and very deficient in form (round or compressed). Rough and irregular surface and core open at maturity. Flesh colour yellow. Seeds are numerous and small, embryo white.
4. Citrus Kama Raf. – Kharna Khatta:
Medium to large trees are of upright spreading growth habit. Spines are thicker and larger than lemon. New growth faintly coloured. Leaves large and lemon like but broader and darker green. Petioles longer and permanently winged. Flowers are large and well coloured. Fruit is orange coloured, medium to large, oval with well-developed papilla and rough and irregular. Rind is surface thick, core open at maturity and flesh colour orange moderately seedy and cotyledon white.
5. Citrus Aurantifolia Swingle (L.)- Lime:
Small to medium tree are numerous small but stiff and sharp spines and faintly coloured new growth. Twigs and shoots slender. Leaves small, elliptic ovate or oblong ovate, obtusely pointed at the tip and rounded at the base, pale green and petioles narrowly winged. Flowers are very small, white in the bud. Fruits are greenish yellow, small, round to oval. Peel very thin and aromatic, flesh greenish and highly acidic. Seeds are small and white inside.
6. Citrus Latifolia Tanaka- Tahiti or Persian Lime:
It resembles aurantifolia in most respect. It is a large vigorous tree with many fewer and thicker thorns and new growth more faintly coloured. The flowers are considerably larger and very faintly coloured in the bud. The fruits are much larger. Seeds are very few or lacking. The tree is much harder than aurantifolia and more resistant to pest diseases.
7. Citrus Limettioides Tanaka- Sweet Lime:
A medium sized tree with spreading habit of growth. Leaves medium sized, pale green in colour and characteristically somewhat rolled, leaf margin serrate, tip notched, big thorns present generally in the axils of leaves. Flower non coloured. Fruits are medium in size, globose to ellipsoid.
B. The Orange Group:
8. Citrus Aurantium L.- Sour Orange:
A medium sized tree upto 10 metres height with a rounded top; twigs angled when young, with single, slender spines, often short or stout spines (upto 5-8 cm long) on rapidly growing shoots. Leaves medium sized, ovate, bluntly pointed at the top and broadly rounded at the base. Flowers are large, very fragrant. Fruits are sub-globose, usually slightly depressed at both base and top, peel thick, with a rather rough surface, becoming brilliant orange with a reddish tint at maturity.
9. Citrus Myrtifolia Raf. – Myrtle-Leaf Orange:
A shrub dwarf tree with very short internodes often spineless and small myrtle like leaves. The fruits are small, sour or bitter, orange coloured at maturity and contain few or no seeds.
10. Citrus Bergamia Risso – Bergamot Orange:
Small to medium sized trees are of irregular habit. Thorns are variable and not especially numerous. Leaves medium, sharp pointed, with bitter orange aroma, but pale green colour. Petiole long, strongly marginal to moderately wing in upper necked, lemon yellow, often with low flat papilla and persistent style. Seeds are few, white inside.
11. Citnis Natsudaidai Hayata – Japanese Summer Grapefruit:
A medium sized, round topped tree with few thorns, leaves medium sized, long-pointed with main vein prominent above and dark green in colour. Petiole long and strongly margined from tip to base or winged in upper position as in sour orange. Flowers are large and white. Fruit is large, sub-globose to oblate, yellow at maturity. Flesh yellow. Seed is medium large and white within.
12. Citrus Sinensis (L.) Osbeck – Sweet Orange:
A medium-sized tree with a rounded top and regular branch; twigs angled when young, usually with slender, somewhat flexible, rather blunt spines in the axils of the leaves. Leaves medium- sized, pointed at the base and petioles narrowly winged. Flowers are in small racemes or singly in the axils of the leaves. Fruits sub-globose, oval or flattened globose.
C. The Pummelo-Grapefruit Group:
13. Citrus Maxima Osbeck – Chakotra:
A large and round-topped tree with angular twigs, often pubescent. Leaves large to very large, oval or elliptic-oval, with a blunt tip and a broadly rounded base and even slightly overlapping the winged petiole, mid-rib and large veins often pubescent; petioles broadly winged and more or less cordate. Flowers are very large, borne singly or in axillary clusters or in sub-terminal inflorescence. Fruits are large or very large, sub-globose, oblate-spheroid. Seeds are large, thick, wrinkled.
14. Citrus Paradisi Macf. – Grapefruit:
A large spiny, round topped tree with dense foliage; twigs angular when young; glabrous or nearly so. Leaves larger than those of sweet orange, small than those of chakotra; ovate, bluntly tipped and broadly rounded at the base, glabrous or nearly so; petioles rather broadly winged but not so broad as those of the chakotra. Large flowers, borne-singly or in small clusters in the axils of the leaves. Fruits are larger than those of the sweet orange but smaller than those of most chakotras. Seeds are smaller than those of the chakotra.
D. The Mandarin Group (Loose Skin Orange):
15. Citrus Reticulata Blanco- Sangtra:
A small to medium tree is upright, irregular growth habit and relatively few thorns. Leaves medium in size, lanceolate in form, with prominent midrib and long narrowly winged petioles. Flowersare medium small. Fruits depressed globose or sub-globose, with thin, loose peel easily separating from the segments. Seeds small, pointed with cotyledons green.
16. Citrus Uttshiu Marc. – Satsuma Mandarin:
A small, spreading, round toppered, virtually thorn less tree. Leaves medium large in size, long and sharp pointed with midrib highly prominent above and dark green in colour. Petioles long and narrowly winged from end to end. Flowers are medium in size. Fruit is medium sized, compressed, orange at maturity and generally seedless.
17. Citrus Deliciosa Tenore – Willow Leaf Mandarin:
A highly symmetrical, broad tappered tree of drooping growth habit, branches fine. Leaves small, long and narrow and sharp pointed, yellowish green leaves. Fruit is small to medium with thin rind. Strongly compressed. At maturity yellow to light orange and rind and segments loose. Flavours are aroma mild and distinctive. Seed cotyledons green.
18. Citrus Rashni Tanaka – Billikichilli or Cleopatra Mandarin:
The tree is attractive, round-topped, symmetrical, and thornless, with small, dark-green leaves. The fruit is orange red, small, oblate and highly depressed at the apex, with thin, somewhat rough rind. It is used as rootstock.
19. Citrus Nobilis Loureiro – King of Kunembo:
The tree and foliage are orange-like in appearance but the fruit is large and mandarin like with a rough, more or less bumpy exterior, a thick, fleshy rind. Flesh colour is deep orange. Seeds few to many having cream-coloured cotyledons.
20. Citrus Tangerina Hort. (Tanaka) – Tangerins:
Tree vigorous and large, upright spreading in habit, nearly thornless; foliage moderately dense and of the mandarin type. Fruits are medium to large, of high colour, deep orange to red and more acid flavour.
E. Papeda Group:
21. Citrus Inchangensis Swing – Ichang Papeda:
A spiny shrub or small tree usually 5-15 ft high; twigs angular when young, with stout, sharp spines, 1.5 – 2.5 cm long. Leaves narrow, 4-6 times longer than wide; petioles very large, broadly winged, obovate or oblong-spatulate, evenly rounded at the tip and narrowed abruptly at the base. Fruits small, glabrous, 3-4 cm diameter in dried specimens, peel rough, seeds large.
22. Citrus Junos Siebold – Yuzu of Japan:
The Yuzu is a medium-sized spiny tree; leaves lanceolate- acuminate, with rounded bases but with pointed, usually accuminate tips, slightly crenulate-margined towards the tips, leaf blades 5-7 x 2.5 x 3.5 cm; winged petioles obovate. Fruits depressed- globose, 5-7 cm diameter, greenish in colour when ripe, pulp very acid, seeds plump.
23. Citrus Latipes Swing – Khasi Papeda:
A thorny tree having leaf blades more variable in size and shape; with the tips sub-acute or even bluntly rounded, not apiculate or sub-candate with blunt points. Fruits are borne singly. Seeds are smaller and numerous.
24. Citrus Macroptera Montr. – Melanesian Papeda:
A tree 15-16 feet high,Petioles broadly winged, distinctly articulated. Leaves elongate – accuminate, only twice as long as the petiole. Twigs sub-compressed with one long spine on young twigs and one short spine on old twigs in the axils of the leaves. Fruit with 10-12 segments, pubescent, segments 1-2 seeded with scanty pulp, depressed, almost without juice.
25. Citrus Histrix DC – Mauritius Papeda:
Low tree or shrub, 2-12 m high; trunk crooked asymmetric or angular, rather thin, branched near the base; crown irregular, densely branched, branchlets thin; spines short, stiff, subulate, green with hard brown or orange coloured tips. Leaves alternate, stalked unifoliate, orbicular-ovate, lanceolate, above dark green, shining, beneath light green or yellowish green, dull, fragrant when bruished. Fruit- pendulous, globose, ovoid, ripe fruit yellowish green.
26. Citrus Macrophylla Wester – Alemow:
It shows promise as a salt-resistant rootstock for lemons. Leaves are large with blade 12-14 cm long and 6-8 cm wide with much smaller, sub-triangular, short-winged petioles. Fruits are very large 8.5 to 10 cm in diameter, sub-globose to oblong, more or less narrowed at the base. Pulp sour, considered inedible.
F. Other Species:
27. Citrus Limonia Osbeck – Rangpur Lime:
Tree usually vigorous and productive, medium sized, spreading and drooping, with slender twigs, comparatively few and small thorns; foliage dull-green and mandarin like, and new shoot growth lightly purple tinted. Flowers are small and mandarin-like and bud and petals deeply purple-tinged. Hardy to cold.
28. Citrus Limetta Risso – The Limette of the Mediterranean or Limettas:
Small to medium round topped tree of less vigour and more compact growth habit. There appear to be two forms which are identical with the exception of the colour factor. In both, the fruit is small and round shaped or depressed lemon yellow and acid-less at maturity. It’s most distinctive feature are the turncate apex, with a strongly depressed ciruclar furrow in the centre of which is a prominent fleshy papilla or nipple.
29. Citrus Maderaspatana Tanaka – Kitchli, Vadlapudi and Guntur Sour Orange:
An old Indian fruit of unknown origin, the kichli somewhat resembles the bittersweet orange though it is smaller, flatter and rougher in surface texture. Fruit medium sized, depressed globose to broadly obovoid; sometimes slightly necked; colour yellowish orange; seedy; rind rough.
30. Citrus Madurensis Loureiro – Calamondin:
Tree of medium vigour, highly productive, upright and columner, nearly thornless; leaves small, broadly oval and mandarin-like. Strongly cold resistant. Fruit very small, oblate to spherical; red colour orange to orange-red; very thin, smooth; sweet and edible-seeds few.
31. Citrus Indica Tanaka – Indian Wild Orange:
Branches are terete, spiny, and glabrous. Leaves are oblong or lanceolate, thick, sub-entire, attenuate at the apex, acute at the base, veins curved. Fruits small, broadly obovoid or sub-pyriform, solitary on terminal twigs, pedicels very short; seeds, large, smooth. The leaves resembles with Citrus sinensis but small, fig- shaped, fruit containing extremely large seeds is entirely different from any other Citrus.
32. Citrus Pennivesiculata Tanaka – Gajanimma of India:
Tree vigorous having thick shiny leaves, large spines, and pitted surface of the fruit. Pulp greenish with juice sacs arranged in a herringbone fashion and the presence of opaque dot. It is used as a rootstock. This species is found in South India.
In citrus (mandarin, sweet orange, grapefruit), type of fruit is hesperidium and edible portion is juice vesicles.
Essay # 5. Choice of Varieties of Citrus:
There are a large number of citrus varieties grown in different citrus growing regions of India.
1. Sweet Orange (Citrus Sinensis):
A. Common Group or Mediterranean Oranges –(i) Pineapple, (ii) Hamlin, (iii) Jaffa, (iv) Valencia, (v) Sathgudi, (vi) Shamouti
B. Acid-Less Group- (i) Mosambi, (ii) Succari
C. Pigmented Group- (i) Blood Red, (ii) Ruby, (iii) Moro, (iv) Tarocco, (v) Blood oval or Doblefina
D. Naval Group- (i) Washington Naval, (ii) Roberston, (iii) Bahianiana
2. Mandarin (Citrus Reticulata) – Loose Skinned Orange:
A. Reticulata Group- (i) Nagpur santra or Ponkan (Chhina), (ii) Coorg, (iii) Khasi mandarin, (iv) Local
B. Mediterranean Group or Deliciosa Group- (i) Kinnow (King x Willow leaf), (ii) Wilking (Sister hybrid of Kinnow), (iii) Willow leaf
C. Satsuma Group- (i) Ovary, (ii) Wase, (iii) Kara
D. Tangerine group- (i) Dancy, (ii) Beauty, (iii) Naartja
E. Nobilis group- (i) King, (ii) Kunembo
F. Mitis group- (i) Calamondin, (ii) Billikichilli, (iii) Cleopatra
3. Mandarin-Like Tangers (Hybrid between Tangerine x Sweet Orange):
(i) Temple (Natural hybrid)
4. Mandarin-Like Tangelos (Hybrid between Grapefruit x Tangerine):
5. Grapefruit (Citrus Paradisi):
A. Seeded Group- (i) Duncan, (ii) Triumph, (iii) Pink marsh, (iv) Ruby, (v) Foster, (vi) Star Ruby
B. Seedless Group- (i) Marsh seedless, (ii) Cecily, (iii) Red blush
6. Pummelo (Citrus Maxima):
(i) Kao pan
(ii) Red fleshed
(v) Jorhat (Pink flesh)
7. Lime (Citrus Aurantifolia):
A. Acid or Sour Lime– (i) Kagzi, (ii) Mexican, (iii) Palmetto
B. Large Fruited or Tahiti Lime- (i) Tahiti, (ii) Pond, (iii) Bearss
C. Mandarin Lime- (i) Rangpur lime
D. Sweet or Acidless Lime (Citrus Limettioides)- (i) Palestine, (ii) Sweet, (iii) Local
8. Lemon (Citrus Limon):
A. Eureka Group- (i) Eureka, (ii) Villafranca, (iii) Nepali oblong, (iv) Galgal, (v) Italian round, (vi) Punjab Baramasi Lemon, (vi) PAU Baramasi Lemon-1
B. Lisbon Group- (i) Bonnie, (ii) Kennedy, (iii) Lisbon
C. Anomalous Group- (i) Meyer, (ii) Cuban, (iii) Ponderosa
D. Sweet or Acidless Lemon Group- (i) Mill sweet
The brief description of important cultivars is given below:
1. Nagpur Santra:
This is the premier mandarin of India and is one of the finest mandarin varieties grown in the world. It does well under Nagpur conditions where it is usually raised by budding on the rough lemon rootstock. The fruits are medium in size, sub-globose in shape. The fruit colour is often greenish orange to light orange. The surface is smooth and glossy.
The stalk end (base) is slightly drawn out and warty with glandular furrows. The rind is thin and slightly adherent. The segments are 10-11. Juice content is abundant, yellow in colour with excellent flavour, sweet in taste. The number of seeds per fruit is 6-7. The maturity period is generally January-February.
It is a hybrid between King x Willow leaf. It was brought to Fruit Research Station Abohar from California in 1958-59 and to Jalandhar a litter earlier. Fruit medium to globose to oblate. Skin is golden yellow when fully ripe. Acidity moderate with fine sugar/acid blend, flavour very rich. Seeds 12-25; Ripen in January-February. Less prone to fruit drop. The average yield is 150-200 kg fruits per plant.
Fruit is small to medium, oblate to sub-globose. Skin cadmium coloured. Base short necked and furrowed. Flavour fair, Juice abundant, slightly acidic. Seeds 3-7 Ripens in December- January.
It is commercially grown in Assam. It is a prolific bearer. Fruits are depressed, globose to oblate in shape. Colour of mature fruit is orange yellow to bright orange. The surface of the fruit is smooth, glossy. The stalk end is even or obtuse, occasionally necked, slightly ribbed.
The rind is thin and is separated very easily, number of segments 8-10, rag little to medium. The pulp vesicles uniformly orange coloured, coarse, very melting, juice abundant, orange coloured. Sweetness and acidity well blended. Seed 9-25.
It is the important commercial variety of South. The fruits are oblate to globose, bright orange yellow in colour. The base necked or depressed with glandular ribs extending through the collar. The rind is thin and soft, slightly adherence, easily separated. The numbers of segments are 9-11. Rag is little; juice abundant, deep chrome in colour. Seed 14-30.
It is a cross between Fortune and Fremont mandarin. Fruit is medium to large, mid- season fruit with an attractive dark orange rind. Fruit weight is 210 g. It peels and sections moderately well. The tree produces a heavy crop with the fruit held in large clusters.
Moderately seedy with 1-3 seeds per section, seed number 9. TSS is 11.5 per cent, acidity 0.54 per cent and juice content 41.8 per cent. Ripen early in 5-20 November. It is suitable for the area having soil pH less than 8 and raised on carrizo rootstock.
7. W. Murcott:
Tree is moderate in size and vigour. Fruit is usually flattened with a thin, smooth orange rind, easy to peel. Fruit weight is 200 g, seed number 10. Low seeded in the absence of cross-pollination but seedy when cross- pollinated. The flesh is orange coloured and juicy, with a rich and sweet flavour. TSS is 9.6 per cent, acidity 0.68 per cent and juice content 39 per cent. Ripen in 1-20 January being a mid-season variety. It is suitable for the area having soil pH less than 8 and raised on carrizo rootstock.
B. Sweet Orange:
Fruits are small to medium, sub-globose. The fruit surface smooth with longitudinal furrows. Apex marked with a circular ring. The colour of the flesh is pale yellow or whitish. Juice has low acidity. Seeds 20-25 per fruit Ripens in November.
Fruit is medium to large, round to oblate in shape. Skin is orange yellow to orange red. Acidity and sweetness well blended. Flavour rich. Seeds- 8-10 Ripens in December. The average yield per plant is 54 kg.
3. Blood Red:
Fruit is medium to large, roundish to slightly oblong in shape. Kind thin, deep orange, tight and glossy. Flesh is fully red when ripe, rich flavour with sweetness and acidity well blended. It is an excellent variety. Seeds 8-10, Ripens in December. The tree can yield 42 kg fruit per plant.
Fruit is medium to large, round to slightly oblate and deep orange. Juice is abundant, acidity and sweetness well blended, flavour excellent. Seeds 12-25 Ripens in December.
Fruit is medium slightly oval. Skin is deep golden yellow. Juice abundant, sub-acid in taste. Flavour rich. Seeds 2-6 Ripens during February-March.
Fruit is medium, sub-globose, areole absent. Rind is medium thick smooth and finely pitted. The pulp is straw coloured, juicy with good flavour. Seeds- 12-20. This is a famous variety of Andhra Pradesh and Tamil Nadu. Ripens from, October to February.
The fruit is ellipsoidal in shape, medium to large sized. Rind thick, firm, surface finely pitted, but relatively smooth. Pulp colour is light orange, juice medium, sweet in taste with rich in flavour. It is practically seedless (0-1 seed/fruit)
Fruit is medium, oblong, apex nippled. Skin lemon yellow, smooth. Juice is abundant, clear, and strongly acidic with excellent flavour. Seeds rarely present. Ripens in, August-September.
2. Punjab Baramasi Lemon:
The trees of baramasi are vigorous, spreading and thornless. New growth and flowers are purple. The trees are flower and fruit throughout the year. The fruit is medium to large, lemon yellow, round, tapering towards the base, apex is rounded. The skin is smooth and thin. Fruit is very juicy with low seed content. This variety is more suitable for growing in the irrigated arid region of Punjab. It matures in first week of July. Average yield is 84 kg fruit/plant.
Its trees are vigorous. Fruit is medium in size, oval in shape, peel is smooth, glossy, medium thick and yellow at maturity. Its juice has 5.2 per cent acidity and 5-8 seeds per fruit. It matures in last week of November in North India and gives 80-100 kg fruit per tree.
4. Pant Lemon-1:
Fruits are medium in size, round in shape, smooth, juicy with thin rind. This lemon is a selection from kagzi kalan at Pantnagar (Uttaranchal).
5. PAU Baramasi Lemon-1:
The fruit is lemon yellow, round, tapering towards the base and apex is round. Skin is smooth and thin. Fruit is very juicy and seedless and contains about 7 per cent acidity.
Fruit is small, round and thin-skinned. Pulp is greenish white. Juice is strongly acidic.
1. Marsh Seedless:
Fruit is medium to large, oblate-roundish in shape. Skin is lightly yellow, smooth, Acidity and sweetness medium. Seeds 0-6 Ripens in December-January. Average yield is 93 kg fruit/plant.
Fruit is large, oblate in shape. Skin is pale light yellow, flesh pink. Acidity and sweetness well blended, bitterness well- marked. Seeds 40-50 Ripens late in January. Average yield is 84 kg fruit/plant.
Fruit is medium to long, oblate in shape. Skin is pale yellow, flesh pink. Acidity and sweetness well blended, bitterness well marked. Seeds 40-50 Ripens in November-December. It yields 51 kg fruit per plant.
4. Red Blush:
Fruit is small to medium, oblate, peel smooth, glossy and deep yellow having crimson colour in patches at maturity. Deep in bright crimson blush in juice vesicles. Mildly acidic and high in TSS. Seeds 0-8, mostly aborted, Ripens during last week of November. Average yield is 77 kg fruit/plant.
5. Star Ruby:
The trees are medium in size. Fruits are small to medium having oblate- roundish shape. Peel smooth, glossy, yellow with distinct bright red blush. Flesh colour is deep red. Fruits juicy, have high TSS, well blended with acidity and rich in vitamin C. Fruits are seedless (1-2 seeds/fruit). It is an early variety which ripens during last week of November. The average yield is 53kg fruit/tree.
F. Sweet Lime:
Fruit is medium globose to ellipsoid. Rind is smooth with distinctive aroma, juice abundant, lacking in acidity and insipid. Seeds 5-6, ripen in the beginning of September.
Essay # 6. Raising of Rootstock of Citrus:
i. Preparation of Seedbeds and Sowing of Seed:
For raising the rootstock, seeds freshly extracted from mature fruits of Jatti Khatti collected from healthy and vigorous tress are sown on raised beds. The land used for preparing the seedbeds should be well drained and fertile. The beds should be 2-3 meters long, 60 cm wide and 15 to 20 cm high from the ground level. There should be sub-channels on both sides of the beds for irrigation. The seeds of Jatti Khatti may preferably be sown in September. The sowing of seed on the raised beds is done in the first week of September. If the sowing is delayed, the germination reduces due to onset of winter and also the growth is slowed down.
The seed is sown in rows 10 cm apart and in these furrows the seeds are placed 2 cm apart and 1 cm deep. After the seeds are sown, they are covered with layer of sand and farmyard manure mixture about 1/2 cm thick. The seedbeds are irrigated immediately after sowing. The first irrigation is usually applied by sprinkling with hand hose and the next few irrigations are applied in a way that the beds are moistened through seepage.
The seeds should be sown immediately after extracting from the fruit as its viability decreases during storage. For facilitating sowing, the seeds should be washed and dried in shade.
ii. Care of Young Seedlings and Its Transplanting:
The germination of seed starts about 3 weeks after sowing. These young seedlings are likely to be damaged by frost during winter. It is advisable to cover them with Sarkanda to avoid any damage from cold. It will also improve the growth of seedlings. The seedbeds should be kept free from weeds by doing hand weeding or with small khurpa from time to time.
Light dressing of nitrogenous fertilizers makes the seedlings to attain the height of about 15 cm by the next March, which is the optimum size of transplanting. By sowing the seed in September and transplanting the seedling in March, one can save a year in the propagation of plants. If the seedlings do not attain the transplanting size by March, their transplanting should be done in August-September.
From most of citrus species used as rootstocks, many seedlings arise from one seed. One of these seedlings is sexual seedling and others are nucellars. So, while transplanting only the uniform seedlings are selected and too vigorous and too week seedlings are rejected. This helps in maintaining the uniformity of rootstocks used for nursery production. Generally 20% seedlings are rejected at the time of transplanting.
The field, in which the seedlings are to be transplanted, should be well prepared and levelled thoroughly. The seedlings of 10-12 cm height should be transplanted at the distance of 15 cm in rows which are 30 cm apart and a distance of 60 cm after every two rows should be kept for facilitating the budding and hoeing operations. After transplanting a light irrigation is applied to the field. Thereafter the irrigation is given at 8-10 days interval.
iii. Budding the Seedlings:
The transplanted seedlings become buddable 6 to 12 months after transplanting depending upon the time of transplanting. The seedlings which are to be budded should be of pencil thickness at about 20 cm from the ground level. All the seedlings may not attain the buddable size at the same time. Inspite of the fact that the uniformity was maintained at the time of transplanting, some of them may become more vigorous and some may remain week.
Most of them, however, grown uniformly. It is necessary to do second culling at this stage. About 10 per cent seedlings are discarded at the time of budding. The remaining uniform seedlings are budded. Spray of 1.5 per cent urea on Rough lemon seedlings at monthly interval from March to December increases number of buddable plants, improves budding success and produces healthy kinnow plants. Citrus plants can be budded either during February-March or August-September when the sap flows in the seedlings. ‘T’ budding or shield budding is the common method of propagation in citrus.
iv. Selection of Scion Wood, Preparation of Rootstock and Budding Operation:
For the propagation of quality plants, the scion should be hue to variety, excellent in vigour and productivity. Select virus free bud wood. If not available, it may be taken from perfectly trees showing no symptoms of decline and ill-health. Trees from which bud-sticks are taken should have a good record of producing satisfactory crops of high quality fruits over a number of years.
In citrus, budwood selected for taking the buds should be round especially in Kinnow variety of mandarins where the availability of round budwood is a problem. It should be taken from trees which are vigorous, heavy bearer and free from diseases.
Before budding, the stock should be prepared by removing the leaves and thorns from the place where the bud is to be inserted. The bud removed from the bud stick is used without any piece of wood. A ‘T’ cut is given on the stock at a height of about 20 cm from ground level. The flaps are lifted with the help of the back side of the knife and the bud is inserted into it. To hold the bud in a position tightly, it is wrapped with alkathene tape both at the upper and lower ends, leaving actual bud uncovered.
v. Containerized Nursery Production of Kinnow:
Mix two parts of soil, one part of FYM and one part cocopeat for preparation and sterilization of potting mixture and stack on concrete floor. Solarize the mixture with 100 micron UV stabilized polythene sheet during last week of April and May for 4-6 weeks and fumigate with Basamid Granular (Dozomet 98%) @ 50 g/m2 during May-June. For raising rootstock, sow rough lemon seed (2 seeds/bag) in black plastic polythene bags of 250 gauges (12″ x 7″) filled with sterilized potting mixture during second week of August under screen/ shade house. About 75 per cent seedlings attain buddable size in first fortnight of May and become saleable during September-October.
Essay # 7. Insects Pests in Citrus:
1. Citrus Psylla- Diphorina Citri (Kuwayana):
It is more active in March-April, June-July and September- October. The population density of pests is more in arid-zone. The adult psyllid is grey coloured and actively flying. It rests on the leaves with closed wings and hind end raised upwards. Orange yellow nymphs and grey adults of citrus psylla suck the plant sap from the growing shoot which ultimately dries up. It also acts as a vector of greening disease.
Spray 1250 ml of Rogor 30 EC (dimethoate) or 200 ml Imidacloprid 200 SL or 160 g Actara 25 WG (thiamethoxam) or 200 ml Confidor/Crocodile 17.8SL in 500 litres of water per acre in the second week of March and again in the first week of September. Adjust time of application with the appearance of the pest.
2. Citrus Leaf-Miner- Phyllocnistis Citrella (Stainton):
It is serious pest and cause substantial economic damage to mandarin, acid lime and sweet orange. It attacks tender leaves in which larvae feed making shinning silvery serpentine mines. It also mines young tender shoots. The leaves become distorted and crumple. Severe infestation causes defoliation. The pest is more serious problem in the nursery and young plantation during flushing seasons. The pest is active from end March to November with its maximum infestation during April-May and September-October. The attack of this pest encourages the development of citrus canker.
The pest can be controlled by spraying on nursery plants 250 ml of Sumicidin 20 EC (fenvalerate) or 1000 ml of Ripcord 10 EC (cypermethrin) or 1250 ml Hostathion 40 EC (triazophos) or 1875 ml Durmet 20 EC (Chlorpyriphos) or 200 ml Imidacloprid 200 SL or 160 g Actara 25 WG (thiamethoxam) or 200 ml Confidor/Crocodile 17.8SL in 500 litres of water during April-May and August-September.
3. White or Black Fly- Dialeurodes Citri (Ashmead) and Aleurocanthus Woglumi (Ashby):
White fly became devastating in Vidharba region of Maharashtra. Both nymphs and adults suck the sap from the foliage and reduce the plant vigour. Severely infested foliage turns yellowish green, becomes curled and finally shed. Sooty mould developed on honey dew excreted by the whitefly, give black appearance to the foliage. Affected trees have less chlorophyll, nitrogen and crude protein and produce few flowers which may shed.
The fruits are insipid. Nymphs of whitefly are small pale yellow insects with red eyes. Citrus black fly lays eggs in spiral rings on the lower side of new leaves and nymphs are black in colour. Freshly emerged adults are, redish but later on gets covered with a heavy pulverulence of salty bluish look. Both the species are active from March to November with their peak period of infestation during April – May and September – October.
It can be effectively checked by spraying 1000 ml Fosmite 50 EC (ethion) or 1250 ml Hostathion 40 EC (triazophos) in 500 litres of water, per acre during April-May and during September-October.
4. Citrus Leaf Folder- Psorostica Zizyphi (Stainton):
This is gaining importance of serious pest in Punjab especially in young citrus plantations and nursery. It remains active from May to October. The larvae feed inside the leaves by webbing them together and start feeding from top to downwards. The plants become stunted.
The pest can be controlled by spray of 1250 ml Dursban 20 EC (chlorphyriphos) or 1000 ml Quinalmass 25 EC or 1000 ml Ekalux 25 EC (quinalphos) in 500 litres of water.
5. Mites- Oligonychus Citri (McGregor):
Mites damage the leaves, flowers and fruits. Their incidence is maximum during dry and hot period (May – June) or sometimes become serious in August-September. The larvae have minute white specks left by the feeding of mites. Leaves are generally covered with dust.
For control, spray 670 ml of Rogor 30 EC (diamethoate) or 750 ml of Fenazaquin 10 EC in 500 litres of water as soon as mite population appears.
6. Barkeating Caterpiller- (Indarbela Quadrinotata (Walkar)):
It causes damage by boring holes into the stem and branches and feeding on the bark under the cover of its excreta. The pest is active in neglected orchards.
Remove webbing and apply kerosene into the holes during September-October and again in January-February. Treat all the alternate host plants in the vicinity.
7. Aphids- (Toxoptera Aurantii, Aphis Gossypii and Myzus Persicae):
These aphids are becoming the regular pest of citrus. Toxoptera aurantii and Myzus persicae are active from first week of February to first week of May with their critical period of infestation from first week of March to first week of April. These two species along with Aphis gossypii are also causing damage to citrus plant from last week of August to second week of November with their critical period of infestation from second week of September to first week of October.
The nymphs and adults suck the cell sap from young leaves and tender twigs. This impairs the vitality of the tree and causes severe curling and deformation of young leaves resulting into stunted growth. The honeydew excreted by the aphids also provides a good substrate for the growth of sooty mould which affects the photosynthetic activity of the plant. Control measures are the same as for citrus psylla.
8. Citrus Thrips- (Scirtothrips Citri):
The pest starts appearing with the initiation of flowering in first week of March. It causes damage to petals, stamens and the basal part of the ovary. The attacked flowers dry up and shrivel. Its attack continued up to third week of April. As soon as the petals start drying, adults and nymphs of thrips within the floral parts starts lacerating the developing fruits. At the initial stage, the damage on the rind of the fruits appears as light silver white abrasion. With the increase in size of fruit, the scarring becomes prominent and deep on the rind of the fruits.
The pest can be controlled by spraying 1250 ml Hostathion 40 EC or 1000 ml Fosmite 50 EC in 500 litres of water per acre in mid-March and again in mid-April.
9. Mealybugs- (Planococcus Citri, P. Lilacinus, Nipaecoccus Viridis and Maconellicoccus Hirsutus):
Mealy bugs are active during July to October in citrus plantation. Planococcus citri is a major pest in citrus. These cause damage to leaves, tender shoots, twigs, branches and fruits. Nymphs and females of these mealy bugs suck cell sap and reduce plant vigour. The severe feeding causes drying up to tender shoots and growing point. Heavy infestation also encourages the growth of sooty mould due to which the leaves, shoots and fruits become black in colour. These mealy bugs hibernate on the twigs and branches.
Proper sanitation in orchard is very important. Observe the underside of leaves, young shoots, branches and fruits regularly. Never allow the branches to touch the ground. Prune infested branches and destroy them. All the ant nests in the orchards should be destroyed. Drench the plants with 1875 ml Durmet/Dursban/Coroban/Massban 20 EC (qtilorpyriphos) in 500 litres of water on appearance of bugs. Repeat the spray if need arises.
Essay # 8. Disorders Seen in Citrus:
Fruit-drop is a serious problem in citrus. Generally the trees bear large numbers of flowers and fruits, all of which they are unable to carry to maturity. It is a common observation that not more than 7-8 per cent of the flowers develop into mature fruits. First, the unfertilized flowers drop from the trees and, later, some of the fruits also drop in two or three definite waves.
A considerable number of fruits drop in April soon after the fruit- set. Another drop comes when the fruit is about 3-5 cm in diameter. Usually, these two drops are not of such intensity as to materially affect the total yield. The last fruit-drop, known as pre-harvest drop, occurs just before the fruit is matured. It, however, reduces the yield considerably.
There are two main causes of fruit drop:
i. Physiological Causes of Fruit-Drop:
The following are the possible physiological causes of fruit drop– (i) Climatic factors (ii) Disturbed water relations (iii) Lack of nutrition (iv) Relation of seed to fruit drop.
The flower-drop, as well as the fruit-drop is primarily due to the formation of an abscission layer at the point of attachment of the fruit with the twig. The growth-regulator balance within the tree is responsible for setting in motion the processes leading to the abscission layer.
For checking excessive pre-harvest fruit drop, spray the trees with 10 ppm of 2, 4-D (Sodium salt of horticultural grade) in September about 2 months before harvesting. For spraying one acre of sweet orange trees add 5 g of 2, 4-D in 500 litres of water. Do not spray 2,4D when dicot crop is intercropped in citrus orchard. Do not spray 2, 4-D when the adjacent fields are cultivated with cotton or other dicot crops. Spray 200 ppm GA3 instead of 2, 4-D when cotton or other broad leaf crops are cultivated in or around the orchard.
ii. Pathological Causes of Fruit-Drop:
A good proportion of fruit-drop in citrus has also been reported because of incidence of pests and diseases.
(i) Stylar-end rot
The casual organism of the stem-end fruit rot is Colletotrichum gloeosporioides and Altemaria citri. Dark circular depressions with yellowish margins appear on leaves, branches, and fruits. Later the spots become raised, rough and light brown and the yellow margins disappear. Sand paper texture on the surface of leaves and fruit.
The stem-end-fruit rot can be effectively checked by spraying the trees with Ziram 27SC (1250 ml) or Propiconazole 25 EC (500 ml) or Bavistin 50 WP (500 g in 500 litres of water) in mid-April, August and September and two additional sprays of Ziram 27SC (1250 ml) or propiconazole 25 EC (500 ml)or Bavistin 50 WP (500 g) in end July and September in 500 litres of water per acre.
Granulation is a complex pre-harvest disorder of citrus fruits characterised by apparent drying up of juice vesicles which become hard, assume a greyish colour and are enlarged with an increase in pectin, lignin and other polysaccharides, resulting in considerable decrease in total soluble solids, acidity and juice percentage and sugars. A good proportion of fruits is affected by this malady causing huge economic loss to the orchardists, particularly in the arid- irrigated areas of Punjab i.e. Ferozepur, Fazilka Bathinda and Faridkot districts as well as in the adjoining states of Rajasthan and Haryana.
The problem of granulation has been reported from other places of India, though it constitutes a major problem in aforementioned areas. The sweet orange cultivars such as Mosambi, Hamlin, and Blood Red are much more prone to this disorder than mandarins. However, this disorder has also been reported in other citrus fruits like grapefruits, pummelos and tangelos. Dancy tangerine is highly prone to this disorder, whereas most of the mandarins, notably Kinnow are almost free from it.
Factors Affecting Granulation:
This disorder has been reported to be influenced, to varying degrees by weather conditions. Citrus trees growing in humid climates are reported to have a higher incidence of granulation than trees growing in dry regions. In Punjab, incidence of granulation was the highest at Ludhiana followed by at Abohar, Attari, Hoshiarpur and Pathankot.
ii. Species and Cultivars:
Sweet oranges are more prone to granulation than mandarins, grapefruits and tangelos. Under Delhi conditions, Valencia Late and Kinnow were found to be almost free from granulation. Granulation is reported to be serious in Hamlin, Blood Red, Mosambi, Jaffa, Valencia Late and Pineapple sweet oranges; Dancy, Kinnow, Wilking and Kara mandarins; Duncan and Marsh grapefruits; and Pearl tangelos. Kinnow was found less susceptible than Nagpur mandarin.
The vigours rootstocks like rough lemon induced higher incidence of granulation. Highest incidence of granulation was also noted in Blood Red on Jalandhari Khatti, a strain of rough lemon. It was followed by the trees budded, on Kharna khatta, sweet orange and grapefruit. Blood Red budded on galgal (Citrus Union) and sour orange (Citrus aurantium) rootstocks had the lowest percentage of granulated fruits. Fruits of Blood Red, Mosambi, Valencia and Pineapple exhibited the highest incidence of granulation on rough lemon while those of Jaffa did it so on Kharna khatta. Blood Red on Cleopatra and Pineapple on Troyer exhibited the least granulation.
iv. Mineral Nutrition:
The granulation is considered to be due to nutritional disorder. The trees having boron and zinc deficiency were found to have a greater tendency to produce granulated fruits, whereas manganese and iron were of little consequence in this regard. Trees with high nitrogen content in the leaves showed the highest granulation in the adjacent fruits. With the development of granulation in the fruits of Mosambi and Blood Red, the leaf N, P, K, Mg, Zn and Cu were found to increase, whereas Ca, B and Fe decreased but Mn content remain unaffected.
v. Enzymes and Plant Growth Regulators:
An enhanced formation of lignin, probably due to Zn shortage, induced low auxin content and an increase in pectin and a decrease in pectin esterase activity were associated with granulation. The activity of diastase was found to be 15- 25% lower in the granulated fruits of Kaula, Dancy and Butwal mandarins as compared to normal fruits. It was observed that a higher diastase activity in Kinnow was associated with little granulation. Higher level of auxins, cytokinins and abscisic acid and low gibberellins were noted in the granulated fruits than in the normal fruits.
vi. Crop Load:
Higher incidences of granulation were recorded in trees carrying a heavy load.
vii. Tree Location:
Incidence of granulation was noted more on northern side and in interior of the tree.
Although, no successful method to control granulation has yet been found but certain measures for reducing its incidence and intensity have been reported. Early picking of larger fruits before the granulation become serious has been recommended. Restricted amount and frequency of irrigation has been reported to reduce granulation. Sprays of lime, zinc sulphate and Bordeaux mixture singly or in combination reduced granulation.
A combined spray of ZnSO4 and CuSo4 each at 0.5% was more effective than their individual application. Three sprays of 25 ppm boric acid, 1% potassium nitrate and 2% calcium hydroxide at monthly intervals starting from 10 September reduced granulation.
Granulation was reported 5% less with 2, 4-D and 23 to 42% less by 10 or 20 ppm GA. Three sprays of 300 ppm planofix and 15 ppm GA each in August, September and October decreased granulation by 50% in Kaula mandarin.
Lead arsenate at 250 to 500 ppm was found effective in checking granulation in sweet orange and mandarin. In Dancy tangerine, three applications of GA, 2, 4-D and 2, 4, 5- T (20 ppm each) and NAA (200 ppm) in August, September and October significantly reduced the incidence of granulation.