The aonla popularly known as amla (Emblica officinalis syn. Phyllanthus emblica) is one of the most important minor fruits and a crop of commercial significance. It belongs to the family Euphorbiaceae. It is quite hardy, prolific bearer and much remunerative even without much care. It is also known as Indian gooseberry amlaki, amla, amia, amali, ambala, nelli,etc. Its importance lies in its high richness of vitamin C. It is the second highest source of vitamin C among fruits next only to Barbados cherry which is not grown in India.
Aonla ( amla ) is believed to have been originated in tropical, south eastern Asia, particularly in central and southern. India. It is also reported to be the native of India, Sri Lanka, Malaysia and China where it grows well and is found growing in wild form.
In India, its commercial cultivation is done in Uttar Pradesh. Pratapgarh, Varanasi, Azamgarh, Sultanpur, etc. are the famous amla growing districts of Uttar Pradesh whereas, in Jammu province it performs well in rainfed areas.
USES AND COMPOSITION
Amla fruit is very rich in vitamin C and pectin, therefore, regarded very important for medicinal value in Ayurvedics. Undoubtedly, amla is the richest natural source of vitamin C in India. A tannin, containing garlic acid, ellagic acid and glucose in its molecule, which is naturally present in the fruit prevents or retards the oxidation of vitamin C and renders it as a valuable antiscorbutic in the fresh as well as in the dried and processed condition. The fruits are made into preserve (murabba), sauce, candy, dried chips, tablets, jellies, pickles, tophies, dried aonla fruits, etc. The amla powder is superior to synthetic vitamin C in treating deficiencies.
The fruit is also useful in haemorrahages, diarrhoea, dysentery, anaemia, jaundice, dyspepsia and cough. It is an important ingredient of ‘Triphala’ and ‘Chawanprash’ in Ayurvedic medicines. It is also used in the preparation of ink, hair dyes, hair oils etc. It is a great health and vitality restorer.
Table 1. Composition of aonla fruits
|4||Mineral matter||0.7 %|
|10||Calorific value||59 mg/100 g|
|11||Vitamin B1||30 mg/100g|
|12||Nicotinic acid||0.2 mg/100 g|
|13||Vitamin-C (ascorbic acid)||600 mg/100 g|
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Aonla ( amla )can be grown in light as well as heavy soils except in very sandy ones. The plants have capacity for adaptation to dry regions and can also grow in moderately alkaline soils. It has great tolerance to salinity and sodicity and cultivated in pH range of 6.0 to 8.0 very successfully. However, its production is high in deep and fertile soils.
Aonla ( amla )is a subtropical fruit but its cultivation in tropical climate is quite successful. In India, it is being grown near sea coast upto 1800 m altitude. The tree is not much influenced either by hot wind or frost. However, the young plants should be protected from desiccating wind in summer and frost in winter, at least upto the age of 3-4 years especially in north Indian condition. In spring, soon after fruit set, the fruits remain dormant throughout summer without any growth. This quality makes it a highly suitable fruit crop for dry arid region.
Most of the aonla ( amla ) plantations have been raised from seed, therefore, exhibit great variability and the fruits are of inferior quality. There has been no standardization of aonla varieties and they are mostly known on the basis of size, colour or after the name of places where they are mainly grown: Some of them are described below.
It is an oldest early maturing variety of amla. The fruit weight is 45-50 g per fruit. It has light yellow colour and six segments which appear as joined together, is one of the characteristic features of this variety. Fruits are generally used for making murabba (preserve), candy etc. It starts fruiting in later stages (6-10 years tree age) and is a shy bearer which gives only 10-15 kg fruits per tree at 10 years of age and 100 to 200 kg per tree at the age of 20-30 years.
The branches of this variety are drooping type. Therefore, it is also called Hathi jhool. Fruit weight is around 40-45g. It is an earlier bearing variety than Banarasi. A 10-year old tree yields about 50 kg fruits while at 20-30 years age it yields 300-400 kg fruits per tree. But in those areas where calcium or calcium carbonate is excess in soil, the fruits suffer from internal fruit necrosis during maturity. This is due to excess of calcium and deficiency of boron.
The fruit size and tree size, both are smaller than Banarasi and Francis. Fruits are slightly flat and green in colour having approximate weight of 30-35 g per fruit. Fruit contains more fibres and, have longer storage life than Banarasi and Francis. The large fruits are suitable for preserve and candy purposes, but the smaller fruits are used for making pickles etc. Fruiting starts from 3rd year and a 10-year old tree may yield about 100 kg fruits while 15-year, 20-year, 30-year old trees yield 200, 300, and 400 kg fruits per tree per year, respectively.
It is a high yielding and early variety of aonla. Fruits are of medium size with average weight of 40 g. Since its pulp is fairly free from fibres, it is highly suitable for murabba making (preserve).
5. Kanchan (NA 4)
A seedling selection from Chakaiya, it is heavy and regular bearer (7.7 female flowers/branchlet), with medium-sized fruits, having higher fibre content. Trees of this variety are of spreading nature. Fruits are of medium size with average weight 30-35 gram. Its pulp is highly fibrous, therefore, suitable for pickles.
A seedling selection from Chakaiya, it is prolific and heavy beared (10.8 female flowers/ branchlet). It is ideal for preserve and candy, owing to low fibre content.
A seedling selection of Francis, it is precocious, prolific and regular bearer (9.7 female flowers/branchlet). This is an ideal variety for preparation of products and has a great promise.
Aonla is propagated by seed as well as by vegetative methods. They are described below.
1. Propagation by seed
Amla plants have been raised by seeds but the plants do not come true to type and there is a high variability. Besides, plants raised through seed are late in bearing. But for raising rootstocks, seedlings are required to be raised through seeds. Seeds attain full maturity by February when they are extracted from the fruits and sown in the last week of February for getting high percentage of germination. Since there is no seed dormancy in aonla, fresh seeds give almost 100% germination. Process of germination can be quickened by soaking dried seeds in 500 ppm GA3 (Gibberellic acid) solution for 24 hours. Seedlings can be raised in seed beds or in polythene bags which takes about four months to attain buddable size.
2. Vegetative propagation
In order to overcome the disadvantages of seed propagation multiplication of superior types of aonla ( amla )has been suggested by adopting vegetative methods. Out of all the various methods of propagation, budding has been found to be the most practical and shield budding is the commercial method of aonla propagation under north Indian conditions.
One year old aonla seedlings with a girth of about 50-75 cm (pencil thickness) should be shield budded in early June with healthy and plump buds from new growth. Forket and patch budding are also very successful. They can be done at any time from June to September. The most important factor of budding of aonla is the proper selection of mother plant which is highly fruitful and the bud is taken from such a branch which has good number of female flowers, otherwise, the plants will be unfruitful due to the presence of large number of male flowers.
For the rejuvenation of old aonla trees or orchards, T -budding or soft-wood grafting can be successfully practiced. For soft-wood grafting, seedlings are raised in situ and headed back severely in the month of May for forcing new vigorous side shoots. On these new shoots, soft-wood grafting method can be employed by way of wedge grafting. For this purpose, use of new apex of rootstock and activated scion is necessary.
Grafts or buddings of aonla are best planted in the beginning of monsoon i.e. in the months of June to July. Since the trees grow to a huge size a distance of 8 to 10 m both ways is recommended. In areas with irrigation facilities, planting can be done in spring (February-March). Before planting, 1 cubic metre size pits are made well in summer and kept open for about a fortnight. In each pit, 3 to 4 baskets of farmyard manure (FYM) is mixed with dug soil and filled. After first rain, the plants are planted in the centre of these pits and staked properly. Immediately after planting, a light irrigation of the pit is carried out.
Regular orcharding of aonla is a rare phenomenon, therefore, nutrition is hardly practised. However, beneficial effects of nitrogen, phosphorus, potash, zinc, copper, manganese and boron have been recorded. According to a study, nitrogen increases vegetative growth and female flowers, while phosphorus increases sex ratio, initial set, fruit retention and yield, total soluble solids (TSS) and vitamin C content of the fruits. Potassic fertilizer increases the fruit retention and the quality.
Therefore, the young plants should be given 15-20 kg of well rotten farmyard manure and the mature tree requires 30-40 kg in each year during September-October. In addition, application of 30 g nitrogen for each year age of the plant up to 10-years and afterwards 680-700 g of nitrogen per year per tree should be provided. Every mature tree should also be fertilized with 1 kg superphosphate and 1-1.5 kg muriate of potash. The above fertilizers should be given in two equal split doses to mature bearing trees, once during September-October and again during April-May after setting of fruits. The plants need to be irrigated after application of fertilizers.
Foliar spray of 0.6 % borax thrice in the months of September and October at about 10-15 days interval has also been recommended to control fruit necrosis which develops due to deficiency of boron.
Aonla trees are hardy and stand very well against drought. Therefore, hardly any irrigation is practised. However: the crop shall be benefited by giving 2-3 irrigations at the time of full bloom and fruit set. During summer, when the fruit is dormant, there may not be any benefit to irrigate trees. However, the young plants require watering during summer months at fortnightly interval, particularly till they have fully established.
Training and Pruning
Aonla ( amla ) tree does not require regular pruning. However, pruning in early years for giving proper shape and development of strong frame may be necessary for which tree should be trained to single stem up to the height of about 1 m and then primary branches can be allowed to regular space all around the trunk.
The pruning of bearing plants can be done after the termination of the crop each year. While pruning, dead, diseased, broken, weak, crossing branches and suckers appearing from rootstock should be removed.
Mulching with organic wastes is very effective tool for establishment of aonla orchards in sodic and ravinous areas. Paddy straw, sugarcane trash and farmyard manure have shown better response. Mulching with organic wastes over a number of years shall be helpful in improving the organic-matter content, infiltration rate, and restricting the upward movement of soluble salts and thus escaping their toxicity menace in salt-affected soils.
Aonla is a quite fast growing tree. Therefore, it is better to follow clean culture in aonla plantation except during the rains when leguminous crops such as moong, cowpea, urd etc. can be grown up to 6 years of tree age. At this age plants usually remain in non-bearing stage and their root system and top growth are not much developed.
ORCHARD SOIL MANAGEMENT
It refers to the management of soil in such a way that productivity is maintained and soil losses are minimum. The technique should be compatible to crop behaviour. In aonla, flowering takes place in February and after the fruit set the fruits remain dormant through summer until monsoon when fruits begin to grow and are ready for harvest in December-January depending upon the climate of the place. Therefore, in summer soil should not be disturbed and natural cover can be allowed to grow. In the beginning of the monsoon the basin can be cleared, fertilizer and manurial application can be affected and the place between rows could be brought under green manure to be ploughed in at flowering stage and left as such.
FLOWERING AND FRUITING
In aonla, flowering takes place on determinate shoots appearing in spring season. The flowers commence opening from the last week of March and the blooming period lasts for three weeks. Male flowers appear in clusters in the axil of the leaf all over the branchlet while female flowers on the upper end of the few branchlets only.
Aonla is a wind pollinated crop as the pollen grains are light and are produced in abundance. Pollination is also helped by honey bees. The initial percentage of fruits set may vary from 12 to 18. The initial poor fruit set is due to low sex ratio and lack of pollination or pollinizer or both. Soon after fertilization which take place within 36 hours of pollination, the zygote rests for 120 to 130 days and endosperm nucleus may also rest for 70 to 80 days after fertilization. Therefore, fruits do not show any symptoms of growth during summer. This zygote dormancy breaks by the end of July as a result of division in endosperm nucleus. Fruits begin to grow with maxi- mum growth in September and attain maturity by the end of November. During this growth phase, flowers and fruits also undergo abscission which has been divided into three waves:
– The fruit drop consists of unfertilized ovaries and degenerated ovules. This is the heaviest drop as 70 % flowers drop off within three weeks of flowering;
– The second drop consists of drop of young fruit-lets at the time of dormancy break; and
– The third drop is spread over a period of rapid growth from August to October. It may be due to embryological and physiological factors such as lack of auxins, improper nutrition and moisture stresses.
When the colour of seed changes from creamy white to brown, it is the proper time to harvest the aonla fruit. Also, the size and shape of the fruit should be kept into consideration. Generally aonla fruits are ready for harvest in November-December. The fruits are light green at first, but when they mature, the colour becomes dull greenish yellow, or rarely brick red.
HARVESTING AND YIELD
Aonla plants starts bearing quite late. Generally, vegetatively propagated tree starts bearing commercial crop after 6-8 years of planting, while seedling trees may take 10-12 years to begin commercial bearing. Productive life of trees is estimated to be 50-60 years under good management conditions.
Maximum vitamin C content is observed in mature fruits, while immature fruits are acrid and low in vitamin C content and minerals. It has been observed that the best time of harvesting aonla fruits is February when the fruits have maximum vitamin C content. Besides, the mature fruits are hard and unyielding to the touch and so are well suited for bulk harvesting as well as distant transportation and marketing.
As far as yield is concerned, the production varies from cultivar to cultivar. ‘Banarasi’ is a poor yielder as compared to ‘Chakaiya’ and ‘Francis’. On an average, a grown up tree should yield 150 to 200 kg fruits per annum.
PESTS, DISEASES AND PHYSIOLOGICAL DISORDERS
Aonla trees are attacked by number of insects and pathogens which significantly reduces the yield. Moreover, it also suffers from some physiological disorders. These are described here under.
There are four insects attacking the tree which includes
1. Bark eating caterpillar (lnderbela tetraonis)
It damages stem and branches of grown up trees by eating bark and making tunnel into them. This insect is the problem of neglected orchards.
The pest can be controlled by spraying 0.03 % Endrin or injecting kerosene oil or petrol in the holes and plugging them with cotton or wet soil during September-October and February-March.
2. Gall caterpillar (Betonsa stylophora)
The young caterpillars bore into the apical portion of the shoot during rainy season and make tunnel. Due to this, damaged region bulges out abruptly into a gall which provides space for movement of the caterpillar. Due to this, apical growth is checked, side shoots develop below the gall and subsequent growth in following season is badly hampered.
This can be controlled by pruning the affected parts and spraying with 2 % Parathion. Prophylactic spray of systemic insecticide like Roger 0.03 % is also suggested.
3. Leaf rolling caterpillars
This caterpillar roll& the leaf and feeds inside it resulting in reduced photosynthetic capacity of leaves and subsequent leaf shedding. It can be controlled by spraying 0.08 % Malathion or 0.04 % Monocrotophos
4. Mealy bug (Nipaecoccus vastatas)
Both nymphs and adults are reported to feed on aonla trees from April to November. Monocrotophos 0.04% or Malathion 0.08 % or methyl parathion 0.03 % are effective in controlling mealy bug.
Aonla is mainly attacked by fungi.
1. Aonla rust
Aonla rust is caused by Ravenellia emblicae. It appears as circular or semicircular, reddish solitary or gregarious spots on leaves from the beginning of August. Generally, one or two pustules measuring 10 to 20 cm in diameter appear on infected fruits. Its occurrence can be prevented by spraying 0.2 % Dithane Z- 78 at the interval of 7 to 20 days during the months of July to September.
2. Fruit rot
It is caused by the fungus Pencillium oxalicum. This disease does not affect fruits much in orchard. The major loss takes place during transit to the market. The earliest symptoms of infection are seen as water soaked lesions on the fruit surfaces which enlarge in size, followed by development of small pin head type colonies of golden yellow colour. The older colonies turn olive green.
As control measures, it is recommended that fruits showing such symptoms are discarded. Bruising injury at the time of harvesting should be avoided as a preventive measure. Fruits may also be treated with borax and salt solution.
3. Leaf rust
It is caused by the fungus Phakospora phyllanthi. It is commonly seen on leaves in the months of July and August. To control it, spray of 0.1 % Bordeaux mixture is recommended.
4. Blue mould
It is caused by the fungus Pencillium islandicum.
Brown patches with water soaked areas are formed and the fruit is ultimately covered with bluish green pustules. Hygienic storage and treatment with Borax and weak solution of sodium chloride have been suggested to control this.
C. Physiological disorders
The main physiological disorders of the tree are internal fruit necrosis and unfruitful which are described below.
1. Internal fruit necrosis
In this disorder, necrosis symptoms start with browning of innermost part of the mesocarpic tissues at the time of en do carp hardening in the second and 3rd week of September; Browning of mesocarp extends towards the epicarp resulting in brownish black areas on the fruit surface in the second and third week of October. Depending upon the severity of the disorder, mesocarp of the affected fruit turns black and becomes corky and gummy pockets develop.
This disorder has been reported to be due to the deficiency of boron for which spray of 0.6 % Borax thrice in the month of September and October at about 10-15 days interval is recommended to control the disorder.
2. Unfruitfulness in aonla
Like other fruits such as mango, apple, etc. unfruitfulness is a problem in aonla orcharding too. This problem is more pronounced in the variety, ‘Banarasi’. Studies have indicated that this problem is not due to lack of pollination as often believed, but it is largely due to absence of female flowers in the tree.
In aonla, fruits are borne in leafy shoots. These shoots bear male flowers in their upper end and female flowers in the lower end. On the basis of male and female flowers these bearing shoots can be divided into two types: (1) shoots bearing both male as well as female flowers, and (2) shoots bearing only male flowers. In the Banarasi variety of aonla, the number of female flowers or shoots containing female flowers are inadequate and, as such, it is highly prone to unfruitfulness. This problem is not encountered in other varieties such as ‘Chakaiya’, ‘Francis’ etc. For overcoming this problem, two points should be borne in mind while raising an aonla orchard.
1. While selecting branch as scion, it should be ensured that scion is taken from the branch bearing maximum number of female flowers.
2. An aonla orchard should have the trees of two or three varieties in order to avoid unfruitfulness of a variety due to lack of female flowers.
Marketing and Storage
After harvesting, grading of fruits on the basis of size should be done. ,Diseased and injured fruits should be discarded and proper packaging of graded fruits in card board boxes or wooden baskets is done.
Aonla fruits can be stored for 7-10 days at room temperature, and for 7:-8 weeks in cold storage at 0-1.66°C temperature with 85-90 % relative humidity.
Dr. Parshant Bakshi and Dr. Amit Jasrotia
Scientists Fruit Science, SKUAST-Jammu