Everything you need to know about amaranth cultivation, production and harvest. Learn about:- 1. Introduction to Amaranth 2. Origin and Distribution of Amaranth 3. Composition and Uses 4. Taxonomy 5. Botany 6. Climate Required for Cultivation 7. Soil Required for Cultivation 8. Sowing Time 9. Manurial Requirement for Cultivation 10. Irrigation Requirements for Cultivation and Few Others.
Contents:
- Introduction to Amaranth
- Origin and Distribution of Amaranth
- Composition and Uses of Amaranth
- Taxonomy of Amaranth
- Botany of Amaranth
- Climate Required for Cultivating Amaranth
- Soil Required for Cultivating Amaranth
- Sowing Time of Amaranth
- Manurial Requirement for Amaranth Cultivation
- Irrigation Requirements for Amaranth Cultivation
- Intercultural Operations of Amaranth
- Harvesting and Yielding of Amaranth
- Insect-Pests of Amaranth
- Diseases of Amaranth
- Cultivated Varieties of Amaranth
1. Introduction
to Amaranth:
Amaranth is one of the ancient groups of plant having great potential for combating under- and mal-nutrition problem. It is also called poor man’s spinach, and is the most common leafy vegetable grown in India during summer and rainy season.
Because of very fast growing short duration crop and large yield production of edible matter per unit area, it fits well in a crop rotation. The statistics on the extent of its cultivation are not available since leafy type amaranth is usually grown in kitchen and market gardens and the grain types as mixed crops along with cereals, pulses, and vegetables.
The grain type species of Amaranthus are popular in the high lands of tropical and sub-tropical America. Recently, the grain types have gained some importance in the Indian plains also, particularly in Gujarat and Maharashtra. Amaranth is unique in many respects that it is easy to cultivate in kitchen garden or on large scale. In taste, nutritional value, and yield, the grain compares favorably with maize and other true cereals.
2. Origin and Distribution
of Amaranth:
The leafy type amaranth is said to be the native of India and the centres of diversity for amaranth are Central and South America, India and Southeast Asia with the secondary diversity in West Africa and East Africa. A wide variation is reported to exist within each species in growth habit, disease resistance, taste, and quality, thus, offering considerable scope for future breeding programmes.
Among the leafy types, Amaranthus tricolor occupies a predominant position in India with different morphological forms in colour and shape of leaves. Watts (1989) reported that this species was extensively cultivated in Bengal by the natives. According to Chandrasekara Ayyar (1941) and Sankaran (1943), Amaranthus tricolor is an important amaranth cultivated in South India.
Amaranthus blitum and Amaranthus tristis are the other species under cultivation. In India, grain amaranth is grown along the whole length of the Himalayas from Kashmir to Bhutan, on the South Indian hills and also in the plains of India. Amaranthus cruentus is cultivated in Guatemala and Amaranthus edulis is restricted to Argentina. The species Amaranthus caudatus is chiefly cultivated in the Andes of America and also distributed in Asia, and probably, in Africa.
3. Composition and Uses of Amaranth:
Composition of Leafy Amaranth:
The leaves and tender stems of amaranth are rich in carbohydrates, protein, calcium, magnesium, potassium, sodium, phosphorus, sulfur, iron, vitamin A, and C. The nutritive values of leafy amaranth have been shown in Table 19.1.
The harvested amaranth plant is 50-80% edible, which only 20-30% of most vegetable plants is utilized directly for human consumption in the United States. The major unsaturated fatty acids in Amaranthus tricolor are linoleic in seeds (49%) and stems (46%) and linolenic in leaves (42%), while the major saturated fatty acid in seeds, stems, and leaves is palmitic acid at 18-25% of the total fatty acids.
Nutritional Composition of Grain Amaranth:
The grains are the rich source of carbohydrates, proteins, crude fibers, calcium, phosphorus, and number of amino acids. The nutritional composition of amaranth grains per 100 g is presented below in Table 19.2.
Grain amaranth protein contains around 5% lysine and 4.4% sulfur, which are the limiting amino acids in other grains. The total lipid content of grain amaranth ranges from 5.4 to 17.0% on dry weight basis, and its grain has a high level of unsaturated fatty acids (about 75%), containing almost 50% linoleic acid.
Effects of Processing on Nutritional Composition:
Most of the work on the effects of processing on vegetable amaranth deals with the effects of various preparation methods on the vitamin C content of Tete (A. hybridus), which is widely consumed in Central Africa and parts of South Africa.
Keshinro and Ketiku (1979) reported an 80.3% loss of ascorbic acid from parboiling for 5 minutes and up to 91.5% after final cooking for 5 minutes. Cooking of fresh Amaranthus hybridus leaves resulted in a 35% loss of ascorbate and a reduction of the chemical score from 71 to 58.
Blanching of 1 g (fresh-weight) portions of A. hybridus for 5 minutes in 10 ml of distilled water resulted in a reduction of total vitamin C content from 560 to 228 mg/100 g dry matter. When boiling of whole leaves and boiling of finely chopped leaves were compared to steaming of leaves, steaming produced the least loss of nutrients such as ascorbic acid, iron, and protein, and also of oxalate.
Uses:
The fresh tender leaves and stern of amaranth are delicious when cooked like other fresh leafy vegetables. Its grains are used as human food in a number of ways but the most common usage is to grind the grain into flour for use in breads, noodles, pancakes, cereals, granola, cookies, or other flour-based products. The grain can be popped like popcorn or flaked like oatmeal. More than 40 products containing amaranth are currently in the markets of United States.
The grain amaranth is a rich source of protein and essential amino acids like lysine, leucine, isoleucine etc., which are essentially required for growth of children. In Kumoan hills of India, local people consider that the grains help in curing measles in children by bringing down the body temperature when the children sleep over the grains of amaranth.
In Tamil Nadu hills, the tribes use the juice of leaves and stems of Amaranthus spinosus for the treatment of kidney stones. Behari et al. (1986) reported that A. viridis is used in treating snakebites.
4. Taxonomy
of Amaranth:
Amaranth belongs to the genus Amaranthus and the family Amaranthaceae, which comprises of 65 genera and 850 species. The genus Amaranthus includes 50-60 species, the leaves of which are edible. These are the most important leafy vegetables of the tropical countries in South Asia, Southeast Asia, East Africa, Central Africa, West Africa, Ethiopia, the Pacific, and Far East.
The important species of leafy amaranth are Amaranthus tricolor L., Amaranthus dubius Mart. Ex Thell., Amaranthus lividius, Amaranthus blitum, Amaranthus tristis L., Amaranthus spinosus L., Amaranthus viridis L. and Amaranthus graecizans L.
The most popular grain amaranth species are Amaranthus hypochondriacus L., Amaranthus cruentus L. and Amaranthus caudatus L. Interspecific and inter-varietal hybridization in nature have caused a wide variation differing in pigmentation of plant parts as well as in the inflorescence. Taxonomists recognize two sections in amaranth, viz. Amaranthus and Blitopsis with equal number of species in each.
Bailey (1966) described Blitopsis as a section, where all species under this have flower clusters in axils, while species under Amaranthus section have only terminal flower clusters. Section Amaranthus includes important grain types, while section Blitopsis consists of the green types.
Cytologically Chandrasekara Ayyar (1941) studied the taxonomy of eleven Amaranthus species that are given below:
5. Botany
of Amaranth:
Amaranth is an annual herb, erect or trailing, mostly unarmed and rarely armed, scarce to profuse branched; shallow to deep tap root system; stem green to purple or with mixed shades of these two colors, glabrous and succulent; leaf simple, alternate or opposite, exstipulate, entire, obviate to lanceolate with acute tip, green to purple or with different shades of these two colours, purple coloration prominent in young leaves and fades away at maturity; inflorescence terminal and axillary, branched spikes differently colored from green to deep purple and orange, and with different shades of these colors.
The basic unit of the inflorescence is dichasial cymes called glomerule; flowers small, regular, mostly unisexual, monoecious, pentamerous, bracteate and bracteolate, which are scaly, perianth 4-5, imbricate, membranous, often persistent; stamens 2-5 placed opposite to perianth parts, often some reduced to staminodes, filaments either free or united below, anthers one or two celled; carpels 2-3, syncarpous; ovary superior with commonly one campylotropus ovule; style single to 2 or 3 branched; fruit utricle, indehiscent, enclosed by the persistent perianth parts; seeds varying in colour, black, brown or white, compressed, smooth and shiny with floury endosperm.
In general, most of the cultivated species are monoecious. The proportion of male and female flowers varies in the inflorescence. Each glomerule consists of an initial staminate flower and an indefinite number of pistillate flowers. The extent and degree of cross-pollination is governed by the proportion of the staminate and pistillate flowers in an inflorescence and the position of the inflorescence on the plant.
In monoecious species including grain amaranth, two types of arrangement of the staminate and pistillate flowers in the glomerule of inflorescence occur. In all species except Amaranthus spinosus, the first flower of each glomerule is staminate and the rest are pistillate. In Amaranthus spinosus, each glomerule bears flowers of same sex with pistillate flowers in the axils of branches and at the base of terminal inflorescence, while the staminate flowers are terminal on the main axis and lateral branches.
The following table indicates a simplified provisional key to a few Amaranthus spp.:
6. Climate Required for Cultivating Amaranth
:
Amaranth is a warm season crop adapted to the conditions of hot and humid tropics, however, also suitable for cultivation in temperate climate during summer. A temperature range of 20-30°C is optimal for its better vegetative growth.
Amaranthus species that grow under varying climatic conditions differ in their day length requirements and respond differently to changes in photo and thermoperiodism. A. caudatus, A. cruentus and A. edulis are short-day species, while the commonly grown grain Amaranthus species, viz. A. hypochondriacus is reported to be day-neutral.
All the species, however, have early and late cultivars. Grain type Amaranthus is highly resistant to drought but lodges because of heavy rainfall or high wind velocity resulting in loss of yield. The grain type Amaranthus are adapted to both tropical and temperate conditions, while the leafy ones are best grown in the plains.
7. Soil Required for Cultivating Amaranth
:
Though amaranth can be grown in a wide range of soils, sandy loam slightly acidic in nature is preferred. Heavy clay soils with very poor drainage or sandy soils with very poor water holding capacity are unsuitable for its cultivation. It requires a very good tilth and thorough field preparation for getting the best growth.
The ideal pH range is between 5.5 and 7.5, however, some strains of amaranth can be grown in soils with pH as high as 10.0. Since the crop is directly sown and the seed size is small, the seedbed should be thoroughly prepared and free from clods.
8. Sowing Time
of Amaranth:
In north India, summer crop is sown in February-March and the rainy season crop in June-July. In southern parts, amaranth is sown almost throughout the year. For grain amaranth, the crop is, generally, sown in the first or second week of June just after the first monsoon shower.
The seed rate of amaranth is 2 kg/ha for direct sowing and 1 kg/ha for the transplanted crop. Anonymous (2004) recommended a seed rate of 2.5 kg/ha for sowing in Tamil Nadu state. In case of grain amaranth, a seed rate of 1½ to 2 kg/ha is used for good grain yield.
1. Direct Sowing
The seeds are sown directly in the field by either broadcasting or drilling in lines 20-30 cm apart, according to variety and kind of the crop. For direct sowing, the seed is mixed with 10 parts of sand for even distribution. Because of its small seed size, shallow sowing about 1-1.5 cm deep is recommended.
In grain amaranth, traditionally, the seeds are broadcast but better crop stand is achieved if seeding is done in rows. The depth of sowing should be less than 2 cm in view of very small grain size, with 50 cm spacing between rows and 20 cm between plants.
The field is prepared to a fine tilth and beds of 2.0 x 1.5 m are formed. In the prepared beds, the seeds are sown in rows spaced at 20 cm, and later, 10-15 days after sowing thinned to a spacing of 20 cm between plants, leaving one or two plants per hole. Fasheun (1989) viewed that flat beds were better than ridges or raised beds since they had high infiltration rate and conserved water for longer period.
In south India, there is also a practice of transplanting amaranth with a seed rate of 1 kg/ha, especially the variety Badi Chauli either as a pure crop or along the border of beds of other vegetables. Transplanting 20-30 day old seedlings in trenches at a distance of 20 cm is recommended by the Kerala Agricultural University.
A study on the effect of population density and age at transplanting on the growth, frequency of harvests and total vegetative yield revealed that transplanting at 10 x 10 cm spacing is advantageous for obtaining higher yield per unit area, however, plants transplanted at a spacing of 20 x 10 cm exhibited better growth and more number of harvests since the plants transplanted closely flowered faster than the widely spaced ones. Age of seedling at transplanting had an influence on yield and transplanting of 15-20 day old seedlings gave higher yield and more number of harvests.
9. Manurial Requirement
for Amaranth Cultivation:
Amaranth responds very favorably to fertilizers and organic matter, hence, a farmyard manure of 25 tonnes, nitrogen 50 kg, phosphorus 50 kg, and potash 20 kg/ha is recommended as basal application. For clipping type of amaranth like CO 3, a higher fertilizer dose of 75 kg nitrogen and 25 kg each of phosphorus and potash per hectare is recommended. Nath (1976) recommended 25 to 30 tonnes of farmyard manure at the time of field preparation and 27 kg each of nitrogen and phosphorus and 54 kg of potash per hectare.
Singh et al. (1985) reported that in variety CO 3, nitrogen at 60 kg/ha applied in split doses, one-half as basal dressing and the rest half as top dressing after the fifth clipping (eight weeks after sowing) registered the highest plant height and optimum leaf – stem ratio and the highest leaf yield.
Yawalkar and Ram (2004) recommended 25 tonnes of farmyard manure and nitrogen 100 kg, phosphorus 50 kg and potash 50 kg/ha and also advocated to supply the entire dose of farmyard manure at the time of last ploughing and full dose of phosphorus and potash and half dose of nitrogen before sowing, and the remaining half of nitrogen at 15 days after sowing.
Gopalakrishnan (2004) recommended 50 tonnes of farmyard manure and 100: 50: 50 kg of NPK/ha for Kerala conditions. A study on Azotobacter and Azospirillum inoculants for nitrogen economy reveals that plant height, root biomass, leaf area index, and yield were significantly higher in treatment combination of Azospirillum inoculation along with farmyard manure and 75% fertilizer nitrogen, and this treatment significantly delayed flowering in amaranth. A basal dose of 25 tonnes of farmyard manure, Azospirillum 2 kg, Phosphobacteria 2 kg, nitrogen 75 kg and potash 25 kg/ha is recommended for best results.
The effect of nitrogen (50, 100 and 150 kg ha-1), phosphorus (50, 75 and 100 kg ha-1) and potash (50, 75 and 100 kg ha-1) and frequency of cuttings (no leaf cutting, one leaf cutting and two leaf cuttings) on a cultivated variety Arun revealed a significant increase in yield due to increasing levels of all the three nutrients. Plants with no leaf cutting recorded the highest seed yield (1073 kg ha-1).
Neither the nutrients nor the cuttings had significant effect on seed germination and seedling vigour. The optimum number of leaf cuttings that can be taken from a seed crop to get maximum net return was found to be one leaf cutting. After taking one leaf cutting at 30 days after planting, the crop should be left for seed production.
10. Irrigation Requirements
for Amaranth Cultivation:
The crop is generally sown in field having enough moisture, however, if moisture in the field at the time of sowing is not sufficient the first irrigation is given immediately after sowing, and thereafter, the field is irrigated on third day. Subsequent irrigations are given at 3 to 5 day intervals during summer, and in rainy season as and when required.
In general, irrigation has to be given at weekly intervals after germination. The irrigation water should be supplied slowly and steadily since rapid water-flow may wash-off the seeds to one end of the bed resulting in uneven stand of crop.
Working with amaranth Sheela (1988) evaluated a low cost drip irrigation system fabricated with the cheapest and locally available materials. With half the quantity of water given in basin method, drip method of irrigation gave significantly higher yield than basin method of irrigation. Weed growth was also found to be less in the plots irrigated by drip method. Rajan (1991) studied the response of red and green varieties to different water management practices and nitrogen doses.
The treatments consisted of four irrigation levels (irrigation at IW/CPE ratio of 0.75, 1.00 and 1.25 and the farmer’s practice of daily irrigation) and four levels of nitrogen (50, 75, 100, and 125 kg ha-1). Biometric characters were favorably influenced by frequent irrigations and higher nitrogen levels. Total yields were also higher in more frequently irrigated treatments and at higher nitrogen levels.
As the frequency of irrigation and levels of nitrogen were increased, protein content also increased and the maximum was recorded at a daily irrigation treatment and at nitrogen 125 kg ha-1. The uptake of nitrogen, phosphorus, and potassium were enhanced by frequent irrigations and nitrogen application up to 125 kg ha-1.
11. Intercultural Operations
of Amaranth:
Amaranth is sown at a closer spacing, hence, weeds do not pose much problem in this crop, even though, removal of weeds periodically in early stages of crop is essential to reduce competition with crop for nutrients, light, moisture and space, resulting in better growth of crop. In addition, hoeing in early stages not only razes the weeds but also makes better aeration into the soil and mixes the fertilizers that are top-dressed in standing crop.
Usually, hoeing is done after each cutting with a hand hoe where the crop is sown in lines. In case of leafy amaranth, the plants 10-15 days after sowing are thinned to a spacing of 20 cm between plants, leaving one or two plants per hole, while in grain amaranth, the plants are thinned to have a spacing of 30 x 30 cm on 25th day, and they are allowed to flower.
In case of grain amaranth, the seed germinates within 4 to 5 days after sowing and needs maximum care until it attains a height of about 25-30 cm. In fact, this is the most critical stage for obtaining maximum yield potential of the crop. During this phase, it must be properly spaced, made free from weeds and must receive adequate moisture. One more weeding is necessary after 30 days of sowing.
At seedling stage, one spray of some systemic fungicides to check the attack of damping-off disease is necessary at the seedling stage. Once the stand is established, maintenance is relatively easy. The broad leaves and erect habit quickly create a close canopy, making under strong weeds only a minor problem.
12. Harvesting
and Yielding of Amaranth:
In greens type varieties like CO 1 and CO 2, the plants have to be pulled out along with their roots on 25th day of sowing for tender greens and at 40th day after sowing for immature stems.
In clipping types like CO 3, the first clipping can be had on 25th day of sowing, and further, clippings are repeated once in a week up to 90th day. However, in grain type amaranth, the grains mature much earlier and the plant dries up quite late. If the heads are allowed to remain until the plant dry up, heavy shattering of grains, which leads to heavy grain loss, is noticed.
The heads are cut when the plant is still somewhat green and start weathering and kept for sun drying for 6-7 days in the threshing yard. Threshing is done by beating. The produce is threshed and winnowed like other cereals. Unusually, the harvesting is done early in the morning when the plants are somewhat wet due to night dew to avoid grain shattering in cutting heads.
The crop will be ready for harvest in 80-120 days depending on the variety and season. In West Bengal and in the South, thickened stems of the fully-grown plants are also used for cooking after peeling the outer bark.
Leafy amaranth does not stand storage for more than a few hours under ambient conditions. Normally, it is not stored under CA storage. Among different methods of storage, refrigerated storage is better than other methods. In case of grain amaranth, the dried spikes are threshed to separate the grains, which are used to prepare popped grain, gruel, cakes, and other preparations like amaranth malt.
Working with amaranth Jijiamma (1989) estimated the nutritional composition and organoleptic qualities of red and green varieties of A. tricolor. The concentration of nutrients was highest when harvested around 20 days after transplanting. Storage of leaves for different duration has not affected the nutrients content except ascorbic acid. Loss of nutrients during cooking was found to be lesser during steaming, while it was higher in respect to ascorbic acid in leaves cooked by boiling.
Different types of vessels had no influence in altering the nutrients content of leaves. The iron content was found to increase when cooked in cast-iron pan. Loss of ascorbic acid was found to be significantly higher when cooked in copper and iron vessels. An analysis of the acceptability of leaves cooked under different methods indicates that boiling in water was the most acceptable and aluminium and steel vessels were found more suitable for retaining the qualities of leaves.
Among the recipes prepared by Suman (2000), Cheera minced meat Thoran obtained the highest score and Cheera pittu scored the lowest in the acceptability study among 120 adolescents. Assessment of nutritional status of adolescents after the supplementation study reveals significant increment in anthropometric measurement and haematological indices.
The yield of amaranth depends on species, variety, soil fertility, growing season, climatic conditions, and cultural practices followed during the cultivation of crop. A healthy crop with good management practices gives a greens yield of about 20 to 40 tonnes per hectare depending on the variety. The higher yield is realized in March sown crop as compared to June sown crop.
The yield of different types of produce is given below:
13. Insect-Pests
of Amaranth:
Since tender leaves and stems are the economic parts, normally no insecticide is used for the control of insect-pests, however, if pests like leaf Webbers or caterpillars occur, the insecticide like Malathion 1.5 ml/litre of water can be sprayed.
Studies conducted by Srinath (1990) on the management of amaranth pests demonstrate that the use of plant extract of Thevatia neriifolia followed by Azodirachta indica, Clerodendron infortunatum and Eupatorium odoratum was highly effective against leaf Webber Psara basalis. Clerodendron infortunatum and T. neriifolia followed by A. indica, Nerium oleander, and E. odoratum were effective against Amarasca biguttula biguttula.
Spray of 4% extract of A. indica, 2% of T. neriifolia and 4% of C. infortunatum protected the amaranth against A. crenulata and R. basalis. Toxicity of the extracts of A. indica and T. neriifolia was augmented with soap at lower concentration. The seed extract of T. neriifolia was at par with insecticides in controlling leaf Webber caterpillars. In another study conducted at Kerala Agricultural University, the seed oil emulsions of neem/samanea at 10% were also found effective for the control of leaf Webbers.
Leena (2001) tested 13 different commercial formulations of neem and microbial and chemical pesticides for the control of leaf Webbers, viz. H. recurvalis and P. basalis, weevil, H. truncatulus and grasshopper, A. crenulata but found six formulations, viz. Econeem, Neemazal, Halt, Dipel, Delfin, and Nuvan the most effective. Dipel @ 0.7 ml/litre of water and Halt @ 0.7 g/litre of water gave better results for the control of leaf Webbers and weevils, respectively.
Unnikrishnan (1986) studied differential pathogenecity of various exotic strains of Bacillus thuringiensis (HD 1, HD 2, HD 109, and indigenous strain locally isolated from dead larvae of Sylepta derogata on amaranth leaf Webbers, Psara basalis and Hymenia recurvalis and their possible use in controlling pests in the field. The LC 50 of HD 1, HD 2, HD 109, and local strain against second instars larvae of H. recurvalis were 8.57 x 107, 3.7 x 107, 2.719 x 107, and 8.03 x 107 spores per ml, respectively.
The LC 50 of Malathion was 0.02549%. The plots sprayed with HD 109 at 4.6 x 108 spores per ml gave superior control of the pests. The leaf damage inflicted was the least and the yield was the highest. The effect of HD 1 was at par with the effect of HD 109. All treatments were superior to control.
For controlling ants, termites and other burrowing insects, lindane 13% dust @ 10 kg/ha is recommended.
14. Diseases
of Amaranth:
Diseases are not a severe problem in amaranth. However, leaf spot and white rust are two diseases, which affect the amaranth plants.
1. Leaf Spot (Cercospora Sp.):
This disease is characterized by the presence of numerous small brown circular spots on the leaves. In the beginning, the spots are small round with concentric rings but later on these spots increase in size, and sometimes, they coalesce. During rainy season, disease infection occurs within 15 days of planting and results in the highest percentage of disease severity.
Experiments on seasonal influence of diseases recorded the highest disease severity in July and the least in April. Low temperature, high relative humidity, and high rainfall weather conditions favor the development of disease.
i. Avoid cultivation of red leaved varieties since they are highly susceptible compared to green types.
ii. Spray Bordeaux mixture (5:5: 50) or Blitox 0.3% three times at an interval of 15 days.
2. Leaf Blight (Rhizoctonia Solani):
The symptoms are wilting of the foliage and a dull leaf color, followed by yellowing and death of tissues usually beginning on the older leaves. Petioles remain attached to the crown after they die. The base of the petioles will have dark brown to black lesions, and the infected root tissues are dark brown to black.
Rhizoctonia solani survives as mycelium or sclerotia in the soil, primarily in organic debris. The fungus becomes active when soil temperatures reach 25-33°C. The disease is favored by poor soil structure and high soil moisture.
i. Grow resistant green amaranth variety CO 1 in combination with red amaranth to get a mixed stand of resistant and susceptible types.
ii. Avoid splash irrigation.
iii. Research on application of microbial antagonists reveals that Trichoderma longibrachiatum and a fluorescent Pseudomonas sp. were effective in suppressing the disease in vitro. Application of microbial antagonists Trichoderma longibrachiatum in the soil followed by foliar spray at 15 days interval starting from 25 days after sowing was very effective in controlling the disease in field conditions than by applying bacterial antagonists.
iv. Spray the crop with mancozeb 0.4% in 10% cow dung supernatant (CDS) as fine droplets thoroughly so that the spray solution may reach the under surfaces of the leaves also. The spraying should be done at weekly intervals initially and stopped two weeks prior to harvest.
The disease is characterized by white blisters like circular or irregular pustules on the lower surface of the leaf and opposite each pustule on the upper surface a yellow patch develops. Severe infection causes the leaves to die and turn brown, giving the field a blighted look.
i. Follow long crop rotation with non-host crops.
ii. Spray the crop with Indofil M-45 or any other copper fungicide 0.2% at 10-12 days intervals.
Viral Diseases:
The effect of mosaic disease on certain chemical constituents of amaranth was studied by Daniel (1968) who found higher total nitrogen content, low total carbohydrate and chlorophyll contents, and narrow C : N ratio in the diseased leaves than that of healthy leaves.
The virus is found readily sap transmissible, however, the insects Bemisia tabaci, Aphis craccivora and the caterpillars of Hymenia fascialis fail to transmit the virus. The role of weeds in the perpetuation of 13 virus diseases in amaranth was studied by Mathew (1981).
Mosaic virus of A. viridis was transmitted by sap inoculation and insect vectors such as Aphis craccivora and A. gossipii. It had a dilution point of 1 : 1500 to 1 : 200, thermal inactivation point of 55-60°C, and longevity in vitro at room temperature 48-72 h and at refrigerated conditions 72-96 h.
Mosaic virus of A. viridis infected A. caudatus, A. gangeticus, Celosia cristata and Gomphrena globosa causing mosaic symptoms. Based on symptoms, modes of transmission, physical properties, and host range, mosaic virus of A. viridis was identified as strains of amaranth mosaic virus.
i. Control the vectors like aphids by spraying Acephate 75 SP 1 g/liter, methyl demeton 25 EC @ 2 ml/liter, or phosalone 35 EC @ 2 ml/liter.
ii. Sufficient waiting period should be given after spray for harvesting of greens.
15. Cultivated Varieties
of Amaranth:
A cultivar tolerant to insect-pests and diseases developed at Tamil Nadu Agricultural University, Coimbatore in 1968 through a selection from a local type belongs to the species A. dubius. It is mainly grown for tender greens as well as immature stems, which are thick and fleshy.
The leaves are broad, thick, and dark green in colour. The crop duration is 25 days for tender greens and 50-60 days for immature stems. It produces 7-8 tonnes of green matter from a hectare. Seeds are small and black in color.
A variety tolerant to insect-pests and diseases developed at Tamil Nadu Agricultural University, Coimbatore through a selection from local type (A. tricolor) and released in the year 1976 is especially suitable for early harvest. The stems remain tender and succulent, thus, both leaves and stems are used as vegetable.
Plants medium tall with 125 cm height; leaves green, lanceolate, slightly elongated; stem green, succulent; spikes terminal and axillary; seeds bolder and black and exhibit early germination with vigorous growth. The crude fibre content is less (1.3%) with 19.0 mg of iron and 20.0 mg of calcium per 100 g. The crop duration is 25 days for tender greens and 35-50 days for immature stems. It produces green matter of 10-11 tonnes per hectare.
A clipping type variety developed at Tamil Nadu Agricultural University in 1981 belongs to A. tristis (Synonym – A. tricolor var. tristis). The leaf to stem ratio is high (2.0), and this enhances the palatability of cooked greens to a great extent. The greens of this cultivar are nutritious with 25.2 mg of ascorbic acid per 100 g of fresh matter and 2.48% calcium, 0.8% iron and 1.74% crude fibre.
As a seed crop, this cultivar flowers in 35-40 days after sowing and matures in 85- 90 days. The cultivar lends itself for ten clippings commencing from 25 days after sowing and provides a continuous supply of luscious tender green for a period of three months at weekly intervals. The total green matter yield would be 31.0 tonnes per hectare.
A variety developed at Tamil Nadu Agricultural University, Coimbatore through a single plant selection (A 166-1) from an OP plant introduction has double color (green and pink) large obovate leaves. The plants are medium tall with high biomass and nutritive value. It gives a rosette growth in early stages.
The stem and petiole, which are free of fibre, are pinkish red in color. It is also ideal for patio or container cultivation. The crop can be harvested at 30 days for tender greens (10 t/ha) and at 50 days for immature tender stem (30 t/ha).
A variety developed at Indian Agricultural Research Institute, New Delhi belongs to the species A. blitum, and responds well to cuttings, thus, is suitable for its leafy shoots. Plants are erect in growth habit and slightly dwarf with thin stem. Its leaves are small, green in colour. Flowers are borne in clusters in leaf axils. It is best suited for cultivation in early summer but can be grown in rainy season too.
Another variety developed at Indian Agricultural Research Institute, New Delhi belongs to the species A. tricolor, and responds well to cuttings since the economic part of this cultivar is leafy shoots. Stem is thick and green and leaves large and green. This variety is distinguishable by its much longer growing period. It is best suited for cultivation in summer season.
A variety developed at Indian Agricultural Research Institute, New Delhi through a selection from a heterozygous collection from TNAU, Coimbatore belongs to the species A. tricolor. The leaves are green with broad ovate lamina and stem is green. The leaves will be ready for harvest in 30-35 days after sowing and the harvest extends up to 70-85 days. The variety is specifically suited for cultivation in summer season. On an average, it produces green matter yield of 55 tonnes/ha.
Another variety developed at Indian Agricultural Research Institute, New Delhi through a selection (S 44-6) from a natural cross between A. tricolor and A. tristis is a combination of good characters of both the species but predominantly of A. tricolor. The leaves are glossy green with broad ovate lamina. The stem is glossy green, and stem leaf ratio is 1 : 4.6.
The leaves will be ready for harvest in 21-25 days after sowing, and the duration of harvest extents up to 70-75 days. It takes 90-100 days from sowing to flower. It is best suited for growing during Kharif season in plains of North India. The average green matter yield is 35 tonnes per hectare.
A vegetable amaranth variety developed at Indian Agricultural Research Institute, New Delhi belongs to the species A. tricolor. The upper surface of the leaf is deep red or magenta, whereas, the lower surface is purplish red. It provides first flush of leaves in 24-33 days after sowing. Subsequently, four cuttings can be taken at an interval of 8-10 days. On an average, its green matter yield is 45-49 tonnes/ha. It can be grown in Kharif as well as in spring season.
A multi-cut purple variety developed at Indian Institute of Horticultural Research (Hesserghatta) Bangalore through pure line selection from a local collection IIHR 49 produces broad dark purple color leaves. It becomes ready for first cutting 30 days after sowing and two subsequent cuts at 10-12 days interval. Leaves are rich in calcium and iron. Its average yield is 270 quintal per hectare.
An amaranth variety belongs to the species A. polygonoides. The plants are short with alternate leaves on the main stem. The leaves are small when compared with A. dubius, obovate with blunt bifurcated tip and have long petioles. The juncture of the stem base and root is dark pink in colour. A miniature branch, which has very small alternate leaves, starts from each leaf axil. Uprooting plants 25 days after sowing the leaves and tender stems are used.
1. CO 4:
A green-cum-grain type variety developed at Tamil Nadu Agricultural University, Coimbatore through a selection belongs to the species A. hypochondriacus. The plants that make rapid vegetative growth within a period of 20-25 days are dwarf in growing habit, for which they are thinned at a spacing of 30×30 cm. By this way of thinning, a greens yield of 7-8 tonnes/ha can be obtained. The remaining plants are allowed to produce the inflorescence and set seeds.
The grains are separated after attaining proper maturity. The grain yield is 2.0-2.5 t/ha in 80-90 days. The seeds are rich in protein (15.95%) and essential amino acids like lysine (7.5 mg/100 g), phenylalanine (5 mg/100 g), leucine (1.2 mg/100 g) and isoleucine (1.8 mg/100 g). The grain can be substituted for minor millets like Ragi and Thenai. It is amenable for various food preparations like any other grains.
A variety developed in Montana, USA from the line RRC-A362 belonging to A. cruentus species has a central main panicle with thick and erect to drooping finger-like branches. Days to maturity vary from 122 to 127. It is 198 cm tall under irrigated conditions and shows no sign of lodging.