Panicum miliaceum (PROSEA)
Panicum miliaceum L. cv. group Proso Millet
- Protologue: Sp. pl.: 58 (1753); cv. group Proso Millet: name is proposed here.
- Family: Gramineae
- Chromosome number: 2n= 36
- Panicum miliaceum L. subsp. miliaceum sensu Tsvelev (1968).
- Proso millet, common millet, Russian millet (En)
- Brown-corn millet (Am)
- Grand millet, millet commun (Fr)
- Indonesia: sekoi sejati (Javanese)
- Philippines: kabug (Bisaya)
- Vietnam: kê, cỏkê.
Origin and geographic distribution
Proso millet is of ancient cultivation (5000 years in China, 3000 years in Europe); it is mentioned in the Bible and was the "milium" (millet) of the Romans. It was domesticated in central China and spread as a cereal and as a weed to many, mainly temperate, regions all over the world. As a cereal it is most important in northern China, Mongolia, Korea, Russia, Afghanistan, Pakistan, India and southern Europe. In the Bronze Age it spread widely in Europe, including to northern regions where the cold-susceptible foxtail millet (Setaria italica (L.) P. Beauvois) could not be grown. In Europe and the United States its popularity as a cereal declined after the large-scale introduction of potato and maize, and it is now mainly cultivated as a feed for cage birds. In Africa it is cultivated in Malawi, Zimbabwe and Ethiopia. In South-East Asia it is occasionally cultivated in the drier areas.
The husked grain of proso millet has a slightly nutty flavour and can be eaten whole after roasting or after cooking or boiling like rice. Millet flour is used for making mush, porridge, flat bread or chupatty. If mixed with wheat flour it may be used to make leavened bread, but some cultivars have glutinous endosperm. The flour is also used for making wine or beer. The grain is a feed for animals, fowls and cage birds. The green plant is used as a forage, but the quality of the straw is poor. Brooms are made from the straw. Starch from the grains is used for sizing textiles.
Production and international trade
Proso millet is usually used locally and, since it is quick-maturing, may fill periods of scarcity before the main crops of other cereals are harvested. The crop is of some importance locally, but statistics are scarce and data on proso millet are usually lumped with data on other millets. Estimated annual world production of proso millet is 5 million t (Russia 2-3 million t, China 1.5 million t, India 0.5 million t) from about 5.5 million ha. However, when irrigation facilities are available, the area under proso millet declines in favour of other crops such as rice, wheat or sesame.
The whole grain of proso millet contains per 100 g edible portion approximately: water 10 g, protein 11 g, fat 4 g, carbohydrates 61 g, fibre 8 g and ash 4 g. The energy value is about 1580 kJ/100 g. The approximate composition of flour per 100 g edible portion (dry matter basis) is: protein 12.3 g, fat 1.7 g, carbohydrates 83.7 g, fibre 0.9 g and ash 1.4 g. The energy value is about 1720 kJ/100 g. Proso grain is rich in minerals such as phosphorus, calcium and iron, with traces of manganese, copper and zinc. It contains some of the B vitamins and is rich in choline, but as in most cereals, the limiting amino acid is lysine. The 1000-grain weight is 5.5 g for husked grain, 7.1 g for unhusked grain.
- An erect annual grass, up to 1 m tall, usually free-tillering and tufted, with a rather shallow root system.
- Stem cylindrical, internodes hollow, glabrous to variously hairy.
- Leaf blade linear-lanceolate, 15-30 cm × 0.6-2 cm, variously hairy as is the cylindrical sheath; ligule membranous, about 1 mm tall, with cilia about 2 mm long.
- Inflorescence a slender panicle up to 45 cm long, open or compact, erect or drooping; pedicels of all spikelets without joints; spikelet ovoid-elliptical, 4-5 mm long, 2-flowered, glabrous; glumes unequal, upper glume as long as spikelet; lower floret sterile; upper floret hermaphrodite with coriaceous broad (1.7-2.2 mm) lemma and palea, 2 lodicules, 3 stamens and 2 styles with plumose stigmas.
- Caryopsis broadly ovoid, up to 3 mm × 2 mm, smooth, variously coloured but often white, enclosed by the persistent lemma and palea but shedding easily.
Growth and development
Proso millet has a short growing cycle and is adapted to areas of low rainfall. On average, after sowing it needs 1-2 months to reach the 50% flowering stage and it matures in 2-4 months after sowing. Proso millet is partly self- and partly cross-pollinated.
Other botanical information
P. miliaceum is a complex species with wild and cultivated taxa. In the literature those two groups have been classified as subspecies (for the wild taxa: subsp. ruderale (Kitag.) Tsvelev (synonyms: var. ruderale Kitag., P. spontaneum Lyssov ex Zhukovsky); for the cultivated taxa: subsp. miliaceum), but here it is proposed to classify the cultivated forms into cultivar group Proso Millet. The wild taxa have broadly lax panicles, usually jointed pedicels and narrow lemmas, while the culta have either lax or compressed panicles, unjointed pedicels and wider lemmas.
The true wild form of subsp. ruderale is native to central China and is considered to be the ancestor of the cultivated forms. In temperate Europe, temperate Asia and in the United States, however, wild forms occur that differ from the wild form in China and are most probably derivatives of cultivated forms which have regained the ability of natural seed dispersal and spread as weeds.
Cv. group Proso Millet comprises many cultivars and landraces, and 5 cv. subgroups can be distinguished:
- cv. subgroup Compactum (synonyms: convar. compactum Koernicke, race Compactum): Inflorescence small to large, more or less elliptical in outline, drooping at maturity, with spikelets crowded along the panicle branches. Grown in Japan, the former Soviet Union, Iran and Iraq. Together with subgroup Ovatum it comprises the highest evolved Proso Millet cultivars.
- cv. subgroup Contractum (synonyms: convar. contractum Alefeld, race Contractum): Inflorescence large, semi-compact, drooping at maturity, with spikelets crowded along the length of the panicle branches. Grown in Europe, Transcaucasian Russia, and China. The cultivars grade morphologically into the subgroups Compactum and Patentissimum.
- cv. subgroup Miliaceum (synonyms: convar. effusum Alefeld, race Miliaceum): Plants with numerous decumbent culms, each producing several racemes. Inflorescence large with spreading branches bearing relatively widely spaced spikelets and lacking spikelets at the base. This subgroup closely resembles the wild subsp. ruderale , and the other subgroups were derived from this subgroup under cultivation. It is grown across the whole range of proso millet cultivation and comprises the most primitive cultivars.
- cv. subgroup Ovatum (synonym: race Ovatum): Difficult to distinguish from subgroup Compactum (its inflorescences are usually smaller) with which it comprises the most advanced cultivars. Its cultivars are grown in the former Soviet Union, Turkey and Afghanistan.
- cv. subgroup Patentissimum (synonym: race Patentissimum): Resembles subgroup Miliaceum in its lax inflorescences with spreading branches having a sterile zone at the base and becoming curved at maturity. It is grown in India, Bangladesh, Pakistan, Afghanistan, Turkey, Hungary, the former Soviet Union and China. Just like subgroup Miliaceum, it comprises primitive cultivars.
Within the subgroups, the cultivars are mainly distinghuised on the basis of grain colour (varying largely from white, yellow, brown, red, to almost black) and on ecological adaptation.
Proso millet is mostly grown in temperate and subtropical regions. Although it has a C4-cycle photosynthetic pathway, it is cultivated further north than any other millet, the limit being the June isotherm of 17 °C and the July isotherm of 20 °C. It is adapted to conditions which are too hot and too dry, and to soils too shallow and poor for successful cultivation of other cereals. It is tolerant of a very wide temperature range but susceptible to frost. Cultivation occurs up to 3000 m altitude in the Himalayas. Proso millet has one of the lowest water requirements of all cereals. An average annual rainfall of 200-450 mm is sufficient, of which 35-40% should fall during the growing period. Most soils are suitable for its cultivation, except coarse sand.
Propagation and planting
Proso millet is commonly propagated by seed, either broadcast or drilled in rows 20-25 cm apart and at a distance of 7.5 cm in the row. This corresponds with a seed rate of 10-12 kg/ha. For optimal germination seed should be soaked in water for 24 hours and planted no deeper than 4 cm. In the Bombay area in India, the crop is grown from transplanted seedlings. In Russia grains are often dressed with fungicides to combat soilborne diseases.
In Russia, weeds are eradicated mechanically with a cultivator. When necessary, herbicides are applied at the 3-5-leaf-stage. Per t proso grain, the crop extracts about 30 kg N, 8 kg P and 34 kg K from the soil. Usually, per ha 30-60 kg N, 15-25 kg P, and 25-35 kg K is applied in autumn, with an additional 10 kg N during the growing season. In Russia, proso millet is usually grown in rotation with a forage grass, winter wheat, spring wheat or barley. In Bangladesh, the rotation may comprise a pulse, wheat, jute, rice, potato or a Brassica crop.
Diseases and pests
Proso millet is relatively little affected by diseases and pests and none of them is serious. Smuts (Sphacelotheca destruens and Ustilago spp.), ergot (Claviceps spp.), rusts (Puccinia and Uromyces spp.), downy mildew (Sclerospora graminicola), leaf blight (Helminthosporium sp.) and foot rot (Sclerotium rolfsii) may cause some damage. The bacterium Xanthomonas holcicola can cause melanopathy, a darkening of the endosperm.
Insect pests like stem borers (Chilo partellus, C. suppressalis and Sesamia inferens), midges, bugs, army worms and shoot flies (Atherigona miliaceae) are sometimes troublesome. Rats and birds may destroy a considerable part of the harvest.
Harvest takes place 2-4 months after sowing, when the grain has a moisture content of 14-15%. Delayed harvesting should be avoided, as the seed shatters easily. If proso millet is harvested during the rainy season with high relative humidity, the grain must be dried to 14% moisture content. Households usually do this above the domestic fire.
Under rainfed conditions, average yield of proso millet is 400-600 kg/ha. With sufficient rain or under irrigation and with application of fertilizers, a yield of 1-2 t/ha can be reached. The milling recovery is 70-80%.
Handling after harvest
Proso millet is threshed immediately after harvest. The grain stores well for up to five years. In India, storage is in granaries with clay walls, or in clay jars; sometimes the grain is mixed with ash or slightly baked before storage. Because of its small size, the grain is barely susceptible to insect attack.
China, India and Russia hold the largest proso millet germplasm collections. In China there are 5500 accessions in the National Gene Bank (Institute of Germplasm Resources, CAAS, Beijing), 4200 of which have been described (53% are non-glutinous and the remaining 47% are glutinous). The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), India, has a collection of 1200 accessions (from 26 countries) and the All India Coordinated Minor Millets Improvement Programme possesses 1100 samples. Smaller collections are available in the Czech Republic, Germany, Hungary, Japan and the United States.
Since ancient times man has selected proso millet on drought tolerance and short growing cycle. Russian cultivars are said to be much earlier than those from China or India. Breeding programmes in Russia and India aim at a high productivity (drought resistance and early or late maturity), disease resistance (especially to smut) and grain quality (uniform size and shape, yellow endosperm with high carotenoid content). High-yielding cultivars in Russia generally mature 14 days later than standard cultivars. Several improved cultivars, including some hybrids, have been released recently in Russia ("Sartovskoye 8") and China ("Jinsu No 1" and "Jinsu No 2").
The production of proso millet is declining and the crop is being replaced in the human diet by other cereals, especially rice, wheat and maize. However, it will continue to be an important staple in some areas of the semi-arid tropics where hardly any other cereal can be grown. Its use as a food might be important in rural areas, as consumption in urban centres appears to be constrained by a lack of regular supply and by changing food habits.
Proso millet could gain in importance by being incorporated in crop rotations in more humid regions, e.g. in South-East Asia. Because of its low water requirement and short duration, it can be cultivated during the dry season and grow mainly on residual soil moisture.
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