Contributors: F.J. Muehlbauer and Abebe Tullu
Copyright © 1997. All rights Reserved. Quotation from this document should cite and acknowledge the contributor.
Pea, dry pea, (UK, USA), Batani (Ind), Erbese (Ger), Ater (Eth), pois (Fra), Takarmany borso (Hun)
Species: Pisum sativum L.
Peas are cultivated for the fresh green seeds, tender green pods, dried seeds and foliage (Duke, 1981). Green peas are eaten cooked as a vegetable, and are marketed fresh, canned, or frozen while ripe dried peas are used whole, split, or made into flour (Davies et al., 1985). In some parts of the world, dried peas are consumed split as dahl, roasted, parched or boiled. "Green peas are the number one processed vegetable specifically in UK and USA. Green foliage of garden pea is also used as vegetable in parts of Asia and Africa. Leaves are used as a pot herb in Burma and parts of Africa" (Kay, 1979). Some cultivars are grown for their tender green pods, which are eaten cooked or raw. "Oil from ripened seed has antisex hormonic effects; produces sterility and antagonizes effect of male hormone" (Duke, 1981). "Based on protein digestibility of peas in broilers, it is reported that the natural protein of peas and faba bean is almost entirely digested in the small intestine and the impaired performance in literature was attributed to an increased secretion of endogenous protein" (Huisman and Van der Poil, 1994). Pea is being used in a growing snack market. One snack item is prepared by soaking the peas overnight and frying them in palm oil or coating them with other food items such as rice flour before frying for the purpose of imparting different flavors. Another product is prepared by finely grinding the peas and extruding them under pressure to create different shapes. The different shapes are then fried, seasoned and packaged (Jambunathan et al., 1994). "Cultivars such as 'Alaska' 'Super Alaska,' 'Supergreen,' and 'Alaska Wilt Resistant have long been the standard type of canning pea. Wrinkled-seeded garden peas are sweeter than smooth seeded types. Marrowfat is a large flattened pea type that is popular for making snack items and are also used for reconstitution and canning in the UK. Canning peas are divided into two classes: Alaska and sweet. Of the sweet type is 'Surprise' (most important) and 'Resistant Surprise' (gaining in popularity because of its disease resistance). Some midsummer varieties are: 'Pride,' 'Early Perfection,' 'Ace,' and 'Wasatch'. Late cultivars, which ripen about 14 days after 'Alaska,' are: 'Perfection' and its various strains, as 'Dark-green Perfection,' 'Bridget,' 'Superior,' 'New Era,' ëPugetí and 'Shoshone.' New cultivars, too numerous to mention, have been entered into production in the US and other countries. Canning cultivars usually have a tough skin that holds its shape during canning. For home garden use, 'Little Marvel,' 'Laxton Progress,' 'World's Record,' 'Wando' holds quality well in hot weather" (Duke, 1981).
"Seeds are thought to cause dysentery when eaten raw. In Spain, flour is considered emollient and resolvent, applied as a cataplasm. It has been reported that seeds contain trypsin and chymotrypsin which could be used for contraceptive, ecbolic. fungistatic and spermicide"(Duke, 1981). Smart (1990) reported that there are no significant amounts of toxicity or anti-metabolites in peas.
The protein concentration of peas range from 15.5-39.7% (Davies et al., 1985; Bressani and Elias, 1988). "Fresh green peas contain per 100 g: 44 calories, 75.6% water, 6.2 g protein, 0.4 g fat, 16.9 g carbohydrate, 2.4 g crude fiber, 0.9 g ash, 32 mg Ca, 102 mg P, 1.2 mg Fe, 6 mg Na, 350 mg K, 405 ug b -carotene equivalent, 0.28 mg thiamine, 0.11 mg riboflavin, 2.8 mg niacin, and 27 mg ascorbic acid, while dried peas contain: 10.9% water, 22.9% protein, 1.4% fat, 60.7% carbohydrate, 1.4% crude fiber, and 2.7% ash" (Duke, 1981; Hulse, 1994). "Flour contains: 343 calories, 10.9% moisture, 22.8 g protein, 1.2 g fat, 62.3 g total carbohydrate, 4.2 g fiber, 2.8 g ash, 72 mg Ca, 338 mg P, 11.3 mg Fe, 0.86 mg thiamine, 0.18 mg riboflavin, and 2.8 mg niacin" (Duke, 1981). An average amino acid composition, reported in terms of grams per 100 grams of protein: 6.9-8.2 lysine, 1.4-2.7 methionine+cystine, 3.9 threonine, 0.9 tryptophan, 0.8-1.7 cystine (Huisman and van der Poel, 1994; Bressani and Elias, 1988). Methionine and cystine are the main limiting amino acids. The largest chemical component in peas as in other legumes is carbohydrate (CHO) which constitute about 56.6% of seed weight (Bressani and Elias, 1988). The most abundant pea carbohydrate is starch, 36.9-48.6%, while amylose is about 34% of seed weight in peas (Bressani and Elias, 1988). "Nutrient composition of milled and polished peas as measured per 100 grams of edible portion of dried matured whole seeds are 1.4 g oil, 6 g crude fiber, 16.7 g dietary fiber, 54.1% starch, 8.1% sugars, 4.4 mg iron, 0.77 mg thiamin, 0.18 mg riboflavin, 3.1 mg niacin and 330 kcal energy" (Newman et al., 1988). Fertilizing peas with sulfur has increased their methionine content from 1.3 to 2.2 g per 100 g protein. "Pea hay (at 88.6% DM) contains (zero moisture basis): 10.7-21.6% crude protein, 1.5-3.7% fat, 16.8-36.1% crude fiber, 6.0-9.3% ash, and 41.9-50.6% N-free extract" (Duke, 1981).
Pea probably originated in southwestern Asia, possibly northwestern India, Pakistan or adjacent areas of former USSR and Afghanistan and thereafter spread to the temperate zones of Europe (Kay, 1979; Makasheva, 1983). Based on genetic diversity, four centers of origins, namely, Central Asia, the Near East, Abyssinia and the Mediterranean have been recognized (Gritton, 1980). Non-pigmented peas to be used as a vegetable were grown in United Kingdom in the middle Ages (Davies et al., 1985). Pea was introduced into the Americas soon after Columbus and a winter type pea was introduced from Austria in 1922. Pea was taken to China in the first century (Makasheva, 1983). Peas were reported to be originally cultivated as a winter annual crop in the Mediterranean region (Smart, 1990).
Duke (1981) reported that garden peas are treated as P. sativum ssp. hortense Asch. & Graebn., field peas as P. sativum ssp. arvense (L.) Poir., and edible podded peas as P. sativum ssp. macrocarpon; early dwarf pea as P. sativum var humile. Later, Smart (1990), based on studies undertaken by Ben-Zeíev and Zohary (1973), and Polhill and van der Maesen et al., (1985) reported that pea comprises only two species, viz; Pisum sativum and P. fulvum Sibeth. & Smith. "It is a self pollinated annual herb, bushy or climbing, glabrous, usually glaucous; stems weak, round, and slender, 30-150 cm long; leaves alternate, pinnate with 1-3 pairs of leaflets and a terminal branched tendril leaflets ovate or elliptic, 1.5-6 cm long" (Duke, 1981). The leaf type could be conventional, semi-leafless and leafless (Davies et al., 1985). Leaf size in most cases increases up to the first node bearing the first flower. Stipules are large, leaflike and up to 10 cm long. The inflorescence of pea is a raceme arising from the axil of the leaf. Corolla white, or pink, or purple; pods swollen or compressed, short-stalked, straight or curved, 4-15 cm long, 1.5-2.5 cm wide, 2-10 seeded, 2-valved, dehiscent on both sutures (Gritton, 1980; Duke, 1981). The node at which the first flower emerges is characteristic of a given variety; in temperate regions the number of nodes at which the first flower emerges is reported to vary from 4 in the earliest to about 25 in late maturing types under field conditions (Gritton, 1980). Flowers borne on the same peduncle produce pods that mature at different times, the youngest being at the tip. On a whole plant basis, flowering is sequential and upwards from node to node. Seeds are globose or angled, smooth or wrinkled, exalbuminous, whitish, gray, green, or brownish; 100 seeds can weigh from 10 to 36 grams; germination cryptocotylar (Duke, 1981).
Peas require a cool, relatively humid climate and are grown at higher altitudes in tropics with temperatures from 7 to 30°C (Duke, 1981; Davies, 1985) and production is concentrated between the Tropics of Cancer and 50° N (Davies, 1985). As a winter annual, pea tolerates frost to -2°C in the seedling stage, although top growth may be affected at -6°C. Winter hardy peas can withstand -10°C, and with snow cover protection, tolerance can be increased to -40°C (Slinkard et al., 1994). As described in Slinkard et al. (1994), the optimum temperature levels for the vegetative and reproductive periods of peas were reported to be 21 and 16°C, and 16 and 10°C (day and night), respectively. "Temperatures above 27°C shorten the growing period and adversely affect pollination. A hot spell is more damaging to peas than a light frost. Peas can be grown successfully during midsummer and early fall in those areas having relatively low temperatures and a good rainfall, or where irrigation is practiced. For very early crops, a sandy loam is preferred; for large yields where earliness is not a factor, a well-drained clay loam or silt loam is preferred" (Duke, 1981).
Dry peas serve as rotational crops in the Palouse area in a state of eastern Washington and Northern Idaho. It is considered as an alternative to the cereal grain production and provides the basis to break disease cycles in winter wheat, improve soil fertility status and improve weed control. "Peas reduced the fertilizer requirements of maize by 20-32 kg/ha in India compared with wheat or fallow, respectively; in France it was estimated that about 50 kg/ha of N are returned to the soil by peas" (Davies et al., 1985). Pea growing seasons vary from 80-100 days in semi-arid regions and up to 150 days in humid and temperate areas (Davies et al., 1985).
Peas are propagated only from seed. "At higher temperatures germination is rapid, but seedlings may die from various pathogens in the soil. As temperature rises during growing season, yield drops off rapidly. In New York, yields are highest when seeds are planted during first 2 weeks of April; for each 2-week delay in planting, yield of shelled peas decreased about 400 kg/ha" (Duke, 1981). Thorough preparation of soil is very important, especially when the seed is broadcast or planted with a grain drill, as no subsequent cultivation is given thereafter. In the Palouse region of eastern Washington and northern Idaho peas are sown between March 25th at lower elevations to May 10th at higher elevations when the soil temperature is above 4°C; for planting winter peas, September 15th to the 30th has been recommended (Muehlbauer et al., 1983). Recommended plant densities vary tremendously depending on soil type, cultivar, seed size, and biotic factors, particularly diseases. In the Palouse area of Washington state, USA, spring peas are sown at the rate of 140-195 kg ha-1 or 89-108 seeds m-2, while fall sown peas are planted at the rate of 85-135 kg ha-1 or 71-104 seeds m-2 (Muehlbauer et al., 1983).
Peas are relatively unresponsive to fertilizers, particularly nitrogen; additions are necessary when nodulation is poor or fails completely. When the seeds are treated with the Rhizobium, care must be taken in the choice of fungicide seed treatments to prevent potential toxicity (Muehlbauer et al., 1983). The amount of nitrogen fixed through symbiosis with Rhizobia is reported to vary from 71 kg N per hectare in Alabama to 119 kg N per hectare in Wisconsin (Mahler et al., 1988). The N concentration in pea leaf tissue is reported to range from 1.8 to 2.3% (Mahler et al., 1988).
Peas grown for home use or for fresh market are picked by hand before the seeds are fully matured and still in the pod and are used for immediate consumption. In some cases, gardeners and commercial growers make two or three pickings, depending on maturity, while other growers make only one picking, in which the vines are pulled and all pods are removed. "Peas for processing are harvested with machines of various types. Sometimes vines are cut with a mowing machine, windrowed and loaded onto trucks with a hay loader. Pea harvesters that mow the peas and load directly onto trucks are common in major pea growing areas. Pea vines are hauled to a vining station, where pods are separated from vines, after which seeds are separated from pods" (Duke, 1981). Current methods of processing pea harvest involve the use of "viners" that harvest the pods and remove the peas from the pods in one operation in the field. The peas are then transported to the processing plant where they are quickly processed. Dry peas are harvested when the pods are completely dry and can be threshed directly in the field by a combine. For dry peas timely harvest is important for maintaining quality and is usually done when the seed moisture content is less than 13%. Both premature harvesting and harvesting too late reduce the quality of the dry pea crop. If the pea crop is overmature, harvesting early in the morning or during the evening when relative humidity is low will minimize shattering and seed breakage (Muehlbauer et al., 1983).
Pea is among the four important cultivated legumes next to soybean, groundnut, and beans (Hulse, 1994). Total world dry pea production rose from 8.127 million metric tons in 1979-81 to 14.529 million metric tons in 1994 while acreage varied from 7.488 to 8.060 million hectares for the same years (FAO, 1994). The highest productivity for pea was reported in France at 5088 kg per hectare in 1994, about eight times more than the African average yield. In 1994, USA total acreage was 54, 000 hectares with an average yield of 2587 kg per hectare (FAO, 1994). Important production areas of the world include France, Russia, Ukraine, Denmark and United Kingdom in Europe; China and India in Asia; Canada and USA in North America; Chile in South America; Ethiopia in Africa, and Australia (FAO, 1994). "Throughout temperate regions both green and dried peas are an important garden and field crop. In the United States, ca. 550,000 MT are produced commercially for food annually, and ca. 200,000 MT of field peas for feed" (Duke, 1981).
Pea is the predominant export crop in world trade and represents about 40% of the total trade in pulses (Oram and Agcaoili, 1994). The major exporting countries, excluding the European Economic Commission (EEC), are Australia, Canada and the USA (Oram and Agcaoili, 1994). Most of the peas from USA were exported to India, Haiti, Peru, and the Philippines in 1995 and had a total value of US$ 24,210,499 (Directory of US Suppliers & Industry Information, 1996).
Peas are adversely affected by: Ascochyla pisi, Cladosporium pisicola (leaf spot or scab), Erysiphe polygoni (powdery mildew), Fusarium oxysporum (wilt), Peronospora pisi (downy mildew), Phythium sp. (pre emergence damping-off), Botrytis cinerea (grey mold), Aphanomyces euteiches (common root rot), Thielaviopsis basicola (black root rot), and Sclerotina sclerotiorum (sclerotina white mold). Pea Early Browning Virus (PEBV), Pea Enation Mosaic virus (PEMV), Pea Mosaic Virus (PMV), Pea top yellows (PTY), Pea seed-borne Mosaic Virus (PSbMV) and Pea Streak Virus (PSV) constitute diseases caused by viruses, while the most important bacterial disease is caused by Pseudomonas pisi (bacterial blight) (Muehlbauer et al., 1983; Davies et al., 1985; van Emden et al., 1988).
Insect pests include Aphis cracivora (Groundnut aphid), Acyrthosiphon pisum (Pea aphid), Kakothrips robustus (Pea thrips), Bruchis pisorum (Pea seed beetle), Callosobruchus chinensis (Adzuki bean seed beetle), Apion sp. (Seed weevil), Sitona lineatus (Bean weevil), Contarina pisi (Pea midge), Helicoverpa armigera (African bollworm), Diachrysia obliqua (Pod borer), Agriotis sp. (Cut worms), Cydia nigricana (Pea moth), Phytomuza horticola (Leaf minor), Heliothis Zea (American bollworm), Etiella Zinckenella (Lima bean pod borer), Ophiomyia phaseoli (Bean fly), Delia platura (Bean seed fly), Tetranychus sp. (Spider mites), Pratylenchus penetrants (Root lesion nematodes), Ditylenchus dipsaci (Stem nematode), Heterodera goettingiana (Pea cyst nematode), and Meloidogyne javanica (Root knot nematode) (van Emden et al., 1988; Muehlbauer et al., 1983).
Crop improvement depends on the germplasm diversity existing in the crop of interest. Pea and other cool season food legume crops are produced under the vagaries of stresses, both biotic and abiotic. Evaluation of the germplasm for these stress conditions is critical to sustained pea production. Also incorporation of new traits into existing cultivars has been reported (Summerfield and Roberts, 1985; Muehlbauer, 1991). To this effect, selection against devastating diseases such pea root rot caused by Aphanomyces euteches, fusarium wilt, downy and powdery mildew, virus resistance and insect resistance has been successful (Muehlbauer, 1991). Incorporation of traits available in germplasm collections into adapted backgrounds has been proposed and appropriate breeding methods have been suggested (Muehlbauer, 1991). "Assigned to the Near Eastern, Mediterranean, and African Centers of Diversity, peas are reported to exhibit tolerance to aluminum, disease, frost, fungus, hydrogen fluoride, high pH, heat, laterite, low pH, mildew, slope, smog, virus, and wilt" (Duke, 1981). The Regional Plant Introduction Station located at Pullman, Washington maintains a collection of 2800 pea accessions. There are at least 16 other gene banks reported to have a considerable number of pea accessions (Muehlbauer and Kaiser, 1994). Most of the genetic diversity present in peas is reported to be available in the Near East, Mediterranean region Central Asia and Ethiopia (van der Maesen et al., 1988). The wild prototype of garden pea has never been found, but some writers believe that it was an ancient Egyptian plant. At present, it is grown throughout the world.
Research geneticist, USDA-ARS
Pullman, WA 99164-6439
Tel: (509) 335-9521
Fax: (509) 335-7692
Regional Plant Introduction Station
59 Johnson Hall, WSU
Pullman, WA 99164-6402
Tel: (509) 335-1502
Fax: (509) 335-6654
Regional Plant Introduction Station, USDA-ARS
Washington State University, 59 Johnson Hall
Pullman, Washington 99164-6402
Crop Development Center
University of Saskatchewan, Saskatoon,
Saskatchewan S7N 0W0, Canada
Contributors: F.J. Muehlbauer and Abebe Tullu
Copyright © 1997. All rights Reserved. Quotation from this document should cite and acknowledge the contributor.