Table 2.2 Origin, morphological and genetic composition of Roots and tuber crops
Plant Solanum tuberosum
Origin Native to South America, Andean origin hypothesis is mainly accepted.
Morphological features/ Identification marks
― Roots/tubers White skin tubers are mainly found in white flowering varieties, whereas pinkish skin has been found in colored flowering varieties
― Stem 0.4–1.4 m tall herbs, erect or semi-erect, lying or trailing on ground. Green-Purplish green stems with base diameter 5–19 mm, covered with short soft hairs.
― Leaf Odd-pinnate arrangement, medium to dark green pappery-membranous appearance possessing dull-shiny, slightly hairy at adaxial and abaxial sides of leaf surface, 5–13 cm blades in 8–22 number, 3–8 lateral leaflet pairs.
― Flower/Fruits 5–11 cm Inflorescences, with 0–25 perfect flowers with axes pubescent with hairs. Flowers homostylous, pentamerous. Calyx 0–10 mm long. Corolla 2–6 cm in diameter and flat edges slightly glabrous, white, pink, lilac, blue, purple, red-purple, uniform or with white acumens. Stamens with the filaments 1–2 mm long; anthers 3–8 mm long. Ovary glabrous. Fruit a globose to ovoid berry, green to green tinged with white or purple spots or bands when ripe, glabrous.
Genetic Makeup Chromosome number: 2n = 2x = 24 2n = 3x = 36 2n = 4x = 48 cultivated potato with 2x, 3x, 4x and whereas in wild potatoes above levels coupled with 6x are found.
References Ovchinnikova et al., 2011; Wikipedia.org
Plant Ipomoea batatas
Origin The Yucatan Peninsula of Mexico. Primary center of diversity Lies at the mouth of the Orinoco River, Venezuela, Central America.
Morphological features/ Identification marks
― Roots/tubers Long, tapered edible tuberous root, smoothly skinned, widely colored like yellow, orange, red, brown, purple, and beige. Gamut of colored flesh ranging from beige through white, red, pink, violet, yellow, orange and purple.
― Stem Perennial, herbaceous vine.
― Leaf Alternate heart-shaped or palmately lobed leaves.
― Flower/Fruits Medium-sized sympetalous flowers.
Genetic Makeup 2n = 6x = 90
References Srisuwan et al., 2006; Wikipedia.org
Plant Manihot esculenta (M. utilissima)
Origin Primary center of diversity is in Brazil, whereas secondary center being Mexico and Guatemala.
Morphological features/ Identification marks
― Roots/tubers Yellow or white fleshed, brown outer skin, inner side skin color is red or yellow, 38.6 cm Long roots, 1–4" in diameter. Root covered with fibrous bark.
― Stem Woody, unbranched stems, usually with leaf scars, yellow-dark green stem with 1.96 cm diameter and 22.36 cm Length.
― Leaf 5–7 slender Lobed leaves. Red-pale green petiole, mostly palm shaped leaves. 18.2 cm in length.
― Flower/Fruits Cyathia inflorescences, subglobose, green (to light yellow, white, dark brown), smooth, with 6 longitudinal wings possessing fruit.
Genetic Makeup x = 9, 2n = 36
References Bahekar and Kale, 2013; Perera et al., 2012; Tribadi et al., 2009; Nassar, 2000
Plant Xanthosoma spp.
Origin Northern South America
Morphological features/ Identification marks
― Roots/tubers Leaves and corms resemble common taro. Characterized morphologically by subterranean stems, corms, enclosed by dry scale-like leaves. Tuber 1–1.5 cm in diameter. Generally grouped into three types, white, red and yellow on the base of the tuber flesh color.
― Stem Tannia has the stalk attached to the Leaf edge.
― Leaf Petiole attaches at the margin or between the two upper lobes compared to taro where underside of the leaf is attached to the stem, entire leaf blades.
― Flower/Fruits At Least 6 different types of styles, spathe tube usually subglobose, inflated (except Xanthosoma feuersteiniae); female zone of spadix free; styles mostly discoid and laterally swollen or thickened and coherent or not; synandrodes between female and male flowers; prismatic.
Genetic Makeup The white and red cocoyam types are diploid (2n = 2x = 26), whereas the yellow type is tetraploid (2n = 4x = 52)
References Mead 2013, Owusu-Darko et al., 2014; Mead 2013; Oumar et al., 2011; Markwei, 2010; Bogner and Gongalves, 2005
Plant Colocasia esculenta
Origin North-eastern India
Morphological features/ Identification marks
― Roots/tubers A Long central corm and few side-corms called cormels are found in a dasheen variety, whereas well-developed cormels are usually seen in an eddoe variety.
― Stem Tall herb, with caudex either tuberous or stout short in nature. Above ground stem arising from rhizome (tapered or tuberous), which may be slightly swollen at the base of the Leaf-sheaths. In taro stalk emerges near the center of Leaf. Suckers and stolons sometimes present.
― Leaf Simple leaves, stout petiole, peltate lamina, ovate- or sagittate-cordate in nature. Spadix shorter than the petiole and spathe. Inflorescences much Larger than the Appendix.
― Flower/Fruits Female flowers 3–4 gynous; ovoid or oblong ovary, uni-locular with several or many, biseriate ovules.
Genetic Makeup 2x = 28 and 3x = 42
References Matthews 1995; Nguyen et al., 1998; Parvin et al., 2008; Prajapati etai, 2011; Mead, 2013; Owusu-Darko etai, 2014