4 | Democratic Republic of the Congo | 16 000 000
5 | Ghana | 14 547 279
6 | Brazil | 23 044 557
7 | Angola | 10 636 400
8 | Mozambique | 10 051364
9 | Vietnam | 9745545
10 | India | 8746500
11 | Cambodia | 7613697
12 | United Republic of Tanzania | 5462454
13 | Uganda | 4 924 560
14 | Malawi | 4692202
15 | China, mainland | 4 560 000
16 | Cameroon | 4 287177
17 | Sierra Leone | 3520000
18 | Madagascar | 3621309
19 | Benin | 3 295 785
20 | Rwanda | 2716421
Sweet potato
S. no | Country | Production (MT)
1 | China, mainland | 77 375 000
2 | Nigeria | 3 400 000
3 | Uganda | 2 645 700
4 | Indonesia | 2 483 467
5 | United Republic of Tanzania | 3 018 175
6 | Vietnam | 1422 501
7 | Ethiopia | 1185 050
8 | United States of America | 1 201 203
9 | India | 1 072 800
10 | Rwanda | 1005 305
11 | Mozambique | 900 000
12 | Kenya | 859 549
13 | Japan | 875 900
14 | Burundi | 659 593
15 | Angola | 644 854
16 | Papua New Guinea | 580 000
17 | Madagascar | 1 144 000
18 | Philippines | 516 366
19 | Argentina | 400 000
20 | Democratic People's Republic of Korea | 450 000
Yam
S. no | Country | Production (MT)
1 | Nigeria | 38 000 000
2 | Ghana | 6 638 867
3 | Côte d’Ivoir | 5 674 696
4 | Benin | 2 739 088
5 | Togo | 864 408
6 | Cameroon | 537 802
7 | Central African Republic | 460 000
8 | Chad | 420 000
9 | Papua New Guinea | 345 000
10 | Colombia | 344 819
11 | Haiti | 298 437
12 | Ethiopia | 1 117 733
13 | Cuba | 366 182
14 | Japan | 166100
15 | Brazil | 246 000
16 | Jamaica | 145 059
17 | Gabon | 200 000
18 | Burkina Faso | 113 345
19 | Venezuela | 128 931
20 | Democratic Republic of the Congo | 100 000
Taro
S. no | Country | Production (MT) | Country
1 | Nigeria | 3 450 000
2 | China, mainland | 1760 000
3 | Ghana | 1 270 266
4 | Cameroon | 1614103
5 | Papua New Guinea | 250 000
6 | Madagascar | 232 000
7 | Japan | 172 500
8 | Rwanda | 130 505
9 | Central African Republic | 125 000
10 | Egypt | 118 759
11 | Philippines | 111482
12 | Burundi | 92 973
13 | Thailand | 90 000
14 | Democratic Republic of the Congo | 70 000
15 | Fiji | 82145
16 | Côte d’Ivoir | 71772
17 | Gabon | 63 000
18 | China, Taiwan | 50 000
19 | Solomon Islands | 42 000
20 | Liberia | 27500
Source: FAO (2012)
1.5 Constraints in Tropical Root and Tuber Production
Cassava is now commercially exploited in a number of products. However, the mechanization at the domestic and industrial level is required to be updated. The manual peeling of cassava root using knives is tedious and time-consuming, so there is a need to explore better methodology for cassava peeling. Moreover, the fermentation time is too long for the required profitable results, so there is still a need for research to confirm the role of fermentation in cassava processing. Not all cultivars of cassava are suitable for processing. The non-suitability of different cultivars and the conversion into value-added products by reviewing all the unwanted causes is a challenge. There is a need to investigate appropriate products from new cassava cultivars, which can be promoted in different countries. Inadequate storage facilities, high transportation costs and poor access to information on processing and marketing have also been identified as severe problems by the majority of processors in different areas of the world.
One major constraint for large-scale, commercial production of yam is the quantity of tubers needed for seed. About 30 % of yam must be set aside for this task (Kabeya et al., 2013). Another constraint for yam production is the need for staking material. Yam tubers grow deep in the ground, therefore harvesting becomes a difficult process. It is estimated that about 40 % of the total costs of yam production is for labor (Eyi-tayo et al., 2010). Yams are affected by many pests and pathogens, including insects, nematodes, fungal and bacterial diseases, and viruses.
There are constraints that restrict the scope of taro cultivation and production. The major constraints are taro leaf blight disease and taro beetle. These diseases are the major hindrances to the development of taro export trade in a number of countries, and in some cases threaten the internal food supply (Frison and Lopez, 2011). Therefore, effective controlling measures are required to be developed and disseminated to farmers. Taro production is also labor-intensive and is difficult to transport. At present, the bulk of taro produced is handled and marketed as the fresh corm. Taro corms contain a high moisture content, which makes them unable to be stored for more than a few days at room temperature.
Taro corms do not possess any particular shape at the time of harvesting, thereby creating difficulties in various unit operations like peeling, cutting, etc. There is a lot of variation in the internal color of taro corms as it ranges from yellow, white to a certain blend of colors which further depend on various cultural practices. Poi manufacturers like their products to be as purple-colored as possible, whereas the creamy white color is appreciated in the Asian region in the preparation of vegetables. The texture of taro corms varies within themselves, when exposed to certain processing operations like cooking. The outer portions are not as starchy as the center portions, hence the portions differ in specific gravity. This particular phenomenon poses a serious problem if taro corms are processed into chunks and patties, requiring a uniform texture (Hollyer and Sato, 1990).
The acridity principle in the taro corms and leaves also poses certain problems. The degree of acridity varies within different varieties. But proper treatment can provide the solution to resolve this problem (Kaushal et al., 2012). The shelf life of fresh taro corms ranges from two or three weeks to several months, depending on the source of information (Patricia et al., 2014). Taro deteriorates rapidly as a result of its high moisture content, but it has been estimated to have a shelf life of up to one month if undamaged and stored in a cool, shady area (Baidoo et al., 2014).
The tubers of the elephant foot yam (Amorphophalluspaeoniifolius) are highly acrid and cause irritation to the throat and mouth due to the calcium oxalate present in the tubers (orissa.gov.in). A systematic strategy needs to be adopted to preserve the product for farmers who depend mostly on commission agents to procure seed material, as well as to sell the harvested produce. In general, the major constraints in production of tropical roots and tubers are lack of automation, inadequate processing equipments, improper packaging, poor storage techniques, limited prospects of marketing and poor keeping quality.
1.6 Classification and Salient Features of Major Tropical Roots and Tubers
Tropical roots and tubers exist in different forms. The classification and their salient features are presented in Table 1.5.