The sweet potato (Ipomoea batatas) is a dicotyledonous plant belonging to the morning glory family, Convolvulaceae. Its starchy, sweet-tasting tuberous roots serve as a staple food in many parts of the world. Cultivars have been developed with a wide array of flesh and skin colors, and the young shoots and leaves are also consumed as greens. The sweet potato originates in South America in what is present-day Ecuador. Domestication occurred in either Central or South America.
The sweet potato is not closely related botanically to the common potato, though they share a similar etymology. The first Europeans to taste sweet potatoes were members of Christopher Columbus's expedition in 1492. Later explorers found many cultivars under an assortment of local names, but the name which stayed was the indigenous Taíno name of batata.
In Ethiopia, sweet potato is a significant root crop utilized for both food and feed. It is considered a food security crop, particularly in regions prone to drought. Bench-Sheko zone mid-altitudes, in general, are among the most important sweet potato growing regions in southwest Ethiopia. The plant is a herbaceous perennial vine, bearing alternate triangle-shaped or palmately lobed leaves and medium-sized sympetalous flowers.
The plant does not tolerate frost. It grows best at an average temperature of 24 °C (75 °F), with abundant sunshine and warm nights. Annual rainfalls of 750-1,000 mm (30-39 in) are considered most suitable, with a minimum of 500 mm (20 in) in the growing season.
Crop descriptors follow a standard codification and are regarded as a universally understood language for germplasm data. The International Board for Plant Genetic Resources recommends a list of 26 descriptors related to the plant morphology, storage root and inflorescence.
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Improved Sweet Potato Varieties in Ethiopia
In Ethiopia, an ‘improved variety’ is defined as one that has undergone testing by breeders, demonstrating its superiority over traditional or local varieties. Since 1990, a total of 25 improved sweet potato varieties have been released.
Breeding and germplasm maintenance activities have been concentrated in the Southern Nations, Nationalities and Peoples’ Region (SNNPRS) and Oromia. Visual-aid protocols offer advantages over the existing methods of data collection. Pictures have the potential to overcome language and translation barriers, which could be a huge advantage on data quality.
The list of improved sweet potato varieties released in Ethiopia is provided in Table 1.
Table 1: Improved Sweet Potato Varieties Released in Ethiopia (1990-2013)
| Variety | Characteristics |
|---|---|
| Koka-12 | Orange-fleshed variety (OFV) |
| Guntutie | Orange-fleshed variety (OFV) |
| Kero | Orange-fleshed variety (OFV) |
| Kulfo | Orange-fleshed variety (OFV) |
| Tulla | Orange-fleshed variety (OFV) |
Five orange-fleshed varieties have been released and promoted for their higher nutritional content: Koka-12, Guntutie, Kero, Kulfo and Tulla.
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A study was carried out in the Semen-Bench district of the Bench-sheko zone, southwestern Ethiopia, to investigate the adaptability and performance of improved sweet potato varieties and to identify the best performer variety. The results of both years and over year combined statistical analysis indicated that the varieties significantly varied in terms of all yield and yield-related traits. As a result, the Awassa-83 variety acquired the greatest values of average root diameter in both the 2017 (11.9 cm) and 2018 (10.1 cm) growing seasons, followed by the Berkume variety. In both 2017 and 2018 growing seasons and over year combined analysis, the highest average storage root length (21.5 cm), marketable storage root yield (29.06 ton/ha), total storage root yield (43.22 ton/ha), and storage root dry weight (42%) was recorded from variety Awassa-83.
Variety Beletech and Berkume were found to be statistically similar and the next highest in terms of marketable storage root yield, and total storage root yield; moreover, variety Berkume was found to be the next highest in terms of storage root dry weight in two years combined result. On the other hand, the variety Beletech, which was closely followed by Awassa-83, had the highest average number of roots per plant (8.28) and the greatest number of marketable roots per plant (7.04).
Adaptability and Yield Performance
Adaptability evaluation was conducted in Sankura district (in the Siltie Zone) and Meskan District (in the Guraghe Zone). The experiment was conducted using four orange-fleshed sweet potato varieties laid out in the RCBD and three replications were performed. Analysis of variance (ANOVA) revealed that there was a highly significant difference (P ≤ 0.01) in the fresh weight yield per hectare and a significant difference (P ≤ 0.05) in the dry matter per plant (g) among the tested varieties and varieties*across environments, while there were nonsignificant differences among the tested varieties for the remaining parameters.
The observed yield variation between varieties may be due to meteorological or climatic factors and the genetic potential of the varieties grown under Sankura and Meskan conditions. The results of the combined ANOVA showed that there was significant variation in yield and yield between Orange-Fleshed Sweet Potato (OFSPs) varieties and these parameters support the present findings (Ejigu, F., et al., 2022). This variation was generated due to environmental effects and genetic variability among the varieties.
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According to the mean values of the tested varieties, significant differences in the root fresh weight per plant (g), root dry matter per plant (g) and root fresh weight yield per hectare (tone/hectare) were recorded, as indicated in Table 2. Kulfo (29.59a) t/ha was the first variety identified according to the mean yield, followed by Kabode (27.57b) t/ha according to the fresh weight of the roots, whereas the least common yielder was Alamura (16.37b) t/ha. Again, the Kulfo (500.8a) variety had the highest amount of root dry matter per plant, followed by the Kabode (264.7b) variety, while the Alamura (196.0b) variety had the lowest amount of root dry matter per plant.
Table 2: Average Values for Yield-Related Traits and Tuber Yield per Hectare
| Variety | Root Fresh Weight per Plant (g) | Root Dry Matter per Plant (g) | Root Fresh Weight Yield per Hectare (tone/hectare) |
|---|---|---|---|
| Kulfo | - | 500.8a | 29.59a |
| Kabode | - | 264.7b | 27.57b |
| Alamura | - | 196.0b | 16.37b |
From the Ground Up - Growing Sweet Potatoes
Nutritional Impact and Food Security
Food biofortification is an appropriate solution to improving health and nutrition in this region. While cereal-based diets predominate, sweetpotato is grown widely, and is an ideal food security crop. Sweetpotato is highly efficient in transforming water into calories, has a short maturity period, and can be harvested during the ‘hunger months’ before the cereals ripen. This project builds on previous successes in improving vitamin A status in young children in Mozambique and Uganda through OSFP consumption.
In addition to providing a valuable source of energy, orange-fleshed sweetpotato is rich in vitamin A. It is an ideal staple to grow in densely populated and drought-prone countries, like Ethiopia. Food insecurity and poverty, exacerbated by frequent drought, continue to blight Ethiopia. One of the most serious consequences is a high rate of malnutrition in children, which effectively impedes the country’s prospects for economic growth. Vitamin A deficiency is a key contributor to child undernourishment; it limits growth, weakens immunity, affects eyesight and increases mortality.
Meaningful impact on the health and economic growth of the SNNP region will be accomplished only when OFSP is widely adopted by farmers and consumers. Widespread dissemination will be achieved by evaluating project successes and using the findings to develop models that promote cost-effective scaling up of activities.
