**7. Breeding and distribution of improved sweet potato varieties**

New high-yielding and early maturing sweet potato varieties that are resistant to local insect pests and diseases and resilient to climate change; varieties rich in nutrients; and varieties that have a long shelf life are needed to increase sweet potato farmers' productivity and income [2].

*Sweet Potato (*Ipomoea batatas *(L.) Lam): A Review of Modern Varieties and Production… DOI: http://dx.doi.org/10.5772/intechopen.106586*

#### **7.1 Factors affecting farmers' choice of sweet potato varieties**

Understanding farmers' perceptions on improved sweet potato varieties is crucial to develop new varieties that will suit farmers' different needs in different countries and regions. In addition to high yields, farmers consider crop duration, labour requirement, drought and pest tolerance, cooking time, taste, firmness of roots, storability and shelf life, and profitability. While most farmers prefer short duration varieties with stable yield to suit shortening rainy seasons, others favour varieties with good tolerance to drought and insect pests and diseases; still others choose dual purpose varieties with high biomass yield for fodder and some roots [15, 24]. Commercial farmers go for varieties with high starch yield for industrial processing [2]. In addition, nutrient-rich sweet potato varieties such as the YFSP varieties are urgently needed to address the problem of malnutrition among the poor [2, 27].

#### **7.2 Sweet potato breeding in Asia and Africa**

There is a high diversity of sweet potato varieties as exhibited by the colour, width, thickness, and shape of leaves [28]; skin and flesh colours, size, shape, texture, and taste of the edible roots [28, 29]. This huge diversity of sweet potato can be used to breed improved varieties with desirable traits.

The International Potato Centre (CIP) has been collaborating with national sweet potato breeders in Africa and Asia to develop high-yielding, climate-resilient, and pest- and disease-tolerant sweet potato varieties suitable for different growing environments, farming systems, and market demands. These collaborative breeding programs placed higher priority to developing beta-carotene-rich YFSP varieties to tackle the problem of vitamin A and micronutrient (iron and zinc) deficiency, specifically in women and children. As a result, more than 100 pro-vitamin-A–rich sweet potato varieties suitable for local agro-ecologies and consumer preferences have been developed and released in more than 20 countries of Africa and Asia [30].

Most popular sweet potato varieties and their key traits are given in **Table 3**. Some of the varieties are climate-resilient by their tolerance to drought and high temperatures [2, 31], some are tolerant to salinity [32, 33], and others have wide adaptability to varying environments [2]. Among the 19 OFSP and three other sweet potato varieties released in Mozambique in 2011 and 2016, Alisha, Irene, and Sumaia are the three best varieties with high vine survival rates under drought; they yielded 18–25 t/ha in rain-fed fields with low or no fertilizer application [34]. The variety Irene with wide adaptability has been released in four African countries, and it performed well in saline soils under irrigation in Abu Dhabi [2]. The South African varieties A15 and Resisto are tolerant to deficit irrigation or restricted water supply [35]. The Vietnamese varieties such as Khoai ruot vang, Khoai cao san, and Khoai voi were selected for their tolerance to salinity [36].

Most OFSP varieties are richer in beta-carotene than some common carotenoidrich vegetables and fruits such as carrot, mango, and tomato [37]. Thus, OFSP varieties are an inexpensive source of dietary vitamin A and essential micronutrients to fight the widespread malnutrition [38]. It is estimated that more than 6.8 million farm families in Africa and South Asia are now growing and eating vitamin-A–rich OFSP varieties [30].

The purple-fleshed sweet potato (PFSP) roots are rich in anthocyanin and chlorogenic acid which are excellent antioxidants [39]; anthocyanin is also used as a natural


#### **Table 3.**

*Most popular improved high-yielding white-, purple-, and orange-fleshed sweet potato varieties in selected countries.*

*Sweet Potato (*Ipomoea batatas *(L.) Lam): A Review of Modern Varieties and Production… DOI: http://dx.doi.org/10.5772/intechopen.106586*

food colour. They are less popular in most countries except China, Indonesia, Japan, and USA. PFSP roots are used to prepare vegetable dishes, bakery products, beverages, etc.

Some sweet potato varieties (e.g. CX-1 in China) are rich in complex carbohydrates and bioactive compounds, and they are used in industries.
