Advances in sweetpotato breeding from 1992 to 2012.

Abstract

Sweetpotato, with a global annual planting area of approximately 9 million ha, is the second most important tropical root crop. It is widely adapted, being grown in more than 110 countries. Early maturing varieties grow in 3-4 months. It is hardy and has multiple uses. Both roots and foliage are edible and provide energy and nutrients in diets. Distinct quality types have different uses, with orange-fleshed sweetpotato being valued for its extremely high provitamin A content, and other types used in varied fresh and processed forms. Sweetpotato is easily bred, as true seed is easily obtained and generation cycles are short. There are five objectives of this review. The first objective is to briefly describe recent production and utilization trends by region; the second is to review knowledge about the origin and genetic nature of sweetpotato; the third is to review selected breeding objectives. The fourth objective is to review advances in understanding of breeding methods, including: (i) generation of seed through polycross nurseries and controlled cross breeding; (ii) a description of a new accelerated breeding approach; (iii) recent efforts to systematically exploit heterosis; and (iv) new approaches of genomic selection. The fifth objective is to provide information about variety releases during the past 20 years in West, East and Southern Africa, South Asia, East and South-east Asia, China and the Pacific.

Gene Pool Subdivision of East African Sweetpotato Parental Material

“…Sweetpotato gene pools have so far only been established at CIP in Peru (Grüneberg et al, 2015). It is preferable that these pools be mainly formed by local material.…”

“…This nurtures the expectation that heterosis is important for sweetpotato performance, and that systematic exploitation of heterosis can improve the efficiency of population improvement (Grüneberg et al, 2015). Population improvement is challenging because the crop is a highly heterozygous hexaploid hybrid.…”

Variance component estimations and mega‐environments for sweetpotato breeding in West Africa

“…Storage root yields of CRI-Apomuden and CRI-Ligri, used as check clones, were consistent across the three datasets. Storage root yield was reported in this study as the sum of commercial and noncommercial root weight but the need to measure both commercial and noncommercial root weight is debatable (Grüneberg et al, 2015). Harvest index can be a predictor of yield stability as evidenced in wheat and maize (Zea mays; Bolaños & Edmeades, 1993).…”

“…is cultivated across a wide range of agro-ecological conditions, but storage root yields are low in many countries. Improving storage root yields can be achieved through genetic improvement and replacing old varieties by new ones, cultural practices such as timely planting, weed control, crop rotation and fertilizer input, and the use of pathogen-tested clean planting material (Grüneberg et al, 2015). As most farmers in Sub-Saharan Africa (SSA) do not have access to pathogen-tested planting material, they rely on "apparently" healthy planting material obtained by negative selection which, in some cases, can be as effective as using pathogen-tested planting material (Abidin, Akansake, Asare, Acheremu, & Carey, 2017).…”

“…Most released sweetpotato varieties in Ghana have been exotic introductions, coming from the International Institute of Tropical Agriculture's (IITA) sweetpotato breeding program (which phased out in 1987), East Africa (comprising a number of landraces), and Bangladesh. Sweetpotato introductions can bring about considerable genetic diversity because of the extreme heterozygosity of the crop (Grüneberg et al, 2015), but in countries with intensive production and established breeding programs, a large genetic diversity is already available for breeding (David et al, 2018). Expression of attributes and traits across environments can vary differentially by genotype, a phenomenon known as genotype × environment (G × E) interaction in multi-environmental trial (MET) series.…”