In developed, nations sweetpotato (Ipomoea batatas) is grown predominantly for high-value fresh consumption and processed food markets, but is also increasingly used for producing value-added foods and bio-based industrial products (United States Sweet Potato Council, 2011; Ziska et al., 2009). Sweetpotato is compositionally well suited to these end uses, but crop production is relatively costly, which has restricted an expansion of these alternative markets.
The high cost of sweetpotato production can be attributed in part to the need for manual labor during crop establishment and harvest. Establishment of sweetpotato crops in developed countries involves the production and transplanting of unrooted sprouts, known as “slips.” In the United States, slip production and transplanting are together estimated to comprise between 15% and 20% of total production costs (Estes et al., 2002; Hinson and Boudreaux, 2007; Martin et al., 2000; Mississippi State University, 2007). Various workers have investigated a planting system for sweetpotato that uses root pieces, similar to the system used for potatoes (Solanum tuberosum) (George et al., 2011). Root piece planting systems can be mechanized more readily than slip planting and therefore have the potential to reduce labor needs, thereby reducing production costs. Despite a long history of research and development, the root piece planting technique is not commonly used in commercial sweetpotato production anywhere in the world.
Existing commercial sweetpotato clones tend to be poorly suited to planting from root pieces, producing lower yields, lower stand establishment, and poorer quality roots than the same clones grown from slips (George et al., 2011). There are examples, however, where different clones, environments, and cultural practices result in yields, stand counts, and root quality comparable to commercial clones grown from slips (George et al., 2011). It has been known for decades that both genetic and environmental factors play a role in the outcome of root piece planting, but the nature and extent of their contribution remain poorly understood (George et al., 2011).
Attempts have been made to select and breed sweetpotato clones that are better adapted to root piece planting, but these attempts have achieved only mixed success with selected clones often having unpredictable and/or unstable yields (George et al., 2011). Sweetpotatoes commonly exhibit a genotype × environment (G × E) interaction (Collins et al., 1987; George et al., 2011; Grüneberg et al., 2005; Kanua and Floyd, 1988; Manrique and Hermann, 2002; Ngeve, 1993). If G × E effects also influence sweetpotato crops established from root pieces, and breeding programs have not taken this into account, it may explain the mixed success of attempts to develop clones that are better adapted to root piece planting. The objective of this work was to investigate G × E effects in sweetpotato grown from root pieces so as to better understand the phenomenon and provide guidance for future research and development activities relating to root piece planting.
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