Assessment of the genetic diversity of sweetpotato germplasm collections for protein content

Abstract

Sweetpotato [Ipomoea batatas (L.) Lam.] is a relatively cheap source of nutrients for humans in most developing countries, including those in sub-Saharan Africa. Breeding for essential quality traits is an important goal of sweetpotato breeding programs. This may include root protein content (RPC), since protein-energy malnutrition is a common problem worldwide. The objective of this study was to quantify the genetic diversity in RPC present among sweetpotato accessions maintained in the genebank of the Agricultural Research Council (ARC) of South Africa in order to characterize and select the most promising clones for breeding. Both, Dumas combustion and Near-infrared Spectroscopy (NIRS) were used to determine RPC for a diverse set of accessions. In addition, total root yield and dry matter content were determined and root flesh colour recorded. Data was subjected to standard analysis of variance. A total of 227 sweetpotato accessions (53 introduced accessions, 18 local cultivars, 24 local landraces and 132 ARC breeding lines) were screened for total RPC, and a large variation was observed. As measured by the Dumas combustion, RPC values varied from 2.65 to 6.45% on a dry weight basis (dwb). RPC estimated by NIRS ranged from 0.68 to 11.51%. The NIRS proved to be an efficient and quick tool that can be useful in sweetpotato breeding programs towards selecting for quality traits such as RPC. A total of 31 medium to high yielding accessions with high, intermediate and low RPC were selected for genetic analysis and breeding for enhanced nutrition. Some promising germplasm included the local informal market cultivar ‘Impilo’ (orange-fleshed) at 6.18%, and the breeding line ‘2012-29-4’, seed imported from Mozambique, at 6.45%. NIRS values for ‘Tanzania’ and ‘Maria Angola’ were promising. The study is one of only a few that provides protein data for a large set of sweetpotato accessions from various parts of the world and is useful for sweetpotato breeding programs. Future work can focus on the determination of the concentrations of individual amino acids.