Sweet potato (Ipomoea batatas, Lam.) is an important root vegetable in developing countries. After its domestication in Neotropical America, human migration led to the distribution of the sweet potato plant throughout the world. Both leaf and storage root are high in compounds of nutritional value. Yet, the storage roots are of particular value due to their significant content of provitamin A (β-carotene). The breeding effort for elite sweet potato lines led to the reduction of genetic diversity and the potential to improve other traits. The focus of the present study was to assess the metabolic diversity of 27 sweet potato cultivars including landraces and improved varieties. A metabolite profiling approach was optimised for sweet potato leaf and storage root tissue and 130 metabolites identified with three different analysis platforms. The data highlighted a lack of correlation between storage root phenotype and leaf metabolism. Furthermore, the metabolic diversity of storage roots was based on the secondary metabolism, including phenylpropanoids and carotenoids. Three cultivars of three different flesh colouration (yellow, orange and purple) showed a significant difference of the primary metabolism. This data demonstrates the value of metabolite profiling to breeding programs as a means of identifying differences in phenotypes/chemotypes and characterising parental material for future pre-breeding resources.

Starch properties can be modified by mutating genes responsible for the synthesis of amylose and amylopectin in the endosperm. However, little is known about the effects of such targeted modifications on the overall starch biosynthesis pathway and broader metabolism. Here we investigated the effects of mutating the OsSBEIIb gene encoding starch branching enzyme IIb, which is required for amylopectin synthesis in the endosperm. As anticipated, homozygous mutant plants, in which OsSBEIIb was completely inactivated by abolishing the catalytic center and C-terminal regulatory domain, produced opaque seeds with depleted starch reserves. Amylose content in the mutant increased from 19.6 to 27.4% and resistant starch (RS) content increased from 0.2 to 17.2%. Many genes encoding isoforms of AGPase, soluble starch synthase, and other starch branching enzymes were up-regulated, either in their native tissues or in an ectopic manner, whereas genes encoding granule-bound starch synthase, debranching enzymes, pullulanase, and starch phosphorylases were largely down-regulated. There was a general increase in the accumulation of sugars, fatty acids, amino acids, and phytosterols in the mutant endosperm, suggesting that intermediates in the starch biosynthesis pathway increased flux through spillover pathways causing a profound impact on the accumulation of multiple primary and secondary metabolites. Our results provide insights into the broader implications of perturbing starch metabolism in rice endosperm and its impact on the whole plant, which will make it easier to predict the effect of metabolic engineering in cereals for nutritional improvement or the production of valuable metabolites.

Cassava (Manihot esculenta Crantz) is the predominant staple food in Sub-Saharan Africa (SSA) and an industrial crop in South East Asia. Despite focused breeding efforts for increased yield, resistance, and nutritional value, cassava breeding has not advanced at the same rapidity as other staple crops. In the present study, metabolomic techniques were implemented to characterize the chemotypes of selected cassava accessions and assess potential resources for the breeding program. The metabolite data analyzed was applied to describe the biochemical diversity available in the panel, identifying South American accessions as the most diverse. Genotypes with distinct phenotypic traits showed a representative metabolite profile and could be clearly identified, even if the phenotypic trait was a root characteristic, e.g., high amylose content.

Summary Roots, tubers, and bananas (RTB) are vital staples for food security in the world's poorest nations. A major constraint to current RTB breeding programmes is limited knowledge on the available diversity due to lack of efficient germplasm characterization and structure. In recent years large‐scale efforts have begun to elucidate the genetic and phenotypic diversity of germplasm collections and populations and, yet, biochemical measurements have often been overlooked despite metabolite composition being directly associated with agronomic and consumer traits. Here we present a compound database and concentration range for metabolites detected in the major RTB crops: banana (Musa spp.), cassava (Manihot esculenta), potato (Solanum tuberosum), sweet potato (Ipomoea batatas), and yam (Dioscorea spp.), following metabolomics‐based diversity screening of global collections held within the CGIAR institutes. The dataset including 711 chemical features provides a valuable resource regarding the comparative biochemical composition of each RTB crop and highlights the potential diversity available for incorporation into crop improvement programmes. Particularly, the tropical crops cassava, sweet potato and banana displayed more complex compositional metabolite profiles with representations of up to 22 chemical classes (unknowns excluded) than that of potato, for which only metabolites from 10 chemical classes were detected. Additionally, over 20% of biochemical signatures remained unidentified for every crop analyzed. Integration of metabolomics with the on‐going genomic and phenotypic studies will enhance ’omics‐wide associations of molecular signatures with agronomic and consumer traits via easily quantifiable biochemical markers to aid gene discovery and functional characterization.

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