Recent understanding of starch biosynthesis in cassava for quality improvement: A review.

Abstract Background Starch is the most important carbohydrate source of plant species. Both amylose and amylopectin are components of starch whose content and structures contribute to its unique properties used in food processing and industrial applications. Cassava (Manihot esculenta Crantz) is a starchy root crop used as a staple food for human consumption in tropical and sub-tropical regions, as well as in numerous industrial applications. Starch biosynthesis is controlled by various isoforms of several enzymes which are expressed during root development, and considerable effort has been made in understanding the mechanisms of starch biosynthesis and regulation. The improvement of cassava starch for both consumption and the starch industry has been a major goal of breeders. Scope and approach The review summarizes the identification of genes and enzymes involved in starch biosynthesis and the mechanisms of gene regulation in cassava. Quantitative trait loci (QTLs) and candidate genes associated with the important quality traits and mutations affecting starch physicochemical properties are also summarized. Key findings and conclusions A total of 45 genes participating in starch biosynthesis in cassava including ADPG pyrophosphorylase (AGPase), granule bound starch synthase (GBSS), starch synthase (SS), starch branching enzyme (SBE), de-branching enzyme (DBE) and glucan, water dikinase (GWD) have been identified and their functions have been characterized. A total of 110 QTLs for starch content and pasting properties have been identified. These genes and QTLs will contribute to the improvement of starch quality by current biotechnologies, such as transgenic breeding and molecular marker assisted selection. Highlights • Cassava starch quality depends on how starch is biosynthesized. • Identification and function of 43 isoforms in starch biosynthesis are summarized. • Forty seven QTLs for starch content and 63 for pasting properties have been reported. • Mutations affecting starch properties have been identified. • Molecular breeding can be conducted for starch quality improvement in cassava. [ABSTRACT FROM AUTHOR]