Identification of cassava mutants with high-starch and low-lignin through in vitro mutagenesis

Abstract

Cassava ( Manihot esculenta Crantz) is a tropical crop with storage roots containing large amounts of starch, but excessive lignin deposition negatively affects processing properties and quality. Developing cassava germplasm with enhanced starch accumulation and reduced lignin content is therefore an important breeding objective. Nevertheless, it remains unclear whether induced genetic variation can modulate starch and lignin accumulation and produce genotypes with improved compositional traits. In this study, an in vitro mutagenesis approach combining atmospheric and room temperature plasma (ARTP) and ethyl methanesulfonate (EMS) was established in cassava cultivar SC205. A total of 184 regenerated lines were obtained, among which 16 lines exhibiting vigorous growth and stable storage root formation were selected for further evaluation. Considerable variation in storage root composition was observed among the mutant lines, and starch accumulation was consistently negatively correlated with lignin content across two consecutive planting years. Notably, mutant line A18 exhibited increased starch accumulation and reduced lignin content compared with the wild type (WT), whereas E27 displayed the opposite phenotype. To investigate the molecular basis underlying the differences in starch and lignin accumulation, metabolomic profiling and qPCR analyses were conducted using storage roots from A18, E27, and WT plants. Metabolomic and transcriptional analyses revealed that A18 exhibited enhanced starch and sucrose metabolism and increased expression of starch biosynthesis-related genes, whereas E27 showed activation of phenylpropanoid metabolism and elevated expression of lignin biosynthesis-related genes. This study demonstrates that ARTP- and EMS-induced mutagenesis generated substantial compositional diversity while maintaining the negative association between starch accumulation and lignification. The identified high-starch/low-lignin mutant A18 provides a valuable genetic resource for elucidating the regulatory relationship between starch accumulation and lignin biosynthesis in cassava storage roots.