Micro-Mel and Mini-Mel short life cycle dwarf lines with Solanum anguivi introgressions as the first model varieties for eggplant research and breeding

Abstract

Eggplant (Solanum melongena) research has been hindered by the lack of suitable model plants. The development of Micro-Mel and Mini-Mel, two short-cycle dwarf model lines with introgressions from the wild relative S. anguivi, represents a breakthrough in eggplant research. Both lines were characterized with 30 phenotypic descriptors and compared to their parental lines and the Micro-Tom tomato. Micro-Mel has determinate growth, early flowering (41.0 days post-transplantation), and physiological fruit maturity at 103.7 days. Mini-Mel exhibits indeterminate growth, later flowering (57.2 days) and fruit maturity (114.7 days), with a more conventional architecture. Micro-Mel and Mini-Mel complete 3.5 and 3.0 full seed-to-seed cycles per year, respectively. Their compact size makes them ideal for space-limited environments, controlled growth chambers, speed breeding, ornamental horticulture, and urban horticulture. To validate their potential for gene editing, in vitro regeneration experiments were performed on a medium containing zeatin riboside. Regeneration was similar to parental S. melongena (1.2 shoots/explant), with Micro-Mel developing 1.0 and Mini-Mel 0.8. Whole-genome sequencing (23X coverage) identified 179,653 SNPs between the parental lines, revealing heterozygosity rates of 0.00098% for Micro-Mel and 0.00123% in Mini-Mel. Approximately 8.50% and 10.79% of their genomes were introgressed from S. anguivi, respectively. Analysis identified 18 shared introgressions from S. anguivi among Micro-Mel, Mini-Mel, and four backcross dwarf materials derived from the same original plant. Notably, three orthologues of genes associated with dwarfism in tomato (SlDREB1, SlER, and SlSERK1) were identified within these introgressions. Micro-Mel and Mini-Mel represent transformative tools for eggplant research, accelerating genetic, physiological, and breeding studies.