Phenotypic evaluation of worldwide germplasm of arugula (Eruca sativa Mill.) and identification of underlying latent factors contributing to phenotypic variation under indoor farming conditions

Abstract

Eruca sativa (arugula) is often consumed fresh in regions where raw salads are a dietary staple. Studies investigating the phenotypic diversity of E. sativa have been reported in the past differentiating them by gene pools according to geographical origins. We expanded the scope of analysis to include deep phenotypes, and the diversity of germplasm. Furthermore, there is no report of such crop being evaluated in a large scale under indoor farming conditions. In this study, 185 accessions were subjected to phenotypic evaluation across 68 phenotypic traits. High-throughput phenotyping machines and image processing platforms employed were efficient to measure vegetative yield-, hyperspectral-, and plant architecture-related traits of E. sativa. Wide phenotypic variations were evidenced in the collection and significant differences were observed between accessions in majority of the traits evaluated. The population genetic structure divided the germplasm collection into three major continental clusters (Asia, Africa, and Europe). In addition, the three major continental clusters also showed significant differences in the tendency to flower early, vegetative leafy plant yield, plant height, vegetative index, hairiness and leaf blade color. Factor analysis revealed nine underlying latent factors contributing approximately 70 % of the total phenotypic variations, with each potentially enhancing crop’s productivity and quality. Based on desirable agronomic traits that are suitable for controlled environment agriculture (CEA), bivariate analysis was conducted using four latent factors (Total yield-, plant height-, post-harvest-, and flowering-related). Subsequently, three ideal accessions (ERU12, PI 178901, and PI 251491) were highlighted as high-yielding, short, long shelf-life crops for potential future plant breeding and genetic improvement.