Exploring grass pea (Lathyrus sativus L.) genetic diversity in Mediterranean changing climate conditions

Grass pea (Lathyrus sativus L.) is an annual cool-season grain legume, recognized as a stress-resilient crop, able to thrive in unfavourable growing conditions. It is widely cultivated in different world regions, with two main ecotypes based on seed traits. Particularly, in the Mediterranean region, climate change has amplified environmental instability, creating a fundamental need for producing more resilient or adaptable plant varieties. With the present study, we aimed to identify, among grass pea germplasm, new sources of interesting agronomic traits that can be used in breeding programs for adaptation to climate change. Hence, we trialled a worldwide grass pea collection of 182 accessions in Alvaiázere, Portugal, a Mediterranean climate region, across four growing seasons. We characterized the accessions for plant growth-, inflorescence-, seed-, and yield-related traits. By applying linear mixed models analysis, we assessed the diversity among accessions, as well as the genotype, the environment, and the genotype-by-environment effects. A principal component analysis was performed to summarize multivariate similarities among grass pea accessions and/or growing seasons. Additionally, we estimated the main ecotype clustering parameters, seed coat colour, seed size, and geographical origin, effects on the measured traits. Great diversity among accessions for all traits was observed. For most traits, the effect of the growing season was the most prominent, although significant genotype and genotype-by-environment interaction effects were also observed. Yield was higher on large and light seed accessions, with no significant yield differences detected across geographical origins. Nevertheless, South Asian accessions showed the tallest plants at the first flower and the highest number of seeds per plant (although with the smallest seed sizes), two of the most important yield components in the study. The Sub-Saharan African accessions showed the shortest growth cycles and mainly dark coat colours, trait associated with a reduced infestation by Bruchus weevils. The last two traits are of great interest as breeding targets. The Sub-Saharan accessions may thus be of significant value as potential donor material in breeding programs.