Culture Medium Composition and Light Intensity Shape Alternative Morphogenic Pathways from the Mature Embryo Shoot...

Eragrostis curvula (weeping lovegrass) is a perennial C₄ forage grass and a model for apomixis whose genetic transformation and genome editing remain constrained by the lack of efficient regeneration systems. Here we assessed the effect of culture medium composition and light intensity during the induction phase on morphogenic responses from explants of mature embryos of cv. Tanganyika INTA. Eleven media were tested: nine designed to induce somatic embryo-like structures (SELSs; Group 1) and two to promote multiple shoot proliferation (Group 2). Four light regimes-low, medium, high, and darkness-were applied during an 8-week induction period. Responsive and non-responsive explants were recorded at the Petri dish level and analyzed separately within each functional group using binomial generalized linear models (GLMs) in R 4.5.0. Morphogenic responses originated from the apical region of the embryonic axis, encompassing the shoot apical meristem. Medium composition influenced the predominant morphogenic response, whereas light intensity affected the efficiency of the response (significant medium × light interaction). Medium I (WPBS + 2,4-D + low BAP) under medium light resulted in the highest morphogenic response within Group 1, corresponding to an estimated 60.6% of explants exhibiting SELSs and/or associated shoot-forming meristematic tissue, although this estimate was not statistically distinguishable from those obtained for the same medium under low and high light intensity. Medium J (WPBS + high BAP:2,4-D ratio) under medium light resulted in a 74.0% multiple shoot proliferation response. Darkness reduced morphogenic responses in both groups. These protocols provide a reproducible regeneration platform for future genetic transformation and genome-editing studies in E. curvula.