Seed germinability of Stylosanthes spp. (Fabaceae) accessions under water stress conditions

This study aimed to evaluate and compare the germinative performance of seeds from accessions of Stylosanthes spp. held in the Forage Germplasm Bank of the State University of Feira de Santana (BGF-UEFS), Brazil, under water stress conditions during the initial phases of germination. Germination tests were conducted using seeds from six accessions subjected to different osmotic potentials (0.0MPa – distilled water, -0.2, -0.4, -0.6 and -0.8MPa) prepared with polyethylene glycol 6000 (PEG 6000). The experimental design was completely randomized, using 25 seeds per replicate for each treatment. The seeds were evaluated over a period of 5 days under water stress conditions, followed by an additional 5-day recovery period in distilled water for the seeds remaining from the -0.8MPa treatments. The following variables were measured: germination percentage (G%), mean germination time (MGT), germination speed index (GSI), and germination recovery (GR). The results indicated an interaction between factors affecting the germinative behaviour of the Stylosanthes spp. accessions for all variables. The genotypes showed significant reductions in G%, with accessions BGF 12-014, BGF 10-018 and BGF 10-029 exhibiting the best performance under the most severe osmotic potential (-0.8MPa). MGT and GSI were also significantly affected by increased water stress. Accessions BGF 12-014, BGF 10-018 and BGF 10-029 were the most promising based on their germinative performance under water stress conditions simulated with PEG 6000 during the early germination phase.