Seed germinability and seed dormancy breaking from Portuguese cilantro (Coriandrum sativum) Landraces

Coriandrum sativum L. (Cilantro) is an aromatic and medicinal taxon often used for food flavouring. The goal of this study was to test seed germination from seed accessions harvested in Alentejo and evaluate the seed dormancy breaking of one wild growing accession (CS31), compared with commercial cultivars. The plant material, a total of 18 accessions, comprised 15 traditional accessions (landraces) collected in late spring / summer 2011 at various locations in Alentejo region (Portugal), one wild accession (CS31) from same region and two commercial samples (one Portuguese and one Spanish), considered as controls. The first germination test, considering the 18 accessions was done in December 2011, followed by a test with 17 accessions after freezing at -20 degrees C for 48 hours. The 3rd test was done in December 2012 with a sub-sample of 8 accessions. In these three tests, the seeds were incubated at 20 degrees C with a 12 h photoperiod. Seeds from the wild growing accession obtained null germination, so several seed dormancy breaking treatments were carried out (at 20/30 degrees C with 8h dark/16 hours light): (1) seed at 40 degrees C for 7 days, (2) gibberellic acid 0.5 g.l(-1); (3) manual scarification, (4) soaking in distilled water for 3 days, drying at 30 degrees C for 8 h, (5) pre-chilled at 8 degrees C for 7 days; (6) gibberellic acid at 5g.l(-1), (7) 40 degrees C for 1 month, soaking for 3 days, and drying at 30 degrees C for 8 h; (8) 40 degrees C for 1 month followed by boiling water; (9) 40 degrees C for 1 month followed by soaking for 3 days at 8 degrees C and drying at 30 degrees C 8 h, then pre-chilling at 8 degrees C for 7 days and gibberellic acid 5g.l(-1); (10) 40 degrees C for 1 month followed by pre- chilling at 8 degrees C for 21 days. We also considered the germination results of the wild accession CS31 and the Portuguese control at 20/30 degrees C with 8h/16 h, totalizing 12 treatments. The germination of the seeds showed high variability between accessions in tests conducted in 2011 and 2012 (from 0% to 76.5%). Seed germination decreased an average of 8.3% with one additional year of storage. Freezing the seed didn't modify significantly their ability to germinate. The best results for the wild accession (CS31) were obtained with the application of gibberellic acid.