Methods for overcoming dormancy in Brachiaria brizantha seeds

Brachiaria brizantha is a forage species widely used in Brazilian pastures and its seeds have contamination in several areas of countries. Its high germination is fundamental in pasture formation. However, it is common for seeds of this species to have natural dormancy, negatively influencing pasture formation, resulting in losses to the producer. Thus, the objective of this study was to determine a methodology to overcome dormancy of ‘Marandu’ and ‘Piatã’ B. brizantha seeds. Four batches from the 2016/2017 and 2017/2018 harvests were used. Initially, batch profile was evaluated by the following characteristics: determination of moisture content, weight of a thousand seeds, first germination count, germination, germination speed index, initial stand, emergency, emergency speed index and fungi incidence in seeds. The seeds were subjected to the following treatments to overcome dormancy: mechanical (removal of glume, palea and lemma), sulfuric acid (98%, 36 N), potassium nitrate (0.2%), heat treatment (70 °C and 85 °C, during 5h, 10h, 15h and 20h) and a control. The obtained results allow inferring that the causes of dormancy of ‘Piatã’ seeds are of a physical nature, with the tissues surrounding the seed being the main factor that prevent germination. The mechanical method and scarification with sulfuric acid the most efficient in overcoming dormancy. The mechanical treatment with removal of the glumella is efficient to overcome the dormancy ofB. brizantha seeds, providing an increase in the germination percentage