Seed Storage and Germination of Three Grass Species: Effect of Spikelet Weight and Dormancy

Dormancy is a plant strategy that distributes germination over time. Domestication changed this in many cultivated species. However, many still retain this characteristic because it has not been completely removed or domesticated, especially in apomictic plants. Urochloa is a tropical grassland; for cultivated materials, apomixis is the rule, except for U. ruziziensis. This work evaluated spikelet dormancy release in three Urochloa species in two storage conditions. Different lots were cleaned and split into two portions: light (LS) and heavy spikelets (HS) that were split again into two storage conditions at 4.5% RH (relative humidity) or at 50% RH. Spikelets were analysed at three-month intervals during the first year and then until 44 months for U. brizantha and U. humidicola and 40 months for U. ruziziensis through germination and the tetrazolium test. The results showed that storage at low RH maintained the germination and vigour of “Marandu”, “Basilisk”, “Llanero” and “Kennedy’ but not for “Tully”. Dormancy released was achieved after 3 months of storage for all cultivars of U. brizantha, “Tully” and “Kennedy’, “Llanero” maintained a high amount of dormancy until 12 months. U. brizantha cultivars and “Kennedy” exhibited a lower dormancy than U. humidicola “Llanero. The heaviest spikelets conserve better at 4.5 and 50% RH conditions studied.