Germination of tropical forage seeds stored in ambient and controlled temperature and humidity conditions

Abstract

Correct storage of tropical forage seeds in the humid tropics is critical in order to safeguard germination. Storing Mulato hybrid brachiaria (Brachiaria ruziziensis x B. brizantha) seed under ambient conditions could be safely done for 8−12 months in Thailand, but rapid deterioration in viability occurred with longer storage, with seed being totally non-viable after 20 months storage (Hare et al. 2008). However, Mulato seeds kept in cold storage (10 C and 40% RH) for 3 years still maintained 80% germination. Similar results were found in northern Australia (Hopkinson and English 2005), where loss of viability of Panicum maximum, Brachiaria decumbens, Brachiaria humidicola, Setaria sphacelata and Chloris gayana seeds was rapid under ambient conditions with total death at 3 years. Under cold storage, maximum seed viability was still maintained after 6 years of storage. Embryo dormancy is reduced with age (length of storage) and is usually short-lived (i.e. several months) in many Brachiaria species. Hare et al. (2008) found that dormancy was quickly lost in Mulato seed stored at ambient temperatures but still persisted strongly after 3 years in cold storage. Hopkinson and English (2005) found that dormancy persisted longer under cool storage than under ambient storage. Forage seeds produced by Ubon Forage Seeds at Ubon Ratchathani University (Hare et al. 2013) are stored in a large commercial cool room (18−20 C and 50% RH), but there are no data on how long seeds can be safely stored in this room. The objectives of this trial were to study: the effects of ambient storage and cool-room storage on germination of our range of tropical forage seeds; and the persistence of embryo dormancy with storage.