Improved seed germination and biomass yield in five Mediterranean ecotypes of Piptatherum miliaceum – A native grass species for bioenergy purposes

Piptatherum miliaceum (L.) Coss. [syn. Oryzopsis miliacea (L.) Asch. et Schw.], common name smilo grass, is a native Mediterranean perennial species, recently considered an important genetic resource for bioenergy purposes. Unfortunately, the germination of “seed” of P. miliaceum is generally poor and slow, due to seed dormancy and may create serious problems to the establishment of the crop, so knowledge of germination behaviour is an indispensable requirement for a potentially widespread use of this species for bioenergy production in the future. The aim of this research was to evaluate the effects of 4 seed treatments: (control, sulphuric acid, osmopriming with PEG + GA3, sulphuric acid + osmopriming with PEG + GA3), 5 ecotypes collected in Sicily (South Italy), 2 storage seed temperatures after treatments (4 ± 1 °C and 20 ± 1 °C) and 7 storage times after treatments (from 0 to 6 months) on seed germination performances. Daily and final (12 days) germination were recorded and total percentage germination and Mean Germination Time (MGT) were calculated. In addition, the biomass production, along two growing seasons in a semi-arid environment, was evaluated in the field experiment. Germination, on the average of the other factors, was 0.8% in the control (untreated seeds), 2.1% in seeds treated with osmopriming and 5.9% in sulphuric acid treated seeds; it was significantly enhanced (88.8%) by the treatment with sulphuric acid + «osmopriming», which also meant a significant reduction in the MGT. The effectiveness of the latter treatment was persistent for 6 months, especially if seeds were stored at 20 ± 1 °C. Among ecotypes, there emerged a discrete variability both in response to seed treatments, storage temperature and storage time, as well as for aboveground dry biomass yield, which ranged from 6.1 to 11.5 t ha−1 in the first and from 10.0 to 14.6 t ha−1 in the second growing season. This knowledge could contribute to facilitating the use of smilo grass seed and to favouring a widespread of the crop for bioenergy purposes.