Melilotus albus is recognised as an important source of forage for ruminant animals in rangelands, particularly some of the germplasm of Melilotus collected in Argentina. This study was designed to evaluate the effects of 2 years of selection in M. albus for late flowering and branching on forage yield in a 2-year field plot experiment and to evaluate the effects of selection for late flowering on photoperiodic requirements in a 1-year pot experiment under natural and artificial lighting conditions. Three populations were evaluated, namely original population (T), a population selected for late flowering and greater number of basal branches (ET1), and a population selected only for late-flowering plants (ET2). The field plot experiment showed that total DM yield per year was higher for ET1 and T than for ET2 in Year 1 and higher for ET1 than T and ET2 in Year 2. Relative leaf yield was higher for ET1 and ET2 than for T in both years. Leaf number was greater for ET1 than for ET2 and T in both years. The number of new basal and total branches was greater in ET1 than in ET2 and T for both years. The pot experiment showed that days to flowering, calculated as the average of natural and artificial lighting treatments, were higher in ET2 and ET1 (83.4 days ± 15 and 72.8 days ± 19, respectively), than in T (61.2 days ± 21). Supplementary lighting reduced days to flowering compared with natural lighting conditions for all populations (58.7 days ± 13 v. 86.1 days ± 12). Results showed that 2 years of selection proved to be efficient in breeding for late flowering and greater number of basal branches in M. albus. The longer vegetative stage observed in the improved populations can be explained by the selection of plants which require a longer photoperiod to flower. Selection for late flowering and greater number of basal branches resulted in a population with more leaves and higher relative leaf yield.

The false Rhodes grasses [Leptochloa crinita (Lag.) P.M. Peterson and N.W. Snow and Leptochloa pluriflora (E. Fourn.) P.M. Peterson and N.W. Snow] are considered valuable native forage resources for arid and semiarid rangelands in Argentina and the United States. Effectively using plant materials as forage under aridity conditions requires understanding their resource allocation under those conditions. In the present study, plant functional traits were evaluated in six populations of each false Rhodes grass species from different geographic origin in a humid and an arid region. The evaluation was focused on seed weight, due to the key role of this trait in plant survival. The implication of seed weight in germination under osmotic stress and trade-off relationships between functional traits were also analysed. A fixed ontogenetic variation was found in both species, since populations maintained a stable seed weight across environments. The tolerance to osmotic stress at germination stage was more related to seed weight than to population origin or maternal environment of seeds; heavier-seeded populations produced heavier seedlings instead of a higher number of germinated seeds or higher germination rates. Some traits varied between environments but other traits exhibited a fixed response. Variation patterns among populations were similar within environments and in some cases even for populations from the same geographic origin, revealing a fixed ontogenetic variation; this phenomenon was clearer in L. crinita than in L. pluriflora. Moreover, several different trade-off strategies were detected in both species. These results reinforce the knowledge about the key role of seed weight in survival and performance of seedlings at initial growth stages under arid conditions; however, at advanced stages, other traits would have an important function in growth and development of false Rhodes grasses.

The objective of this study was to determine the effect of different germination temperatures and dry storage on the germinative behaviour of E. scabrifolius. Seeds of three lines from different populations, which showed contrasting germinative behaviour in preliminary experiments, were incubated under four temperature regimes: 15°C, 20°C, 15-20°C and 25°C. Germination tests were performed with freshly harvested seeds and seeds kept dry for nine months in paper bags at 25°C. The results presented in this work suggest that in E. scabrifolius: a) seeds do not have putative dormancy; b) seeds require low temperature for germination; c) germination is prevented at 25°C; d) alternating temperature was better than a constant 15°C temperature regime for final percentage germination.