Seed dormance variability among and within species of Sesbania

Seed dormancy variability was analised among species and families of Sesbania SCOP. Thirteen families of the following five Sesbania species were evaluated: S. rostrata, S. exasperata, S. tetraptera, S. sesban and S. virgata. The trial was conducted at 20-30°C, for 15 days, in a completely randomized design with three replications of 50 seeds each. An analysis of variance was conducted unfolding the degrees of freedom of families within species. The coefficients of intraspecific genetic variation (CVg i) and genotypic determination (b) were estimated. Germination rates, measured indirectly by the average germination time, were also evaluated. High variability for seed dormancy was observed among species (P<0.01) and among families (P<0.01). S. virgata and S. tetraptera presented the highest dormancy, with average germination of 13.5 and 13.9%, respectively, while S. rostrata and S. sesban showed the lowest dormancy, with average germination of 68.3 and 60.5%. The estimated values of CVg i were low for all species, varying from 9.9 to 14.9%, indicating that most of the variability found in relation to dormancy in these populations is due to non-genetic factors. The estimated values of b were higher for S. tetraptera (b = 0.6769), S. sesban (b = 0.6332) and S. exasperata (b = 0.6306), indicating a possibility of selection for higher or lower dormancy levels. As for the germination rates, S. virgata was the slowest, in contrast with S. tetraptera and S. sesban, which presented the fastest germination rates. No significant differences for germination rates were observed among families.

germination; genetic parameters