Variability in seed coat dormancy in Dimorphandra mollis

Information concerning the genetic diversity of most tropical tree species is lacking, causing many with economic potential to be overlooked for tree domestication and reforestation efforts. This study was conducted to determ ine whether variation in seed coat dormancy exists among seeds collected fr om 14 different maternal families of the native Brazilian tree species, Dim orphandra mollis Benth. Seed dormancy differences were found in germination capacity, rate, and viability. Families differed by pretreat ment in their relative germination success. Variation in germination among families was eliminated with the filing pretreatment, while sulfuric acid pretreatment w as the most effective method of reducing variation in germination rate. The resultant high uniform germination among all families from mechanically ru pturing the seed coat suggests that the mechanism of dormancy lies in the s eed coat. Repeatability measures suggest the presence of relatively high ge netic control of germination capacity and a moderate genetic control of ger mination rate, though the differential microclimates in which seeds from di fferent trees developed could also play a role in this variability. This st udy also demonstrated the benefits of maintaining seed samples from differe nt families separate and the need for determining pretreatments that can el icit uniform germination across a number of families.