MITOCHONDRIAL-DNA DIVERSITY IN WILD AND CULTIVATED SORGHUM

Cultivated sorghum (Sorghum bicolor ssp. bicolor) is classified into f ive main races on the basis of spikelet morphology. Isozyme analyses p rovided new insight into the genetic diversity of sorghum and revealed marked geographic grouping, while nuclear restriction fragment length polymorphisms showed racial differentiation and intraguinea race diff erentiation. Wild sorghum is diploid or tetraploid and African sorghum (S. bicolor ssp. arundinaceum) is classified into four races, that ar e considered to be progenitors of cultivated sorghum. We performed mit ochondrial DNA analyses to compare the diversity of wild and cultivate d sorghum and to study the genetic origin of guinea margaritiferum. Th e same overall patterns were obtained with the different phenogram con struction techniques. Our results confirmed the specificity of guinea margaritiferum and demonstrated the presence of two generic entities w ithin this subrace. Another guinea group was also noted, which corresp onded to Asian guinea roxburghii. In wild sorghum, the arundinaceum ra ce appeared to be homogenous, while the verticilliflorum race was sepa rated into two groups, one of which was associated with the arundinace um race. The diversity observed in cultivated forms was found to be en compassed within the wild pool, except for one guinea margaritiferum g roup. There did not seem to be any particular relationship between wil d races and cultivated races.