Molecular phylogenetic relationships among species in the genus <I>Sorghum</I> based on partial <I>Adh1</I> gene

Abstract

The genus Sorghum contains some important grain crops and economically important forage grasses as well as agricultural weeds. The goals of this study were to elucidate the phylogenetic relationships between Sorghum species and ascertain the taxonomy status of the quarantine weeds which provide bases for effective utilization of its germ resources on molecular breeding and improvement of crop qualities and thus provide important guidance for port detection. In the present study, total DNA from the seeds of 8 Sorghum species (four S. almum, two S. halepense, one S. silk and one S. sudanense)were extracted, and the partial Adh1 gene of about 2,000 bp in length were amplified by PCR using specific primers designed from conserved regions of Adh1 gene reported in the GenBank (AF050456) and sequenced. Based on these sequences and other 24 Adh1 sequences registered in the GenBank, the phylogenetic trees constructed by multiple methods (MP, ML, and NJ) with the corresponding Adh1 sequence of Cleistachne sorghoides as the outgroup shared almost the same topology. The results showed that: (1) there were obviously three lineages for the genus Sorghum. One included two subgenera Chaetosorghum and Heterosorghum, and another included subgenus Eusorghum, both of which consisted of 2n=20 and 2n=40 species with small chromosomes. Still another lineage contained the two subgenera Parasorghum and Stiposorghum with 2n=10 species and their polyploid relatives with relatively large chromosomes; (2) geographical divergence clearly existed in the S. almum; (3) S. purpureosericeum, S. versicolor, S. nitidum and S. leiocladum of subgenus Parasorghum clustered together, but S. matarankense, S. grande, and S. timorense of the same subgenus clustered with the species of subgenus Stiposorghum, showing closer relationship with subgenus Stiposorghum; (4) S. macrospermum was more closely related to S. laxiflorum than the other species of the genus Sorghum.