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Geographical distribution and phenotypic diversity of wild/weedy sorghum [Sorghum bicolor (L.) Moench] in Ethiopia: implications for germplasm conservation and crop–wild gene flow

  • Asfaw Adugna (a1) (a2) and Endashaw Bekele (a1)

Extensive studies of genetic diversity and population structure important for conservation of wild sorghum are yet lacking in Ethiopia, the centre of origin for cultivated sorghum. To assess both genetic diversity and the probability of gene flow between wild and cultivated types, collections of wild Sorghum bicolor were made from regions in Ethiopia where wild and cultivated sorghum coexist. Morphological data were recorded in situ for both quantitative and qualitative characters from 30 populations in five diverse geographical regions and eight agroecologies. High phenotypic diversity was observed among the wild and weedy sorghum populations. The overall standardized Shannon–Weaver diversity index (H′), computed from the frequencies of all qualitative traits, ranged from 0.47 to 0.98 with an average value of 0.76. Moreover, warm semi-arid lowland (SA2) agroecologies, which contain Tigray populations, supported the highest diversity for these traits. Subspecies verticilliflorum and drummondii (the two major subspecies of wild S. bicolor) were observed in diverse habitats throughout northern and central Ethiopia. In some areas, weedy types showed domestication traits including the absence of awns and reduced seed shattering. The existence of morphologically intermediate forms indicates that gene flow between cultivated and wild forms has likely occurred. Deployment of transgenic crop sorghum, therefore, would pose a distinct risk for transgene movement into wild Ethiopian populations.

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