Crop wild relatives as a genetic resource for generating low-cyanide, drought-tolerant Sorghum

Using a Sorghum bicolor cultivar and seven wild Sorghum species endemic to Australia as our experimental system, we monitored their different responses to drought by assessing growth and morphological, physiological and biochemical parameters. Drought stress significantly decreased height, biomass, the maximum potential quantum efficiency of photosystem II, photosynthetic rate and relative water content in S. bicolor, while several of the wild species were much more tolerant. Drought significantly increased dhurrin concentration in aboveground tissue in S. bicolor but not in the wild species. Root dhurrin content was unaffected by drought in S. bicolor, in contrast to the varied responses observed in the wild species. Sorghum macrospermum and S. brachypodum maintained relatively high growth and photosynthetic performance under drought, with negligible aboveground dhurrin content. These wild species are promising candidates for sorghum crop improvement.