Quantification of sorgoleone in sorghum accessions from eight southern African countries

Allelopathic effects of sorghum (Sorghum bicolor(L.) Moench) can ease weed pressure and improve grain yields if cultivars capable of producing high levels of natural chemicals effective in suppressing weeds of economic importance are identified. Three hundred and fifty three sorghum accessions fom Botswana, Malawi, Mozambique, Namibia, South Africa, Tanzania, Zambia and Zimbabwe were screened for sorgoleone content using high-performance liquid chromatography (HPLC) in 2016. Three replicates of seeds of each accession were germinated in petri dishes at the University of Zimbabwe. Roots of six-day-old seedlings were excised from shoots and immersed in methanol to extract sorgoleone. The crude extract was filtered, evaporated and dissolved in the mobile phase (1 mg mL−1) prior to HPLC analysis. One-way ANOVA showed that there were highly significant differences in sorgoleone production among the sorghum cultivars (p< 0.001). The South African landrace IS9456 yielded the highest sorgoleone (584.69 μg mg−1root fresh weight). High levels of sorgoleone were also detected in accessions from Botswana as well as in wild sorghum from Zimbabwe. Improved sorghums had very little sorgoleone. It was concluded that some landraces and wild sorghum have high potential for use in allelopathic weed control.