COMPARATIVE ANALYSIS OF STRIGOLACTONE PRODUCTION IN BAMBARA GROUNDNUT AND COWPEA GENOTYPES

This study examined strigolactones (SLs) in 12 Bambara groundnut root exudates. A mixture of three strigolactones, orobanchol, orobanchyl acetate, and fabacyl acetate, were detected by LC-MS/MS in the root exudates of all Bambara groundnut genotypes investigated. Fabacyl acetate was not detected over ten days of P-starvation. Two of these strigolactones, orobanchol and orobanchyl acetate, were previously identified in cowpeas. The levels of orobanchol and orobanchyl acetate secreted varied significantly between genotypes (p<0.001) and (p<0.04), respectively. Over 21 days of P-starvation, meagre amounts of fabacyl acetate (< 10-12 M) were detected in Bambara groundnut root exudates, and there were no significant differences between genotypes. Among all the genotypes studied, Mana was the highest producer of the strigolactones detected, while DodR was the genotype whose exudates contained the lowest amount of strigolactones. The relative proportion of orobanchol contained in the strigolactone mixture of root exudates was very high across all 12 genotypes. These detected SL mixtures induced the germination of A. vogelii seeds at concentrations as low as 10-12 M but did not lead to S. gesnerioides germination, suggesting that A. vogelii is more sensitive to SL induction than S.gesnerioides and therefore differences inSL quantity maybe a key factor determining host specificity of parasitic plants. Although Alectrabutnot Striga parasitized the 12 BGN genotypes studied in a separate TETFund IBR grant awarded to the Federal Polytechnic Ekowe, genotypes with lower concentrations of SL mixtures result in lower Alectra shoot counts, suggesting that Bambara groundnut may be resistance/tolerance to root parasitic plants based on reduced SL production.