Cadmium toxicity in African yam bean (Sphenostylis stenocarpa (HOCHST. EX A.RICH.) HARMS genotypes

摘要

The aim of the study was to investigate the growth responses of African yam bean ( Sphenostylis sternocarpa (Hochst. ex A. Rich.) Harms (AYB) to cadmium pollution. Top garden soil (0 – 10 cm) was obtained as pooled and polluted with cadmium (as CdCl 2 ) at the rate of 12 mg kg -1 , which is equivalent to 3 times the ecotoxicological screening value of Cd. The polluted soils were made ready for use 3 days later. Nine selected AYB accessions (TSs-87, TSs-89, TSs-90, TSs-91, TSs-92, TSs-93, TSs-94, TSs-95, and TSs-96) were pre-soaked for 30 minutes and then sown in the polluted and unpolluted soils. Data collected were subjected to ANOVA, and means were separated at 95?% confidence interval. Results showed that incidence of cadmium pollution significantly delayed seedling emergence in all tested AYB accessions by at least one day (p 0.05). Despite exposure to Cd, TSs-96 attained 50 % emergence faster than other accessions. Although there were general reductions in yield due to exposure to Cd, TSs-92 showed the least percentage yield reduction (50?%), compared to 74?% yield reduction in TSs-93, thereby suggesting a comparatively better yield capacity compared to the other test accessions. Overall, decrease in total chlorophyll content seems to be the major reason of injury in Cd-exposed plants.