A comparative study on Striga hermonthica interaction with a sensitive and a tolerant sorghum cultivar

In this study, the effects of Striga hermonthica (Del.) Benth. on a sensitive and a tolerant sorghum genotype were investigated, and the underlying tolerance mechanisms were distinguished. The sensitive sorghum cv. CK60-B and the tolerant sorghum landrace Tiemarifing were grown in pots with and without seed infestation. Both sorghum genotypes responded to infection by the parasite, but it was evident that CK60-B was more strongly affected than Tiemarifing. Sorghum plant height, final leaf number, green leaf area, kernel yield, number of kernels and 1000-kernel weight were significantly reduced by infection, which also had a marked effect on the phenological development of CK60-B; the majority of the plants remained vegetative and, in the remaining plants, flowering was delayed by about 2 weeks. No effect on the phenological development of Tiemarifing was observed. The tolerant landrace showed significantly lower and delayed emergence of S. hermonthica than the sensitive cultivar, and this could be explained by a delay in the onset of attachment. Significantly higher numbers of reproductive parasitic plants were found in the pots with the sensitive sorghum plants. It is concluded that differences in root architecture and the resulting early infection and higher S. hermonthica numbers are partly responsible for the stronger effects of the parasite on the sensitive cultivar.