Tropical grasses vary in their resistance to Striga aspera, Striga hermonthica, and their hybrids

Abstract

The genus Striga contains some of the most damaging parasitic plant species of the world, and it causes large problems in agricultural systems of Africa and Asia. Effective, cheap, and easy applicable methods for Striga control do not yet exist. One method with great potential may be the use of resistant crops. However, resistant crops are not widely available, hence, these genetic traits will have to be obtained from another source. Here we report the results of a screening in which it is shown that several native African savannah grass species possess a high level of resistance to Striga hermonthica (Del.) Benth., Striga aspera (L.) Kuntze, and interspecific hybrids of these two Striga species. This trait could be of potential value for the development of resistant crops. Resistance to Striga was not expressed at the levels of germination and attachment. Root exudates of all 14 grass species tested induced Striga seeds to germinate. Furthermore, attachment to the host roots was always observed. Subsequent development of the Striga seedlings, however, was absent or heavily impaired in resistant grasses. Preliminary observations suggested that the parasite could not breach the endodermal barrier of the roots. The host range of interspecific hybrids of S. aspera and S. hermonthica appeared to be a combination of the host ranges of their parents. They could not attack grass species that were resistant to both parents.Key words: Striga aspera, Striga hermonthica, interspecific hybrids, germination, attachment, tropical grasses, resistance.