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.

Can wild relatives of sorghum provide new sources of resistance or tolerance against Striga species?

“…Resistance to parasite infection has been demonstrated in Sorghum versicolor (Andersson) infested by S.hermonthica (Lane et al ., 1994), S. arundinaceum inoculated with Striga aspera (Kuiper et al ., 1998) and in Sorghum drummondii (Nees ex Steud.) Millsp.…”

Evaluation of ecologies and severity of Striga weed on rice in sub-Saharan Africa

“…These areas tend to be managed traditionally with low inputs and continuous cereal cropping without crop rotation. The use of inorganic nitrogen and organic fertilizers such as manure and compost has been reported to reduce Striga infestations (Kuiper, 1998). Manure applications have been shown to be as effective as fallowing in maintaining soil productivity.…”

Parasitic plants, wild relatives and the nature of resistance

“…A battery of resistance mechanisms against O. cumana has been recently described in wild species of Helianthus (Labrousse et al ., 2001) and is being transferred into cultivated sunflower. Similar approaches for identification and exploitation of genetic resources in breeding against parasitic weeds have been followed in other crops (Kuiper et al ., 1998), and this includes the work of Gurney et al . Gurney et al .…”