Overview of tolerance and resistance of maize to Striga hermonthica and S. asiatica
1995
Kim, S.K. | Adetimirin, V.O.
Two species of witchweed, Striga hermonthica (Del.) Benth and S. asiatica (L.) Kuntze infest millions of hectares of arable land in sub- Saharan Africa, and they threaten production of cereal crops. The International Institute of Tropical Agriculture (IITA) has worked on breeding maize (Zea mays L.) for tolerance (the ability of the host to withstand the effects of parasites that are already attached) and resistance (the ability of a host to prevent attachment of the parasite to its roots and/or subsequent reduction of emergence) against Striga. A simple and reliable field infestation technique was developed at IITA. With this new infestation technique, individual maize plants were screened. Tolerance and/or resistance sources were identified in both temperate and tropical maize germplasm Inbreds developed at IITA (notation TZi) with tolerance to Striga are TZi 3, TZi 12, TZi 25, TZi 30 and those showing resistance are TZi 11, TZi 17, TZi 25, TZMi 302 and perennial maize (Z. diploperennis). With these inbreds, IITA developed Striga tolerant and resistant (STR) hybrids. Genetic studies on tolerance and resistance revealed that additive genes play a major role for tolerance and non-additive genes play a major role for resistance. Six genes are involved for tolerance. In a pot study at 5 weeks after planting (WAP), maize inbreds infested with Striga produced on average, three times more root dry matter than those of the uninfested controls. At 7 WAP, the tolerant inbreds had significantly higher root dry matter than the susceptible inbreds when infested. Three cereals were evaluated under 12 Striga collections. Results showed that different strains of S. hermonthica were present in west Africa. S. hermonthica tolerant and resistant genotypes showed similar levels of tolerance and resistance to S. asiatica.
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