Determination of levels of Striga germination Stimulants for maize gene bank accessions and elite inbred lines

Abstract

Parasitism by Striga hermonthica (Del) Benth is a severe constraint in maize<br />production in sub-Saharan Africa. Varying levels of tolerance to Striga attack have<br />been identified and exploited in breeding programs of several crops. However, the<br />level and stability of the tolerance is generally unacceptable in field-practice. Only<br />limited exploration has been undertaken among the farmers' landraces to find the<br />presence of viable sources of resistance to Striga. The objective of this study was to<br />examine and document the presence of the Striga germination stimulants from a<br />collection of some 420 maize landraces, populations and elite inbred lines. The<br />genotypes were variously sourced from International Maize and Wheat Improvement<br />Center (CIMMYT), International Institute for Tropical Agriculture (IITA) and Kenya<br />Agricultural Research Institute (KARI). The ability to effect germination as a<br />measure of the amount of germination stimulant produced was used to assess the<br />materials, using the standard procedures. Data were recorded on Striga germination<br />by counting Striga seeds with protruding radicle. Highly significant (P=0.001)<br />differences were observed among the germplasm screened. Several landraces were<br />found to stimulate low levels of Striga germination compared to the commercial<br />checks. Landraces CRIC 51, CUBA T-31, BRAZ 1758, BRAZ 1279 and VERA 217<br />exhibited the lowest Striga germination, an indication of high level of resistance to<br />Striga. The inbred lines were found to have a higher Striga germination percent<br />compared to the landraces, a likelihood of a higher concentration of strigol, the<br />stimulant causing chemical. CIMMYT lines CML 202 IR, CML 445 IR and CML<br />204 IR induced the least amount of Striga seeds to germinate. Higher levels of<br />germination of Striga seeds were found in the IITA lines which are known to be resistant, depicting a probable avoidance root architecture mode of resistance as<br />opposed to low production of strigol. It was concluded that the landraces with low<br />Striga germination percent can be used by breeders in the extraction of new Striga<br />resistant inbred lines. The resistant inbred lines can be recommended for direct use in<br />the formation of maize synthetics and hybrids resistant to S. hermonthica.