H.O. Ngesa, J.O. Okora, J.A.W. Ochieng

Maize in western Kenya is devastated by Striga hermonthica weed, and current grain yield in fields under Striga infestation is below 1 t ha–1. Teosinte (Zea deploperennis), a close relative of maize, has considerable resistance to S. hermonthica. Advanced backcross derivatives of maize x teosinte with resistance or tolerance to Striga were crossed to locally adapted maize inbred lines and populations at the Kibos Striga field station in western Kenya in 1999. This formed the basis of a breeding program to develop Striga-resistant maize varieties. Crosses of Striga-resistant sources with adapted local germplasm were evaluated in Striga hotspots in a preliminary yield trial in 2000/01. Selected entries were evaluated in an advanced yield trial in 2002 and outstanding entries were used to develop lines and constitute open-pollinated varieties (OPVs) to pyramid the genes for resistance and tolerance to Striga. Elite OPVs were evaluated in 2003 at Kibos and Alupe. Six varieties significantly (p > 0.05) outyielded recommended commercial hybrids and OPVs in western Kenya, yielding 3.5 to 5.2 t ha–1. The seed project of the International Maize and Wheat Improvement Center (CIMMYT) and the Kenya Agricultural Research Institute (KARI) evaluated 18 varieties in the 2003 long rains season. From the KARI Striga program GFVC-4 was ranked second (4.0 t ha–1) and GFVC-3 fourth (3.7 t ha–1) in grain yield across nine locations.

The national performance trial evaluation of 12 varieties in 10 Striga hotspots in western Kenya was conducted in the 2004 long rains season. GFVC-4 yielded 3.9 t ha–1 across locations, which was higher than all recommended commercial Striga-tolerant varieties. Only imidazolinone-resistant (herbicide-treated seed) entries had higher yield and lower Striga count and severity rating than GFVC-4.

We should be able to get pre-release status for GFVC-4 in 2005 and proceed to produce and disseminate seed at 75–80% of the current price of commercial hybrid seed, because it is an OPV. This should establish a revolving fund for further commercial production, registration and dissemination of varieties.