Monday, November 5, 2007
59-9

Herbicide Resistant Maize to Control Striga in Eastern and Central Africa.

Alpha Diallo, Dan Makumbi, Fred Kanampiu, and Stephen Mugo. CIMMYT, PO Box 1041, PO Box 1041, Nairobi, 00621, Kenya

The parasitic weed Striga affects maize on 20 million ha in Africa and contributes significantly to its low productivity there (1.3 t/ha versus the world average of 4.2 t/ha). A single Striga plant produces over 50,000 seeds that remain viable in soil for up to 20 years. CIMMYT and partners have developed a technology  that combines low doses (<30 g/ha) of imazapyrŪ herbicide applied as a seed coating to non-transgenic Imidazolinone resistant (IR) maize, thereby controlling Striga before or during attachment to maize roots. We evaluated 22 CIMMYT open-pollinated IR varieties (OPVs) for mid-altitude ecologies of Eastern and Central Africa at 10 Striga-free and 12 infested sites in 4 countries. Under Striga infestation, the best IR-OPV yielded twice as much (2.6 vs. 1.3 t/ha) as the best check. Seventeen IR-OPVs had 62-144% higher grain yield than KSTP94, the commercial, Striga tolerant check. Two IR-OPVs significantly out-yielded the tolerant commercial check under Striga-free conditions. Striga density averaged 1 plant/m2 on the IR-OPVs and 5 plants/m2 on the checks across environments. The correlation between Striga plants/m2 and grain yield was low but significant (r = -0.22, P<0.001). There were highly significant (P<0.001) genotype and genotype x environment interactions (GxE) for Striga plants/m2 and grain yield, implying varying efficacy of the IR practice across environments. GxE accounted for 19% of the total variation in Striga plants/m2. Significant GxE for Striga emergence underscores the need for multilocational testing to verify the viability of the IR practice and to adapt it to diverse production settings in sub-Saharan Africa.