Development of a pearl millet Striga-resistant genepool: Response to five cycles of recurrent selection under Striga-infested field conditions in West Africa

Striga hermonthica (Del.) Benth. is a persistent threat to pearl millet [Cenchrus americanus (L.) Morrone, comb. nov.] production, especially in West Africa. This study aimed at evaluating the response of a diversified pearl millet genepool to five cycles of recurrent selection targeting Striga resistance and panicle yield, and to a lesser extent downy mildew [Sclerospora graminicola (Sacc.) J. Schroet.] resistance. Two-hundred full-sib families (FS) representing the C5 selection cycle were evaluated together with the genepool parental landraces, experimental varieties derived from previous cycles and local checks in Striga-infested fields at Sadoré (Niger) and Cinzana (Mali). Substantial and mostly significant selection progress could be documented. The accumulated percentage gain from selection amounted to 51%/1% lower Striga infestation (measured by area under Striga number progress curve, ASNPC), 46%/62% lower downy mildew incidence, and 49%/31% higher panicle yield of the C5-FS compared to the mean of the genepool parents at Sadoré/Cinzana, respectively. Experimental varieties selected from previous cycles also revealed lower ASNPC and mostly higher yield compared to genepool parents at their selection sites. Significant genetic variation among the C5-FS and operative heritabilities of 76% (Cinzana), 84% (Sadoré) and 34% (combined across locations) for ASNPC will enable continued selection gain for Striga resistance. High genotype × environment interaction variances for all target traits suggest that different experimental varieties need to be extracted from the genepool for different sites. The genepool-derived varieties will be further validated on-farm and are expected to contribute to integrated Striga control in pearl millet in West Africa.