Genetic Improvement of Extra‐Early Maize Cultivars for Grain Yield and <i>Striga</i> Resistance during Three Breeding Eras

Abstract

Maize ( Zea mays L.), a food security crop in West Africa (WA) is threatened by Striga hermonthica (Del.) Benth. infestation. A study was conducted at five locations in WA for 2 yr to determine genetic gains in grain yield of 56 extra‐early maturing cultivars developed during three breeding eras, 1995 to 2000 (Era 1), 2001 to 2006 (Era 2), and 2007 to 2012 (Era 3) under Striga ‐infested and Striga‐ free conditions. Yield ranged from 1827 kg ha −1 for Era 1 cultivars to 2292 kg ha −1 for Era 3 cultivars under Striga infestation with average rate of increase in grain yield of 42 kg ha −1 yr −1 corresponding to 2.56% annual genetic gain. Under Striga ‐free conditions, yield ranged from 2939 kg ha −1 for Era 1 cultivars to 3549 kg ha −1 for Era 3 cultivars, but the average rate of increase in grain yield of 54 kg ha −1 yr −1 corresponding to 1.3% annual genetic gain was not significant. The increase in yield under Striga was associated with increased plant height. Although there was no significant gain in yield under Striga ‐free conditions, significant increase in plant height and decrease in root lodging were observed. Cultivars 53, 17, and 45 from Era 3 and 23, 21, 34, and 28 from Era 2 were the highest yielding and most stable under Striga infestation. Cultivars 53 and 55 from Era 3 were the most outstanding under Striga ‐free conditions. Considerable progress has been made in breeding for high yielding and Striga resistant or tolerant extra‐early maize cultivars during the last three decades.