Relationship of Genetic Diversity of Inbred Lines with Different Reactions to Striga hermonthica (Del.) Benth and the Performance of Their Crosses

Abstract

Striga hermonthica causes significant yield loss in maize (Zea mays L.) and other cereals. Limited studies have been conducted to determine the relationship between marker‐based genetic distance among maize inbred lines expressing varying levels of field resistance to S. hermonthica and the reaction patterns of the resulting crosses to S. hermonthica. Forty‐five diallel crosses of 10 parental lines were evaluated with and without S. hermonthica infestation at two locations each in Benin Republic and Nigeria for 3 yr. Canonical discriminant analysis using nine traits separated the crosses into three distinct groups in each country depending on doses of resistance obtained from their parental lines. Hybrids formed from two resistant parents had the highest levels of resistance, while those formed from two susceptible parents exhibited the lowest levels of resistance to S. hermonthica Crosses that involved one resistant line as a parent showed intermediate levels of field resistance to S. hermonthica Assessment of genetic divergence among the 10 parental lines using 18 amplified fragment length polymorphism (AFLP) primer combinations generated a total of 1176 polymorphic AFLP fragments. The genetic distance (GD) estimates among all pairs of parental lines varied from 0.44 to 0.93, with an average of 0.63 ±0.023. The correlation between the AFLP‐based GD estimates of parental lines and the means observed in diallel crosses under S. hermonthica infestation were not significant for grain yield and other traits. Some hybrids formed from inbred lines with GD estimates both below and above 0.50 exhibited good performance under S. hermonthica infestation. The observed broad range of genetic divergence detected with AFLP markers indicates the presence of a significant reservoir of diversity among resistant lines that can be exploited in breeding.