Screening for Fall Armyworm ( Spodoptera frugiperda J. E. Smith) Resistance in Early‐Maturing Tropical Maize Adapted to Sub‐Saharan Africa

Fall armyworm (FAW) ( Spodoptera frugiperda J. E. Smith) has emerged as a serious pest since 2016 in Africa, affecting the food security and livelihoods of millions of smallholder farmers, especially those growing maize. Native genetic resistance to FAW is essential for reducing yield loss. The objectives of the study were to assess genetic variability, identify promising genotypes for FAW‐resistance, and propose a new easy‐to‐use multi‐traits selection index for ideotype selection under FAW infestation. Three hundred and ten genetic materials comprising inbred lines, hybrids, OPVs and landraces were evaluated under artificial fall armyworm infestation at Ile‐Ife, in 2021 and 2022. All the trials were laid out in alpha lattice design with two replications. Data were collected on FAW foliar and ear damage and grain yield estimated. The Lme4 R package was used to perform an analysis of variance (ANOVA) using a mixed linear model with environment and replicate as random effect while genotype was kept as fixed effect. Three multi‐traits selection strategies—desired index (DI), multiple traits selection index (MI) and multi‐traits‐genotype ideotype distance index (MGIDI) were used to identify FAW‐resistant genotypes. Significant ( p < 0.01) mean squares were detected among the genotypes (G), environments (E) and G × E interaction for grain yield and most measured traits. For each trial, FAW foliar damage scores at 6, 8 and 10 WAP varied. In the hybrid trial, the scores ranged from 3.8 to 6.6, 1.6 to 5.5 and 2.7 to 5.8, respectively. The score ranged from 4.2 to 7.2, 2.5 to 7.3 and 1.7 to 8.1, respectively among the inbred lines. In the landrace trial, the scores ranged from 3.5 to 6.5, 4.5 to 6.3 and 3.9 to 6.4, respectively. In the OPV trial, the scores at 6, 8 and 10 WAP were from 3.7 to 6.4, 2.4 to 5 and 3.8 to 5.5, respectively. At 15% selection intensity, the three selection indices identified 15, 14, 10 and 8 hybrids, inbreds, landraces and OPVs, respectively as ideotypes under FAW infestation. There was higher agreement and consistency between MGIDI and MI, often identifying more genotypes in common compared to DI. Significant negative correlations were detected between grain yield and FAW‐induced foliar damage scores at 6, 8 and 10 WAP, and ear damage. Substantial genetic variability existed in the germplasms panel for FAW resistance improvement. The ideotypes identified in the diverse genetic backgrounds could facilitate the development of productive hybrids and serve as source populations for improved tolerance/resistance to FAW.