Researchers at Ladoke Akintola University of Technology in Ogbomoso evaluated 32 maize hybrids, including 26 experimental top-cross hybrids developed by the Maize Improvement Programme of the International Institute of Tropical Agriculture and six commercial checks, across two planting dates in the 2024 season. The trials were deliberately left exposed to natural fall armyworm infestation, and the plants received no insecticide against the pest. The team scored foliar damage at four, eight, and twelve weeks after sowing using a modified Davis rating scale, alongside a full suite of agronomic measurements from flowering time to husk cover, plant height, and grain yield adjusted to standard moisture.

The standout performer was hybrid G1, bred from the cross FAWSYN-1/(TZLComp. 1 C6-W-39-1-1)-B-B, which produced 5,223.3 kilograms of grain per hectare across environments, a 26.8 percent yield advantage over the best commercial check, Oba Super 9. Roughly 30.7 percent of the tested hybrids outyielded that top check, and eight of the 26 experimental hybrids beat all six commercial controls. The new hybrids also showed improvements of 9 to 13 percent in husk cover, plant aspect, and ear aspect ratings, 5 to 12 percent better tolerance of southern corn leaf blight and ear rot, and 12 to 35 percent improved tolerance of foliar fall armyworm damage across the scoring intervals.

The statistical architecture of the trial revealed as much about the environment as about the genetics. Analysis of variance showed highly significant differences among hybrids, environments, and their interactions for grain yield and most agronomic traits. When the total variation in grain yield was partitioned, the environment accounted for 54 percent, hybrids for 21 percent, and the hybrid-by-environment interaction for 11 percent. In other words, where and when the maize grew mattered more than which hybrid was in the ground, a sobering reminder of how strongly rain-fed African farming systems are governed by weather. The two planting dates produced dramatically different outcomes: grain yield ranged from 715.4 to 3,241.2 kilograms per hectare in the early planting, but from 901.8 to 7,205.3 kilograms per hectare in the later sowing, a gap of more than 2,300 kilograms per hectare between environment means.

The reason for that gap lay in the rainfall record. A prolonged drought between July and August struck the later-planted crop during the critical periods before anthesis and after silking, stretching the anthesis-silking interval from one or two days in the first environment to three to seven days in the second. Maize is notoriously sensitive to moisture stress during flowering and grain filling, and the combined burden of drought and heavy fall armyworm pressure drove yields down in the first planting. The authors note that erratic rainfall, including a cessation of rain after planting that stressed seedlings and excessive rain near maturity that caused lodging, complicated the evaluation, yet the pest pressure remained sufficient to differentiate the hybrids consistently.

Correlation and regression analyses pinpointed which traits actually mattered for yield under pest attack. Grain yield correlated significantly and negatively with foliar fall armyworm damage, plant aspect, and husk cover ratings, meaning that hybrids with cleaner leaves, more compact and appealing plant architecture, and tighter husk coverage yielded more. Plant aspect showed the strongest individual association with yield, explaining 42 percent of its variability in regression analysis, with each unit worsening in the score costing roughly 1,402 kilograms per hectare. Foliar armyworm damage itself explained 13 percent of yield variation, and every unit increase in the damage score reduced grain yield by about 864 kilograms per hectare. Plant height and ear height, by contrast, correlated positively with yield, reflecting the larger leaf area and photosynthetic capacity of taller plants.

The genetic analysis added an important caveat. Broad-sense heritability was moderate for flowering traits and foliar diseases, ranging from 42 to 55 percent, but low, between 3 and 13 percent, for grain yield and fall armyworm damage scores. Environmental variance exceeded genetic variance for every trait measured, and genotypic coefficients of variation were consistently lower than phenotypic ones. This means that much of what breeders observe in any single season reflects the environment rather than stable genetic differences, and the authors caution that these estimates are population- and environment-specific, requiring validation across additional locations and years before broader breeding inferences can be drawn.

To cut through the complexity of selecting for many traits at once, the team applied the genotype by yield times trait biplot, a multivariate technique that ranks hybrids by how well they combine grain yield with each desirable characteristic. The first two principal components captured about 82 percent of the variation, and the analysis identified five hybrids, G1, G9, G21, G18, and G3, as superior combinations of high yield and moderate fall armyworm tolerance. Hybrid G1 and its close relative G9 excelled at pairing yield with low ear rot and Curvularia leaf spot scores, while G21 and G18 combined yield with strong rust tolerance and favorable plant and ear aspects. The same analysis flagged the weakest performers, including the commercial hybrid Oba Super 2, which yielded only 1,502.7 kilograms per hectare.

Notably, the commercial checks revealed how far standard market varieties still lag. Most checks showed consistent baseline susceptibility to fall armyworm, with several leaves bearing holes and lesions across the scoring weeks, while two experimental hybrids, G7 and G19, maintained low, stable damage ratings throughout the season. Among the commercial options, only SAMMAZ 51 stood out as an outlier with meaningful tolerance. The mean damage ratings of all top-cross hybrids stayed below 6 on the nine-point scale, and scores generally declined as plants matured, consistent with earlier reports that infestation pressure eases with crop age.

The study, published in Discover Plants, stops short of recommending the hybrids to farmers just yet. The authors emphasize that the five promising candidates must now advance to multi-location, multi-year uniform yield trials to confirm their adaptation and stability across the derived savanna agroecology and beyond. Still, the findings carry weight for a region where Nigerian farmers harvest an average of just 2.2 tonnes of maize per hectare against a global average of 4.5 tonnes. Host plant resistance, which works through antixenosis, antibiosis, and tolerance, imposes minimal selection pressure on pest populations and, integrated with biological and cultural controls, offers a durable, environmentally safe, and affordable line of defense. In a warming, pest-threatened world, breeding resilience directly into the seed may prove one of the most powerful tools African agriculture has.

Subject of Research: Phenotypic evaluation of fall armyworm-resistant top-cross maize hybrids under rain-fed conditions in a derived savanna agroecology

Article Title: Variation in the phenotypic performance of top-cross fall armyworm resistant maize hybrids under rain-fed growing conditions in a derived savanna agroecology

Article References: Olayinka, A. O., Odewole, A. F., Akande, O. S., Adebayo, P. A., & Ujah, G. O. (2026). Variation in the phenotypic performance of top-cross fall armyworm resistant maize hybrids under rain-fed growing conditions in a derived savanna agroecology. Discover Plants, 3(1), Article 424. https://doi.org/10.1007/s44372-026-00896-3

Image Credits: AI Generated

DOI: 10.1007/s44372-026-00896-3

Keywords: fall armyworm, maize hybrids, host plant resistance, grain yield, derived savanna, Nigeria, plant breeding, GYT biplot, heritability, genotype by environment interaction, Spodoptera frugiperda, food security