Multi environment Evaluation of Three-Way Cross Maize (Zea mays L.) Hybrids for Fall Armyworm (Spodoptera frugiperda) Resistance and Grain Yield- Performance and Stability

Maize ( Zea mays L.) is a vital staple food crop for millions of people in Sub-Saharan Africa, but its productivity is affected by fall armyworm ( Spodoptera frugiperda , FAW), a transboundary pest native to the Americas. This study aimed to (i) assess the severity of foliar and ear damage due to FAW under natural and artificial infestation (ii) evaluate the grain yield (GY) performance and stability of three-way cross maize hybrids and agronomic traits across maize growing locations in East Africa. A total of 84 hybrids were evaluated over two years across 15 locations under natural and/or artificial infestation of FAW. The phenotypic coefficient of variation was higher than genotypic coefficient of variation for all traits in artificial and natural infestation experiments. Experimental hybrids were tolerant to moderately susceptible under artificial infestation as well as under natural infestation. GY was positively correlated with ears per plant (EPP) ( r  = 0.37, p  ≤ 0.001) and grain moisture at harvest MOI ( r  = 0.27, p  ≤ 0.05) and negatively correlated with anthesis silking interval (ASI) ( r = -0.31, p  ≤ 0.01), ear Aspect (EA) ( r = -0.57, p ≤ 0.001) and foliar damage at 21 days after infestation (FD3) ( r = -0.27, p  ≤ 0.05) under artificial infestation. Under natural infestation GY was positively correlated with anthesis date (AD) ( r  = 0.33, p  ≤ 0.001), plant height (PH) ( r  = 0.43, p  ≤ 0.001), and MOI ( r  = 0.43, p  ≤ 0.001), while negative correlations were observed with (ASI) ( r = -0.42, p  ≤ 0.001), EA ( r = -0.58, p  ≤ 0.001), ear rot (ER) ( r = -0.25, p  ≤ 0.05), and gray leaf spot (GLS) ( r = -0.43, p  ≤ 0.001). Three experimental hybrids CKHFAW180299, CKHFAW190474 and CKHFAW190529 were among the highest yielding genotypes under both artificial and natural infestation while CKHFAW190386 and CKHFAW190477 exhibited the highest yield stability. These hybrids are promising candidates for national performance trials and future commercialization as FAW tolerant hybrids in East Africa.