Characterization of fall armyworm (Spodoptera frugiperda J. E. Smith) resistance in maize

Maize host resistance (HR) is critical to reduce fall armyworm (FAW, Spodoptera frugiperda J. E. Smith) damage threatening global food security. Fifteen hybrid maize (Zea mays L.) genotypes were field evaluated over in consecutive two years 2022 and 2023 to determine HR to natural FAW infestations. Cluster analysis classified genotypes into five resistance groups, with the most resistant and highest yielding group consisting of lines BHM-6, BHM-7, and BHM-9. Lines from this group are potential parents for breeding programs to improve FAW resistance. Principal component (PC) analysis determined PC1 accounted for 79.78% of the total variation among lines with positive loadings associated with FAW resistance traits, while yield/plant and ear number/plant contributed to positive loadings of PC2 explaining 9.49% of the total variation observed. Both ear length and 100 seed kernel weight declined by 0.05 cm and 0.14 g, respectively, per unit increase in area under the pest progress curve (AUPPC). When AUPPC reached a critical threshold >350, significant losses were observed in kernel weight and ear length impacting yields. Regression analysis determined there was a 0.007 MT grain yield reduction/ha per unit increase in AUPPC. Plants with heights ranging from 167-190 cm and ear lengths 16-20 cm yielded more than shorter plants (<158 cm) and ear lengths (<14 cm) under FAW pressure and are critical parameters to consider when breeding for resistance. Each unit increase in plant height (cm) and ear length (cm) increased yield/plant by 5.4 and 23.4 g, respectively, with 61% and 60% variability explained.