Panicle-Stage Resistance to Spodoptera frugiperda (Lepidoptera: Noctuidae) in Converted Sorghum Accessions

Abstract

Differential developmental responses of fall armyworm, Spodoptera frugiperda (] . E. Smith), were compared after larvae were fed milk stage spikelets (complete florets) of field-grown converted sorghum ( Sorghum bleolor (L.) Moench) accessions incorporated into a meridic diet. Larvae fed diet supplemented with spikelets of ‘International Sorghum (IS) 12592 Converted (C)’ were significantly smaller compared with those fed diet supplemented with spikelets of the released resistant hybrid ‘Northrup King Savanna 5’. Feeding on diet containing the genotypes‘ISI34OC’,‘IS2246C’,‘IS2569C’,‘IS7498C’,‘IS12617C’, or ‘IS12683C’ resulted in a significantly longer duration of the larval stage of fall armyworm than feeding on diet containing the resistant check NK Savanna 5. Pupal weights of fall armyworm that were fed diet supplemented with ‘IS2403C’, ‘IS2569C’, ‘IS7498C’, ‘IS12617C’, or ‘IS12657C’ were significantly less compared with those of fall armyworm fed the resistant check. Weights of fall armyworm larvae were positively correlated with higher concentrations of crude protein (total nitrogen) in sorghum spikelets. The concentrations of lignin were inversely correlated with the duration of the larval development. When resistant and susceptible sorghum genotypes were considered separately, the concentration of tannin and the ratio of lignin/neutral detergent fiber were negatively correlated with the duration of the larval development in the resistant genotypes but positively correlated in the susceptible genotypes.