SORGHUM RESISTANCE TO WHORL FEEDING BY LARVAE OF THE FALL ARMYWORM (LEPIDOPTERA, NOCTUIDAE)

Converted sorghum, Sorghum bicolor (L.) Moench, accessions were compared with the available resistant genotype CM1821 for whorl-stage resistance to feeding by larvae of the fall armyworm, Spodoptera frugiperda (J. E. Smith). When the sorghum lines were infested in the field 4 wk after planting and rated 7 d later, IS4023C and IS7399C were significantly less damaged (rating 3-4) than the resistant check CM1821 (rating 5). At 14 d after infestation, IS4023C, IS7399C, IS6962C, IS7724C, IS7695C, and IS1151C had significantly less leaf damage (rating < 5.5) than the resistant check CM1821 (rating 6.3). When infestations were made 5 wk after planting, IS1056C, IS1151C, IS2246C, IS2541C, IS3598C, IS4023C, IS6962C, IS6964C, IS7013C, IS7367C, IS7399C, IS7498C, IS7668C, I87695C, IS7724C, and IS12633C were more resistant (rating < 2.5) than the resistant CM1821 (rating 4) at 7 d after infestation. Except for IS1151C, IS4023C, and IS7399C all these lines plus IS12680C had significantly less damage (rating < 2.7) at 14 d after infestation compared with the resistant check (rating 3.7). Laboratory bioassays showed that IS1056C, IS2177C, IS2246C, IS4023C, IS7399C, and IS12680C had a significantly higher antibiotic resistance than CM1821. No significant relationship was established between resistance and acid detergent fiber, neutral detergent fiber, or tannin concentrations in the leaves. Resistance was, however, positively correlated with higher concentrations of total nitrogen in sorghum leaves.