Evaluation of diets from various maize hybrids reveals potential tolerance traits against <i>Spodoptera littoralis</i> (Boisd) as measured by developmental and digestive performance

<i>Spodoptera littoralis</i> (Boisd) (Lepidoptera: Noctuidae) is a highly polyphagous insect that significantly reduces agricultural production of several food staples. We evaluated performance of <i>S. littoralis</i> on several meridic diets based on various maize hybrids, including Oteel, Simon, Valbum, SC703, and SC704. Growth, feeding behaviours, and activity of digestive enzymes of <i>S. littoralis</i> were examined under laboratory conditions. In addition, selected biochemical characteristics of maize hybrid seeds were evaluated, including starch, protein, anthocyanin, as well as phenolic and flavonoid contents, to examine relationships between plant properties and digestive performance of <i>S. littoralis</i>. Performance of <i>S. littoralis</i> on maize hybrids, as measured by nutritional indices, was related to both proteolytic and amylolytic activities quantified using gut extracts. Larval <i>S. littoralis</i> reared on SC703 exhibited the highest efficiency of conversion of digested food, while the lowest was recorded in those fed on the Oteel hybrid. <i>S. littoralis</i> reared on SC703 and Oteel also exhibited the highest and lowest relative growth rates, respectively. The highest levels of proteolytic activity in <i>S. littoralis</i> were measured from larvae reared on the SC703 hybrid, while the lowest levels occurred on the Oteel and Valbum hybrids. Amylolytic activity was lowest in larvae reared on SC703 and Valbum hybrids and highest in larvae reared on the Oteel hybrid. Our results suggest that the SC703 hybrid was the most suitable host for <i>S. littoralis</i>, while the Oteel hybrid demonstrated the greatest level of tolerance against <i>S. littoralis</i> of those evaluated. We discuss the potential utility of maize hybrids exhibiting tolerance traits against this cosmopolitan pest with reference to cultivation of tolerant varieties and identification of specific tolerance traits.