Field damage of sorghum ( Sorghum bicolor) with reduced lignin levels by naturally occurring insect pests and pathogens.

Sorghum ( Sorghum bicolor (L.) Moench) brown midrib ( bmr) mutant lines have reduced levels of lignin, which is a potentially useful trait for bioenergy production, but the effects of this trait on insect and plant pathogen interactions are unknown under field conditions. Field-grown bmr6, bmr12, and wild-type (WT) plants were examined for insect and disease damage. In most cases, observed frequency, population, or leaf area damage caused by insects or pathogens on bmr6 or bmr12 plants were not greater than those observed on WT plants in the field or laboratory assays. European corn borers [ Ostrinia nubilalis (Hübner)(Lepidoptera: Pyralidae)] often caused lower amounts of leaf damage to bmr6 leaves compared to bmr12 and sometimes WT leaves in the field study. Leaf damage by corn earworms [ Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae)] and fall armyworms [ Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)] in laboratory assays was often lower for bmr versus WT leaves. Incidence of disease lesions was significantly higher on bmr6 compared to WT plants for one of three samplings in 2011, but the opposite trend was observed overall in 2012 and no significant differences were noted in 2013. When corn earworms and fall armyworms were fed the excised pith, bmr6 and/or bmr12 pith caused significant morality to one or both insect species in all 3 years. Damage variability between the 3 years may have been due to hotter and drier than normal conditions in 2012. Thus, bmr lines of sorghum suitable for bioenergy production have potential for sustainable production in the field. [ABSTRACT FROM AUTHOR]