K. Murugan

Evaluation of Bryophyte Protein-Based Defense Against Selected Phytophagous Insects

Insect-resistant proteins have been one of the major successes of applying plant genetic engineering technology to agriculture. Relatively little is known about insect defense mechanisms in the lower plants. The current paradigm is that secondary metabolites and physical barriers are most important in conferring insect resistance in plants. We investigated whether protein-based resistance exists in representatives of bryophytes. We screened a total of 20 bryophytes such as Porella acutifolia, Fissidens asperifolius, Fissidens crispulus, Hypopterygium tamarisci, Brachymenium nepalense, Brachythecium buchananii, Campylopus pilifer, Marchantia linearis, Leucobryum bowringii, Plagiochila beddomei, Isopterygium albescens, Taxiphyllum taxirameum, Octoblepharum albidum, Bryum argenteum, Riccia frostii, Philonotis fontana, Racopilum cuspidigerum, Funaria hygrometrica, Pallavicinia lyellii, and Polytrichum commune for protein-based insecticidal activity against the two common lepidopteran pests: corn earworm (Helicoverpa zea) and armyworm (Spodoptera litura). Protein extracts from bryophyte species were compared with those from a lepidopteran-susceptible Glycine max cultivar (Cobb) in bioassays for insect resistance. The Octoblepharum albidum, Fissidens asperifolius, Bryum argenteum, and Marchantia linearis protein extracts caused the greatest decrease in damage in leaf-disk assays and insect larval growth. The results from dietary utilization experiments showed a reduction in efficiency of conversion of ingested food and digested food and an increase in approximate digestibility and metabolic cost. The in vivo effects of proteins of bryophytes showed varied response toward the parameters such as larval weight, growth rate, and proportion of survivors. These bryophyte species are potential candidates for further evaluation.