Examination of Different Tobacco (Nicotiana spp.) Types Under- and Overproducing Tobacco Anionic Peroxidase for Their Leaf Resistance to Helicoverpa zea
First-instar larvae of the false tobacco budworm (corn earworm, Helicoverpa zea) that fed on either intact plants, leaf disks from undamaged plants, or leaf disks from insect-damaged plants of Nicotiana sylvestris and N. tabacum Coker plants overproducing a tobacco anionic peroxidase generally caused significantly less damage than those caged with corresponding material from wild-type plants. In some cases mortality was significantly higher and weights significantly less for caterpillars feeding on leaf material from overproducing vs. wild-type plants. First-instar H. zea fed on the same type of leaf material from N. tabacum Xanthi underproducing tobacco anionic peroxidase generally caused significantly more damage than those fed leaf material from wild-type plants. However, first-instar H. zea fed on underexpressing leaf material from N. sylvestris did not cause significantly greater damage compared to wild-type material. In cases where peroxidase enzyme activity was determined, significantly higher mean peroxidase activity was seen in leaves of plant types that also had significantly less mean feeding ratings. This information suggests that peroxidase activity can contribute to leaf resistance to chewing insects. However, the context of the peroxidase (cooccurring substrates, additional inducible factors) can mediate the degree of influence seen by changes in individual peroxidase isozyme levels.
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