Increase of peroxidase activity in tropical maize after recurrent selection to storage pest resistance

Farmers worldwide experience substantial postharvest grain losses of maize (Zea mays L.) caused by the maize weevil, Sitophilus zeamais. Resistance to this pest has recently been demonstrated in Population 84 (P84) maize kernels. This resistance has been correlated with the presence of cell-wall bound phenolic compounds and endosperm peroxidase (POD) activity. However, the specific role of peroxidases in insect resistance remains unknown. The aim of this study was to expand the knowledge of this role by evaluating the association between POD activity and resistance to S. zeamais during four cycles of recurrent selection of P84. This evaluation involved the use of kernel insect interaction assays combined with proteomic, biochemical and histological methods. Histological staining confirmed POD activity in the germ, pedicle and aleurone layer. Endosperm POD activity was increased over three cycles of recurrent selection, mainly in advanced red kernels, but this increased activity was not associated with the thickness or number of aleurone layers in the endosperm. A significant negative correlation (P < 0.05) was found between endosperm POD activity and grain weight loss (GWL) in whole kernels and kernels without pericarp, adult progeny (AP) in kernels without pericarp, and number of damaged kernels (DK) in single endosperms, produced by S. zeamais infestation. Our findings provide strong evidence of a specific relationship of peroxidases in the biophysical and biochemical resistance mechanism against S. zeamais, supporting the possible application of peroxidases as a breeding trait for the development of maize varieties resistant to storage pests. (C) 2017 Elsevier Ltd. All rights reserved.