Phytochemical Changes during Recurrent Selection for Resistance to the European Corn Borer

Abstract

Feeding performance of herbivorous insects is influenced by host plant nutritional quality which can be improved for insect resistance by artificial selection. This study was conducted to determine which biochemical constituents in maize (Zea mays L.) change during recurrent selection for resistance to first‐ and second‐generation European corn borer (ECB) [Ostrinia nubilalis (Hübner)]. Four cycles of selection (C0, C2, C4, and C5) from the BS9 population were field grown, artificially and naturally infested with ECB, and the following tissues sampled for biochemical analysis: immature and mature leaf blade, leaf sheath, rind, node, and pith. Tissue was analyzed for percent protein, DIMBOA [2,4‐dihydroxy‐7‐methoxy 2H‐l,4‐benzoxazin‐3 (4H)‐one], fiber, and cell wall‐bound phenolics, which included p‐coumaric acid (pCA), ferulic acid (FA), cyclobutane dimers (CBD), and diferulic acid (DFA). Leaf and stalk toughness were also determined and showed significant increases over cycles of selection. Protein content was lowest in stalk tissues with advanced cycles having lower levels, but leaf protein content did not differ significantly. DFA reached high levels in the rind (0.85 mg/g) and leaf sheath (1.35 mg/g) tissues, and increased significantly in immature leaf tissue (0.55–1.02 mg/g) over cycles of selection and may serve to fortify tender whorl tissue. Number of tunnels per stalk was negatively correlated with DFA content in the pith (r = − 77, P = 0.02). Microspectrophotometer determinations of epidermal cell wall absorbance for leaf blade and rind tissue showed increased absorbances (23 and 27%, respectively) in the spectral region characteristic of phenolic acids over cycles of selection. Phenolic acids, in particular DFA, have increased over cycles of selection to render maize tissue more resistant through fortification of cell walls, especially in leaf and rind epidermal tissue.

Formation of syringyl-rich lignins in maize as influenced by feruloylated xylans and p-coumaroylated monolignols

“…Xylans are cross-linked by peroxidase-mediated coupling of ferulate monomers into a complex array of dimers and trimers and by extensive copolymerization of ferulates into lignin (Grabber et al 2004). Ferulate and diferulate cross-links contribute to cell wall stiVening, anchoring of lignin in cell walls, cessation of plant growth, enhanced plant pest resistance, and reduced enzymatic hydrolysis of cell walls (Schopfer 1996;Bergvinson et al 1997;Grabber et al 1998;Casler and Jung 1999;MacAdam and Grabber 2002;Bily et al 2003). Ferulate and diferulates may also act as nucleation sites for lignin formation (Ralph et al 1995;Grabber et al 2002) and they play a role in the physical and antioxidant properties of foods Schooneveld-Bergmans et al 1999;Ferguson et al 2003).…”

Mechanisms and Sources of Resistance in Tropical Maize Inbred Lines to Chilo partellus Stem Borers

“…Leaf toughness was an important factor that influenced European corn borer feeding behavior (Malvar, Burtron, Ordas, & Santiago, 2008). In selecting for European corn borer resistance, investigations on morphological changes proved that leaf toughness increased over cycles of selection and the trait was highly and negatively correlated to leaf damage (Bergvinson, Arnason, & Hamilton, 1997). Stem penetrometer resistance is a type of physical resistance which results in reduced digestibility and/or increased hardness and abrasiveness of plant epidermal tissues (Arabjafari & Jalali, 2007).…”

Comparative transcription profiling analyses of maize reveals candidate defensive genes for seedling resistance against corn earworm

“…Some maize seeds can contain a lectin-like protein, cysteine protease inhibitor and a-amylase inhibitor (Blanco-Labra and Iturbe 1981; Abe and Whitaker 1988;Baker et al 2009) that may be present in the seedling also. Maize leaves and seeds can produce a number of phenolic compounds that impact insect performance, including ferulic acid, diferulic acid, and p-coumaric acid (Arnason et al 1994;Bergvinson et al 1997). Lipids present in maize leaves can also contribute to insect resistance (Yang et al 1991).…”