DIMBOA levels in hexaploid Brazilian wheat are not associated with antibiosis against the cereal aphids Rhopalosiphum padi and Sitobion avenae

The objective of this study was to evaluate the natural levels of the plant defence compound DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) in young leaves of eight hexaploid Brazilian wheat genotypes and the impact of the genotypes upon development of cereal aphids, Rhopalosiphum padi and Sitobion avenae . HPLC analysis revealed that the DIMBOA levels varied from 5.376 (in BRS Guabiju) to 30.651 mmol kg FW −1 (in BRS Timbaúva) with two genotypes outperforming Solstice, a UK variety used as reference. Bioassays were conducted to evaluate the development and fecundity of both aphids when grown on the wheat genotypes. Although BRS Guabiju and BRS Timbaúva were among the genotypes showing the highest susceptibility and resistance, respectively, against both aphid species, no correlation could be found between DIMBOA levels and antibiosis effects. The cultivar BRS 327 was among the genotypes showing lower intrinsic rate of population increase for the two aphid species. Elucidating the role of secondary metabolites in plant resistance to aphids and the characterization of the genotypes that allowed reduced development of R. padi and S. avenae are important steps to achieve a better natural resistance in hexaploid Brazilian wheat.