PROBING BEHAVIOR OF DIURAPHIS-NOXIA ON 5 CEREAL SPECIES WITH DIFFERENT HYDROXAMIC ACID LEVELS

The feeding behaviour of Diuraphis noxia (Kurdjumov) (Homoptera: Aphid idae) was electronically monitored on five cereal species (Triticum ae stivum L., T. turgidum L., Secale cereale L. and x Triticosecale Wittm ack) containing different hydroxamic acids levels and on Hordeum vulga re L., lacking these compounds, by means of a DC-System. With increasi ng DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) levels D. nox ia showed less probing particularly before reaching the phloem phase a nd a lower percentage of aphids achieved sustained phloem ingestion. H owever, no significant correlation was found between DIMBOA levels and the total time of phloem feeding. These findings indicate that factor s from the mesophyll and vascular tissues appear to be involved in the effects of resistance. The underlying mechanism, however, remains unc lear. Thus, DIMBOA seems to be only part of the chemical defenses of t he cereal plants that might be implicated in D. noxia resistance.