Bogumil LESZCZYNSKI, Tomasz BAKOWSKI
Department of Biochemistry, Agricultural & Pedagogic University, ul.B.Prusa 12,
PL-08110 Siedlce, Poland
An integrated crop production require ecologically friendly methods of plant protection against pests and pathogens. One of them is natural plant resistance used in an integrated pest management (IPM), together with biological methods. Within the resistance mechanisms (antixenosis, antibiosis and tolerance) at least antixenosis and antibiosis are conditioned by cereal allelochemicals eg. phenolics, hydroxamic acids and indole alkaloids. Hitherto studies showed that there are clear relations between quantity of the xenobiotics in winter wheat cultivar and the grain aphid infestation. The present paper deals with quantitative and qualitative changes of the phenolic compounds in the resistant and susceptible wheats under the grain aphid, Sitobion avenae (Fabr.) infestation.
Four varieties of winter wheat, two moderately resistant - Grana and Saga and two susceptible - Emika and Liwilla were used in the study (Leszczynski 1987). Analysis of the phenolic compounds was performed on control (without aphids) and infested flag leaves of the studied wheats. Ethanolic extracts were partitioned three times with ethyl acetate, and evaporated finder vacuum to dryness. The phenolics were silylated with BSTFA and the mixture was separated using GLC method according to (Vande Casteele et al. 1976). Identification and quantification of the cereal phenolics was done on the base of the HP G1030A MS ChemStation and comparison with retention times of the phenolic standards.
GLC-MS analysis showed presence of seventeen phenolic compounds in the resistant and susceptible wheats: 1) phenolic acids: benzoic, m-hydroxybenzoic, gallic, syringic and vanillic; 2) phenolpropenoids: trans-cinnamic, o-coumaric, m-coumaric, caffeic, ferulic and chlorogenic acids; 3) coumarins: coumarin and umbelliferone, 4) flavonoids: flavone, (+)catechin and quercetin. Flag leaves of the control plants (without aphids) of the resistant varieties were generally richer in the phenolics than susceptible ones. There were considerable higher amounts of m-hydroxybenzoic and ferulic acids and (+)catechin in the flag leaves of the moderately resistant wheats. After the grain aphid infestation, slight changes in the quantity of the identified phenolics were observed. Some of the studied wheats showed increase instead other decrease in content of the phenolics. However there was no clear difference in reaction of tile resistant and susceptible varieties to the grain aphid infestation.
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