WOUND-INDUCED MOLECULAR ALTERATIONS AND ITS RELATIONSHIP TO PEROXIDASE ISOZYMES OF FUNGAL-INFECTED MELON GENERATIONS

Guirgis,, A. A.; Abd El-Raheem, A. A.; El-Shimi, I. Z. A.

doi:10.21608/jpp.2000.258784

WOUND-INDUCED MOLECULAR ALTERATIONS AND ITS RELATIONSHIP TO PEROXIDASE ISOZYMES OF FUNGAL-INFECTED MELON GENERATIONS

Document Type : Original Article

Authors

¹ Genetic Engineering and Biotechnology Research Institute, Menoufiya University

² Agricultural Botany Department, Faculty of Agriculture, Suez Canal University

³ Horticultural Crops Research Institute, Agriculture Research Centre, Cairo, Egypt

10.21608/jpp.2000.258784

Abstract

A transitory inhibition of either Prx₁ locus or its functional protein was observed in parental, F₁ and F₂ melon generations as a result to fungal infection with Pseudoperonospora cubensis. This locus was found to be activated again in leaf tissues of all generations either 48 hours after fungal elicitation or transcriptionally stimulated by unknown elicitors induced through 2 hours of wound treatment.
Rapid increase in peroxidase isozymes intensity after 24 hour of fungal inoculation was observed for resistant melon genotypes especially, P₁; PI 140471, F₁; P₁ x P₅ and P₂; PI 124111. Similar increments in isoperoxidase activity in resistant genotypes after 2 hours of wounding suggesting stimulation of the transcription level of all leaf isoperoxidases specially the four-banded Prx₂ locus. Meanwhile the susceptible genotypes; P₃; Honey dew and P₅; Ismaillawi did not show rapid changes in peroxidase isozymes.
Positive Spearman rank correlation coefficients were observed between downey mildew resistance and the highest isoperoxidase activity scores over all melon generations; 0.73 and 0.55, at 72 and 24 hours after fungal infection, respectively. The time course of wound induction of peroxidase activity suggests the inducibility of fungal resistance in leaf tissues by wound treatment. The results also suggest an indirect role for Prx₁ locus in inducing not only intermediate compounds, but also in stimulating transcription of genes involved in the plant defence system.

Keywords