Abstract

Isothiocyanates (ITCs) is a group of defense related compounds synthesized byBrassicas that have positive effects on human health which suggest that they are environmentally friendly compounds to control fungi infections. However, the development of ITC-resistant strains of fungi is a matter of concern.  The objective of the present work was to study the response of  Alternaria  alternata to allyl-isothiocyanate (AITC) and benzyl isothiocyanate (BITC) chronic exposure and the effect of the treatment on some of the inter simple sequence repeats (ISSR) regions. Five strains of A. alternata isolated from tomato and five isolated from cabbage were independently exposed in vitro to AITC and BITC. Concentrations were increased until it reached 0.08 and 0.6 mg/mL of AITC and BITC, respectively. Genomic DNA from both wild type and isogenic adapted strains to ITCs was isolated and five primers were used for ISSR amplification:  (GACA)₄: 5´-GACAGACAGACAGACA-3´; M13:5´-GAGGGTGGCGGCGGTTCT-3´;(AAG)₈:5´-AAGAAGAAGAAGAAGAAGAAGAAG-3´; (ACA)₅: 5´-ACAACAACAACAACA-3´ and T3B: 5´-AGGTCGCGGGTTCGAATCC-3´. A lower degree of polymorphism was found to be induced by the treatment in the wild-type strains isolated from cabbage as compared with the wild-type strains isolated from tomato.  It can be concluded that ITCs exposure induced random mutations in different ISSR regions of the A. alternata genome which does not lead to the development of strains with a hereditable resistant phenotype.

Key words: Alternaria alternata, fungicide, allyl-isothiocyanate, benzyl-isothiocyanate, inter-simple sequence repeat