Isolation of Colour and Resistant Mutants in Alternaria alternata

Abstract

A total of ( 31) white (W) and/or resistant to potassium chlorate (Chl) or sodium selenate (Sel) mutants were isolated from strain AA1; a black wild type strain of the plant pathogenic fungus Alternaria alternata. Exposing conidia of this stain to 20 min UV at a 20 cm – distance was found to kill more than 90% of the conidia and these conditions were adopted to isolate various mutants.Three white mutants; SW1, SW2 and SW3 were isolated as white sectors after two days of irradiating two-day old colonies of AA1. Concentrations of 100, 60, 100 and 80mM potassium chlorate or concentrations of 200, 280, 280 and 200mM sodium selenate completely inhibited the growth of strains AA1, SW1, SW2 and SW3 respectively and these concentrations were used to isolate the various resistant mutants. Twenty spontaneous chlorate- resistant mutants were isolated from strain AA1(Chl5-Chl9) and strain SW3(Chl13-Chl27). Five Sel mutants (Sel1-Sel5) and one chlorate resistant (Chl10) mutants were isolated from irradiating conidia of SW2 and AA1respectively. The double mutants SW4, white conidia and chlorate resistant, was isolated by irradiating conidia of Chl10. This collection of mutants should allow starting the genetic analysis of this important fungus.