THE USE OF ERGOSTEROL AS A QUANTITATIVE MEASURE OF THE RESISTANCE OF CULTURED-TISSUES OF BRASSICA-NAPUS SSP OLEIFERA TO LEPTOSPHAERIA-MACULANS

A simplified method for the quantitative assessment of the fungal lipid ergosterol was used to assess the levels of infection in tissue cultures of oilseed rape (Brassica napus ssp. oleifera) inoculated with Leptosphaeria maculans. The growth of L. maculans in liquid culture throughout a 36-day period correlated well (r = 0.92) with the amount of ergosterol extracted from the mycelium. There were significant differences (P < 0.05) in the amount of ergosterol extracted from infected thin cell layer (TCL) explants and callus tissue of two resistant and three susceptible cultivars of oilseed rape. Amounts of ergosterol extracted from resistant cultivars were < 100 mug and from susceptible > 100 mug. The mean amounts of ergosterol extracted from shoot cultures of two resistant and four susceptible cultivars were similar to those for TCL explants and callus tissue, although the values obtained were variable. This technique can be used in in vitro breeding programmes to accurately assess the resistance of tissue cultures of B. napus to L. maculans and could also have value in conventional breeding programmes.