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 lipi d ergosterol was used to assess the levels of infection in tissue cult ures of oilseed rape (Brassica napus ssp. oleifera) inoculated with Le ptosphaeria maculans. The growth of L. maculans in liquid culture thro ughout a 36-day period correlated well (r = 0.92) with the amount of e rgosterol extracted from the mycelium. There were significant differen ces (P < 0.05) in the amount of ergosterol extracted from infected thi n cell layer (TCL) explants and callus tissue of two resistant and thr ee susceptible cultivars of oilseed rape. Amounts of ergosterol extrac ted 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 var iable. This technique can be used in in vitro breeding programmes to a ccurately assess the resistance of tissue cultures of B. napus to L. m aculans and could also have value in conventional breeding programmes.