HAPLOID PLANTLET SCREENING IN THE DEVELOPMENT OF BLACKLEG RESISTANT DH LINES OF BRASSICA-NAPUS

This study was conducted to expedite disease-resistance breeding in ca nola by screening haploid plants against blackleg disease. Microspore- derived haploid plantlets from 14 unrelated crosses were inoculated wi th Leptosphaeria maculans pycnidiospores and were rated as resistant, intermediate or susceptible. Blackleg-inoculated and control haploid p lants were then colchicine-treated to produce doubled haploid (DH) lin es. The DH lines thus produced were again screened against blackleg us ing the cotyledon bioassay. In general, the proportion of the resistan t DH lines derived from selected resistant haploid plants was much hig her than the proportion of resistant DH lines from control haploid pop ulations. There was no detrimental effect on the survival of haploid p lants after the combined treatment of blackleg inoculation and colchic ine. The importance of the micro-environment on the final outcome of p lant-pathogen interaction in case of non-obligate pathogens is also di scussed.