Haploid plantlet screening in the development of blackleg resistant DH lines of Brassica napus

This study was conducted to expedite disease‐resistance breeding in canola by screening haploid plants against blackleg disease. Microspore‐derived haploid plantlets from 14 unrelated crosses were inoculated with Leptosphaeria maculans pycnidiospores and were rated as resistant, intermediate or susceptible. Blackleg‐inoculated and control haploid plants were then colchicine‐treated to produce doubled haploid (DH) lines. The DH lines thus produced were again screened against blackleg using the cotyledon bioassay. In general, the proportion of the resistant DH lines derived from selected resistant haploid plants was much higher than the proportion of resistant DH lines from control haploid populations. There was no detrimental effect on the survival of haploid plants after the combined treatment of blackleg inoculation and colchicine. The importance of the micro‐environment on the final outcome of plant‐pathogen interaction in case of non‐obligate pathogens is also discussed.