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One hundred and twenty-two cultivar/lines of rapeseed ( Brassica rapa L. and B. napus L.), mustard [ B. juncea (L.) Czern. and Coss and Sinapis alba L.], and other brassicas [ B. nigra (L.) Koch., B. tournefortii Gouan., B. oleracea L. var. capitata, B. oleracea L. var. botrytis, Raphanus sativus L. and Camelina sativa L.] were evaluated in a growth chamber for resistance to pre-emergence damping-off and postemergence seedling root rot caused by an isolate of AG-2-1 of Rhizoctonia solani Kuhn. Twenty-six selected genotypes also were evaluated in artificially infested field plots. None of the cultivars/lines were immune, but significant differences in the susceptibility levels were observed among and within species. In growth chamber tests, when compared with the B. napus check cultivar (cv.) Westar, significantly ( p =0.05) higher percentage emergence was recorded for all lines of S. alba ; for cultivars Arlo, Span, and Torch of B. campestris ; for B. napus cvs and lines Golden, Midas, Nugget, Target, R-533, and DM56AH, as well as the B. juncea cvs and lines Commercial Brown, Cutlass, Domo, CJ86Z, and BJB-80-1543. Significant correlations were obtained between percentage pre-emergence damping-off and percentage disease ratings of 3-week-old ( r = 0.75) and 5-week-old ( r = 0.76) plants. The plants became less susceptible with age. Progenies from disease-free plants of B. napus cv. Midas showed a higher level of resistance than the original parental strains, indicating that resistance could be improved through selection. |
