F2 segregation analyses of DNA restriction fragment length polymorphisms (RFLPs) detected between a cabbage line (No. 86-16-5) resistant to race 2 of Plasmodiophora brassicae (Woronin), the fungus responsible for clubroot disease, and a rapid cycling line (CrGC No. 85) was used to construct a detailed genetic map of Brassica oleracea. RFLP markers were random and seedling-specific cDNA clones. The 201 loci so far mapped in B. oleracea covered 1112 cM. They are assembled into nine major linkage groups and four small linkage groups. Twelve loci were found unlinked to any other markers. Twenty-one loci were detected with the 18 seedling-specific cDNAs. Two dominant QTLs for resistance to race 2 of the clubroot disease causal agent were also identified. Leaf morphology and biennial flowering appeared to segregate as single Mendelian traits, but only leaf morphology could be linked to other markers. This RFLP study in B. oleracea is providing additional information on genome organization and complements current RFLP mapping effort in B. napus.Key words: genetic mapping, Brassica oleracea, Plasmodiophora brassicae, breeding, clubroot resistance, DNA markers, RFLP.

T w o clubroot-susceptible cabbage cultivars, Red Acre and Golden Acre, were crossed with the resistant line, 8-41. I;, data showed that susceptibility was dominant over resistance and data from I;? and backcross progenies supported a duplicate gene I~ypothcsis. Genes Pb, and Pb, were proposed t o designate susceptible loci. All genotypes of these n v o genes were susceptible cxccpt the homozygous recessive pb,, pb,, pb,, ph, which was resistant.

No abstract

Abstract. A method is described for measuring the force and the rate at which it is applied to fruits and vegetables by the consumer's hands in judging firmness. Halves of the product were mounted on a force transducer, squeezed and the forces recorded. Preliminary results from an untrained panel indicated that the rates and maximum forces used by males and females are different and depend on the firmness of the product. The data also suggest that the rate of force application in sensory testing is significantly greater than that customarily used in instrumental tests. Limitations of the technique and its potential usefulness in establishing more rational conditions for objective firmness tests are discussed.

Ministdre de l'Agriculture du Canada, Saint-J ean et L' Assont ption, Qudbec-lRegu pour publication Ie 23 janvier, 19631 RESUME Contre Ia herrie, Plds-modiophora brassicae'Wor., des crucifdres le bichlorure de mercure fut Ie seul foneicide i permettre i la fois une auementation de rendement et une r6duction-de l'infection des racines du choul aussi bien en un sol min6ral qu'en un sol organique. Le Terraclor a 6t6 plus effcace en un sol min6ral ilors qu'en un-sol oreanique. ii fur inf6rieui au t6rnoin.Le Mylone a 6t6 l6gdremint plus efficaci en-un sol min6ral. L'Emmi et Ie Chemagro B-18,i3 ont I'un et I'autre diminu6 Ia r6colte en un sol min6ral, mais.l'infec.tion y fyr mieu.x r6primie qu'en un sol .organique. Ces deu-x rongrcldes lurent t_res pnytotoxrqucs, suftout en un sol mtneraL.