Glucosinolates in Clubroot-resistant and -susceptible Selections of Broccoli

Abstract

Broccoli (Brassica oleracea Italica Group) plants resistant or susceptible to clubroot (Plasmodiophora brassicae Wor. races 2 and 6) produced from 10 segregating breeding lines were analyzed for their composition of glucosinolates as determined in terms of their hydrolytic breakdown products: goitrin, volatile isothiocyanates, and thiocyanate ion. Unlike goitrin and volatile isothiocyanates, the average content of thiocyanate ion was significantly lower (548 μg·g-1 dry weight) in resistant plants than in susceptible ones (712 μg·g-1). Of 15 resistant plants derived from 10 breeding lines containing zero goitrin and/or relatively low concentrations of one or more glucosinolate products, 10 plants were free of goitrin, three were low in volatile isothiocyanates (≤100 μg·g-1), two were low in thiocyanate ion (≤200 μg·g-1), and two were low in total glucosinolates (≤600 μg·g-1).