Impact of Glucosinolate Content in Broccoli (Brassica oleracea (Italica Group)) on Growth of Pseudomonas marginalis, a Causal Agent of Bacterial Soft Rot

Abstract

Glucosinolate degradation products are known to suppress microbes. Brassica species produce glucosinolates. Previous investigations determined that susceptibility to bacterial soft rot of broccoli (Brassica oleracea (Italica group)) varied significantly by cultivar. To evaluate the impact of glucosinolates on Pseudomonas marginalis, a causal agent of bacterial soft rot, glucosinolates were measured in lyophilized florets from broccoli ‘Arcadia’, ‘Emperor’, ‘Green Comet’, ‘Green Valiant’, ‘Marathon’, ‘Packman’, ‘Premium Crop’, and ‘Shogun’. Total glucosinolate content was highest in ‘Shogun’ (29.8 μmol/g) and lowest in ‘Emperor’ (0.5 μmol/g). In an in vitro assay, simple linear regression analysis showed that 48% of differences in suppression of P. marginalis growth could be explained by differences in total glucosinolate content (P ≤ 0.01). Plant breeding efforts should include glucosinolate levels as a factor in selecting for disease resistance.