Assessing Broccoli Cultivar Susceptibility to Alternaria brassicicola in Georgia

Abstract

Alternaria leaf blight and head rot (causal agent: Alternaria brassicicola and other Alternaria species) in broccoli (Brassica oleracea L. var. italica) can lead to decreased yields, reduced head quality, and postharvest losses. While cultural practices and fungicides can decrease disease severity, further work is needed to determine resistance or susceptibility in commercial cultivars. This study evaluated susceptibility of 26 cultivars against A. brassicicola in Fall 2021 and 2022 at two locations in Georgia (Tifton and Watkinsville). Commonly used cultivars in the Eastern U.S. were selected and grown in a randomized complete block design. Approximately 20 days after transplant, plants were inoculated with a conidial suspension of A. brassicicola and monitored for disease development. Foliar disease severity, foliar area under disease progression curve (AUDPC), head disease severity, and yield were determined for each cultivar at each location. Significant differences existed among cultivars (year × location) for foliar AUPDC and head disease severity. Foliar AUPDC ranged from 299 to 1818 for both years and locations and head disease severity ranged from 1 to 81% across both years and locations. In this study, cultivars, ‘Eastern Crown’, ‘Emerald Jewel’, ‘Lieutenant’ and ‘Abrams’, had greater foliar and head disease severity and low marketable yields in both locations and years. The cultivars ‘Vallejo’, ‘Emerald Pride, ‘Burney’, ‘Belstar’ ‘Iron Man’, and ‘Marathon’ exhibited low disease severity across both locations and years and maintained greater marketable yields. Proper selection of commercially-available cultivars could help growers maintain yields in areas with high A. brassicicola pressure.