Evaluation of resistance of selected cucumber lines to angular leaf spot (Pseudomonas syringae pv. lachrymans)

Abstract

Angular leaf spot caused by bacteria Pseudomonas syringae pv. lachrymans is a very common cucumber disease, which causes serious yield losses. The objective of this study was to examine the selected cucumber lines regarding their resistance to this pathogen. Twelve cucumber lines bred at the Research Institute of Horticulture were evaluated and compared with the resistant inbred line GY 14 and the susceptible cv. ‘Wisconsin SMR 18’. Plants were inoculated under controlled conditions at cotyledon stage (experiment I) and at leaves stage (experiment II) with the highly aggressive strain of P. s. pv. lachrymans BO 1537. Dis-ease severity was scored 8 days after inoculation using a nine-point rating scale (9 – no symptoms or a few pin-point lesions; 1 – damage up to 100% of leaves). Distribution of plants across severity classes and low variation coefficient indi-cate that all evaluated cucumber lines showed rather good uniformity in their re-spective degrees of resistance to this pathogen. All the materials tested presented lower disease severity in cotyledons stage than in leaves stage. It was also noted that greater differentiation among the lines in regard to their resistance to the bacteria was observed in the leaves stage. Two lines PW 2 and PW 7 exhibited the highest resistance against P. s. pv. lachrymans and can serve as a useful source of this trait in future breeding efforts