Evaluation of cucumber (Cucumis sativus) cultivars grown in Eastern Europe and progress in breeding for resistance to angular leaf spot (Pseudomonas syringae pv. lachrymans)

Abstract

Increased occurrence of cucumber angular leaf spot, Pseudomonas syringae pv. lachrymans, has caused significant losses in cucumber, Cucumis sativus, yield in Poland in recent years. These losses necessitated evaluation of the level of resistance in cucumber cultivars of mainly Polish breeding, cultivated in Eastern Europe, and initiation of a breeding programme for resistance to this disease. Screening for resistance was performed on 84 cucumber accessions under growth chamber conditions using a highly aggressive strain of P. syringae pv. lachrymans. Most of the screened accessions were either susceptible or displayed intermediate resistance. The screening resulted in the identification of five F 1 hybrid cultivars moderately resistant to angular leaf spot. The identified F 1 hybrids were self-pollinated up to the F 4 generation. Individuals resistant to angular leaf spot were identified. These individuals can be used as a source of resistance to angular leaf spot in future breeding efforts.

Automated image analysis for quantification of histochemical detection of reactive oxygen species and necrotic infection symptoms in plant leaves

“…P. syringae pv. lachrymans, causing the angular leaf spot disease and the powdery mildew pathogen E. cichoracearum are important pathogens of Cucurbitaceae crops causing significant losses in cucurbits yield (Olczak-Woltman et al 2008;Cook & Braun 2009). We used the pumpkin/E.…”

Genome analysis of Pseudomonas syringae pv. lachrymans strain 814/98 indicates diversity within the pathovar

“…The symptoms caused by strain 814/98 on cucumber leaves never failed to develop in every single test over the course of many years of testing. This strain did not produce fluorescent pigment on King's medium B but displayed the typical phenotypic and biochemical characteristics of P. syringae in LOPAT tests (Olczak-Woltman et al 2007;Olczak-Woltman et al 2008;Słomnicka et al 2015).…”

“…Novel haplotypes of P. syringae were observed to be common on multiple cucurbit hosts, thus illustrating this species' large ecological diversity (Newberry et al 2016). Moreover, pathovar lachrymans is particularly detrimental because it can facilitate infection by Pseudoperonospora cubensis, which is the most destructive cucumber pathogen that causes downy mildew (Olczak-Woltman et al 2008). Recently, outbreaks of angular leaf spot were reported in several Chinese provinces, where the disease affected 15-50% of growing fields, causing between 30% and 50% of yield reduction (Meng et al 2016).…”

Genetic and pathogenic diversity of Pseudomonas syringae strains isolated from cucurbits

“…After 7 days, inoculated leaves were scored for disease severity and appearance of symptoms. The evaluation using a 1-9 disease severity index (DSI) where the most resistant plants were given the score of nine and the most susceptibility plants were given the score of one, was performed according to the protocol previously described (Olczak-Woltman et al 2008). The pathogenicity tests of each strain were performed using a total of 24 plants (with four replications of six plants in each replication).…”