Articles
Preliminary evaluation of the impact of preharvest UV-C on lettuce: potential for the control of Xanthomonas campestris
Article number
1271_53
Pages
387 – 394
Language
English
Abstract
Two lettuce (Lactuca sativa) cultivars, the susceptible ‘Chief’ and the tolerant ‘Little Gem’, were used to study the effect of ultraviolet-C (UV-C) light on bacterial leaf spot (BLS) development.
Potted plants were irradiated every 48 h with UV-C to obtain a cumulative dose of 1.6 kJ m‑2 over a period of 8 d.
Inoculation with Xanthomonas campestris pv. vitians was performed 2 d after the last UV-C treatment.
Then, 14 d after inoculation, the severity of BLS was assessed on the lettuce seedlings using a six-point scale (0-6). Lettucenin, a known antimicrobial molecule of lettuce, was extracted from controlled and treated tissues and assayed by ultra-performance liquid chromatography.
For the susceptible cultivar ‘Chief’, the severity of BLS was markedly reduced on the UV-C-treated plants in comparison with the non-UV-C-treated plants.
The BLS severity scores for ‘Chief’ were 2.66 and 5.16 in the UV-C-treated plants and the controls, respectively.
Ultraviolet-C treatment did not significantly affect the BLS severity index (<2) in the tolerant cultivar ‘Little Gem’. The lettucenin A content in the leaves was significantly higher in the tolerant cultivar than in the susceptible cultivar.
Ultrastructural changes induced by UV-C on the surface of lettuce leaves were observed by scanning electron microscopy.
These observations revealed the occlusion of the stomata of UV-C-treated leaves by a wax-like matrix that remains to be fully characterized.
This occlusion seemed partial in the susceptible cultivar and more complete in the tolerant cultivar.
The results of this preliminary work suggest a potential antibacterial role of lettucenin in the natural tolerance of lettuce against X. campestris. However, the beneficial effect of UV-C treatment on BLS severity seems to be related at least in part to ultrastructural modifications that restrict the access of the pathogen to the stomatal cavity.
Potted plants were irradiated every 48 h with UV-C to obtain a cumulative dose of 1.6 kJ m‑2 over a period of 8 d.
Inoculation with Xanthomonas campestris pv. vitians was performed 2 d after the last UV-C treatment.
Then, 14 d after inoculation, the severity of BLS was assessed on the lettuce seedlings using a six-point scale (0-6). Lettucenin, a known antimicrobial molecule of lettuce, was extracted from controlled and treated tissues and assayed by ultra-performance liquid chromatography.
For the susceptible cultivar ‘Chief’, the severity of BLS was markedly reduced on the UV-C-treated plants in comparison with the non-UV-C-treated plants.
The BLS severity scores for ‘Chief’ were 2.66 and 5.16 in the UV-C-treated plants and the controls, respectively.
Ultraviolet-C treatment did not significantly affect the BLS severity index (<2) in the tolerant cultivar ‘Little Gem’. The lettucenin A content in the leaves was significantly higher in the tolerant cultivar than in the susceptible cultivar.
Ultrastructural changes induced by UV-C on the surface of lettuce leaves were observed by scanning electron microscopy.
These observations revealed the occlusion of the stomata of UV-C-treated leaves by a wax-like matrix that remains to be fully characterized.
This occlusion seemed partial in the susceptible cultivar and more complete in the tolerant cultivar.
The results of this preliminary work suggest a potential antibacterial role of lettucenin in the natural tolerance of lettuce against X. campestris. However, the beneficial effect of UV-C treatment on BLS severity seems to be related at least in part to ultrastructural modifications that restrict the access of the pathogen to the stomatal cavity.
Authors
O. Nicolas, M.T. Charles, D. Chabot, J. Aarrouf, S. Jenni, V. Toussaint, C. Beaulieu
Keywords
bacterial leaf spot, disease resistance, phytoalexin, stomata, UV-C hormesis
Groups involved
- Division Greenhouse and Indoor Production Horticulture
- Division Precision Horticulture and Engineering
- Division Plant-Environment Interactions in Field Systems
- Working Group Nettings in Horticulture (subgroup of Protected Cultivation in Mild Winter Climates)
- Working Group Light in Horticulture
- Working Group Organic Greenhouse Horticulture
- Working Group Modelling Plant Growth, Environmental Control, Greenhouse Environment
- Working Group Protected Cultivation, Nettings and Screens for Mild Climates
- Working Group Vegetable Grafting
- Working Group Computational Fluid Dynamics in Agriculture
- Working Group Design and Automation in Integrated Indoor Production Systems
- Working Group Mechanization, Digitization, Sensing and Robotics
- Working Group Greenhouse Environment and Climate Control
- Commission Agroecology and Organic Farming Systems
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