Development of phoma lesions on oilseed rape leaves inoculated with ascospores of A‐group or B‐group<i>Leptosphaeria maculans</i>(stem canker) at different temperatures and wetness durations

Toscano-Underwood, C.; West, Jonathan; Fitt, Bruce D.L.; Todd, A. D.; Jędryczka, M.

doi:10.1046/j.1365-3059.2001.00526.x

Cited by 54 publications

(63 citation statements)

References 24 publications

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“…Huang et al (2003) compared the germination and penetration by ascospores of A-group and B-group of L. maculans on winter-type B. napus. Toscano-Underwood et al (2001) reported the development of blackleg lesions on oilseed rape leaves inoculated with ascospores of A-group and B-group. Hammond and Lewis (1987) used inoculations with single ascospores and with pycnidiospores but did not compare germination and penetration phases of the two spore types.…”

Section: Introductionmentioning

confidence: 99%

Germination and invasion by ascospores and pycnidiospores of Leptosphaeria maculans on spring-type Brassica napus canola varieties with varying susceptibility to blackleg

Sivasithamparam

Barbetti

et al. 2004

J Gen Plant Pathol

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The infection processes of ascospores and pycnidiospores of Leptosphaeria maculans were studied on cotyledons of six cultivars of spring-type Brassica napus: one with resistance controlled by a single dominant gene (cv. Surpass 400), three with polygenic resistance (cvs. Dunkeld, Grouse, and Outback), and two susceptible cultivars (Westar and Q2). On all cultivars, ascospore germination, penetration, and development of symptoms on cotyledons were much earlier than that with pycnidiospores. At 2 h after inoculation ascospores began to germinate, by 4 h about 50% had germinated, and by 6-8 h 85%-90% had germinated. In contrast, pycnidiospores began to germinate 1 day after inoculation (dai) and reached only 50% germination by 3 dai. Ascospores began germinating from terminal cells and then later from the interstitial cells. Pycnidiospores germinated predominantly from one end and sometimes from both ends. Germ tubes from ascospores penetrated stomata as early as 4 h after inoculation, whereas those from pycnidiospores penetrated at 2 dai. Symptom development with ascospores was 2 days earlier than that with pycnidiospores. Symptoms on Surpass 400 were evident as early as 3-5 dai with ascospores and 5-7 dai with pycnidiospores. However, on other cultivars, symptoms were not evident until 10 dai with ascospores and 12 dai with pycnidiospores. This report is the first on differences in the infection processes by the two spore types. Ascospore and pycnidiospore attachment, germination, and penetration did not differ between resistant and susceptible cultivars, but there were major differences after penetration. Under high humidity, 80%-90% of stomata of susceptible Westar and Q2 had aerial hyphae emerging from stomatal pores. However, fewer stomata (5%-10%) had aerial hyphae on Surpass 400 by 10 dai with ascospores and 12 dai with pycnidiospores, but even these were usually poorly developed. Host differences in spring-type B. napus in relation to production of aerial hyphae have not previously been reported. In Surpass 400, rapid necrosis of guard cells occurred within a few hours of penetration by either type of spore, and subsequently one or a few cells immediately adjacent to the penetration site died. This necrosis then spread to the cells around the penetration site to form a hypersensitive response (in the form of a small, dark lesion) to both ascospores and pycnidiospores. This is the first detailed report on interactions between spring-type B. napus and L. maculans in relation to single dominant genebased resistance. Neither the cultivars with polygenic resistance nor the susceptible cultivars had such a response.

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Section: Introductionmentioning

confidence: 99%

Germination and invasion by ascospores and pycnidiospores of Leptosphaeria maculans on spring-type Brassica napus canola varieties with varying susceptibility to blackleg

Sivasithamparam

Barbetti

et al. 2004

J Gen Plant Pathol

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“…Temperature is an important parameter for germination of ascospores of L. maculans as well as germ tube elongation on leaf surfaces and for the formation of leaf lesions (Toscano-Underwood et al, 2001;Huang et al, 2003). In controlled-environment experiments performed with increasing temperature from 5°C to 20°C, optimal temperatures of 15-20°C were reported.…”

Section: Discussionmentioning

confidence: 99%

Impact of biotic and abiotic factors on the expression of fungal effector-encoding genes in axenic growth conditions

Meyer

Bourras

Gervais

et al. 2017

Fungal Genetics and Biology

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a b s t r a c tIn phytopathogenic fungi, the expression of hundreds of small secreted protein (SSP)-encoding genes is induced upon primary infection of plants while no or a low level of expression is observed during vegetative growth. In some species such as Leptosphaeria maculans, this coordinated in-planta upregulation of SSP-encoding genes expression relies on an epigenetic control but the signals triggering gene expression in-planta are unknown. In the present study, biotic and abiotic factors that may relieve suppression of SSP-encoding gene expression during axenic growth of L. maculans were investigated. Some abiotic factors (temperature, pH) could have a limited effect on SSP gene expression. In contrast, two types of cellular stresses induced by antibiotics (cycloheximide, phleomycin) activated strongly the transcription of SSP genes. A transcriptomic analysis to cycloheximide exposure revealed that biological processes such as ribosome biosynthesis and rRNA processing were induced whereas important metabolic pathways such as glycogen and nitrogen metabolism, glycolysis and tricarboxylic acid cycle activity were downregulated. A quantitatively different expression of SSP-encoding genes compared to plant infection was also detected. Interestingly, the same physico-chemical parameters as those identified here for L. maculans effectors were identified to regulate positively or negatively the expression of bacterial effectors. This suggests that apoplastic phytopathogens may react to similar physiological parameters for regulation of their effector genes.

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“…Germtubes from ascospores penetrate the leaf through stomata and wounds (Huang et al 2003b). The first symptoms of infection are phoma leaf lesions in the autumn; L. maculans produces pale grey lesions with many pycnidia whilst lesions produced by L. biglobosa are smaller, have a dark margin with a light brown centre and contain few, if any, pycnidia (Brun et al 1997;Biddulph et al 1999;Toscano-Underwood et al 2001). Both L. maculans and L. biglobosa spread asymptomatically from the leaf lamina along tissues of the petiole to the stem Fitt et al 2006b;Huang et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Geographic variation in severity of phoma stem canker and Leptosphaeria maculans/ L. biglobosa populations on UK winter oilseed rape (Brassica napus)

et al. 2009

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Phoma stem canker, caused by Leptosphaeria maculans and L. biglobosa, is the most important disease of oilseed rape in Europe. Differences between L. maculans and L. biglobosa in their lifecycles enable the two species to co-exist on oilseed rape crops over a cropping season. This review considers the factors affecting geographic variation in the severity of phoma stem canker epidemics and in the structure of the population of the pathogens in the UK, where the most severe epidemics occur in the south of England and cankers do not develop in Scotland. It is concluded that this variation is directly related to differences in climate, since weather-based models show that stem canker severity increases with increasing winter/spring temperature and temperatures are greater in the south of the UK. It may also be related to differences in pathogen populations, since surveys showed that the proportion of the more damaging L. maculans in stem cankers was greatest in southern England, with most L. biglobosa in northern England. Regional variation in agronomic practices such as cultivar choice and fungicide use may also indirectly influence phoma stem canker severity. Differences in cultivar choice result in differences in L. maculans race structure, which may influence the severity of epidemics. Differences in fungicide use may also influence pathogen populations, since L. maculans and L. biglobosa differ in their sensitivities to different azole fungicides. These factors are discussed in relation to strategies for sustainable production of oilseed rape by adaptation to threats posed by climate change.

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Development of phoma lesions on oilseed rape leaves inoculated with ascospores of A‐group or B‐groupLeptosphaeria maculans(stem canker) at different temperatures and wetness durations

Cited by 54 publications

References 24 publications

Germination and invasion by ascospores and pycnidiospores of Leptosphaeria maculans on spring-type Brassica napus canola varieties with varying susceptibility to blackleg

Germination and invasion by ascospores and pycnidiospores of Leptosphaeria maculans on spring-type Brassica napus canola varieties with varying susceptibility to blackleg

Impact of biotic and abiotic factors on the expression of fungal effector-encoding genes in axenic growth conditions

Geographic variation in severity of phoma stem canker and Leptosphaeria maculans/ L. biglobosa populations on UK winter oilseed rape (Brassica napus)

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