Effects of temperature on ascospore germination and penetration of oilseed rape (<i>Brassica napus</i>) leaves by A‐ or B‐group<i>Leptosphaeria maculans</i>(phoma stem canker)

Huang, Yongju; Toscano-Underwood, C.; Fitt, Bruce D.L.; Hu, Xiaojing; Hall, Avice

doi:10.1046/j.1365-3059.2003.00813.x

Cited by 38 publications

(45 citation statements)

References 26 publications

(53 reference statements)

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“…Temperature is also critical for the expression of some resistance to L. maculans in B. napus, with, for example, a lesser efficiency of the Rlm6 resistance at temperatures above 25°C (Huang et al, 2006). We have established that the temperature also influences the transcription level of effectors and the optimum of 16°C coincides with the range of optimal temperatures previously reported for ascopore germination and leaf lesion development (Huang et al, 2003). For oilseed rape, an apoplastic pH of 5.8 and an ammonium concentration of 1.3 mM were measured in young leaves of B. napus cv Global but not data for sugar concentrations are currently available (Husted and Schjoerring, 1995).…”

Section: Discussionsupporting

confidence: 80%

“…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%

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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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Section: Discussionsupporting

confidence: 80%

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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“…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.…”

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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“…complex to different temperatures; this parameter affected maturation of pseudothecia of L. maculans and L. biglobosa on oilseed rape stem debris. Moreover, Huang et al (2003) indicated that temperature affected ascospore germination and penetration of leaves of oilseed rape, which further demonstrates the importance of weather parameters on pathogen development. Recognition of relationships between weather parameters and pathogen development has allowed the construction of mathematical models for the prediction of the onset of pseudothecia maturity (Salam et al 2003) and seasonal ascospore showers (Salam et al 2007).…”

Section: Resultsmentioning

confidence: 83%

The effect of fungicide spray time on the incidence of stem canker of brassicas and seed yield of winter oilseed rape in Pomerania

Kaczmarek

Brachaczek²,

Jędryczka³

2014

J Plant Dis Prot

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The aim of this study was to determine the relationship between ascospore release and autumn fungicide spray time as well as, the incidence and severity of stem canker and seed yield. The concentration of ascospores in air was determined using Hirst-type volumetric samplers located in the region of Pomerania in central-north Poland, in the zone of intensive cultivation of oilseed rape, over three consecutive seasons from 2009/2010 to 2011/2012. A fungicide spray was most efficient, when applied 4 to 14 days after the highest concentration of Leptosphaeria ascospores was found in air samples. An application of fungicide at this time reduced the incidence of phoma leaf spotting by 12.5-24.7%, stem canker symptoms by 11.3-33.0% and decreased yield loss by 2.7-5.0 dt ha -1 . The results demonstrate that knowledge about the concentration of pathogen inoculum in the air allows more efficient protection of oilseed rape against stem canker.

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Effects of temperature on ascospore germination and penetration of oilseed rape (Brassica napus) leaves by A‐ or B‐groupLeptosphaeria maculans(phoma stem canker)

Cited by 38 publications

References 26 publications

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

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

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

The effect of fungicide spray time on the incidence of stem canker of brassicas and seed yield of winter oilseed rape in Pomerania

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