Phoma black stem severity and phytoestrogen production in annual <i>Medicago</i> spp. is primarily determined by interaction of cultivar and pathogen isolate

Omidvari, Mahtab; Flematti, Gavin R.; You, Ming Pei; Abbaszadeh‐Dahaji, Payman; Barbetti, Martin J.

doi:10.1111/ppa.13533

Cited by 4 publications

(20 citation statements)

References 35 publications

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“…These were obtained from the Culture Collection at the Department of Primary Industries and Regional Development, Western Australia, as lyophilised cultures in glass ampules. Full isolate details are provided in Omidvari et al (2021).…”

Section: Isolates Of P Medicaginismentioning

confidence: 99%

“…Inoculum preparation was as described by Omidvari et al (2021). Briefly, preserved isolates in lyophilised ampoules were subcultured onto Sanderson and Srb medium B www.publish.csiro.au/cp…”

Section: Inoculum Preparationmentioning

confidence: 99%

“…brevispina (Barbetti 1990(Barbetti , 1995a(Barbetti , 1995b was used to evaluate the virulence of different isolates across multiple inoculations. A single cultivar was chosen in order to avoid cultivar × isolate interactions as found in our earlier study (Omidvari et al 2021). To remove any potential fungal seed contamination and to ensure high germination rates, seeds were surface-sterilised with 70% ethanol for 30 s, washed with sterile distilled water, and then scarified to break hardseed dormancy (when freshly ripened they also contain embryo dormancy) using sandpaper.…”

Section: Virulence Testsmentioning

confidence: 99%

“…Although various management strategies such as close grazing (Barbetti 1989b; Barbetti et al 2006Barbetti et al , 2020 and application of fungicides (Barbetti 1983(Barbetti , 1989b offer reduction of Phoma black stem and leaf spot, locating host resistance remains the most promising approach (Barbetti 1989b(Barbetti , 1990Barbetti et al 2020). In addition, our recent study (Omidvari et al 2021) highlighted that the intrinsic ability of annual Medicago cultivars to produce phytoestrogens in the absence of the pathogen, and their comparative ability to produce phytoestrogens in the presence of P. medicaginis, were together critical in developing more resistant cultivars with improved reproductive outcomes for grazing animals. However, in that study, we utilised a 'once-only' pathogen inoculation, which contrasts with what happens naturally in the field.…”

Section: Introductionmentioning

confidence: 99%

“…Serena, and M. murex cv. Zodiac) (Omidvari et al 2021). The relative virulence of these isolates varied across different assessment parameters and their effects on phytoestrogen production were also different.…”

Section: Introductionmentioning

confidence: 99%

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Sequential infections by 32 isolates of

Omidvari

Flematti

You

et al. 2022

Crop & Pasture Science

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Context. Studies of Phoma black stem and leaf spot disease (caused by Phoma medicaginis) in annual medics (Medicago spp.) normally involve a 'once-only' inoculation not reflecting multiple pathogen infection and phytoestrogen production cycles in the field. Phytoestrogen production by plants can result in lower ovulation rates in grazing animals. Aims. We aimed to determine whether sequential infections by P. medicaginis increase production of phytoestrogens in annual medics, and to measure the genetic diversity of isolates. Methods. In a greenhouse experiment, pathogenicity and virulence were investigated across 32 isolates of P. medicaginis following one, two or three rounds of inoculation of M. polymorpha var. brevispina. Production of the phytoestrogens coumestrol and 4 0 -O-methyl coumestrol was measured, and correlation with disease parameters assessed. DNA sequencing using ITS, β-tubulin, calmodulin and P. medicaginis-specific EFNI-1α was applied for phylogenetic analysis of isolates from Western Australia and elsewhere. Key results. Across isolates, highest leaf disease incidence was 76%, petiole disease incidence 61%, leaf disease severity 52% and petiole disease severity 53%. Stem coumestrol content range was 45-1247 mg kg −1 , and 4 0 -O-methyl coumestrol 0-344 mg kg −1 . All measures were highest after three rounds of inoculation. Overall, there was a positive correlation of leaf disease incidence with coumestrol content (P < 0.05) and of both leaf and petiole disease incidence with 4 0 -Omethylcoumestrol content (P < 0.01, P < 0.05, respectively). Phylogenetic analysis revealed a high degree of genetic similarity among Western Australian isolates, generally grouping into a single separate cluster across the four markers, and genetically distinct from isolates sourced outside Australia. Conclusions. Leaf disease incidence was the best discriminating disease parameter for coumestrol and 4 0 -O-methylcoumestrol content. Western Australian isolates of P. medicaginis were genetically similar and unique, possibly due to geographic separation. Implications. The study emphasised the importance of sequential inoculations when screening annual Medicago genotypes towards developing cultivars with superior disease resistance and enhanced animal reproductive outcomes.

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Section: Isolates Of P Medicaginismentioning

confidence: 99%

Section: Inoculum Preparationmentioning

confidence: 99%

Section: Virulence Testsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sequential infections by 32 isolates of

Omidvari

Flematti

You

et al. 2022

Crop & Pasture Science

Self Cite

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Plant growth stage and Phoma medicaginis inoculum concentration together determine severity of Phoma black stem and leaf spot and consequent phytoestrogen production in annual Medicago spp.

et al. 2023

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Phoma black stem and leaf spot disease (Phoma medicaginis) not only destroys annual Medicago spp. forage and seed yield but also reduces herbage quality by consequent phytoestrogen production that reduces ovulation of grazing animals. Two controlled environment studies evaluated the effects of plant developmental stage in annual Medicago rugosa ‘Paraponto’ and M. scutellata ‘Sava’ and different inoculum concentrations of P. medicaginis in M. littoralis ‘Harbinger’ and M. polymorpha ‘Serena’ on disease development and coumestrol production. Disease incidence and severity and coumestrol production were dependent on plant developmental stage, cultivar and inoculum level (all p ≤ 0.001). Disease was least in 4‐week‐old plants; highest coumestrol was in inoculated 10‐week‐old Sava (1353 mg/kg) and least coumestrol in uninoculated 4‐week‐old Paraponto (87 mg/kg); and there was a positive correlation of disease incidence/severity factors with coumestrol across cultivars and plant growth stages (p < 0.001). Disease levels and coumestrol production were determined by inoculum concentration and cultivar (both p ≤ 0.001). Highest coumestrol was in Serena inoculated with 107 conidia/mL (265 mg/kg); lowest coumestrol was in uninoculated Harbinger (6 mg/kg); and there was a significant positive correlation of disease incidence/severity factors with coumestrol across cultivars and inoculum concentrations (p < 0.001). These studies emphasize both the opportunity for farmers to better use annual Medicago spp. stands for grazing reproducing animals early in the growing season when both disease and coumestrol levels are lowest, and the need for heightened farmer vigilance at later growth stages with greater disease and consequent phytoestrogen risk for grazing animals.

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Temperature and Soil Moisture Drive Coumestrol Concentration in Annual Medicago spp. in the Presence but Not Absence of Phoma Black Stem and Leaf Spot (Phoma medicaginis)

et al. 2022

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Studies were undertaken to determine the impact of environmental variables temperature (12.5/9.5, 20/17, 27/24 °C day/night) and soil moisture (100, 50% WHC), and their interaction with Phoma medicaginis infection, on production of the phytoestrogen coumestrol in annual Medicago rugosa cv. Paraponto and M. scutellata cv. Sava. Disease factors measured included leaf disease incidence/severity, petiole/stem disease incidence/severity, and leaf yellowing severity. Coumestrol levels were determined using gas chromatography–mass spectrometry (GC–MS). Increasing temperature from 12.5/9.5 °C to 27/24 °C in inoculated plants significantly (p < 0.05) increased coumestrol from 193 mg kg−1 to 390 mg kg−1, but there were no differences in coumestrol production across all three temperatures in uninoculated plants. Reducing soil moisture from 100% to 50% WHC at the highest temperature (27/24 °C) caused the greatest increase in coumestrol production from 156 to 269 mg kg−1 in inoculated plants. The greatest coumestrol production (600 mg kg−1) was under 27/24 °C/50% WHC for Sava infected with P. medicaginis and least coumestrol (1.6 mg kg−1) was Sava under 20/17 °C/50% WHC in the absence of P. medicaginis. Clearly, situations of higher temperatures in conjunction with lower soil moisture levels cause greatest elevation in coumestrol in the presence of P. medicaginis, levels far exceeding the animal risk threshold of 25 mg kg−1.

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Phoma black stem severity and phytoestrogen production in annual Medicago spp. is primarily determined by interaction of cultivar and pathogen isolate

Cited by 4 publications

References 35 publications

Sequential infections by 32 isolates of

Sequential infections by 32 isolates of

Plant growth stage and Phoma medicaginis inoculum concentration together determine severity of Phoma black stem and leaf spot and consequent phytoestrogen production in annual Medicago spp.

Temperature and Soil Moisture Drive Coumestrol Concentration in Annual Medicago spp. in the Presence but Not Absence of Phoma Black Stem and Leaf Spot (Phoma medicaginis)

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