RESUMO
Eyespot, caused by the related fungal pathogens Oculimacula acuformis and O. yallundae, is an important cereal stem-base disease in temperate parts of the world. Both species are dispersed mainly by splash-dispersed conidia but are also known to undergo sexual reproduction, yielding apothecia containing ascospores. Field diagnosis of eyespot can be challenging, with other pathogens causing similar symptoms, which complicates eyespot management strategies. Differences between O. acuformis and O. yallundae (e.g., host pathogenicity and fungicide sensitivity) require that both be targeted for effective disease management. Here, we develop and apply two molecular methods for species-specific and mating-type (MAT1-1 or MAT1-2) discrimination of O. acuformis and O. yallundae isolates. First, a multiplex PCR-based diagnostic assay targeting the MAT idiomorph region was developed, allowing simultaneous determination of both species and mating type. This multiplex PCR assay was successfully applied to type a global collection of isolates. Second, the development of loop-mediated isothermal amplification (LAMP) assays targeting ß-tubulin sequences, which allow fast (<9 min) species-specific discrimination of global O. acuformis and O. yallundae isolates, is described. The LAMP assay can detect very small amounts of target DNA (1 pg) and was successfully applied in planta. In addition, mating-type-specific LAMP assays were also developed for rapid (<12 min) genotyping of O. acuformis and O. yallundae isolates. Finally, the multiplex PCR-based diagnostic was applied, in conjunction with spore trapping in field experiments, to provide evidence of the wind dispersal of ascospores from a diseased crop. The results indicate an important role of the sexual cycle in the dispersal of eyespot.
Assuntos
Grão Comestível , Doenças das Plantas , Ascomicetos , Técnicas de Diagnóstico Molecular , Técnicas de Amplificação de Ácido Nucleico , Reprodução , Esporos FúngicosRESUMO
Crop Wild Relatives (CWRs), as potential sources of new genetic variants, are being extensively studied to identify genotypes that will be able to confer resistance to biotic stresses. In this study, a collection of barley wild relatives was assessed in the field, and their phenotypic variability was evaluated using a Barley Description List, reflecting the identified ecosites. Overall, the CWRs showed significant field resistance to various fungal diseases. To further investigate their resistance, greenhouse tests were performed, revealing that several CWRs exhibited resistance against Fusarium culmorum, Pyrenophora teres, and Puccinia hordei G.H. Otth. Additionally, to characterize the genetic diversity within the collection, DNA polymorphisms at 21 loci were examined. We successfully employed barley-specific SSR markers, confirming their suitability for identifying H. spontaneum and even H. marinum, i.e., perennial species. The SSR markers efficiently clustered the investigated collection according to species and ecotypes, similarly to the phenotypic assessment. Moreover, SSR markers associated with disease resistance revealed different alleles in comparison to those found in resistant barley cultivars. Overall, our findings highlight that this evaluated collection of CWRs represents a valuable reservoir of genetic variability and resistance genes that can be effectively utilized in breeding programs.
RESUMO
The reaction of twenty-five winter wheat cultivars frequently grown in the Czech Republic to inoculation with Oculimacula yallundae and Oculimacula acuformis was evaluated in small plot trials from 2019 to 2021. The eyespot infection assessment was carried out visually using symptoms on stem bases and quantitative real-time polymerase chain reaction (qPCR). The cultivars were also tested for the presence of the resistance gene Pch1 using the STS marker Xorw1. Statistical differences were found between cultivars and between years. The lowest mean level of eyespot infection (2019-2021) was visually observed in cultivar Annie, which possessed resistance gene Pch1, and in cultivar Julie. Cultivars Turandot and RGT Sacramento were the most susceptible to eyespot. The method qPCR was able to distinguish two eyespot pathogens. O. yallundae was detected in higher concentrations in inoculated plants compared with O. acuformis. The relationship between the eyespot symptoms and the pathogen's DNA content in plant tissues followed a moderate linear regression only in 2021. The highest eyespot infection rate was in 2020 due to weather conditions suitable for the development of the disease.
RESUMO
Resistance to Fusarium head blight (FHB) of spelt wheat was investigated in field trials carried out at three European locations between 2016 and 2018. Resistance was assessed after artificial inoculation by visual scoring of symptoms and the determination of the contamination of grains and glumes with the mycotoxin deoxynivalenol (DON). It was found that typical spelt traits such as tall plant height, lax spikes, and tough glumes play a role as passive resistance factors. Across all test environments, modern spelt varieties with a significantly reduced plant height showed a significantly higher susceptibility to FHB and a higher contamination of the grains with DON compared to old landraces/varieties and plant genetic resources. Similarly, the lowest mycotoxin levels in grains were found only in old landraces and varieties, while the highest DON concentration was observed mainly in modern varieties. The results obtained can be used for the selection of suitable parental material for breeding spelt with improved FHB resistance.