Potential of transmission of Pyricularia graminis-tritici from plant to seed and from seed to seedling in wheat genotypes with different degrees of blast resistance

Gomes, Delineide Pereira; Rocha, Valterley Soares; Rocha, João Romero do Amaral Santos de Carvalho; Pereira, Olinto Liparini; Souza, Moacil Alves de

doi:10.1590/2317-1545v40n1181833

Cited by 8 publications

(10 citation statements)

References 16 publications

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“…References about seed to seedling transmission are scarce for MoT and limited to experiences in Brazil (Gomes et al, 2018; Goulart et al, 1995; Urashima et al, 2009). More recently, Cruz and Valent (2017) pointed out that MoT can be transmitted from spike to seed, and from infected seeds to seedlings.…”

Section: Discussionmentioning

confidence: 99%

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Tracing seed to seedling transmission of the wheat blast pathogenMagnaporthe oryzaepathotypeTriticum

et al. 2021

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Wheat blast caused by Magnaporthe oryzae pathotype Triticum (MoT), initially restricted to South America, is a global threat for wheat after spreading to Asia in 2016 by the introduction of contaminated seeds, raising the question about transmission of the pathogen from seeds to seedlings, a process so far not well understood. We therefore studied the relationship between seed infection and disease symptoms on seedlings and adult plants. To accomplish this objective, we inoculated spikes of wheat cv. Apogee with a transgenic isolate (MoT‐DsRed, with the addition of being resistant to hygromycin). We identified MoT‐DsRed in experiments using hygromycin resistance for selection or by observation of DsRed fluorescence. The seeds from infected plants looked either apparently healthy or shrivelled. To evaluate the transmission, two experimental designs were chosen (blotter test and greenhouse) and MoT‐DsRed was recovered from both. This revealed that MoT is able to colonize wheat seedlings from infected seeds under the ground. The favourable conditions of temperature and humidity allowed a high recovery rate of MoT from wheat shoots when grown in artificial media. Around 42 days after germination of infected seeds, MoT‐DsRed could not be reisolated, indicating that fungal progression, at this time point, did not proceed systemically/endophytically. We hypothesize that spike infection might occur via spore dispersal from infected leaves rather than within the plant. Because MoT‐DsRed was not only successfully reisolated from seed coats and germinating seeds with symptoms, but also from apparently healthy seeds, urgent attention is needed to minimize the risks of inadvertent dispersal of inoculum.

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Section: Discussionmentioning

confidence: 99%

“…Studies that evaluate the transmission of MoT by wheat seeds are still scarce (Gomes et al, 2018). In Brazil, Goulart et al (1990) and Goulart and Paiva (1990) evidenced the lowest (0%) and the highest (47.3%) percentage of fungal transmission from wheat seeds to seedlings with 2% and 21% of incidence, respectively.…”

Section: Introductionmentioning

confidence: 99%

Tracing seed to seedling transmission of the wheat blast pathogenMagnaporthe oryzaepathotypeTriticum

et al. 2021

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“…As to long distance dispersal, infected/infested seeds or grains are the most probable source of inoculum (Tanaka et al 2009). If infected seeds are sown, the pathogen may be transmitted to young plants, and foliar epidemics may further develop from seed borne inoculum (Gomes et al 2018).…”

Section: Disease Cycle and Epidemiologymentioning

confidence: 99%

“…Both within-canopy or external sources of airborne inoculum contribute to secondary infections on wheat (Gongora-Canul et al 2020). Once the heads are infected, the pathogen may be transmitted to grains and then start a new cycle if used as seeds (Gomes et al 2018). However, the grains positioned above the infection-site, if produced, are deformed with a low weight, and thus inappropriate to be used as seed (Goulart and Paiva 2000;Goulart et al 2007).…”

Section: Disease Cycle and Epidemiologymentioning

confidence: 99%

Taxonomic and pathogenic diversity of the blast pathogen populations infecting wheat and grasses in Minas Gerais

Ascari¹,

Ponte²

2021

Preprint

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The blast disease of Poaceae is caused by a large species complex, among which P. oryzae is composed of several host-specialized lineages. The Pyricularia oryzae Triticum pathotype (PoT) causes the blast disease in wheat, but is also capable of infecting other grasses, which may serve as an inoculum reservoir for epidemics in wheat. In Brazil, severe wheat blast epidemics are most common in the Cerrado region. The dominant hypothesis is that signal grass (Urochloa sp.) and other gramineous plants harbor the wheat blast pathogen, thus serving as a major reservoir of inoculum for epidemics in wheat. A two-year survey of the Pyricularia blast pathogens was conducted in both wheat and non-wheat areas as well as prior (February) and during (May) the wheat growing season in Minas Gerais. A total of 1,368 plant samples representative of 31 Poaceae species, including wheat, were collected and inspected for the presence of blast symptoms. During the isolations, 932 isolates were obtained, being one fourth obtained from gramineous plants. A subset of 572 isolates was selected for identification at the species level based on portions of the CH7-BAC9 gene sequences. Most of the isolates (n = 494) were P. oryzae, within which 68% were PoT and 32% non-PoT based on two PCR assays targeting (MoT3 and C17 PCR assays). The PoT lineage was found predominantly (97%) in wheat and rarely in the other hosts, even nearby wheat fields (2.1%), as well as at longer distances from wheat regions (0.1%). The blast pathogen population isolated from signal grass grouped in different clades from PoT, and therefore referred to Urochloa lineage (PoU). A series of cross-inoculation greenhouse experiments was conducted using wheat (cv. BRS Guamirim and BR 18-Terena) and signal grass (cv. Marandu) as host and 14 PoT and six PoU isolates as pathogen factor. In the first leaf-inoculation experiment, results showed a significant interaction between host and pathogen; PoT was strongly/weakly aggressive towards wheat/signal grass and PoU was strongly/weakly aggressive towards signal grass/wheat. In inoculated wheat heads, PoT was more aggressive (>91% infected spikelets) than PoU (52% infected spikelets). In a third experiment, four signal grass cultivars (Marandu, Basilisk, Piatã, and Xaraés) were inoculated with the same set of 20 isolates. Similarly, signal grass cultivars were generally more susceptible to PoU than PoT. Severity induced by PoU was twice (7.7% severity) as high as PoT (3.8%) and so was the number of conidia/leaf produced by PoU (47,500) and PoT (23,200). Two groups of signal grass cultivars were formed, the most susceptible composed of Marandu and Basilisk and the least susceptible composed of Piatã and Xaraés. Results of our study confirm the host-specialization and the shaping of the blast populations according to the host. We further suggest that grasses in general, especially signal grass, may not play a major role as an inoculum reservoir for PoT, as it harbors mainly the PoU population. However, due to the large extent of pasture-growing regions and cross-infection ability in wheat, signal grass may harbor amounts of PoT inoculum that are sufficient for initiating leaf and head blast epidemics in wheat blast in Minas Gerais state.

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“…oryzae spores are mainly dispersed on short distance by the wind [14]. However, the transport of contaminated seed or grains facilitates the spread of the fungus over long distances [15]. Comparative genomic studies demonstrated that P. oryzae isolates collected from wheat in different parts of Bangladesh and isolates causing epidemics in Brazil were strongly genetically related [12,13].…”

Section: Introductionmentioning

confidence: 99%

A PCR, qPCR, and LAMP Toolkit for the Detection of the Wheat Blast Pathogen in Seeds

Thierry

Chatet²,

Fournier

et al. 2020

Plants

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Wheat blast is a devastating disease caused by the pathogenic fungus Pyricularia oryzae. Wheat blast first emerged in South America before more recently reaching Bangladesh. Even though the pathogen can spread locally by air-dispersed spores, long-distance spread is likely to occur via infected wheat seed or grain. Wheat blast epidemics are caused by a genetic lineage of the fungus, called the Triticum lineage, only differing from the other P. oryzae lineages by less than 1% genetic divergence. In order to prevent further spread of this pathogen to other wheat-growing areas in the world, sensitive and specific detection tools are needed to test for contamination of traded seed lots by the P. oryzae Triticum lineage. In this study, we adopted a comparative genomics approach to identify new loci specific to the P. oryzae Triticum lineage and used them to design a set of new markers that can be used in conventional polymerase chain reaction (PCR), real-time PCR, or loop-mediated isothermal amplification (LAMP) for the detection of the pathogen, with improved inclusivity and specificity compared to currently available tests. A preliminary biological enrichment step of the seeds was shown to improve the sensitivity of the tests, which enabled the detection of the target at an infection rate as low as 0.25%. Combined with others, this new toolkit may be particularly beneficial in preventing the trade of contaminated seeds and in limiting the spread of the disease.

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Potential of transmission of Pyricularia graminis-tritici from plant to seed and from seed to seedling in wheat genotypes with different degrees of blast resistance

Cited by 8 publications

References 16 publications

Tracing seed to seedling transmission of the wheat blast pathogenMagnaporthe oryzaepathotypeTriticum

Tracing seed to seedling transmission of the wheat blast pathogenMagnaporthe oryzaepathotypeTriticum

Taxonomic and pathogenic diversity of the blast pathogen populations infecting wheat and grasses in Minas Gerais

A PCR, qPCR, and LAMP Toolkit for the Detection of the Wheat Blast Pathogen in Seeds

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