Conidia sporulation of Pyricularia oryzae in segments of wheat plants under six different temperatures

Kovaleski, Marcos; Maciel, João Leodato Nunes; Santos, Gustavo Bilibio dos; Silva, Alieze Nascimento da; Deuner, Carolina Cardoso

doi:10.1590/0103-8478cr20190573

Cited by 5 publications

(6 citation statements)

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“…In addition, Danelli et al (2019) established that the increase in MoT spores is due to the mean relative humidity, the mean daily temperature, and precipitation of less than 5 mm/day, managing to predict that the highest number of spores occurred in hours in which the temperature was between 15 and 35 °C and relative humidity >93%. Moreover, Kovaleski et al (2020) established equations which identified that the highest production of conidia occurred between temperatures of 24 and 27 °C in experiments carried out in pots. As the greenhouse temperature and relative humidity were lower than those in laboratory conditions, we could speculate that, among other possibilities, the lack of optimum conditions is associated with the lower sporulation capability of the pathogen, and thus a lower rate of transmission under greenhouse conditions.…”

Section: Discussionmentioning

confidence: 99%

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%

Tracing seed to seedling transmission of the wheat blast pathogenMagnaporthe oryzaepathotypeTriticum

et al. 2021

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“…Senescent plant tissues may also serve as substrate for blast inoculum survival during the off-season for at least five months in wheat-infected residues (Pizolotto et al 2019) and 18 months in rice-infected residues (Raveloson et al 2018). The fungus may survive in stems, leaves and heads (Kovaleski et al 2020).…”

Section: Disease Cycle and Epidemiologymentioning

confidence: 99%

“…The magnitude of spore production in infected segments of wheat plant tissues was dependent on temperature and light, having highest amounts of conidia produced from 24°C to 27°C (Kovaleski et al 2020), constant blue and red light, but also transition across white light and darkness (Leach 1962(Leach , 1980Lee et al 2006).…”

Section: Disease Cycle and Epidemiologymentioning

confidence: 99%

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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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“…The development of wheat blast in the fields depends on several environmental factors, highlighting humidity and temperature as fundamental in determining the limit of damage that the disease can cause (KoVALESKI et al, 2019). Environmental factors also influence the variability of the pathogen in a magnitude that is difficult even to speculate.…”

Section: Introductionmentioning

confidence: 99%

Resistance of Brazilian wheat cultivars to blast under controlled condition

et al. 2022

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The first report of wheat blast in the world was in Brazil, in 1986. Since then, a great effort has been made towards the development of wheat cultivars resistant to this disease, which is caused by the fungus Pyricularia oryzae Triticum (PoT). The objective of this research was to (i) evaluate the resistance of wheat genotypes to blast and (ii) verify the correlation between disease severity on wheat spikes and sporulation rate of PoT on spike rachises. Plants of 40 cultivars grown in pots, at the flowering stage (stage 65 on the Zadoks scale), were inoculated with a suspension of conidia of a PoT isolate representative of the main variant of the fungus reported in Brazil. Severity of blast on the spikes at 5 and 7 days after inoculation (dai) and the rate of sporulation of the fungus on the rachis (conidia per g of rachis) were evaluated. Eighty percent of the cultivars that were classified in the group with the lowest sporulation rate were also classified in the group with the highest resistance at 7 dai. However, the correlation coefficients of the analysis established between the cultivar severity at 5 and 7 dai averages and the PoT sporulation rate averages were not significant (r=0.2464 and r=0.2047, respectively). Results obtained represent the updated characterization to blast of wheat cultivars in Brazil and constitute an important exploratory framework for the evaluation of the reaction of wheat genotypes based on the sporulation rate of PoT on their tissues.

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Conidia sporulation of Pyricularia oryzae in segments of wheat plants under six different temperatures

Cited by 5 publications

References 5 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

Resistance of Brazilian wheat cultivars to blast under controlled condition

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