Caracterização fenotípica de isolados de Pyricularia oryzae de trigo e plantas invasoras

Reges, Juliana Teodora de Assis; Santos, Iago de Jesus; Rodrigues, Josiane Walleria; Souza, Marcelo Henrique de; Silva, Simone Duarte Ramalho da; Jesus, Michelle Nogueira de

doi:10.22491/rca.2018.2628

Cited by 2 publications

(5 citation statements)

References 12 publications

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“…On the other hand, Urochloa-infecting isolates were moderately aggressive to wheat heads under highly conducive conditions to infection, which contrasts with our sampling on wheat heads, where only seven non-PoT isolates were recovered from wheat heads. Our results corroborated previous findings that also reported low aggressiveness of blast isolates cross-inoculated in relation to their primary host (Kato et al 2000;Oh et al 2002;Perelló et al 2017;Urashima et al 2017;Reges et al 2018;Martínez et al 2018;Chung et al 2020), which suggests that cross-infection may also occur in field conditions contributing to new host pathogenicity gain (Valent et al 2021).…”

Section: Discussionsupporting

confidence: 92%

“…Collectively, our results challenge the dominant hypothesis that signal grass is the major natural reservoir for the wheat blast pathogen (PoT) (Reges et al 2018(Reges et al , 2019Ceresini et al 2019;Dorigan et al 2019;Poloni et al 2021b). Actually, considering the strong association with its primary hosts in nature, phylogenetic relationships, and pathogenic specialization, signal grasses from MG are mainly infected by Urochloa pathotypes, regardless of their distance to wheat fields.…”

Section: Discussionsupporting

confidence: 56%

“…Triticum pathotype is usually more aggressive on their primary host, where the fungal colonization at the rachis vassel causes partial or complete head bleaching, leading to larger yield losses in favorable climate conditions at field conditions (Goulart and Paiva 2000;Goulart et al 2007;Urashima et al 2009;Pagani et al 2014). Instead, non-P. oryzae or non-PoT isolates demonstrated low aggressiveness when inoculated in wheat, even under controlled conditions (Kato et al 2000;Reges et al 2016Reges et al , 2018Reges et al , 2019Chung et al 2020).…”

Section: Discussionmentioning

confidence: 99%

“…For example, mixed infections in shared hosts favors gene flow through sexual recombination or non-meiotic parasexual processes, (Talbot et al 1993a, b;Soanes et al 2002;Inoue et al 2017;Monsur and Kusaba 2018;Zheng et al 2018;Gómez Luciano et al 2019;Asuke et al 2019), mutations in avirulence genes through selecting frequently occurs (Orbach et al 2000), or through the moving of a Pot3 transposon across pathogenicity related-genes (Kang et al 2001). Pathogenic effector proteins have been under evolutive selection across blast populations (Sweigard et al 1995;Farman and Leong 1998;Jones and Dangl 2006;Avila-Adame 2014;Tosa et al 2016;Wang and Valent 2017;Inoue et al 2017Inoue et al , 2021Gladieux et al 2018;Langner et al 2018;Gómez Luciano et al 2019), which might explain the ability to infect a new host or the variable levels of aggressiveness across different hosts (Kato et al 2000;Tosa et al 2004;Castroagudín et al 2016;Perelló et al 2017;Urashima et al 2017;Reges et al 2018Reges et al , 2019Qi et al 2021).…”

Section: Taxonomy and Genetic Diversitymentioning

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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Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

Section: Taxonomy and Genetic Diversitymentioning

confidence: 99%

See 2 more Smart Citations

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

Ascari¹,

Ponte²

2021

Preprint

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“…We studied non-PoT strains (other pathotype or even other species) that were collected hundreds of kms away from wheat in the natural landscape, and which were similarly resistant to AZOX compared with PoT strains, but differently with regards to the other fungicides in in vitro experiments. Previous studies have claimed that resistance to DMI and QoIs was pervasive and widespread among pathogen populations obtained from wheat and grasses (Reges et al, 2018(Reges et al, , 2019.…”

Section: Amino Acid Replacementmentioning

confidence: 99%

Sensitivity to fungicides in Pyricularia populations from wheat and signal grass in Minas Gerais

Cazón¹

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Wheat blast, caused by Pyricularia oryzae Triticum pathotype, is a damaging disease of wheat in the Brazilian Cerrado. Fungicides play an important role in management, but their efficacy has been variable. Failures in disease control have been associated with the presence of fungicide resistant populations. To determine if these resistance patterns are also present in Pyricularia populations infecting wheat and signal grass from MG state, we characterized phenotypically and genotypically the resistance of the blast pathogen against seven fungicides belonging to three chemical groups (DMI, QoI and SDHI). The in vitro sensitivity was assessed in 64 isolates obtained from the Triângulo Mineiro and Sul de Minas. For DMIs, the EC 50 was estimated for all isolates. For QoIs and SDHIs, the EC 50 was obtained for 13 isolates prior to determining a discriminatory dose. Control efficacy of each fungicide was also evaluated in vivo upon inoculation of wheat heads with a resistant (R) or a sensitive (S) PoT isolate (determined in vitro) to each fungicide. The presence of mutations in the genes encoding the target proteins of the different groups of fungicides was also evaluated. For the DMIs (TEBU - tebuconazole and EPOX - epoxiconazole), despite showing relatively high EC 50 values for some isolates, the control efficacy on wheat heads was high. We found no association between mutations in the cyp51A region and resistance to DMI. For QoIs, azoxystrobin (AZOX) did not inhibit the in vitro germination of PoT even with an extra dose of 100 µg/ml, and was poorly controlled in vivo (~ 20%). For pyraclostrobin (PYRA), despite the presence of isolates with high leves of spore germination in vitro using a discriminatory dose of 1.3 µg/ml, the control efficacy was also high. The G143A substitution was present in all PoT cytB sequences, even in those of the PYRA sensitive isolates. The non-PoT isolates did not present mutations in the cytB hot spots. For SDHIs, the most fungitoxic in in vitro and in vivo experiments was benzovindiflupyr, followed by bixafen and fluxapyroxad. Molecular analysis of the sdh subunits showed no relationship between mutations and sensitivity to SDHI fungicides. For the seven fungicides tested in this work, the PoT isolates were statistically less sensitive than the isolates from signal grass. Our results demonstrate that PoT populations can be controlled in vivo with at least one fungicide of each of the three chemical groups evaluated. Contrary to previous statements, determining EC 50 values in in vitro experiments was not sufficient to infer loss of efficacy in in vivo experiments. Benzovindiflupyr was the most effective active ingredient evaluated in this work. Conversely, azoxystrobin should not be considered for controlling wheat blast. Keywords: Wheat blast. Fungicide resistance. Epidemiology. Magnaporthe oryzae. Pyricularia oryzae.

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Caracterização fenotípica de isolados de Pyricularia oryzae de trigo e plantas invasoras

Cited by 2 publications

References 12 publications

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

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

Sensitivity to fungicides in Pyricularia populations from wheat and signal grass in Minas Gerais

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