Teste de patogenicidade dos isolados de Pyricularia oryzae nos hospedeiros de trigo, cevada, arroz e braquiária

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

doi:10.32929/2446-8355.2019v28n1p19-28

Cited by 5 publications

(6 citation statements)

References 8 publications

(20 reference statements)

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“…The low frequency of wheat <-> Urochloa cross-infection found in nature seems to be correlated with innate compatibility differences because, using cross-inoculation experiments, we found that PoT members were consistently more aggressive on wheat leaves, and the isolates from Urochloa (PoU3/4 and Pu) were more aggressive on signalgrass. Thus, our findings hold to the general pattern that PoT is usually more aggressive on wheat, while non-PoT/non- P. oryzae isolates tend to be less aggressive, even under favorable, controlled environments (Chung et al 2020; Kato et al 2000; Reges et al 2016, 2019). And, even though the Urochloa pathogens showed incidences on the spikelets up to 50%, after spraying spikelets, the percent diseased area was apparently rather low, and the symptoms were mild, consisting of small, reddish-brown to dark-gray spots, or even hypersensitive reactions.…”

Section: Discussionsupporting

confidence: 76%

PyriculariaPopulations are Mostly Host-Specialized with Limited Reciprocal Cross-Infection Between Wheat and Endemic Grasses in Minas Gerais, Brazil

Ascari

Cazón

Rahnama

et al. 2023

Preprint

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Wheat blast, caused byPyricularia oryzaeTriticum (PoT), is an emergent threat to wheat production. Current understanding of the evolution and population biology of the pathogen and epidemiology of the disease has been based on phylogenomic studies that compared the wheat blast pathogen with isolates collected from grasses that were invasive to Brazilian wheat fields. Genetic similarity between isolates from wheat and grasses lead to the conclusion that significant cross-infection occurs, especially on signalgrass (Urochloaspp.); and this in turn prompted speculation that its widespread use as forage is a key driver of the disease epidemiology. We re-analyzed data from those studies and found that all but one of the isolates from non-wheat hosts were members of PoT and the relatedLolium-adapted lineage (PoL1), which meant that thePyriculariapopulations typically found on endemic grasses had not yet been sampled. To address this shortcoming, we performed a comprehensive sampling of blast lesions in wheat crops and endemic grasses found in and away from wheat fields in Minas Gerais. A total 1,368 diseased samples were collected (976 leaves of wheat and grasses and 392 wheat heads) which yielded a working collection of 564Pyriculariaisolates. We show that, contrary to earlier implications, PoT was rarely found on endemic grasses and, conversely, members of grass-adapted populations were rarely found on wheat. Instead, most populations were host-specialized with constituent isolates usually grouping according to their host-of-origin. With regard to the dominant role proposed for signalgrass in wheat blast epidemiology, we found only one PoT member in 67 isolates collected from signalgrass grown away from wheat fields, and only three members ofUrochloa-adapted populations among hundreds of isolates from wheat. Cross-inoculation assays on wheat and a signalgrass used in pastures (U. brizantha) suggested that the limited cross-infection observed in the field may be due to innate compatibility differences. Whether or not the observed level of cross-infection would be sufficient to provide an inoculum reservoir, or serve as a bridge between wheat growing regions, is questionable and, therefore, deserves further investigation.

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Section: Discussionsupporting

confidence: 76%

PyriculariaPopulations are Mostly Host-Specialized with Limited Reciprocal Cross-Infection Between Wheat and Endemic Grasses in Minas Gerais, Brazil

Ascari

Cazón

Rahnama

et al. 2023

Preprint

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“…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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“…Brachiaria) have received greater attention regarding their possible interference in the wheat blast cycle because they are widely disseminated forages in the Brazilian agricultural system (CASTROAGUDÍN Ciência Rural, v.53, n.4, 2023. Maciel et al et al, 2016;REGES et al, 2016;REGES et al, 2019). An estimate made in 2012 indicated that the participation of species of the genus Urochloa as cultivated pasture in Brazil was 70% of a total area of about 117 million hectares (ZIMMER et al, 2012).…”

mentioning

confidence: 99%

Occurrence of Pyricularia oryzae Triticum in plants of the genus Urochloa in Brazil

et al. 2023

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In this study Pyricularia spp., P. oryzae and the P. oryzae pathotype Triticum (PoT) were detected and identified in leaf segments of forage and invasive grasses located in or next to wheat fields. In 2018 and 2019, 66 samples of lesion leaf segments of Urochloa and other grasses were collected in Londrina (PR), Patos de Minas (MG), and Uberaba (MG). The detection and/or identification of the pathogens on the samples was conducted using moist chamber procedures and with the primers MoT3 and Pot2 by PCR. There were DNA amplification with the primer MoT3 (specific for PoT) for 13 (19.69%) of the samples, all of them from Urochloa. The finding that Urochloa hosts PoT at a relatively high rate raises concerns about the importance which these plants may have on the wheat blast cycle as an alternative host for the pathogen and/or source of inoculum for the disease.

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Teste de patogenicidade dos isolados de Pyricularia oryzae nos hospedeiros de trigo, cevada, arroz e braquiária

Cited by 5 publications

References 8 publications

PyriculariaPopulations are Mostly Host-Specialized with Limited Reciprocal Cross-Infection Between Wheat and Endemic Grasses in Minas Gerais, Brazil

PyriculariaPopulations are Mostly Host-Specialized with Limited Reciprocal Cross-Infection Between Wheat and Endemic Grasses in Minas Gerais, Brazil

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

Occurrence of Pyricularia oryzae Triticum in plants of the genus Urochloa in Brazil

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