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Pyricularia graminis-tritici. a – j. Cultures of isolate 12.1.037 grown for 7 d at 12 h photoperiod and 25 °C in CMA (a, f), MEA (b, g), OA (c, h), PDA (d, i), and SNA (e, j) media; k – l. sporulation on SNA on sterile barley seeds; m – o. scanning electron micrographs of conidiophores and conidia; p – x. bright field microscopy images of conidiophores and conidia. — Scale bars = 10 µm.
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Pyricularia oryzae is a species complex that causes blast disease on more than 50 species of poaceous plants. Pyricularia oryzae has a worldwide distribution as a rice pathogen and in the last 30 years emerged as an important wheat pathogen in southern Brazil. We conducted phylogenetic analyses using 10 housekeeping loci for 128 isolates of P. oryz...
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Context 1
... general, similar colony morphologies were observed for iso- lates of Pgt, PoT, and PoO on the five media tested. No mor- phological differences were observed among the Pyricularia species. Cultural and morphological characteristics observed for Pyricularia graminis-tritici and Pyricularia oryzae patho- types Triticum and Oryza (Fig. 6-8, a-j) are described in the Taxonomy ...
Citations
... Conversely, the cultivation of susceptible forage grass species to wheat blast in adjacent or connected areas to wheat cultivation, especially Brachiaria grass, negates the effect of crop rotation as it represents a continuous source of inoculum for phytopathogens like PoTl, Pp, and Pu (CERESINI et al., 2018). Consequently, there may be recurrent annual disease epidemics and a consequent increase in economic losses associated with the high incidence of wheat blast (CASTROAGUDÍN et al., 2016). ...
... Collections from infected plants to obtain isolates were conducted during the years 2012 and 2013 using the transect system. Pyricularia isolates were previously identified based on sequencing of two to 10 nuclear genes (CASTROAGUDÍN et al., 2016;REGES et al., 2016). Particularly, isolates of P. oryzae Triticum lineage belonging to different races or virulence groups were genotyped with eleven distinct microsatellite loci (CASTROAGUDÍN et al., 2015;PEREIRA et al., 2022) and phenotyped based on the varietal reaction of 10 wheat cultivars (DANELLI, 2015). ...
Fungi of the genus Pyricularia have a wide range of host plants and are capable of infecting more than 50 species of grasses, causing the blast disease, with damage to the ears. Species of the forage signal grass (Urochloa spp.) can be hosts of this genus of fungus and can be an important source of inoculum of the pathogen for other agricultural crops affected by blast, especially wheat. The objective of this study was to determine the reaction of nine cultivars of Urochloa to the pathogens Pyricularia oryzae Triticum lineage (PoTl), P. pennisetigena, P. urashimae, and P. grisea. The virulence of seven races of PoTl to signal grass cultivars was also evaluated. There was variation in the pathogenicity and virulence of Pyricularia species and PoTl races in different signal grass cultivars. The cultivars Ipyporã, BRS Tupi, and Xaraés were the most resistant to the different blast pathogen species and PoTl races. Therefore, it is recommended to cultivate these varieties in areas adjacent to wheat or in crop-livestock integration.
Keywords
Pyricularia grisea; Pyricularia pennisetigena; Pyricularia oryzae Triticum lineage; Pyricularia urashimae; Varietal resistance.
... To exacerbate the situation, PoTl has a broad host range, encompassing other poaceous hosts that grow in close proximity to wheat fields. These hosts may serve as significant reservoirs of inoculum during the initial stages of a wheat blast epidemic, complicating disease management (Castroagudin et al., 2015(Castroagudin et al., , 2016Dorigan et al., 2019). Furthermore, multiple Pyricularia species, including P. pennisetigena and P. urashimae associated with other poaceous hosts, can also cause blast disease on the heads of adult wheat plants (Dorigan et al., 2023). ...
Wheat blast, caused by Pyricularia oryzae Triticum lineage (PoTl), can infect wheat leaves and heads. More information is needed on the pathogen biology and disease epidemiology of the isolate PoTl for the integrated management of wheat blast in Brazilian wheat fields. This study aimed to characterize the incubation period, latent period, and the temporal progress of wheat blast and to fit nonlinear models, describing the nature of an epidemic of the PoTl isolate 12.1.146 compared with the PoTl isolate Py6038, throughout five successive infection cycles of PoTl on wheat leaves and heads. Wheat blast occurred in all infection cycles. The incubation period and latent period of the PoTl isolate 12.1.146 were significantly shorter than that of the PoTl isolate Py6038. The secondary inocula produced by the PoTl isolate on symptomatic wheat leaves caused blast symptoms when inoculated on wheat heads. The area under the disease progress curve (AUDPC) was calculated based on disease severity. In all infection cycles, the AUDPC of the PoTl isolate 12.1.146 was significantly higher than that of the PoTl isolate Py6038. Between the 1st and 5th infection cycle, a significant reduction was observed in the AUDPC of the PoTl isolates. The nonlinear logistic model describe the disease progress curves (DPCs) of PoTl isolates on wheat leaves and heads best. Our findings indicate that the PoTl isolates did not maintain the same temporal dynamics after five successive infection cycles. These findings may have implications for the integrated management of the wheat blast pathogen in Brazilian fields.
... The colony appearance described in the present study was in accordance with studies by Al Noman et al. (2021) and Hussin et al. (2020). Moreover, the colony growth of all P. oryzae isolates grown on PDA plates was 4.87 ± 0.02 cm on day 7, which was in line with the findings by Al Noman et al. (2021) and Castroagudín et al. (2016) that stated P. oryzae can grow in a range of 4.3 cm and reach up to 8.4 cm on day 14. ...
... The conidial shape of Pyriculariaceae varies greatly depending on the host (Longya et al., 2020). The conidial features in this study showed similarities with Al Noman et al. (2021), Castroagudín et al. (2016) and Klaubauf et al. (2014). These studies stated pyriform shaped conidia reported as P. oryzae with the conidial size in the range of 17-28 µm × 6-8 µm. ...
Aims: Rice (Oryza sativa) is one of Malaysia’s most significant crops. Rice blast caused by Pyricularia oryzae is one of the most serious diseases of Oryza sativa, causing significant damage to the Malaysian rice crop and impacting productivity. This study was carried out to isolate and characterize phytopathogenic fungal isolates associated with rice blast collected in a paddy field in Alor Setar, Kedah, Malaysia.
Methodology and results: Morphological characterization of seven fungal isolates obtained showed thin, white, and grayish green mycelia and the reverse colony was light yellow to brown. The fungal isolates produced two-septate pyriform (pear-shaped) conidia with solitary, unbranched and light brown conidiophores. Pathogenicity tests of all isolates on rice leaves revealed diamond-shaped symptoms with a grayish center and brown edge. All isolates showed similar morphological and pathogenicity characteristics; thus, a representative isolate was further identified through DNA sequencing and phylogenetic analysis of the internal transcribed spacer (ITS) region for species confirmation. Based on DNA sequences of ITS and phylogenetic analysis, the representative isolate was confirmed as P. oryzae.
Conclusion, significance and impact of study: Seven isolates morphologically identified as Pyricularia sp. were tested as pathogenic by causing rice blast disease. Representative isolate P2 (USM-PD1) was confirmed to be P. oryzae by DNA sequencing and phylogenetic analysis of the ITS region. This study provides information on the etiology and symptomatology of rice blast disease caused by P. oryzae USM-PD1 that can be applied to diagnose and mitigate the threat posed by this plant pathogen for the disease management.
... We also identified a Brazilian strain, 12.1.181, collected in 2012 (Castroagud ın et al., 2016), in the same phylogenetic clade as B71 and isolates from Bangladesh and Zambia (Fig. 2a). Here, the clade is referred to as the B71 branch. ...
The fungal pathogen, Magnaporthe oryzae Triticum pathotype, causing wheat blast disease was first identified in South America and recently spread across continents to South Asia and Africa. Here, we studied the genetic relationship among isolates found on the three continents.
Magnaporthe oryzae strains closely related to a South American field isolate B71 were found to have caused the wheat blast outbreaks in South Asia and Africa. Genomic variation among isolates from the three continents was examined using an improved B71 reference genome and whole‐genome sequences.
We found strong evidence to support that the outbreaks in Bangladesh and Zambia were caused by the introductions of genetically separated isolates, although they were all close to B71 and, therefore, collectively referred to as the B71 branch. In addition, B71 branch strains carried at least one supernumerary mini‐chromosome. Genome assembly of a Zambian strain revealed that its mini‐chromosome was similar to the B71 mini‐chromosome but with a high level of structural variation.
Our findings show that while core genomes of the multiple introductions are highly similar, the mini‐chromosomes have undergone marked diversification. The maintenance of the mini‐chromosome and rapid genomic changes suggest the mini‐chromosomes may serve important virulence or niche adaptation roles under diverse environmental conditions.
... Not surprisingly, the e cacy of this spraying approach in managing wheat blast has rarely been higher than 60% (Ceresini et al., 2018b). To make the situation even worse, PoTl has a wide host range, including other poaceous hosts, which grow near wheat elds and may be an important reservoir or source of inoculum in the early phases of a wheat blast epidemic, hindering the management of the disease (Castroagudin et al., 2015, Castroagudin et al., 2016, Dorigan et al., 2019. Furthermore, multiple Pyricularia species, including P. pennisetigena and P. urashimae associated with other poaceous hosts, can also cause blast disease on the heads of adult wheat plants (Dorigan et al., 2023). ...
Wheat blast, caused by Pyricularia oryzae Triticum lineage (PoTl), can infect wheat leaves and heads. The pathogen biology and disease epidemiology of the isolates PoTl still need more profound insights for the integrated management of wheat blast in Brazilian wheat fields. This study aimed to characterize the incubation period, latent period, and the temporal progress of wheat blast and to fit the best nonlinear model, describing the nature of an epidemic of the PoTl isolate 12.1.146 compared with the PoTl isolate Py6038, throughout five successive infection cycles of PoTl on wheat leaves and heads. Wheat blast occurred in all infection cycles. The incubation period and latent period of the PoTl isolate 12.1.146 were significantly shorter than that of the PoTl isolate Py6038. The secondary inocula produced by the PoTl isolates on symptomatic wheat leaves caused blast symptoms when inoculated on wheat heads. The area under the disease progress curve (AUDPC) was calculated based on disease severity. In all infection cycles, the AUDPC of the PoTl isolate 12.1.146 was significantly higher than that of the PoTl isolate Py6038. The nonlinear logistic model had the best fit to describe the intensity of the disease progress curves (DPCs) of PoTl isolates on wheat leaves and heads, fitting classic sigmoid-shaped curves. Our findings show that the disease severity of the PoTl isolate 12.1.146 did not reduce under grow chamber conditions, even after five successive infection cycles. These findings may imply the integrated management of the disease wheat blast pathogen in Brazilian fields.
... PoT can infect wheat plants from the vegetative growth stages to the head stage, but head blast is the most destructive symptom (Cruz et al., 2015;Cruz and Valent, 2017;Martínez et al., 2019;Castroagudin et al., 2016). The highest yield losses may occur when the fungal infection starts in the flowering heads or early grain formation (Goulart, 2005). ...
Pyricularia oryzae pathotype Triticum (PoT) causes wheat blast and is associated with other poaceous hosts. In addition, there are four pathogens of the genus Pyricularia found in or near wheat fields, P. oryzae patotype Lolium (PoL), P. grisea (Pg), P. pennisetigena (Pp), and P. urashimae (Pu). The pathogenicity and virulence levels of Pp and Pu on wheat heads are still unknown. The highest yield losses happen when blast pathogens infect wheat heads. In this study, 25 isolates of Pyricularia spp. were recovered from poaceous hosts invasive of commercial wheat fields previously treated with fungicides. Multilocus phylogenetic analyses (ACT-RPB1-CAL) was used for species delimitation. Nine isolates were identified as PoT, seven as Pp, three as Pg, three as PoL, and three as Pu. Isolates' ability to cause blast disease on the wheat head cv. Anahuac 75 was also evaluated. Wheat heads artificially inoculated with PoT, Pu and Pp showed higher severity values (8.84 to 17.60% of injured area) and differed significantly from Pg, which did not cause lesions on heads. Lesions caused by isolates of Pp and Pu were indistinguishable from those caused by PoT in the inoculation tests. We are reporting for the first time that Pp and Pu cause blast lesions on the head of adult wheat plants that are indistinguishable from those caused by PoT. Our findings show that multiple Pyricularia species can cause blast disease on heads of wheat adult plants under greenhouse conditions with indistinguishable symptoms.
... represented by one isolate, so its host-specialization status is unclear. 636 We also report P. maximum as a new host for P. urashimae (Pu), the type isolate of 637 which originally came from Urochloa brizantha (Crous et al. 2016). This seems to be quite a 638 specific interaction from P. maximum's perspective because 12/16 isolates from this grass were CC-BY-NC-ND 4.0 International license perpetuity. ...
Wheat blast, caused by Pyricularia oryzae Triticum (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 ( Urochloa spp.); 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 related Lolium -adapted lineage (PoL1), which meant that the Pyricularia populations 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 564 Pyricularia isolates. 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 of Urochloa -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.
... The occurrence of the wheat blast is more common in the tropic regions where the yield losses caused by this disease may reach 100% (MACIEL, 2018) and its presence is especially associated with wheat head blast (CRUZ & VALENT, 2017). The condition of P. oryzae with a wide range of hosts including forage and weeds plants (MACIEL et al., 2014;TOSA & CHUMA, 2014;CRUZ & VALENT, 2017) raises concerns about the role and importance that these hosts play in the wheat blast cycle, both as a source of primary inoculum and as part of the process of generating genetic variability in this species of fungus (CASTROAGUDÍN et al., 2016). ...
... In Brazil, plants of the genus Urochloa (syn. 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 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). ...
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.
... В 2018 г. заболевание обнаружено в Африке (Замбия) (Tembo et al., 2020). Все возбудители способны поражать другие злаки, кроме пшеницы (Castroagudin et al., 2016). ...
Fungal diseases of wheat are widely studied due to economic importance at global scale. Nevertheless, incorrect names of diseases and respective pathogen species, as well as inaccurate indication of their practical significance, is found in in the scientific literature. This may lead to confusion and misinterpretation of the phytosanitary situation. This review collects and structures the information about the main wheat diseases and pathogenic fungi causing them, as well as species emerging as a potential threat to wheat crops. The modern taxonomic status of the fungal species associated with different organs of wheat is given, their geographical distribution and the impact on the crop yield are characterized. Micromycetes are divided into three groups according to their phytosanitary significance. The first group is represented by fungi possessing great importance as pathogens causing the 25 main wheat diseases. The second group includes three diseases not found in Russia but significant for wheat production in other countries, thus posing potential risk for Russian grain farming. The third group consists of fungi causing 29 minor and poorly studied diseases with unverified harmfulness and controversial significance, for which the available data needs to be reviewed and confirmed. This dataset can be used as a reference for a more accurate and correct description of the phytosanitary situation. The review will also be helpful for more targeted studies using molecular methods to determine the area of fungi that cause wheat diseases, to track changes in their distribution boundaries and to clarify the harmfulness of poorly studied species.
... Despite a long history of research in blast diseases (most notably rice blast), the overall low level of sequence divergence between P. oryzae isolates (~1%) prevented significant progress in understanding its population structure until the development of hypervariable molecular markers (simple sequence repeats -SSRs), and next generation sequencing. Ceresini and coworkers were pioneers with these technologies and used SSRs (Maciel et al. 2014), multilocus sequencing (Castroagudín et al. 2016), and eventually whole genome sequencing (Ceresini et al. 2018 to characterize the wheat blast population. They showed that fungal isolates causing wheat blast are phylogenetically distinct from those found on rice, Digitaria, Eleusine, Setaria and other grasses, and renamed the population as a new species, Pyricularia graminis tritici (Pygt) to reflect this fact (Castroagudín et al. 2016;Ceresini et al. 2019). ...
... Ceresini and coworkers were pioneers with these technologies and used SSRs (Maciel et al. 2014), multilocus sequencing (Castroagudín et al. 2016), and eventually whole genome sequencing (Ceresini et al. 2018 to characterize the wheat blast population. They showed that fungal isolates causing wheat blast are phylogenetically distinct from those found on rice, Digitaria, Eleusine, Setaria and other grasses, and renamed the population as a new species, Pyricularia graminis tritici (Pygt) to reflect this fact (Castroagudín et al. 2016;Ceresini et al. 2019). More recently, however, evidence of gene flow (Gladieux et al. 2018) among other concerns (Valent et al. 2019), has raised this conclusion into doubt. ...
... Unfortunately, if one peruses the phylogenomic data that underpin the foregoing conclusions, and considers them in the light of data produced by the broader research community, major inconsistencies quickly appear with potentially far-reaching consequences for foundational knowledge on wheat blast. Ceresini and coworkers' earliest studies found that wheat blast isolates could be grouped in two main clades, with only one (Pygt) being clearly resolved from the rice blast pathogens (Castroagudín et al. 2016). Later, as genomic sequence data provided greater resolution, additional wheat blast isolates were brought under the Pygt umbrella, along with some of the isolates from grasses (Castroagudin et al. 2017;Ceresini et al. 2018Ceresini et al. , 2019. ...
Wheat blast, caused by the Triticum lineage of Pyricularia oryzae (PoT), is a serious disease that first emerged in Brazil and quickly spread to neighboring countries. The recent appearance of this disease in Bangladesh and Zambia highlights a need to understand the population biology and epidemiology of the disease so as to mitigate pandemic outbreaks. Current knowledge in these areas is largely based on analyses of wheat blast isolates collected in Brazil, and their comparison with isolates from non-wheat, endemic grasses. Those studies concluded that wheat blast is caused by a highly diverse P. oryzae population that lacks host specificity and, as a result, undergoes extensive gene flow with populations infecting non-wheat hosts. Additionally, based on genetic similarity between wheat blast and isolates infecting Urochloa species, it was proposed that the disease originally emerged via a host jump from this grass, and the widespread use of Urochloa as a pasture grass likely plays a central role in wheat blast epidemiology. Inconsistencies with earlier phylogenetic studies prompted us to re-analyze the Brazilian data in the context of a comprehensive, global, phylogenomic dataset. We now show that the seminal studies failed to sample the P. oryzae populations normally found on endemic grasses and, instead, repeatedly sampled PoT and P. oryzae Lolium (PoL) members that happened to be present in these hosts. The resulting lack of accurate and representative information about the grass-infecting populations in Brazil means that current conclusions about wheat blast evolution, population biology and epidemiology are unsubstantiated and could be equivocal.
