ABSTRACT: The use of resistant wheat cultivars is a fundamental strategy to minimize the damages caused by blast, a disease caused by the fungus Pyricularia oryzae Triticum (PoT). The objetive of this stydy was to (a) evaluate the reaction to blast of Brazilian wheat cultivars and (b) determine whether there is correlation between severity of symptoms on wheat spikes and “sporulation rate of PoT conidia per gram of wheat spike rachis” (Rscon). Plants of 16 wheat cultivars were grown in greenhouse until flowering (Zadoks stage 65), when their spikes were inoculated with a suspension formed by mixing the conidia of three PoT isolates. The evaluated variables were blast severity on spikes at 5, 7 and 11 days after inoculation (dai) and Rscon. Rachis were evaluated individually to determine the Rscon. Correlation analyzes were carried out between blast severity means on spikes of cultivars at 5, 7 and 11 dai and Rscon. The cultivars TBIO Mestre, TBIO Aton, ORS 1401, ORS 1403, ORS Destak, ORS Feroz, and CD 116 stood out for being classified in the statistical groups with the highest resistance to blast for the four variables considered in the study. The correlation between blast severity on spikes at 5, 7 and 11 dai and Rscon is at most moderate.

RESUMO: A utilização de cultivares de trigo resistentes é estratégia fundamental para minimizar danos causados pela brusone, doença causada pelo fungo Pyricularia oryzae Triticum (PoT). O objetivo do estudo foi avaliar (a) a reação à brusone de cultivares brasileiras de trigo e (b) verificar a correlação entre a severidade dos sintomas na espiga e a “taxa de esporulação de conídios de PoT por g de ráquis de espigas de trigo” (Txcon). Plantas de 16 cultivares de trigo foram conduzidas em casa-de-vegetação até o florescimento (estádio 65 da escala de Zadoks), quando as espigas das mesmas foram submetidas à inoculação com uma suspensão formada pela mistura de conídios de três isolados de PoT. As variáveis avaliadas foram a severidade de brusone nas espigas aos cinco, sete e 11 dias após a inoculação (dai) e a Txcon. A Txcon foi determinada de forma individualizada para os ráquis. Foram realizadas análises de correlação entre as médias de severidade de brusone nas espigas das cultivares aos cinco, sete e 11 dai e a Txcon. As cultivares TBIO Mestre, TBIO Aton, ORS 1401, ORS 1403, ORS Destak, ORS Feroz e CD 116 se destacaram por terem sido classificadas nos grupos estatísticos de maior resistência à brusone para as quatro variáveis consideradas no estudo. A correlação entre a severidade de brusone nas espigas aos cinco, sete e 11 dai e Txcon é, no máximo, moderada.

The use of resistant wheat cultivars is a fundamental strategy to minimize the damages caused by blast, a disease caused by the fungus Pyricularia oryzae Triticum (PoT). The objective of this study was to evaluate (a) the reaction to blast of Brazilian wheat cultivars and (b) to determine whether there is correlation between severity of symptoms on wheat spikes and “sporulation rate of PoT conidia per gram of wheat spike rachis” (Rscon). Plants of 16 wheat cultivars were grown in greenhouse until flowering (Zadoks stage 65), when their spikes were inoculated with a suspension formed by mixing the conidia of three PoT isolates. The evaluated variables were blast severity on spikes at 5, 7 and 11 days after inoculation (dai) and Rscon. Rachis were evaluated individually to determine the Rscon. Correlation analyzes were carried out between blast severity means on spikes of cultivars at 5, 7 and 11 dai and the log of Rscon. The cultivars ORS Feroz, ORS Destak, CD 116, ORS 1403, ORS 1401, TBIO Aton and TBIO Mestre stood out for being classified in the statistical groups with the highest resistance to blast for the four variables considered in the study. The correlation between blast severity on spikes at 5, 7 and 11 dai and Rscon was not significant.

A utilização de cultivares de trigo resistentes é estratégia fundamental para minimizar danos causados pela brusone, doença causada pelo fungo Pyricularia oryzae Triticum (PoT). O objetivo do estudo foi avaliar (a) a reação à brusone de cultivares brasileiras de trigo e (b) verificar a correlação entre a severidade dos sintomas na espiga e a “taxa de esporulação de conídios de PoT em ráquis de espigas de trigo” (Txcon). Plantas de 16 cultivares de trigo foram conduzidas em casa-de-vegetação até o florescimento (estádio 65 da escala de Zadoks), quando as espigas das mesmas foram submetidas à inoculação com uma suspensão formada pela mistura de conídios de três isolados de PoT. As variáveis avaliadas foram a severidade de brusone nas espigas aos cinco, sete e 11 dias após a inoculação (dai) e a Txcon. A Txcon foi determinada de forma individualizada para os ráquis. Foram realizadas análises de correlação entre as médias de severidade de brusone nas espigas das cultivares aos cinco, sete e 11 dai e o log das Txcon. As cultivares ORS Feroz, ORS Destak, CD 116, ORS 1403, ORS 1401, TBIO Aton e TBIO Mestre se destacaram por terem sido classificadas nos grupos estatísticos de maior resistência à brusone para as quatro variáveis consideradas no estudo. Verificou-se a existência de correlação entre a severidade de brusone nas espigas aos 5, 7 e 11 dai e Txcon.

Pyricularia oryzae Triticum (PoT) is known to survive in wheat seeds and this condition favors its spread. There are, however, many gaps in knowledge regarding the damage caused by this pathogen in relation to the establishment and sanity of wheat seedlings. The objective of this study was to determine whether there is a correlation between incidence of PoT in wheat seeds and variables associated with the establishment and the sanity of the produced seedlings. Seven samples of wheat seeds naturally infected with the pathogen were used. The incidence of PoT in each of the seed samples was determined via the Blotter test, indicating a variation from 0 to 80.5%. The seeds of each sample were sown in 500 mL plastic pots containing autoclaved sand and the seedlings produced were evaluated in relation to the following aspects; emergency, height, lesions in different segments, mortality, abnormalities and transmissibility of symptoms. The study demonstrated that there is a correlation between incidence of PoT in wheat seeds and the following variables related to the seedlings produced; height at 7 days after sowing (DAS), incidence and severity of symptoms at 7, 14 and 21 DAS, and mortality at 14 and 21 DAS. The results confirmed that the establishment and sanity of wheat seedlings directly depend on incidence of PoT in the seeds.

Sabe-se que Pyricularia oryzae Triticum (PoT) sobrevive nas sementes de trigo e esta condição favorece sua disseminação. Há, porém, muitas lacunas no conhecimento relativo aos danos causados por este patógeno em relação ao estabelecimento e à sanidade das plântulas de trigo. O objetivo do trabalho foi verificar se existe correlação entre incidência de PoT em sementes de trigo e variáveis associadas ao estabelecimento e à sanidade das plântulas geradas. Foram utilizadas sete amostras de sementes de trigo naturalmente infectadas com o patógeno. A incidência de PoT em cada uma das amostras de sementes foi determinada via Blotter test indicando variação de 0 a 80,5%. As sementes de cada amostra foram semeadas em copos plásticos de 500 mL contendo areia autoclavada e as plântulas produzidas foram avaliadas em relação aos seguintes aspectos; emergência, altura, lesões em diferentes segmentos, mortalidade, anormalidades e transmissibilidade de sintomas. O estudo demonstrou que existe correlação entre a incidência de PoT em sementes de trigo e as seguintes variáveis relativas às plântulas produzidas; altura aos 7 dias após a semeadura (DAS), incidência e severidade de sintomas aos 7, 14 e 21 DAS, e mortalidade aos 14 e 21 DAS. Os resultados confirmaram que o estabelecimento e a sanidade das plântulas de trigo dependem diretamente da incidência de PoT nas sementes.

RESUMO: Neste estudo Pyricularia spp., P. oryzae e o patótipo Triticum (PoT) de P. oryzae foram detectados e identificados em segmentos foliares de forrageiras e gramíneas invasoras de lavouras de trigo. Em 2018 e 2019, foram coletadas 66 amostras de segmentos foliares lesionados de Urochloa e outras gramíneas em Londrina (PR), Patos de Minas (MG) e Uberaba (MG). A detecção e/ou identificação dos patógenos nas amostras foi realizada por meio de procedimentos de câmara úmida e com os iniciadores MoT3 e Pot2 por PCR. Houve amplificações de DNA com o primer MoT3 (específico para PoT) em 13 (19,69%) das amostras, todas provenientes da Urochloa. O resultado de que Urochloa hospeda PoT em uma taxa relativamente alta levanta preocupações sobre a importância que essas plantas podem ter no ciclo de brusone do trigo como hospedeiro intermediário para o patógeno e / ou fonte de inóculo para a doença.

ABSTRACT: 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.

Abstract The objective of this work was to evaluate the effect of the presence of 2NVS translocation on the inheritance of wheat resistance to head blast, in F2 segregating lines from two biparental crosses. The IPF 86766 and 'Santa Fe' genotypes were used as female parents (both 2NVS carriers), and 'BRS 404', as the common male parent (non 2NVS carrier). Using a mixture of three isolates of Pyricularia oryzae Triticum, wheat spikes and rachises were evaluated for bleaching severity at five (%BS_5dpi) and seven days post-inoculation (%BS_7dpi), as well as for the number of infection points (IPR) and pathogen sporulation (SPO). Chi-square analyses showed that segregation follows a 3:1 Mendelian hypothesis, with a major locus with a dominant allele: %BS_7dpi for IPF 86766 × 'BRS 404' and IPR for 'Santa Fe' x 'BRS 404'. Therefore, this is the first known study to show that the 2NVS translocation responsible for resistance to head blast is a major locus with a dominant allele. In a controlled environment, 'BRS 404' shows bleaching severity and SPO similar with those occurring on IPF 86766 and 'Santa Fe'.

Resumo O objetivo deste trabalho foi avaliar o efeito da presença da translocação 2NVS sobre a herança da resistência de trigo à brusone, em linhagens segregantes F2 de dois cruzamentos biparentais. Os genótipos IPF 86766 e 'Santa Fe' foram usados como genitores femininos (ambos portadores d a 2NVS), e 'BRS 404', como genitor masculino comum (não por tador da 2NVS ). A partir da mistura de três isolados de Pyricularia oryzae Triticum, espigas e ráquis de trigo foram avaliadas quanto à severidade de branqueamento aos cinco (%BS_5dpi) e aos 7 dias após inoculação (%BS_7dpi), bem como quanto ao número de pontos de infecção (IPR) e à esporulação do patógeno (SPO). Análises de qui-quadrado mostraram que a segregação segue a hipótese mendeliana 3:1, com um loco de efeito maior, com alelo dominante: %BS_7dpi para IPF 86766 × 'BRS 404' e IPR para 'Santa Fe' × 'BRS 404'. Portanto, este é o primeiro estudo conhecido a mostrar que a translocação 2NVS responsável pela resistência à brusone de trigo é um loco principal com um alelo dominante. Em condições controladas de ambiente, 'BRS 404' apresenta severidade de branqueamento e SPO similares às que ocorrem em IPF 86766 e 'Santa Fe'.

RESUMO Poucas fontes de resistência do trigo à Pyricualria oryzae B.C. Couch and L.M. Kohn em trigo são conhecidas, estando a principal ligada a uma translocação do segmento 2NS/2AS de Aegilops ventricosa, seguida por outros genes como Rmg8 e Rmg7 localizados nos cromossomas 2B (trigo hexaplóide) e 2A (trigo tetraplóide), respectivamente. É igualmente conhecido que este fungo apresenta especificidade de hospedeiro e uma grande variabilidade genética, pelo que o objectivo deste trabalho foi avaliar a resposta fenotípica do trigo com translocação 2NS/2AS, Rmg8 e Rmg7 para Pyricularia oryzae pathotype Triticum do Paraguai. Para este fim, as infecções foram avaliadas com isolados autóctones e foi observada uma reacção de resistência nos materiais com a translocação do segmento 2NS/2AS e uma reacção de susceptibilidade moderada à suscetível nos materiais com os genes Rmg8 e Rmg7, respectivamente.

ABSTRACT There are few known sources of resistance to Pyricularia oryzae B.C. Couch and L.M. Kohn in wheat, the major of which is linked to a translocation of the 2NS/2AS segment of Aegilops ventricosa, followed by other genes such as Rmg8 and Rmg7 located on chromosomes 2B (hexaploid wheat) and 2A (tetraploid wheat), respectively. The pathogen is also known to have host specificity and wide genetic variability; therefore, the objective of this study was to evaluate the phenotypic response of wheat carrying 2NS/2AS, Rmg8 and Rmg7 translocation to Pyricularia oryzae pathotype Triticum from Paraguay. The infections were evaluated with autochthonous isolates, indicating a resistance reaction for materials carrying translocation of the 2NS/2AS segment and a susceptibility reaction that was moderate to susceptible for materials with Rmg8 and Rmg7 genes, respectively.

RESUMEN Se conocen pocas fuentes de resistencia a Pyricualria oryzae B.C. Couch and L.M. Kohn en trigo. La mayor respuesta de resistencia esta vinculada a una translocación del segmento 2NS/2AS de Aegilops ventricosa, seguido de otros genes como Rmg8 y Rmg7 localizados en los cromosomas 2B (trigo hexaploide) y 2A (trigos tetraploide) respectivamente. Es conocido que este patógeno presenta especificidad por hospederos y una amplia variabilidad genética. Por ello, el objetivo de este trabajo fue evaluar la respuesta fenotipica de trigos con presencia de translocación 2NS/2AS o Rmg8 o Rmg7 a Pyricularia oryzae patotipo Triticum prevalente en Paraguay. Las evaluaciones de espigas con aislados autoctonos mostraron una reacción de resistencia en los materiales con la translocacion del segmento 2NS/2AS y una reaccion de susceptibilidad moderada a susceptibilidad en los materiales con el gen Rmg8 y Rmg7 respectivamente.

RESUMO: O primeiro relato da brusone do trigo no mundo foi no Brasil, em 1986. Desde então, tem-se realizado um esforço muito grande com vistas ao desenvolvimento de cultivares de trigo resistentes a esta doença, a qual é causada pelo fungo Pyricularia oryzae Triticum (PoT). O objetivo deste trabalho foi de (i) avaliar a resistência de genótipos de trigo à brusone e (ii) verificar a correlação entre severidade da doença em espigas e taxa de esporulação de PoT em ráquis de espigas. Plantas de 40 cultivares brasileiras de trigo crescidas em vasos, no estádio de florescimento (estádio 65 da escala de Zadoks), foram submetidas à inoculação com uma suspensão de conídios de um isolado de PoT representativo da principal variante do fungo encontrada no Brasil. A severidade de brusone nas espigas aos cinco e sete dias após a inoculação (dai) e a taxa de esporulação do fungo nas ráquis (conídios por g de ráquis) foram avaliadas. Oitenta por cento das cultivares que foram classificadas no grupo com menor taxa de esporulação também foram classificadas no grupo de maior resistência aos sete dai. Entretanto, os coeficientes de correlação da análise estabelecida entre as médias de severidade das cultivares aos cinco e sete dai e as médias da taxa de esporulação de PoT não foram significativos (r=0,2464 e r=0,2047, respectivamente). Os resultados obtidos representam a caracterização atualizada da reação à brusone de cultivares de trigo do Brasil e constituem-se em importante marco exploratório da avaliação da reação de genótipos de trigo baseado na taxa de esporulação de PoT em seus tecidos.

ABSTRACT: 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.

Abstract Wheat blast disease is responsible for severe production losses. The disease resistance associated with the 2NS/2AS translocation is effective, but its level can be variable. In this study, we evaluated the presence of 2NS/2AS translocation in 310 advanced breeding lines from six crosses (Caninde 2/Milan, Milan/Caninde 2, Maringa/Milan, Milan/Maringa, Ciano79/Milan and Milan/Ciano79), and also studied their wheat blast reaction in the field to three virulent pathogen strains (P13-009, P14-031 and P14-039) collected in Paraguay. Advanced lines of two crosses (Caninde 2/Milan and Milan/Caninde 2) yielded the highest number of blast-resistant entries without 2NS/2AS translocation. Earlier studies have shown Caninde 2 to be a moderately susceptible line, which in combination with Milan, is probably adding non-2NS/2AS type resistance to these crosses. Our result indicates that such a resistance is based on several additive factors derived from multiple sources, which need to be explored further and also used to develop more durable wheat blast-resistant germplasm in the future.

ABSTRACT Chitosan and its derivatives are natural compounds that have potential in agriculture with respect to controlling one of rice diseases; blast (Pyriculariaoryzae) of great importance worldwide. In general, this disease is controlled with synthetic fungicides belonging to the benzimidazole group; however, their use has generated adverse results to the environment together with the low sensitivity of the fungus to them. This article provides a review of published research on chitosan, its physicochemical characteristics, general information on P. oryzaefungus, the chitosan fungicidal action and its derivatives in research carried out in vitro and in situ on this fungus and the possible mechanisms of action of this compound.

RESUMEN El quitosano y sus derivados son compuestos naturales que tienen potencial en la agricultura con respecto a controlar una de las enfermedades del arroz; la piriculariosis (Pyricularia oryzae) de gran importancia a nivel mundial. En general, esta enfermedad se controla con fungicidas sintéticos pertenecientes al grupo de los benzimidazoles; sin embargo, su uso ha generado resultados adversos al medio ambiente aunado a la poca sensibilidad del hongo hacia ellos. En este artículo, se proporciona una revisión de investigaciones publicadas acerca del quitosano, sus características fisicoquímicas, generalidades del hongo P. oryzae, la acción fungicida del quitosano y sus derivados en investigaciones llevadas a cabo in vitro e in situ sobre este hongo y, en general, los posibles mecanismos de acción de este compuesto.

RESUMO As principais doenças fúngicas que acometem a cultura do arroz na região Sul do Brasil são a brusone e a mancha parda, responsáveis por perdas significativas de produtividade e qualidade de grãos. Com o objetivo de disponibilizar alternativas de controle químico para essas doenças, foram avaliados, durante três safras agrícolas, dez tratamentos fungicidas, aplicados nos estádios R2 (emborrachamento) e R4 (pleno florescimento). Para o controle da mancha parda, os tratamentos ciproconazol + picoxistrobina, epoxiconazol + cresoxim-metílico, tebuconazol + trifloxistrobina e triciclazol + tebuconazol foram os mais consistentes nos três anos avaliados. Para o controle da brusone, a mistura triciclazol + tebuconazol e o tratamento somente com triciclazol resultaram na menor incidência da doença, combinada com rendimento de grãos estatisticamente superior aos outros tratamentos. A mistura de triciclazol + tebuconazol apresentou a melhor combinação entre eficiência de controle de ambas as doenças e rendimento de grãos.

ABSTRACT The major fungal diseases affecting the rice crop in southern Brazil are blast and brown spot, responsible for significant yield and grain quality losses. With the aim of providing chemical control alternatives for these diseases, ten fungicide treatments were evaluated during three crop seasons through spraying in R2 (booting) and R4 (flowering) stages. For brown spot control, cyproconazole + picoxystrobin, epoxiconazole + kresoxim-methyl, tebuconazole + trifloxystrobin, and tricyclazole + tebuconazole were the most consistent treatments over the three evaluated years. For rice blast control, the mixture tricyclazole + tebuconazole, as well as tricyclazole alone, resulted in the lowest disease incidence and in statistically superior grain yield, compared to the remaining treatments. Tricyclazole + tebuconazole best combined efficient control of both diseases and grain yield.

ABSTRACT The objective of this study was to evaluate the virulence of Pyricularia oryzae isolates obtained from a single leaf blast lesion on wheat. The wheat cultivars (BRS Louro, BR 18, BRS Tarumã, BRS Parrudo, BRS 208) at the four-leaf stage were inoculated with a suspension of 100.000 conidia/mL. A significant difference was observed in the severity in the cultivars. Among the evaluated isolates, it was possible to observe differences in the susceptibility of the cultivars. Severity data ranged from 3.3 to 99.54% among treatments. Isolates 1 and 2 were the most aggressive for all cultivars tested. The greatest disease severity occurred in the interactions BRS 208 x isolate 1 (99.54%), BRS Louro x isolate 2 (99.34%), and BRS 208 x isolate 2 (99.09%).The lowest disease severity was observed in BRS Tarumã (68%) and BR 18 (75%) cultivars for the isolates 1 and 2, respectively. Isolate 3 presented medium aggressiveness in which the cultivars presented between 44 to 58% of wheat blast severity. The isolate 4 was the least aggressive for all cultivars with severity indexes ranging from 3 to 12%. These data indicate the existence of virulence diversity in P. oryzae isolates obtained from a single lesion.

Abstract: Rice blast, caused by the fungus Pyricularia oryzae L., is considered one of the main threats to world rice production. The development of resistant cultivars is one of the best and sustainable control alternatives. Plant breeding efforts have been accelerated by genetic mapping (linkage and associative) and marker assisted selection. On the other hand, genomic editing techniques, such as meganucleases (MNs), Zinc-finger nucleases (ZFNs), Transcription Activator-like Effector Nucleases (TALENs) and Clustered Regularly Interspaced Short Palindrome Repeats/CRISPR-associated protein 9 (CRISPR/Cas9), can be used to promote specific genetic modifications. Likewise, transgenics can also be used to manipulate specific genes. In this sense, this work aims to characterize rice blast and elucidate available biotechnological alternatives to accelerate the development of improved rice cultivars resistant to rice blast.

RESUMO A brusone (Magnaporthe oryzae) limita a produção do arroz (Oryza sativa), no Brasil e no mundo. Os objetivos foram caracterizar seis isolados bacterianos morfológica, bioquímica e molecularmente, e determinar seu potencial como antagonistas a M. oryzae. Utilizaram se os isolados bacterianos BRM 32109, BRM 32110, BRM 32111, BRM 32112, BRM 32113 e BRM 32114. Avaliou-se o formato e a cor das colônias, coloração de Gram e produção de pigmentos fluorescentes. Identificou-se a produção de celulase, quitinase, fosfatase, ácido indolacético, sideróforo e formação de biofilme. A identificação molecular foi realizada utilizando-se oligonucleotídeos iniciadores específicos para amplificação por PCR da região 16S rRNA, seguidos de sequenciamento. Os dois ensaios envolvendo antagonismo foram realizados em laboratório, em delineamento inteiramente casualizados, um com cultivo pareado entre isolado de bactérias e M. oryzae, e outro com filtrados bacterianos. Um terceiro ensaio em casa de vegetação para avaliar a supressão da brusone. Identificou-se Pseudomonas sp. (BRM 32111 e BRM 32112), Burkholderia sp. (BRM 32113), Serratia sp. (BRM 32114) e Bacillus spp. (BRM 32110 e BRM 32109 ). Os isolados BRM 32112, BRM 32111 e BRM 32113 inibiram o crescimento da colônia de M. oryzae em 68, 65 e 48%, respectivamente. As suspensões bacterianas BRM 32111, BRM 32112 e seu filtrado suprimiram a brusone foliar em 81,0, 79,2 e 66,3%, respectivamente. BRM 32111 e BRM 32112 são antagonistas ao fungo M. oryzae, solubilizam fosfato, produzem sideróforos, celulase e biofilme e suprimiram a brusone foliar, mostrando-se potenciais agentes biológicos para o controle da brusone foliar.

ABSTRACT Rice blast (Magnaporthe oryzae) limits rice (Oryza sativa) grain yields worldwide. The objective of this investigation was to morphologically, biochemically, and molecularly characterize six bacterial isolates, BRM 32109, BRM 32110, BRM 32111, BRM 32112, BRM 32113, and BRM 32114, and to determine their potential as antagonists to M. oryzae. Morphological characterization was based on colony formation and color, Gram staining, and fluorescent pigment production. Biochemical studies were based on cellulase, chitinase, phosphatase, indoleacetic acid, and siderophore production, as well as biofilm formation. The molecular identification used specific primers for PCR amplification of the 16S rRNA region, followed by sequencing. The antagonism studies involved three experiments, which had randomized designs. Two of them were conducted in laboratory conditions, pairing bacterial colonies and M. oryzae, using bacterial filtrates, and the third was conducted in greenhouse conditions. BRM 32111 and BRM 32112 were identified as Pseudomonas sp., BRM 32113 as Burkholderia sp., BRM 32114 as Serratia sp., and BRM 32110 and BRM 32109 as Bacillus spp. BRM 32112, BRM 32111, and BRM 32113 inhibited the colony of M. oryzae by 68%, 65%, and 48%, respectively. The bacterial suspensions of the BRM 32111, BRM 32112, and BRM 3212 filtrates suppressed leaf blast by 81.0, 79.2, and 66.3%, respectively. BRM 32111 and BRM 32112 were determined to be antagonists of M. oryzae and were found to solubilize phosphate, produce siderophores and cellulose, form biofilms, and suppress leaf blast. These isolates should be further investigated as potential biological control agents for leaf blast control.

RESUMO A brusone do trigo, causada pelo fungo Magnaporthe oryzae, está entre os fatores que apresenta maior risco na produção de trigo, pois os danos podem ser superiores a 90% em safras com condições ambientais favoráveis ao desenvolvimento da doença. O objetivo do trabalho foi avaliar o efeito de sulfato de zinco sobre a severidade de M. oryzae em folhas de trigo, a produção de peróxido de hidrogênio e de morte celular da planta. Avaliou-se a severidade da doença em função da aplicação foliar de Zn (0; 0,4; 0,8; 1,2 e 1,6% de sulfato de zinco) em diferentes cultivares de trigo (Mirante, Safira, Madre Pérola e Ônix). Além disso, com objetivo de verificar qual possível componente histológico está envolvido na redução da severidade da brusone, realizou-se um experimento com aplicação de sulfato de zinco a 0,4% na 3ª folha e sem aplicação (água destilada) na cultivar de trigo Safira, que é suscetível a essa doença. Três dias após a aplicação de ZnSO4, as plantas foram inoculadas com suspensão de 104 conídios.mL-1 de M. oryzae e mantidas em câmara úmida durante 24 h, procedendo-se a coleta das folhas às 18; 24; 30; 36; 48 e 72 horas após a inoculação (hai). As folhas foram fragmentadas e clareadas a fim de avaliações histopatológicas, para as respostas de produção de peróxido de hidrogênio e morte celular, durante a infecção de trigo por M. oryzae. Houve redução de severidade da brusone quando aplicado zinco em diferentes concentrações nas cultivares, com exceção da cultivar Ônix. O zinco 0,4% não teve efeito nos eventos de infecção, com exceção de morte celular 48 hai. Cultivar de trigo e concentrações de sulfato de zinco influenciam na eficiência da redução da severidade da doença.

ABSTRACT Wheat blast, caused by the fungus Magnaporthe oryzae, is among the factors of highest risk for wheat production because losses can be greater than 90% in crop seasons with favorable environmental conditions to the development of this disease. The objective of this study was to evaluate the effect of zinc sulfate on M. oryzae infection in wheat leaves, as well as hydrogen peroxide production and cell death in the plant. The disease severity was evaluated as a function of foliar application of Zn (0, 0.4%, 0.8%, 1.2% and 1.6% zinc sulfate) in four different wheat cultivars (‘Mirante’, ‘Safira’, ‘Madre Pérola’ and ‘Ônix’). In addition, with the aim of verifying which histological component is possibly involved in reducing blast severity, an experiment was carried out with application of 0.4% zinc sulfate onto the 3rd leaf and without application (distilled water) in the cultivar ‘Safira’, which is susceptible to this disease. Three days after ZnSO4 application, the plants were inoculated with 104 conidia.mL-1 suspension of M. oryzae and kept in a humid chamber during 24 h; leaves were collected at 18, 24, 30, 36, 48 and 72 hours after inoculation (hai). The leaves were fragmented and bleached for histopathological evaluations of the responses of hydrogen peroxide production and cell death during wheat infection by M. oryzae. Wheat blast severity reduced when zinc was applied at different concentrations in all cultivars, except ‘Onyx’. Zinc at 0.4% had no effect on infection events, except for cell death at 48 hai. The wheat cultivar and the zinc sulfate concentrations influenced the disease severity reduction efficiency.

ABSTRACT Endophytic fungi, in addition to improving plant development, may produce antimicrobial substances that can inhibit pathogens. The objective of this study was to isolate and characterize endophytic fungi of Bambusa oldhamii and evaluate in vitro antagonism to Pyricularia oryzae. Fungal isolates of B. oldhamii shoots were purified and identified by nuclear ribosomal DNA (nrDNA) including internal transcribed spacer regions (ITS1 and ITS4). These isolates were then confirmed by phylogenetic analysis of the ITS1 and ITS2 sequences and morphological analysis. The isolates were evaluated in in vitro experiments of direct and indirect antagonism (volatile production). Five fungal isolates were identified and named as follows: isolate 27 (Arthrinium sp.); isolate 29 (Acrocalymma sp.); isolate 122 (Botryobambusa fusicoccum); isolate 711 (Phoma sp.) and isolate 712 (Phoma sp.). We found that the area of the P. oryzae colony was reduced by more than 80% by all endophytic isolates in this study, with emphasis on isolate 122, with a 96% reduction in area of the P. oryzae. These results were considered promising and will serve as a foundation for future studies on induction of resistance to P. oryzae.