Fitopatologia - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741
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Item Rice grain resistance to brown spot and yield are increased by silicon(Tropical Plant Pathology, 2014-01) Rodrigues, Fabricio A.; Dallagnol, Leandro J.; Mielli, Mateus V. B.; Ma, Jian F.Brown spot, caused by Bipolaris oryzae, is one of the most important diseases of rice and can cause a reduction in yield and grain quality. The effect of silicon (Si) on the resistance of rice grains to brown spot was investigated. Plants from cv. Oochikara and its mutant, defective in the Lsi1 transporter (lsi1 mutant), were grown in hydroponic culture either with Si (+Si; 2 mM) or without Si (-Si). Panicle inoculation with B. oryzae was carried out at the beginning of the milk-grain stage. Panicles were harvested at physiological grain maturity. The supply of Si significantly increased Si concentration in husks compared to -Si plants. Si concentration in husks from cv. Oochikara was up to three times greater than the lsi1 mutant. In the presence of Si, brown spot severity was reduced by 88% in grains from cv. Oochikara and by 53% in grains from lsi1 mutant. Brown spot severity was 77% lower for grains of cv. Oochikara than for the lsi1 mutant, both plant types were grown in the presence of Si. Panicle inoculation reduced significantly the following yield components: number of grains per panicle, the weight of 1000 grains and the percentage of filled grains. Si significantly increased these yield components, especially for inoculated panicles. Considering kernel quality, the panicle inoculation with B. oryzae significantly reduced the yield of husked kernel, yield of whole kernel and kernel diameter, especially for grains from -Si plants. For panicles from +Si plants, the kernel quality was improved under inoculation, compared to -Si plants. Results from this study show that Si improved rice yield and kernel quality in panicles inoculated with B. oryzae. Furthermore the functional Lsi1 gene contributed significantly for increasing the yield of whole kernel and kernel diameter, possibly due to the increasing Si concentration in husks.Item Regional and varietal differences in prevalence and incidence levels of Bipolaris species in Brazilian rice seedlots(Tropical Plant Pathology, 2014-09) Del Ponte, Emerson Medeiros; Funck, Gustavo Daltrozzo; Deibler, Alexandre Nunes; Schwanck, André Aguiar; Caniela, Ana Rita de Almeida; Farias, Cândida Renata Jacobsen de; Meneses, Priscila RossattoA total of 722 rice seed lots were collected at six production regions of Rio Grande do Sul state during three consecutive seasons (2009/10 to 2011/12). For each seed lot, 200 seeds were assessed for the presence of Bipolaris spp. using a standard seed health blotter test. Results showed that B. oryzae and B. cynodontis were found in 62.5% and 10.4% of the seed lots, respectively. Overall mean incidence of B. oryzae and B. cynodontis were 0.5% and 0.06%, respectively. For the two most sampled varieties (75% of the seed lots), IRGA 424 and Puitá INTA CL, mean incidence levels were highest and lowest, respectively. Among regions, infection risk was highest in the southeastern and lowest in the western regions of the state, especially the Fronteira Oeste. The prevalence and the incidence levels of Bipolaris oryzae reported in this study were lower than previous reports in the same region - eighty percent of the seed lots showed incidence levels below the recommended 5% inoculum threshold. In conclusion, rice seeds produced by IRGA-certified growers showed an overall good health quality with regards to B. oryzae infection, which is the main Bipolaris species associated with rice seeds in southern Brazil.Item Efeito da aplicação de silicato de cálcio e de cinza de casca de arroz sobre a incidência de fungos associados a manchas em sementes de arroz irrigado(Summa Phytopathologica, 2016-01) Roma-Almeida, Rafaela Carolina Constantino; Pereira, Olinto Liparini; Dias, Denise Cunha Fernandes dos Santos; Rodrigue, Fabrício Ávila; Prabhu, Anne Sitarama; Filippi, Marta Cristina Corsi de; Duarte, Henrique da Silva SilveiraO objetivo deste trabalho foi avaliar o efeito da aplicação de silicato de cálcio e de cinza de casca de arroz (CCA) na incidência de fungos associados a manchas em sementes de arroz irrigado. Plantas de arroz foram submetidas à aplicação de silicato de cálcio ou CCA nas doses de 0, 51, 153, 256 e 357 kg ha-1de silício (Si). Dois experimentos foram conduzidos, sendo um na safra 2007/2008 e outro na safra 2008/2009 e, posteriormente, amostras de sementes foram analisadas em laboratório. Foram realizadas avaliações do Índice de Escurecimento de Sementes (IES), da concentração de Si no pericarpo das sementes e a determinação da diversidade dos fungos presentes nas sementes. Não houve efeito das duas fontes de Si empregadas, nas doses utilizadas nos dois experimentos no IES e na concentração de Si. Os fungos fitopatogênicos encontrados em ambos experimentos foram Alternaria padwickiii, Bipolarisoryzae, Botrytis cinerea, Curvularia lunata, Fusarium semitectum, F. solani, Microdochium oryzae, Nigrospora oryzae, Phoma sorghina e Pyriculariaoryzae. A incidência destes fungos não foi afetada pela aplicação das fontes de Si nas doses utilizadas.Item Bipolaris oryzae seed borne inoculum and brown spot epidemics in the subtropical lowland rice-growing region of Brazil(European Journal of Plant Pathology, 2015-04-17) Del Ponte, Emerson M.; Schwanck, André A.; Meneses, Priscila R.; Farias, Cândida R. J.; Funck, Gustavo R. D.; Maia, Aline H. N.The effect of increasing seed borne incidence levels (0, 3, 6, 12, 24 and 48 %) of Bipolaris oryzae on brown spot epidemics and crop performance was studied in eleven field trials. These trials were conducted at two sites (Bagé – BA and Cachoeirinha – CA) in the major rice-growing region of Brazil over three seasons (2008 to 2010). Disease variables assessed over time were disease incidence (INC, %) on leaves prior to flowering, and disease severity (SEV, %) on flag leaves after flowering. Kernel infection (KI, %) by B. oryzae was assessed after harvest. Crop-related variables such as plant population density (PD) and yield (YLD) were also assessed. In only three trials, all in the 2009/10 season, which had well above-normal rainfall in the early season, was the disease found at vegetative stages. In those same trials, a significant effect of seed borne inoculum was found for the area under the disease progress curve of INC and SEV. Overall mean SEV at CA (1.67 %) was higher than at BA (0.22 %). Seed borne inoculum levels did not affect final SEV and KI, which was not correlated between each other. PD was significantly reduced with the increase of seed borne inoculum levels in seven out of eight trials and at levels as high as 48 % (2009/10 season). The seed borne inoculum levels did not affect YLD, although significantly reducing PD, which may be due to the rice having a low population compensated through tillering. The risk of yield loss by sowing B. oryzae-infected seeds seems to be low and the early onset of the disease caused by increased levels of seed borne inoculum was dependent on seasonal weather conditions.Item Photosynthesis and sugar concentration are impaired by the defective active silicon uptake in rice plants infected with Bipolaris oryzae(Plant Pathology, 2012-03-15) Dallagnol, L. J.; Rodrigues, F. A.; Chaves, A. R. M.; Vale, F. X. R.; DaMatta, F. M.The effect of soluble silicon (Si) on photosynthetic parameters and soluble sugar concentrations was determined in leaves of rice cv. Oochikara and mutant plants of Oochikara defective in active Si uptake [low silicon 1 (lsi1)]. Plants were grown in hydroponic culture amended with 0 (−Si) or 2 mm Si (+Si), under either low or high photon flux density (PFD) and with or without inoculation with Bipolaris oryzae, the causal agent of brown spot of rice. Leaf Si concentration increased by 141 and 435% in +Si cv. Oochikara and by 119 and 251% in +Si lsi1 mutant plants under high and low PFD, respectively, compared with −Si plants. Plant biomass accumulation was improved by Si regardless of PFD, especially plants for cv. Oochikara. Brown spot severity was highest in −Si plants for cv. Oochikara and lsi1 mutant plants under low PFD. In the presence of Si, disease severity in plants grown under both low and high PFD was reduced, except for lsi1 mutant plants under high PFD. Plant inoculation reduced the photosynthetic parameters measured regardless of plant material or Si supply. A decrease of net carbon assimilation rate (A) of inoculated plants under low PFD compared with non‐inoculated plants was associated with damage in the photosynthetic apparatus, except for +Si cv. Oochikara in which stomatal restriction [low water vapour conductance (gs)] contributed to A reduction. Under high PFD, damage to the photosynthetic apparatus of inoculated plants was the main reason for the reduction in A for +Si and −Si lsi1 mutant plants. In addition, for −Si cv. Oochikara, a reduction in gs contributed to reduced A. However, for +Si cv. Oochikara, gs was the limiting factor for A. Inoculated plants of +Si cv. Oochikara had higher A values than +Si lsi1 mutant plants, regardless of environmental conditions. Soluble sugars were not detected in leaf tissues of plants under low PFD. For high PFD, Si improved the hexose concentration in non‐inoculated plants at 144 h after inoculation (hai) for lsi1 mutant plants and from 96 hai onwards for cv. Oochikara compared with −Si plants. However, plant inoculation reduced hexose concentration compared with non‐inoculated plants, mainly in +Si plants, regardless of plant material. Sucrose concentration increased in leaves of cv. Oochikara in the presence of Si whether inoculated or not. For +Si lsi1 mutant plants, sucrose concentration increased only at 48 hai compared with −Si plants, whether inoculated or not. The results of this study show that a minimum Si concentration is needed in leaf tissues of rice plants to avoid the negative impact of B. oryzae infection on photosynthesis and sugar concentration. High leaf Si concentration resulted in an increased soluble sugar concentration and together, but in independent ways, soluble sugar and Si reduced brown spot severity of rice.Item Physiological changes promoted by a strobilurin fungicide in the rice-Bipolaris oryzae interaction(Pesticide Biochemistry and Physiology, 2015-12-18) Debona, D.; Nascimento, K.J.T.; Gomes, J.G.O.; Aucique-Perez, C.E.; Rodrigues, F.A.Strobilurins are among the most important fungicides that are used for plant disease control worldwide. In addition to their fungicide effect, strobilurins can also improve crop physiology. Nonetheless, the impact of azoxystrobin (Az), the main marketed strobilurin, on rice physiology is still unknown. Detailed gas exchange measurements and chlorophyll a fluorescence analysis were used to examine the Az effects on the photosynthetic performance of rice plants (cultivar Metica-1) either challenged or not with Bipolaris oryzae, the causal agent of brown spot. Az impaired carbon (C) fixation in the non-inoculated plants in a manner that was not related to photochemical or biochemical limitations, but rather to decreased stomatal conductance that limited the CO2 influx into the mesophyll cells. The photosynthesis of rice plants that were not sprayed with Az dramatically decreased upon B. oryzae infection, which was chiefly governed by photochemical and biochemical limitations. The energy surplus that was caused by limited C fixation in the rice plants that were treated with Az and inoculated with B. oryzae was thermally and effectively dissipated until 72 h after inoculation. In Az absence, however, this mechanism was not sufficient to prevent chronic photoinhibition to photosynthesis. The inoculated plants were not able to fully capture and exploit the collected light energy, but these constraints were greatly limited in the presence of Az. In conclusion, Az impaired the photosynthetic performance of non-infected plants by diffusive constraints, but prevented, to a greater extent, the damage to the photosynthetic apparatus during the infection process of B. oryzae.Item Silicon and manganese on rice resistance to blast(Bragantia, 2012-05-14) Cacique, Isaías Severino; Domiciano, Gisele Pereira; Rodrigues, Fabrício Ávila; Vale, Francisco Xavier Ribeiro doBlast, caused by the fungus Pyricularia oryzae, is the most important fungal disease of rice. The effect of silicon (Si) and manganese (Mn), and their interaction, on rice resistance to blast was investigated. Rice plants (cultivar "Metica 1") were grown in hydroponic solution with 0 or 2 mmol L-1 of Si and with 0.5, 2.5, and 10 mmol L-1 of Mn. Sixty-day-old plants were inoculated with a conidial suspension of P. oryzae and the incubation period (IP), the number of lesions (NL) per cm2 of leaf area, the lesion size (LS), and blast severity were evaluated. Blast severity was scored at 48, 72, 96, and 144 hours after inoculation and data were used to obtain the area under blast progress curve (AUBPC). Silicon concentration was significantly higher in leaf tissues of plants supplied with this element than on its absence, regardless of Mn rates. There was no significant difference in Si concentration among the Mn rates for both - Si and +Si treatments. The Mn concentration was significantly higher in the tissues of plants from the - Si treatment as compared to plants of the +Si treatment, but only at the rate of 10 mmol L-1 of Mn. There was a significant increase in Mn concentration as the rates of this micronutrient increased from 0.5 to 10 mmol L-1 regardless of the Si treatments. The IP significantly increased in the +Si treatment. The Mn rates had no effect on the IP regardless of the Si treatments. The NL was significantly lower in the presence of Si regardless of the Mn rates. The Mn rates had no effect on NL regardless of the Si treatments. The addition of Si to the nutrient solution significantly reduced both LS and AUBPC regardless of Mn rates. However, in the absence of Si, the values for LS and AUBPC were significantly lower at the Mn rate of 10 µmol L-1 as compared to the rate of 0.5 µmol L-1. Overall, the results from this study showed the potential of Si to decrease blast development on rice regardless of the foliar concentration of Mn.Item Eficiência de diferentes moléculas na redução dos sintomas da queima das bainhas em arroz e no crescimento de Rhizoctonia solani in vitro(Revista Ceres, 2013-02-21) Schurt, Daniel Augusto; Rodrigues, Fabrício Ávila; Souza, Naiara Fernandes Abreu; Reis, Ricardo DutraEste estudo verificou a eficiência da aplicação de diferentes moléculas em reduzir o comprimento relativo da lesão (CRL) da queima das bainhas em arroz. Plantas dos cultivares BR-Irga 409 e Labelle foram cultivadas em solução nutritiva e inoculadas com Rhizoctonia solani, no estádio de máximo perfilhamento. Às 24 horas antes da inoculação, as bainhas das plantas foram pulverizadas com soluções de silicato de potássio (SP), silicato de potássio + fósforo (SP+F), Acibenzolar-S-Metil (ASM), fungicida Carbendazim, quitosana desacetilada (QD), etileno (ET) e fosfito de potássio (FP). Plantas cujas bainhas foram pulverizadas com água destilada serviram como testemunhas. O efeito das moléculas contidas nesses produtos no crescimento micelial de R. solani foi testado in vitro. Para BR-Irga 409, o CRL foi menor com a aplicação do FP, em relação aos demais tratamentos, exceto o Carbendazim. A aplicação do Carbendazim reduziu em 86,1% o CRL, em relação à testemunha. O CRL foi significativamente menor no cultivar BR-Irga 409 do que no 'Labelle', com aplicação do FP. O crescimento micelial de R. solani foi reduzido apenas pelo FP e Carbendazim, em comparação com os demais tratamentos. Não houve diferença significativa entre os tratamentos testemunha, SP e SP+F para a concentração de Si nas bainhas das plantas dos dois cultivares.Item Microscopic aspects of silicon-mediated rice resistance to leaf scald(Biochemistry and Cell Biology, 2015-07-29) Araujo, Leonardo; Paschoalino, Rayane Silva; Rodrigues, Fabrício ÁvilaThis study investigated the effect of silicon (Si) on the potentiation of rice resistance against leaf scald at the microscopic level. Rice plants (‘Primavera’) were grown in a nutrient solution containing 0 (−Si) or 2 mM (+Si) Si. The foliar Si concentration of the +Si plants (3.6 dag/kg) increased in comparison with the −Si plants (0.3 dag/kg). An X-ray microanalysis revealed that the leaf tissue of +Si plants infected with Microdochium oryzae had higher peaks and deposition of insoluble Si than that of −Si plants. The high foliar Si concentration for the +Si plants reduced the expansion of leaf scald lesions. Scanning electron microscopy revealed that fungal hyphae and appressorium-like structures of M. oryzae were more abundant in the leaf surface of −Si plants relative to +Si plants. At both histopathological and ultrastructural levels, fungal hyphae grew abundantly into the leaf tissue of −Si plants. By contrast, rice cell walls were rarely degraded and fungal hyphae were often surrounded by amorphous granular material in the leaf tissue of +Si plants. Conidiophores emerged from stomata 36 h after fungal penetration, and conidia were noticed inside the leaf tissue of the −Si plants in great abundance. The collective results of the present study showed a high concentration and deposition of Si and a considerable deposition of phenolic-like compounds in the leaf tissue of +Si plants. These results indicate that the potentiation of the phenylpropanoid pathway in these plants supplied with Si was favorable for the increase in rice resistance to leaf scald.