Fitopatologia - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741
Navegar
187 resultados
Resultados da Pesquisa
Item Evidence that the biocontrol agent Bacillus cereus synthesizes protein that can elicit increased resistance of tomato leaves to Corynespora cassiicola(Tropical Plant Pathology, 2010-01) Romeiro, Reginaldo S.; Lanna Filho, Roberto; Macagnan, Dirceu; Garcia, Flávio A. O.; Silva, Harllen S. A.Isolate UFV-101 of Bacillus cereus was selected in previous studies for promoting growth inducing resistance in plants. In a previous study, supernatant from cultures of the microorganism in a liquid medium was found to induce resistance in tomato foliage against the pathogens Pseudomonas syringae pv. tomato, Xanthomonas vesicatoria, Alternaria solani and Corynespora cassiicola. In the present work the microorganism was grown in a minimal medium for 48 h and the cells precipitated for centrifugation. The supernatant was concentrated by lyophilization, dialyzed in a 12 kDa cut-off point membrane and fractioned in column containing Sephadex G25 balanced in PBS buffer. The fractions corresponding to a protein peak were applied to tomato seedlings. After four days leaflets were collected and inoculated with the pathogen. C. cassiicola. The numbers of lesions produced by the pathogen on leaflets exposed to the bacterial supernatant were similar to those exposed to acibenzolar-S-methyl but fewer than in those treated with water. It is concluded that the supernatant contained protein which induced resistance in the tomato leaves against C. cassiicola.Item In vitro production of conidia of Alternaria solani(Tropical Plant Pathology, 2010-07) Rodrigues, Tatiana T. M. S.; Maffia, Luiz A.; Dhingra, Onkar D.; Mizubuti, Eduardo S. G.Sporulation of Alternaria solani can be scarce and is often reduced when the fungus is cultivated in vitro. A series of experiments were conducted to assess the effects of moisture, mycelial wounding, light quality and photoperiod, and culture media on conidial production. A procedure to induce sporulation based on mycelial wounding and dehydration was adapted and validated. Best results were obtained when fungal colonies were grown in V8 medium at 25ºC in the dark with agitation for seven days; the mycelium mass was ground, poured into potato dextrose agar (pH 6.5) in plates, and incubated at 25 ± 2ºC under near ultraviolet light and 12 h-photoperiod. The procedure was validated with 30 isolates of A. solani from different hosts, sampling locations, ages, and storage conditions. Conidial production, germination, and infectivity were quantified. Seventy-five percent of the isolates sporulated and the lowest germination rate was 68%. Inoculations of conidial suspension of all isolates resulted in lesions on tomato and potato plants. The effect of subculturing on A. solani sporulation was also assessed. After six subcultures, every seven days, there was no reduction in sporulation of colonies that were induced with the protocol.Item Silicon improves the emergence and sanity of rice seedlings obtained from seeds infected with Bipolaris oryzae(Tropical Plant Pathology, 2013-11) Rodrigues, Fabrício A.; Mielli, Matheus V. B.; Dallagnol, Leandro J.This study investigated the importance of silicon (Si) in rice grain husk in association with fungicide treatment for preventing Bipolaris oryzae transmission from seed to seedling and the improvement in seedling emergence. Plants from cv. Oochikara and its mutant (lsi1 mutant) defective in active Si uptake were grown in nutrient solution without (-Si) or with (+Si) Si and their panicles were inoculated with B. oryzae. Seeds were evaluated for brown spot severity (BSS) and husk Si concentration. The Si concentration in the husks of cv. Oochikara plants was up to four times higher than the lsi1 mutant plants. BSS was significantly reduced in the husks of the seeds obtained from +Si plants, particularly for cv. Oochikara. A higher percentage of seedling emergence occurred for +Si plant seeds, particularly for cv. Oochikara, and a lower percentage of infected seedlings was observed for the +Si cv. Oochikara treatment, particularly for the fungicide treated seeds. Fungicide was not efficient in preventing seedling infection by B. oryzae for seeds with BSS greater than 50%. High Si concentration in the husk resulted in lower BSS and the fungicide efficiency was greater with a low BSS on seeds from +Si plants, particularly for cv. Oochikara.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 Induction of resistance to Pyricularia oryzae in wheat by acibenzolar-S-methyl, ethylene and jasmonic acid(Tropical Plant Pathology, 2014-05) Rios, Jonas Alberto; Rodrigues, Fabrício Ávila; Debona, Daniel; Resende, Renata Sousa; Moreira, Wiler Ribas; Andrade, Camila Cristina LageThis study investigated the effects of acibenzolar-S-methyl (ASM), ethylene (ET) and jasmonic acid (JA) on the resistance of two wheat cultivars (BRS-229 and BR-18) to infection by Pyricularia oryzae. The treatments included spraying plants with ASM (300 mg L-1), ET (0.5 mM), JA (0.1 mM) and distilled water (control) 48 h before inoculation with P. oryzae. Malondialdehyde concentration, an indicative of oxidative damage to the lipids in the leaf cells, was significantly higher for plants sprayed with ASM compared to plants sprayed with JA and ET. Plants sprayed with JA and ET showed reduced values for the number of lesions per cm2 of leaf area and area under blast progress curve, but these hormones had no effect on the incubation period and lesion size (in mm). Plants sprayed with JA and ET showed reduce blast symptoms in comparison to plants sprayed with ASM due to greater peroxidase, polyphenoloxidase, chitinase and β-1,3-glucanase activities.Item Indutores de resistência no controle da pinta bacteriana do tomateiro e na atividade de enzimas de defesa(Tropical Plant Pathology, 2013-01) Resende, Renata S.; Rodrigues, Fabrício A.; Silveira, Patrícia R.; Rios, Jonas A.; Oliveira, José R.; Mariano, Rosa L. R.; Andrade, Camila C. L.Em três experimentos, avaliou-se o efeito de pulverizações de ácido jasmônico (AJ), etefon (ET) e acibenzolar-S-metil (Bion®) (ASM) a 0,1 mM, 0,5 mM e 0,3 g L-1, respectivamente, nos componentes de resistência do tomateiro (cv. Santa Clara) à pinta bacteriana, causada por Pseudomonas syringae pv. tomato e na atividade de peroxidases (POX), polifenoloxidases (PFO), β-1,3-glucanases (GLU) e lipoxigenases (LOX). Apenas no experimento 3, o período de incubação aumentou significativamente em um dia nas plantas pulverizadas com ASM, em comparação com as plantas pulverizadas com água (controle). O número de lesões por planta foi significativamente reduzido por AJ, ET e ASM nos três experimentos. Para algumas épocas de avaliação, a atividade de POX, PFO e GLU foram maiores para o AJ; de PFO, GLU e LOX, para o ASM; e de GLU e LOX, para o ET em comparação com o controle. Conclui-se que na presença de AJ, ET e ASM, os sintomas da pinta bacteriana foram reduzidos e a atividade das enzimas POX, PFO, GLU e LOX foram maiores.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 Photosynthetic gas exchange and antioxidative system in common bean plants infected by Colletotrichum lindemuthianum and supplied with silicon(Tropical Plant Pathology, 2014-01) Polanco, Leonora R.; Rodrigues, Fabrício A.; Nascimento, Kelly J. T.; Cruz, Maria F. A.; Curvelo, Carmen R. S.; Vale, Francisco X. R.This study investigated the effects of silicon (Si) on the resistance of common bean plants to anthracnose caused by Colletotrichum lindemuthianum. The plants were grown in a nutrient solution containing 0 (control) or 2 mM Si (+Si) and both photosynthesis and antioxidative metabolism levels were evaluated. The Si concentrations in the leaf tissues of +Si plants increased by 33% in comparison to those of control plants. Anthracnose severity was reduced by 34% in +Si plants in comparison to control plants. The net carbon assimilation rate, stomatal conductance to water vapor and transpiration rate values were significantly higher in +Si plants than in control plants. The activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) tended to be higher in +Si plants than in control plants. The hydrogen peroxide concentration was significantly lower in +Si plants than in control plants. In conclusion, the Si supply was associated with lower anthracnose severity and up-regulation of antioxidant enzymes, which in turn might be associated with better gas exchange in +Si plants. The impaired photosynthetic performance in +Si plants was associated with stomatal limitations, whereas in control plants those impairments likely reflected dysfunctions at the level of biochemical reactions involved in CO2 fixation.Item Reappraisal of the black mildews (Meliolales) on Hevea brasiliensis(Tropical Plant Pathology, 2014-01) Pinho, Danilo B.; Honorato Junior, Jaime; Firmino, André L.; Hora Junior, Braz T.; Mizubuti, Eduardo S. G.; Pereira, Olinto L.The rubber tree (Hevea brasiliensis) is host to several fungal species, including Irenopsis heveae as described by Hansford in 1961, which causes black mildew on leaves. One specimen of Irenopsis heveae from the state of Espírito Santo and two from the state of Pará were analyzed and showed some morphological differences. Some structures are similar to morphological characteristics as described and illustrated by Vincens in 1915 for Meliola heveae. Morphological comparisons with the type specimen of I. heveae and the alignment of the nucleotide sequences of the 28S rDNA region, however, indicate that the three samples belong to the same species. According to these data M. heveae and I. heveae are heterotypic synonyms with M. heveae being the older name. As the name I. heveae is already occupied by Hansford, Irenopsis vincensii is proposed as new name for the black mildew on H. brasiliensis. This is the first contribution of molecular sequence data for this species.Item Genetic variability of papaya lethal yellowing virus isolates from Ceará and Rio Grande do Norte States, Brazil(Tropical Plant Pathology, 2012-01) Pereira, Álvaro J.; Cascardo, Renan S.; Alfenas-Zerbini, Poliane; Bezerra-Junior, José Evando A.; Lima, José Albérsio A.; Zerbini, Francisco Murilo; Andrade, Eduardo C.; Daltro, Cleidiane B.The papaya (Carica papaya) is a fruit crop of great economic importance throughout the Brazilian northeast, which is responsible for 60% of the national output. Papayas in the states of Ceará and Rio Grande do Norte are affected by lethal yellowing disease, caused by papaya lethal yellowing virus (PLYV). Previous work suggested that PLYV is a putative sobemovirus. To assess the genetic variability of PLYV, foliar samples were collected in October 2008 and October 2009 in commercial fields from Ceará and Rio Grande do Norte states, and total RNA was extracted. Specific primers based on the sequence of a previously characterized PLYV isolate were used for the RT-PCR-based amplification of a 900 bp fragment corresponding to the central region of the viral genome. Fragments from 21 viral isolates were cloned and sequenced. Sequence analyses indicated >97% nucleotide sequence identity among the isolates, 94-100% identity with the previously sequenced PLYV isolate, and a lower but significant identity with sobemoviruses (43-48.5%). These results suggest a low genetic variability among PLYV isolates, and are in agreement with the provisional placement of PLYV in the genus Sobemovirus. Definitive taxonomic conclusions, however, can only be drawn after the determination of the full-length genomic sequence.