Fitopatologia - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741
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Item Effects of silicon on the penetration and reproduction events of Meloidogyne exigua on coffee roots(Bragantia, 2015-04) Silva, Rodrigo Vieira; Oliveira, Rosângela D’Arc de Lima; Ferreira, Patrícia da Silva; Castro, Douglas Barbosa; Rodrigues, Fabrício ÁvilaConsidering that the root-knot nematode Meloidogyne exigua has caused great yield losses to coffee production in Brazil, this study aimed to determine whether the penetration and the reproduction events of this nematode on the roots of plants from two coffee cultivars with different levels of basal resistance to this nematode could be affected by silicon (Si). Coffee plants from the cultivars Catuaí and IAPAR 59, which are susceptible and resistant, respectively, to M. exigua, were grown in pots containing Si-deficient soil that was amended with either calcium silicate (+Si) or calcium carbonate (–Si). The Si concentration on the root tissue significantly increased by 159 and 97% for the +Si plants from the cultivars Catuaí and IAPAR 59, respectively, compared to the –Si plants of these cultivars. The population of M. exigua, the number of galls and the number of eggs were significantly reduced on the roots of the +Si plants of the cultivars Catuaí and IAPAR 59 compared to the –Si plants of these cultivars. It was concluded that the development and reproduction events of M. exigua were negatively impacted on the roots of coffee plants supplied with Si.Item Methods for Cercospora coffeicola protoplast isolation and genetic transformation with the green fluorescent protein(European Journal of Plant Pathology, 2014-06) Souza, André Gomes Coelho; Herrero, Sonia; Maffia, Luiz Antonio; Daub, Margaret ElizabethCercospora coffeicola is the causal agent of brown eye spot on coffee leaves. Although the disease has significant importance, few molecular studies have been done with C. coffeicola. Here we report a protocol for isolating protoplasts as well as development of a genetic transformation system using Green Fluorescent Protein. High yields of protoplasts (≈108/ml) were obtained from mycelial cultures from five isolates of C. coffeicola. One isolate was transformed with a vector encoding hygromycin resistance and Green Fluorescent Protein. Out of 43 hygromycin-resistant transformants obtained, Green Fluorescent Protein was highly expressed in one (2.3 %).Item DMI and QoI fungicides for the control of coffee leaf rust(Australasian Plant Pathology, 2015-09) Zambolim, Laércio; Lopes, Uilton do Nascimento; Lopes, Ueder Pedro; Honorato Jr., Jaime; Duarte, Henrique da Silva SilveiraThis study investigated the ability of different triazole and strobilurin fungicides either alone or combination when applied to the leaves and triazole to the soil for control of Coffee Leaf Rust (CLR). The experiments were performed in a greenhouse using three month-old coffee seedlings, and in the field with five years old plants using the susceptible variety ‘Catuai vermelho’, at elevation of 750 m, from 2010 to 2012, in Viçosa, Minas Gerais State, Brazil. The effects of triazole (triadimenol, cyproconazole and epoxiconazole) and strobilurin (azoxystrobin, trifloxystrobin, pyraclostrobin) was first studied in a greenhouse to evaluate the translaminar effect on CLR control. Based on the results obtained in the greenhouse, a field experiment was performed to evaluate the effect of triazole applied to the soil and triazole + strobilurin sprayed on CLR control and the effect on coffee berry yield of the plants. The different fungicides applied in the greenhouse reduced CLR severity by 8.9 % (trifloxystrobin), 79.4 % (azoxystrobin), 82.0 % (triadimenol), 93.2 % (cyproconazole), 96.6 % (epoxiconazole) and 98.5 % (pyraclostrobin) compared to that in the control plants. In the field experiment triazole + strobilurin fungicides provided effective CLR control. The co-application of epoxiconazole and pyraclostrobin or azoxystrobin sprayed twice resulted in the most effective CLR control and maintained the highest coffee berry yield. The incidence of CLR was 83.5, 54.0 and 78.5 % for the control treatments, whereas the incidence did not exceeded 24.4, 37.0 and 39.0 % on the sprayed plants. The average coffee berry yield increased by 33.9 % (lowest value) when applying triadimenol to the soil in November followed by cyproconazole + trifloxystrobin sprayed in December and February, and increased by 99.1 % (highest value) in the treatment with epoxiconazol + pyraclostrobin sprayed in December and March compared with plants that did not receive any fungicide application. The control treatment and that of triadimenol applied to the soil in November followed by cyproconazole + trifloxystrobin sprayed in December and February yielded less than 1800 (1320 to 1800) kg/ha of processed coffee, whereas the other treatments more than 2100 (2142 to 2676) kg/ha. Treatments with cyproconazole applied to the soil in November followed by cyproconazole + azoxystrobin sprayed on the leaves in December and February, epoxiconazol + pyraclostrobin sprayed on the leaves in December and March, and cyproconazole + azoxystrobin sprayed on leaves in December, February and April yielded more than 2340 (2340 to 2676) kg/ha of processed coffee. This is the first report indicating that a triazole fungicide applied to the soil and triazole + strobilurin fungicide sprayed on the leaves, efficiently controlled CLR and significantly increased coffee berry yield for three seasons.Item The population structure of Hemileia vastatrix in Brazil inferred from AFLP(Australasian Plant Pathology, 2013-09) Maia, T. A.; Caixeta, E. T.; Mizubuti, E. S. G.; Zambolim, L.; Maciel-Zambolim, E.Efforts to obtain durable resistant cultivars to coffee leaf rust have a long history of disappointment because of the lack of information on the Hemileia vastatrix evolutionary potential. In this study, the AFLP marker was used to analyze the genetic structure of a field population of H. vastatrix from different coffee genotypes cultivated in a wide geographic region of Brazil’s main production areas. A total of 91 isolates were sampled from genotypes of Coffea arabica, C. canephora and Híbrido de Timor/Icatu derivatives. Each isolate exhibited unique multilocus AFLP genotypes with no identical isolates obtained from the same geographical and host origins. This finding was corroborated by a small correlation between genetic similarity and geographic distance (R xy = 0.31, P = 0.23). The analyses showed a low genetic differentiation (G ST = 0.026) between the populations defined by a host and AMOVA analysis, most of the genetic variance (99.56 %) was attributed to differences within populations. In addition, based on the index of association (IA), the random mating possibility was not rejected (IA = 0.225, P = 0.123) for the population of H. vastatrix derived from C. canephora. This result suggested that H. vastatrix in Brazil behaves as a large undifferentiated population with a high level of genotypic diversity that is unstructured with regard to its geographic and host origins.Item Isolation and selection of Hemileia vastatrix antagonists(European Journal of Plant Pathology, 2014-04-21) Haddad, Fernando; Saraiva, Rodrigo M.; Mizubuti, Eduardo S. G.; Romeiro, Reginaldo S.; Maffia, Luiz A.Organic coffee growing is rapidly increasing in Brazil, and many diseases, especially coffee leaf rust (Hemileia vastatrix), are threatening its production. This study is a first step towards a biocontrol program for coffee rust on organically grown plants. In three organic coffee farms in the state of Minas Gerais, 393 microbial strains including 154 bacterial and 239 fungal strains were isolated from leaves, leaf debris, and soil samples, and in 6 month-old coffee plants, 17 of these isolates reduced both the infection frequency (IF) and the number of H. vastatrix urediniospores produced per leaf (UPL) by more than 70 %. The isolates were identified as eight bacteria isolates, seven Bacillus spp. and one Pseudomonas sp., and nine fungal isolates, four Fusarium spp., two Penicillium spp., one Aspergillus sp., one Acremonium sp. and one Cladosporium sp. Each fungal and bacterial isolate was applied 0, 4, 8, 12 or 16 days before and 0, 4, 8, 12 or 16 days after H. vastatrix inoculation, and the efficiency in reducing both IF and UPL was evaluated. The efficiency was higher and lasted longer when the bacterial isolates were applied before H. vastatrix inoculation. Six Bacillus (B10, B25, B143, B157, B171, B175), two Fusarium (F205, F281), and one Pseudomonas (B286) isolates are potentially efficient as biocontrol agents of H. vastatrix and will be tested using field experiments.Item Quantification of yield loss due to coffee leaf scorch(Crop Protection, 2010-10) Rocha, Janilson G.; Zambolim, Laércio; Zambolim, Eunize M.; Vale, Francisco X. Ribeiro do; J. Junior, Waldir C.; Bergamin Filho, ArmandoCoffee leaf scorch caused by Xylella fastidiosa is widespread in major coffee-growing regions of Brazil. This study was done to quantify the yield loss caused by this disease. The severity data of the disease were collected during the 2006, 2007 and 2008 seasons at commercial plantations growing Coffea arabica ‘Catuaí’ in São Gotardo-MG in 250 plants of three blocks of 7000 coffee plants each. Fifty selected plants per block with different disease severities were determined. The linear regression showed a significant relationship (P < 0.01) between disease severity and bean yield and between disease severity and grain size in all years. The relationship between yield and the disease severity was significant (P < 0.01). For each 1% increase in the disease severity, there was a decrease of 1.22, 1.34 and 2.02 bags of bean yield/ha in 2006, 2007 and 2008, respectively, thus showing the importance of the disease in reducing coffee bean yields.Item Detection of corn adulteration in Brazilian coffee (Coffea arabica) by tocopherol profiling and Near-Infrared (NIR) spectroscopy(Journal of Agricultural and Food Chemistry, 2015-11-24) Winkler-Moser, Jill K.; Singh, Mukti; Rennick, Kathy A.; Bakota, Erica L.; Jham, Gulab; Liu, Sean X.; Vaughn, Steven F.Coffee is a high-value commodity that is a target for adulteration, leading to loss of quality and causing significant loss to consumers. Therefore, there is significant interest in developing methods for detecting coffee adulteration and improving the sensitivity and accuracy of these methods. Corn and other lower value crops are potential adulterants, along with sticks and coffee husks. Fourteen pure Brazilian roasted, ground coffee bean samples were adulterated with 1–20% of roasted, ground corn and were analyzed for their tocopherol content and profile by HPLC. They were also analyzed by near-infrared (NIR) spectroscopy. Both proposed methods of detection of corn adulteration displayed a sensitivity of around 5%, thus representing simple and fast analytical methods for detecting adulteration at likely levels of contamination. Further studies should be conducted to verify the results with a much larger sample size and additional types of adulterants.Item Photosynthetic and antioxidative alterations in coffee leaves caused by epoxiconazole and pyraclostrobin sprays and Hemileia vastatrix infection(Pesticide Biochemistry and Physiology, 2015-02-11) Honorato Júnior, J.; Zambolim, L.; Aucique-Pérez, C.E.; Resende, R.S.; Rodrigues, F.A.Coffee leaf rust (CLR), caused by Hemileia vastatrix, is a major disease affecting coffee production worldwide. In this study, an in-depth analysis of the photosynthetic performance of coffee leaves challenged or not with H. vastatrix and sprayed with either epoxiconazole (EPO) or pyraclostrobin (PYR) was performed by combining chlorophyll a fluorescence images, photosynthetic pigment pools and the activities of chitinase (CHI), β-1,3-glucanase (GLU), peroxidase (POX) and catalase (CAT). The CLR severity was higher in the control plants, but reduced in plants sprayed with both PYR and EPO. Also, the CLR severity was reduced in plants sprayed with PYR compared with plants sprayed with EPO. Plants sprayed with either EPO or PYR showed maximal photosystem II quantum efficiency (Fv/Fm) values ranging from 0.78 to 0.80, which were quite similar to those obtained with inoculated plants (values ranging from 0.74 to 0.77). The decreases in the Fv/Fm ratio values and parallel increases in the F0 values in the inoculated plants, which were not observed in the control plants (sprayed with water) and were confirmed by images of the initial fluorescence (F0) and Fv/Fm parameters in the regions of the leaf tissue containing pustules and in the asymptomatic leaf tissue, indicated that photosynthesis was negatively impacted. When effective photosystem II quantum yield (Y(II)) values approached zero with a high photosynthetic photon flux density, high values of quantum yield of regulated energy dissipation (Y(NPQ)) in association with a high carotenoid concentration were noted in the inoculated plants sprayed either with PYR or EPO. The increased CLR severity in inoculated plants in contrast to inoculated plants sprayed with either PYR or EPO was associated with greater POX activity and a reduced photosynthetic pigment concentration. POX and CAT activities were increased in inoculated plants sprayed with either EPO or PYR when compared with control plants. CHI and GLU activities were maintained at high levels in the leaves of inoculated plants, regardless of the fungicide sprayed, indicating that CHI and GLU are less important for coffee resistance against CLR. The results of the present study clearly demonstrated that plants sprayed with either EPO or PYR showed milder CLR symptoms with adequate photosynthetic performance and optimal conditioning of their antioxidant systems.