Fitopatologia - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741
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Item Aggressiveness and host specificity of Brazilian isolates of Phytophthora infestans(Plant Pathology, 2004-08) Suassuna, N. D.; Maffia, L. A.; Mizubuti, E. S. G.The population of Phytophthora infestans in Brazil consists of two clonal lineages, US-1 associated with tomatoes and BR-1 associated with potatoes. To assess whether host specificity in these lineages resulted from differences in aggres- siveness to potato and tomato, six aggressiveness-related epidemiological components – infection frequency (IF), incu- bation period (IP), latent period (LP), lesion area (LA), lesion expansion rate (LER) and sporulation at several lesion ages (SSLA) – were measured on detached leaflets of late blight-susceptible potato and tomato plants. Infection frequency of US-1 was similar on potato and tomato leaflets, but IF of BR-1 was somewhat reduced on tomato. Incubation period was longer on both hosts with US-1, although this apparent lineage affect was not significant. Overall there was no host effect on IP. On potato, BR-1 had a shorter LP (110·3 h) and a larger LA (6·5 cm 2 ) than US-1 (LP = 162·0 h; LA = 2·8 cm 2 ). The highest LER resulted when isolates of BR-1 (0·121 cm 2 h −1 ) and US-1 (0·053 cm 2 h −1 ) were inoculated on potato and tomato leaflets, respectively. The highest values of the area under the sporulation capacity curve (AUSC) were obtained for isolates of US-1 inoculated on tomato leaflets (6146) and for isolates of BR-1 on potato leaflets (3775). In general, higher values of LA, LER, SSLA and AUSC, and shorter values of LP were measured when isolates of a clonal lineage were inoculated on their original host than with the opposite combinations. There is evidence that there are quan- titative differences in aggressiveness components between isolates of US-1 and BR-1 clonal lineages that probably con- tribute to host specificity of P. infestans populations in Brazil.Item Factors influencing infection of eucalypts by Cylindrocladium pteridis(Plant Pathology, 2009-06-08) Graça, R. N.; Alfenas, A. C.; Maffia, L. A.; Titon, M.; Alfenas, R. F.; Lau, D.; Rocabado, J. M. A.The pattern of Cylindrocladium pteridis adhesion, germination and penetration in eucalypt leaves was assessed using scanning electron microscopy. The effects of inoculum concentration, leaf wetness period, plant age and branch position of cylindrocladium leaf blight and defoliation severity were assessed in greenhouse studies using two Eucalyptus grandis E. urophylla hybrid clones. Penetration occurred through stomata, and there was no difference in the number of penetrations between young and old leaves. Percentage leaf area with lesions and defoliation increased with the increase in inoculum concentration (1 · 10 2 to 10 5 conidia mL )1 ), duration of leaf wetness period (6 to 48 h) and plant age (60 to 180 days). Branch position in plants also significantly affected the percentage leaf area with lesions and defoliation, the latter variable being significantly higher at the stem base. The highest values of lesion area were also observed on leaves at the stem base in both clones. The Pearson correlation between defoliation and leaf area with lesions was significant in all experiments (r > 0Æ9) indicating a high association between these two variables.Item Biological control by Clonostachys rosea as a key component in the integrated management of strawberry gray mold(Biological Control, 2009-05-06) Cota, L. V.; Maffia, L. A.; Mizubuti, E. S. G.; Macedo, P. E. F.Gray mold, caused by Botrytis cinerea, is an important strawberry disease. As gray mold control is difficult, there is a need to evaluate integrated methods to successfully manage the disease. The efficiency of integrating Clonostachys rosea sprays, fungicide sprays, and crop debris removal to manage gray mold was evaluated in field experiments conducted in 2006 and 2007. Leaf colonization by C. rosea (LAC), average number of B. cinerea conidiophores (ANC), gray mold incidence in both flowers (Iflower) and fruits (Ifruit), and yield were evaluated weekly. In both years, LAC was higher in the treatments with no fungicide. When compared to the check, ANC, Iflower and Ifruit were most reduced in treatments that included C. rosea sprays. Maximal reductions were achieved with the combination of C. rosea sprays, fungicide sprays and debris removal (96.62%, 86.54% and 65.33% reductions of ANC, Iflower and Ifruit, respectively). Otherwise, maximal yield (103.14% increase as compared to the check) was achieved with the combination of the three treatments. With just C. rosea sprays, ANC, Iflower and Ifruit were reduced by 92.01%, 68.48% and 65.33%, respectively, whereas yield was increased by 75.15%. Considering the individual effects, application of C. rosea was the most efficient treatment. Chemical control was effective only in plots without debris removal. Elimination of crop debris was the least effective method in reducing gray mold incidence in both flowers and fruits. The integrated control approach enhanced the efficacy of the individual methods of gray mold control and provided high strawberry yield. An important component of this integrated approach it the biological control with C. rosea.Item Effectiveness of systemic fungicides in the control of Quambalaria eucalypti and their effects on production of eucalypt mini-cuttings for rooting(Crop Protection, 2008-02) Ferreira, E. M.; Alfenas, A. C.; Maffia, L. A.; Mafia, R. G.; Mounteer, A. H.Eucalypt leaf spot caused by Quambalaria eucalypti is currently one of the main diseases occurring in mini-clonal hedges cultivated in sand beds with drip fert-irrigation or hydroponic tanks. Given the lack of studies on the effectiveness of fungicides for control of this pathogen, the protective, curative and antisporulating effects of systemic fungicides and their influence on production and rooting of eucalypt mini-cuttings were evaluated. Among the nine active ingredients tested, azoxystrobin, epoxiconazole, epoxiconazole+pyraclostrobin, pyraclostrobin and tebuconazole were the most effective against Q. eucalypti. Epoxiconazole, epoxiconazole+pyraclostrobin and tebuconazole presented protective, curative and antisporulating effects against the pathogen. In mini-clonal hedges, only epoxiconazole+pyraclostrobin negatively affected the production of mini-cuttings.Item Brazilian isolates of Clonostachys rosea: colonization under different temperature and moisture conditions and temporal dynamics on strawberry leaves(Letters in Applied Microbiology, 2007-11-15) Cota, L. V.; Maffia, L. A.; Mizubuti, E. S.In a research programme for managing diseases caused by Botryis cinerea, four isolates of the antagonistic fungus Clonostachys rosea (Cr) were obtained from different ecosystems in Brazil. We studied ecological requirements for the colonization of strawberry leaves by these isolates. Temperature effects on both mycelial growth in vitro and leaf colonization by Cr were studied. At 10°C, growth on potato dextrose agar and colonization of leaf discs were poor. Optimum temperature for mycelial growth and leaf colonization was around 25°C. The isolates were applied to leaves which were exposed to 0–48 h intervals of moisture. They were also applied to leaves which remained from 0 to 36 h without wetness. All isolates efficiently colonized leaves, regardless of moisture interval or the delay to begin wetness. Although all isolates survived in green leaves of whole plants, colonization decreased throughout a 49-day period. Brazilian isolates of Cr can establish and colonize strawberry leaves under a wide range of temperature and moisture conditions. It is expected that the Brazilian isolates of Cr will establish efficiently in strawberry leaves where they can compete with B. cinerea.