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 Histopathological study of the Alternaria solani infection process in potato: cultivars with different levels of early blight resistance(Journal of Phytopathology, 2007-06-22) Dita, M. A.; Mizubuti, E. S. G.; Matsuoka, K.; Brommonschenkel, S. H.Histopathological analyses of the infection process of Alternaria solani were accomplished in three potato cultivars with different levels of early blight resistance. Leaflets of Aracy (resistant), Delta (moderately resistant) and Bintje (susceptible) cultivars were inoculated at the beginning of the flowering stage. In order to study the effect of leaf age, leaf samples were collected separately, in the lower, middle and upper third of the plants. Conidia germination, appressoria formation, penetration and number of penetration sites exhibiting hypersensitive response (HR) were qualitatively and quantitatively assessed at 6, 12, 24, 48 and 72 h after inoculation. Penetration occurred most frequently through the junctions of the epidermal cells. Penetrations through stomata were rarely observed. There was no association between the events and the resistance levels, except for the number of penetration sites showing HR that was highest in Aracy, intermediate in Delta and lowest in Bintje. Similarly, the number of sites with HR was the only event associated with the leaf age. Regardless of cultivar resistance levels, the number of the penetration sites with HR was higher in leaves in the upper part of the plant. These results suggest that HR may be one of the mechanisms associated with age‐related and genetic resistance to early blight in potato.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 Validation of decision support systems for tomato early blight and potato late blight, under Brazilian conditions(Crop Protection, 2006-07) Batista, D. C.; Lima, Marcello Arrais; Haddad, Fernando; Maffia, Luiz Antônio; Mizubuti, E. S. G.Early and late blight are the most important foliar diseases of tomato and potato crops in Brazil. Decision support systems (DSS) are important tools in reducing the large amount of fungicides applied to suppress disease intensity. Systems developed for early or late blight were validated in two cropping seasons under Brazilian conditions. For tomato early blight, FAST, CUFAST, and TOMCAST systems were compared in the spring–summer (September–December) (SS) 2002 and summer–autumn (January–April) (SA) 2003. In both seasons, area under disease progress curve (AUDPC) values for FAST (123.2 and 340.3, respectively) and CUFAST (64.0 and 359.2, respectively) did not differ from calendar-based treated plots (82.5 and 225.7, respectively). Plots treated according to TOMCAST were sprayed once and AUDPC values (369.9 and 697.8) in SS and SA seasons, respectively, did not differ from the control plots (397.5 and 836.0, respectively). In SS, four fungicide sprays were recommended by CUFAST and FAST, whereas five were set by fixed calendar treatment; there were no differences in yield loss among treatments. In SA, FAST, CUFAST and calendar, recommended 4, 9, and 11 sprays, respectively. Higher yields were recorded in plots sprayed according to the calendar system compared to control plots, but there were no significant differences between the DSS and the calendar system. For potato late blight, BLITECAST, SIMCAST, NegFry, and Wallin systems were compared in the summer (December–March) and in the autumn (March–June). Despite no late blight developing in the summer, all systems recommended fungicide sprays. In the autumn–winter, late blight was severe but was reduced by fungicide applications according to all DSS, but the number of sprays was similar to the calendar. The AUDPC values in control plots (1193.5) were higher than BLITECAST (19.5), SIMCAST (97.7), NegFry (193.1), Wallin (69.7), and calendar (63.5) but there were no differences among AUDPC values in plots treated according to DSS. The NegFry and Wallin systems recommended five and the calendar six sprays. All DSS were as effective as the calendar treatment in reducing AUDPC. FAST and Wallin were the most effective systems in forecasting tomato early blight and potato late blight, respectively. Decision support systems are potentially useful tools for integrated management of both diseases in Brazil.