Fitopatologia - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741
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Item Genetic diversity and interfertility among highly differentiated populations of Ceratocystis fimbriata in Brazil(Plant Pathology, 2010-07-01) Ferreira, E. M.; Harrington, T. C.; Thorpe, D. J.; Alfenas, A. C.Mating studies showed that isolates of the insect-associated wilt pathogen Ceratocystis fimbriata from Eucalyptus spp., mango, fig, inhame (Colocasia esculenta), Gmelina arborea and sweet potato were interfertile, and progeny from those crosses showed normal segregation for microsatellite markers. Genetic diversity was compared among 13 populations of C. fimbriata collected from six states in Brazil using 15 highly polymorphic microsatellite markers. The gene diversity values of most eucalyptus and mango populations from Minas Gerais, Bahia, Rio de Janeiro and São Paulo states were similar to putatively native populations of Ceratocystis platani and C. cacaofunesta, two other species in the C. fimbriata complex that are homothallic. Index of association values indicated substantial asexual reproduction or selfing in populations on mango and eucalyptus. Most of these eucalyptus and mango populations were not highly differentiated from each other, and these populations and genotypes appeared to be more closely related to each other than to other populations by UPGMA analyses. By contrast, the G. arborea population from Pará and the fig and inhame populations from São Paulo had relatively low lev- els of diversity and were highly differentiated from each other and all other studied populations, suggesting that they were from different origins and had gone through genetic bottlenecks. One of the eucalyptus populations in Bahia consisted of a single genotype and may have been introduced to the site in infected cuttings from another Bahia location. Similarly, a mango population from Mato Grosso do Sul consisted of a single genotype, which was identical to one of the genotypes found on mango in São Paulo. Aside from introductions by humans, mating studies and genetic analyses suggest that limited dispersal distance and a high degree of selfing or asexual reproduction lead to local populations of C. fimbriata that have limited diversity but are highly differentiated from other populations.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 Resistance to rust (Puccinia psidii Winter) in Eucalyptus: mode of inheritance and mapping of a major gene with RAPD markers(Theoretical and Applied Genetics, 2003-09-19) Junghans, D. T.; Alfenas, A. C.; Brommonschenkel, S. H.; Oda, S.; Mello, E. J.; Grattapaglia, D.Rust is one of the most-damaging eucalypt diseases in Brazil and is considered a potential threat to eucalypt plantations worldwide. To determine the mode of inheritance of resistance in the Eucalyptus grandis—Puccinia psidii pathosystem, ten full-sib families, generated from crosses between susceptible and resistant trees, were inoculated with a single-pustule isolate of the pathogen and rust severity was scored. The observed segregation ratios in segregating families suggested major gene control of rust resistance, although clearly incomplete penetrance, variable expressivity and minor genes are also involved in the global rust-resistance response. To identify markers linked to the resistance locus, screening of RAPD polymorphisms was conducted using bulked segregant analysis in a large full-sib family. A linkage group was built around the Ppr1 gene (P. psidii resistance gene 1) encompassing six RAPD markers, with a genetic window spanning 5 cM with the two most-closely linked flanking markers. Besides these two flanking markers, RAPD marker AT9/917 co-segregated with Ppr1 without a single recombinant in 994 meioses. This tightly linked marker should prove useful for marker-assisted introgression and will provide an initial lead for a positional cloning effort of this resistance allele. This is the first report of a disease resistance gene identified in Eucalyptus, and one of the few examples of the involvement of a major gene in a non-coevolved pathosystem.