Tardiani, A. C, Perecin, D., Peixoto-Junior, R. R, Sanguino, A., Landell, M. M. G., Beriam, L. O., Nunes, D. S., Camargo, L. E. A., and Creste S 2014. Molecular and pathogenic diversity among Brazilian isolates oí Xanthomonas albilineans assessed with SSR marker loci. Plant Dis 98-540-546.
Sporisorium scitamineum is the fungus that causes sugarcane smut disease. Despite of the importance of sugarcane for Brazilian agribusiness and the persistence of the pathogen in most cropping areas, genetic variation studies are still missing for Brazilian isolates. In this study, sets of isolates were analyzed using two molecular markers (AFLP and telRFLP) and ITS sequencing. Twenty-two whips were collected from symptomatic plants in cultivated sugarcane fields of Brazil. A total of 41 haploid strains of compatible mating types were selected from individual teliospores and used for molecular genetic analyses. telRFLP and ITS analyses were expanded to six Argentine isolates, where the sugarcane smut was first recorded in America. Genetic relationship among strains suggests the human-mediated dispersal of S. scitamineum within the Brazilian territory and between the two neighboring countries. Two genetically distinct groups were defined by the combined analysis of AFLP and telRFLP. The opposite mating-type strains derived from single teliospores were clustered together into these main groups, but had not always identical haplotypes. telRFLP markers analyzed over two generations of selfing and controlled outcrossing confirmed the potential for emergence of new variants and occurrence of recombination, which are relevant events for evolution of virulence and environmental adaptation.
T his study had as objectives: to determine the most adequate method for detection and identification of sugarcane seedborne fungi; to characterize the associated fungi; to verify the incidences and to relate the fungical incidence in these seeds with the conditions where they were produced. To know the most adequate method of detection, two substrates were compared in Petri dishes: filter paper on agarwater culture medium and only filter paper. Glass and plastic Petri plates were utilized, to verify the recipient influence. It was also compared two light regimens (12h alternating cycles of light and darkness and continuous darkness). The seeds were kept during seven days under constant temperature of 28 ± 2ºC, when the evaluations were proceeded. The requirements for comparison of the methods were sensitivity, economicity and practicity. After the determination of the most adequate method, were done health tests of 29 crosses of the years 2002, 2003 and 2004, to characterize the seedborne fungi and verify their incidences. Later, these incidences were compared to the conditions of temperature and relative humidity from where the seeds were produced at the breeding program. The method considered Martins, T.D.; Menten, J.O.M.; Sanguino, A.. Sugarcane seedborne (Caryopses) fungi: detection methods, incidence and relation between fungical incidence and seed production conditions. Summa Phytopathologica, v.35, n.3, p.173-178, 2009 Keywords: Substract; Light regimen; Petri dishes; Fungical incidence most appropriated, in agreement with the analyzed parameters, was the filter paper in plastic Petri plate and the incubation under light regimen (12h alternating cycles of light and darkness). The detected fungi were: Alternaria alternata; Aspergillus sp.; Bipolaris sacchari; three distinct morphologic groups (GM) of the Bipolaris genera; two morphological groups of the Cladosporium; Colletotrichum sp.; three morphological groups of Curvularia; Epicoccum sp.; Fusarium verticillioides; Fusarium semitectum; Leptosphaerulina sp.; Nigrospora sp.; Penicillium sp.; Periconia sp.; Phoma herbarum; Rhizopus sp. and Trichoderma sp. The most frequently found were: Bipolaris sacchari; Bipolaris spp.; Cladosporium spp.; Curvularia spp.; Fusarium verticillioides; Fusarium semitectum and Phoma herbarum. When the incidence percentage of the diverse fungi was compared with the seed production conditions, the relation of temperature and relative hu midity with fu ngical incidence was not noticed. It was considered that the incidence's variations can be related to different sources of inoculum where the plants were crossed or to genetic characteristics of the seeds. Palavras
ABSTRACT. Brown rust (causal agent Puccinia melanocephala) is an important sugarcane disease that is responsible for large losses in yield worldwide. Despite its importance, little is known regarding the genetic diversity of this pathogen in the main Brazilian sugarcane cultivation areas. In this study, we characterized the genetic diversity of 34 P. melanocephala isolates from 4 Brazilian states using loci identified from an enriched simple sequence repeat (SSR) library. The aggressiveness of 3 isolates from major sugarcane cultivation areas was evaluated by inoculating an intermediately resistant and a susceptible cultivar. From the enriched library, 16 SSR-specific primers were developed, which produced scorable alleles. Of these, 4 loci were polymorphic and 12 were monomorphic for all isolates evaluated. The molecular Genetic diversity among Puccinia melanocephala isolates characterization of the 34 isolates of P. melanocephala conducted using 16 SSR loci revealed the existence of low genetic variability among the isolates. The average estimated genetic distance was 0.12. Phenetic analysis based on Nei's genetic distance clustered the isolates into 2 major groups. Groups I and II included 18 and 14 isolates, respectively, and both groups contained isolates from all 4 geographic regions studied. Two isolates did not cluster with these groups. It was not possible to obtain clusters according to location or state of origin. Analysis of disease severity data revealed that the isolates did not show significant differences in aggressiveness between regions.
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