Downy mildew (Plasmopara viticola) is one of the most important diseases in grape-growing areas worldwide, including Brazil. To examine pathogen population biology and structure, P. viticola was sampled during the 2015/16 growing season from 516 lesions on nine grape cultivars in 11 locations in subtropical areas of São Paulo State, Brazil. For identification of cryptic species, a subsample of 130 isolates was subjected to cleaved amplified polymorphic sequence (CAPS) analysis, and for 91 of these isolates the ITS1 region was sequenced. These analyses suggest that the population of P. viticola in São Paulo State consists of a single cryptic species, P. viticola clade aestivalis. Seven microsatellite markers were used to determine the genetic structure of all 516 P. viticola isolates, identifying 23 alleles and 55 multilocus genotypes (MLGs). Among these MLGs, 34.5% were clonal and represented 93% of the isolates sampled. Four dominant genotypes were present in at least five different locations, corresponding to 65.7% of the isolates sampled. Genotypic diversity (Ĝ = 0.21-0.89) and clonal fraction (0.58-0.96) varied among locations (populations). Most populations showed significant deviation from Hardy-Weinberg expectations; in addition, excess of heterozygosity was verified for many loci. However, principal coordinate analysis revealed no clusters among locations and no significant isolation by distance was found, suggesting high levels of migration. The results indicate that downy mildew epidemics result from multiple clonal infections caused by a few genotypes of P. viticola, and reproduction of P. viticola in São Paulo State is predominantly asexual.
-Seeds can be considered one of the most efficient forms to disseminate pathogens. Therefore, the use of healthy seeds is extremely important to establish a crop, and seed health testing must be performed to determine the seed sanitary quality. This study aimed to compare the efficiency of seed health testing to detect Pyricularia grisea and Fusarium graminearum in three samples of wheat seeds. Methods evaluated were Blotter test with freezing (BTF) and potato-dextrose-agar culture medium (PDA). The incubation temperatures were 20 ºC and 25 ºC. From each sample, a subsample was submitted to seed asepsis using hypochlorite solution (1%) and another analyzed without seed asepsis. The temperatures evaluated did not influence the detection of the pathogens. P. grisea incidence ranged from 4.5 to 17% with BTF without seed asepsis. The BTF with seed asepsis and PDA (with and without seed asepsis) presented pathogen incidence no higher than 1.5%. Moreover, results suggested that most part of P. grisea inoculum was presented externally on seed tissues. PDA medium was more efficient to detect F. graminearum, independently of seed asepsis. By this method, pathogen incidence ranged from 3 to 39%. F. graminearum incidence using BTF with seed asepsis varied from 0.5 to 1.5% and BTF without seed asepsis presented a pathogen incidence of 5.0 to 12.5%. The Blotter test with freezing was more efficient to detect P. grisea while the PDA medium was more efficient to detect F. graminearum.Index terms: Triticum aestivum, detection methods, seed pathology.Eficiência do método do papel de filtro e do meio de cultura agarizado na detecção de Fusarium graminearum e Pyricularia grisea em sementes de trigo RESUMO -Sementes podem ser consideradas como uma das formas mais eficientes na disseminação de patógenos. Portanto, o uso de sementes sadias é de extrema importância para o estabelecimento de uma cultura e testes de sanidade devem ser realizados para determinar a sua qualidade sanitária. O presente trabalho teve como objetivo comparar a eficiência de métodos de sanidade na detecção de Pyricularia grisea e Fusarium graminearum em três amostras de sementes de trigo. Os métodos avaliados foram o papel de filtro com congelamento (PFC) e o meio de cultura batata-dextrose-ágar (BDA). As temperaturas de incubação foram 20 ºC e 25 ºC. De cada amostra, uma submostra foi submetida a assepsia de sementes usando solução de hipoclorito (1%) e outra analisada sem assepsia. As temperaturas analisadas não influenciaram na detecção dos patógenos. A incidência de P. grisea variou de 4,5 a 17% no método PFC sem assepsia das sementes. O PFC com assepsia e o BDA (com e sem assepsia) apresentou incidência do patógeno inferior a 1,5%. Além disso, os resultados sugeriram que a maior parte do inóculo de P. grisea estava presente externamente aos tecidos da semente. O meio BDA foi mais eficiente na detecção de F. graminearum, independentemente da assepsia das sementes. Por esse método, a incidência do patógeno variou de 3 a 39%. A incidência de F. grami...
Soybean root and stem rot caused by the oomycete Phytophthora sojae is a destructive disease worldwide that can affect plants at any growth stage. The use of resistant cultivars is the most effective method of controlling the disease. Therefore, monitoring changes in the population of P. sojae regarding the dynamics of avirulence genes capable of overcoming resistance genes (Rps) is important to reduce yield losses and to enhance the effectiveness of the Rps genes. Forty isolates of P. sojae sampled from a region of high incidence of soybean root and stem rot in Brazil were characterized using 14 soybean differentials and 28 pathotypes were identified. Compared to a study conducted a decade ago there was a major shift in pathotype diversity and complexity towards both higher numbers of different pathotypes and of avirulence genes in a given individual in the current population of P. sojae. Breeding programs aiming at developing soybean cultivars with resistance to root and stem rot should consider the high variability in the population of P. sojae and seek for strategic deployment of genes and germplasm.
ResumoO estado de São Paulo é o terceiro maior produtor de uvas do Brasil e o maior produtor nacional de uvas de mesa, sendo a variedade Niágara Rosada (Vitis labrusca) a mais plantada no estado. O objetivo do trabalho foi verificar a viabilidade econômica do cultivo de Niágara Rosada. O projeto foi dimensionado para uma área de três hectares implantada no município de Piracicaba, SP. As plantas foram conduzidas no sistema em espaldeira em uma densidade de 5000 plantas ha -1 . O fluxo de caixa foi dimensionado para um período de 13 anos. AbstractSão Paulo State is the third largest grapevine producer in Brazil and the largest national producer of table grapes. Niagara Rosada (Vitis labrusca) is the most planted cultivar in the State. This study aimed to verify the economic feasibility of Niagara Rosada production. The project was designed for an area of tree hectares to be implemented in Piracicaba, SP. Plants were conducted in vertical trellis system with 5000 plants ha -1 . The cash flow was dimensioned for a period of 13 years. Costs with implantation and maintenance of the vineyard, bank financing, payment of the Rural Worker Support Fund, and the opportunity cost of land were estimated. The minimum acceptable rate of return [MARR] used was 11.45%. The economic indicators calculated were Net Present Value [NPV], Internal Rate of Return [IRR], simple payback, discounted payback, and benefit-cost ratio. Positive values of NPV (R$ 398,951.36) and benefit-cost ratio (1.81) were obtained. The IRR estimated was 27.34%, higher than the MARR. The simple payback and the discounted payback were five years and six years, respectively, indicating that the period of returning the invested capital was lower than the project period. The estimated economic indicators demonstrated the financial feasibility of the project.
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