RESUMOPalavras-chave adicionais: IC 50 , fungicida resistência, fator de redução da sensibilidade.Experimentos foram conduzidos para determinar, in vivo a IC 50 e CI 9 0 pa ra fu ngicida s inibidores da demetila çã o (IDM)(tria zois) e inibidores da quinona externa (IQe) (estrobilurinas) a cinco raças de Puccinia triticina mais frequentes na safra 2007, no Sul do Brasil. Os experimentos fora m rea liza dos em câ ma ra de crescimento com plâ ntu la s de trigo. Os fu ngicida s IDMs fora m testa dos na s concentrações em mg/L de 0,0; 0,02; 0,2; 2,0; 20,0; 100,0 e 200,0 e os IQes nas concentrações de 0,0; 0,0001; 0,001; 0,01; 0,1, 1 e 10,0 mg de ingrediente activo/L de água. Os fungicidas foram aplicados preventivamente 24 horas antes da inoculação das plântulas com os Arduim, F.S.; Reis, E.M.; Barcellos, A.L.; Turra, C. Redução da sensibilidade de raças de Puccinia triticina, agente causal da ferrugem da folha do trigo, aos fungicidas DMI e QoI, in vivo. Summa Phytopathologica, v.38, n.4, p.306-311, 2012. Fungicides were preventively applied at 24 hours before the inoculation of seedlings with the fu nga l spores. T he effect of treatments wa s Arduim, F.S.; Reis, E.M.; Barcellos, A.L.; Turra, C. In vivo sensitivity reduction of Puccinia triticina races, causal agent of wheat leaf rust, to DMI and QoI fungicides.
Studies on the genetic variability of Puccinia triticina in inoculum collected in Brazil started in 1941 with Vallega (20). The pioneering work in Brazil dates from 1949 (16) at "Instituto Agronômico do Sul", Ministry of Agriculture (MA), in Pelotas, Rio Grande do Sul State (RS), and continued after 1975 at Embrapa Wheat in Passo Fundo, RS. In 2002, analyses for the identification of P. triticina races continued at OR Seed breeding, simultaneously to Embrapa's program, both in Passo Fundo. The investigators involved in the identification of races in Brazil were Ady Raul da Silva in Pelotas (MA), Eliza Coelho in Pelotas (MA) and in Passo Fundo (Embrapa), Amarilis Labes Barcellos in Pelotas (MA) and in Passo Fundo (Embrapa and OR), Camila Turra in Passo Fundo (OR) and Marcia Chaves in Passo Fundo (Embrapa). From 1979 to 2010 growing season, 59 races were determined, according to the differentiation based on the expression of each Lr resistance gene. On average, one to three new races are detected per year. Research has focused on the use of vertical resistance; however, lately some institutes have searched more durable resistance, of the adult-plant type (horizontal, less race-specific). The uninterrupted monitoring of the wheat rust pathogenic population in Brazil during so many decades allowed the understanding of the evolution and virulence of races. The use of international nomenclature adopted by some programs has allowed the comparison of the fungus variability in Brazil with that in other countries, especially where frontiers are not barriers for spore transportation, confirmed by the occurrence of the same races all over one region.
353Leaf rust caused by Puccinia triticina (Pt) Eriks. is one of the major leaf diseases affecting wheat in Brazil. Damage caused to wheat by leaf rust can be assessed by using the normalized function Y = 1,000 -6.4 I (Y = yield kg/ha and I = leaf incidence) (16).The main strategies for leaf rust control have been the development and the cultivation of genetically resistant cultivars, as well as the application of fungicides to aboveground plant parts (16). Genetic resistance of wheat to Pt is not durable due to the high fungal variability, resulting in occurrence of at least one new virulent race at every wheat growing season (3).Resistant cultivars are developed by inoculating Pt in new lines of wheat. For wheat leaf rust, resistance is race-specific; thus, dominant races are individually inoculated into the material to be selected (3). This requires a lot of material, facilities to grow the plants, and facilities to maintain the pure races. Each Pt race should be maintained, multiplied and kept pure, preventing mixtures with other races. RESUMOPalavras-chave adicionais: Ferrugem da folha, raças fisiológicas, Triticum aestivum.O método de preservação de folhas de trigo destacadas , em placa de Petri, foi usado para inoculação e desenvolvimento do fungo Puccinia triticina, agente causal da ferrugem da folha do trigo. Foram comparadas as reações de 26 cultivares de trigo em plântulas cultivadas em vasos (in vivo) e em folhas destacadas (in vitro) inoculadas com quatro raças fisiológicas do patógeno. Inoculou-se também Turra, C.; Reis, E.M.; Barcellos, A.L. Reação de cultivares de trigo e de linhagens da série diferencial à raças de Puccinia triticina, em folhas destacadas. Summa Phytopathologica, v.40, n.4, p.353-357, 2014. 24 linhas da série diferenciadora de raças do fungo nas mesmas condições. Após a inoculação, o material foi mantido em câmara climatizada por 15 dias. A avaliação da reação foi realizada no 15º dia após a inoculação. Os resultados obtidos para cada raça nos genótipos avaliados confirmaram a eficiência do método de folha destacada na avaliação da reação de cultivares de trigo. Reaction of wheat cultivars and differential lines to Puccinia triticina races in detached leaves 10.1590/0100-5405/1993The technique of detached leaves can be an important tool to rationalize the evaluation of the reaction of cultivars in the determination of Pt races.This technique has been used in studies of host-pathogen interaction with obligate parasites, such as fungi that cause rusts. Grass leaves or leaf pieces (wheat, oats, barley, rice and others) have been allowed to float on water or sucrose-based solutions, with or without benzimidazole, cytokine or kinetin (4, 7,10,11,12,17,18).Mignucci (14), Felsenstein (8) and Felsenstein (9) mention that adaptation of the detached leaf method was implemented to monitor the sensitivity of Pt to different fungicides in Europe.Considering Pt new races, race determination in every season and resistance break in some cultivars, the search for new resistant cultivars requi...
Wheat leaf rust caused by the fungus Puccinia triticina may lead to damage of up to 62%. This study aimed to test the effect of different uredospore concentrations on the infectious process of four physiological races. The races MFJ-MN, MFT-MT 4002 S, TPT-HT and TDP-HT were inoculated, when the first leaf was expanded in the seedling stage, on cultivars Ônix, Abalone, Morocco and Quartzo, respectively. The tested concentrations were 0.0; 5 x 103; 10 x 103; 20 x 103 and 40 x 103 uredospores/mL mineral oil (Soltrol). After inoculation, seedlings were kept in a growth chamber at 20°C ± 2, near 100% humidity, in the dark, for 20 hours. Fifteen days after inoculation, the density of uredia/leaf was evaluated. The concentration of 40 x 103 uredospores/mL resulted in a disease intensity that allows safe differentiation between susceptible and resistant cultivars in the seedling stage, without causing leaf senescence due to high uredinium density.
In the present era of climate instability, Canadian wheat production has been frequently affected by abiotic stresses and by dynamic populations of pathogens and pests that are more virulent and aggressive over time. Genetic diversity is fundamental to guarantee sustainable and improved wheat production. In the past, the genetics of Brazilian cultivars, such as Frontana, have been studied by Canadian researchers and consequently, Brazilian germplasm has been used to breed Canadian wheat cultivars. The objective of this study was to characterize a collection of Brazilian germplasm under Canadian growing conditions, including the reaction of the Brazilian germplasm to Canadian isolates/pathogens and to predict the presence of certain genes in an effort to increase genetic diversity, improve genetic gain and resilience of Canadian wheat. Over 100 Brazilian hard red spring wheat cultivars released from 1986 to 2016 were evaluated for their agronomic performance in eastern Canada. Some cultivars showed good adaptability, with several cultivars being superior or statistically equal to the highest yielding Canadian checks. Several Brazilian cultivars had excellent resistance to leaf rust, even though only a few of these tested positive for the presence of either Lr34 or Lr16, two of the most common resistance genes in Canadian wheat. Resistance for stem rust, stripe rust and powdery mildew was variable among the Brazilian cultivars. However, many Brazilian cultivars had high levels of resistance to Canadian and African - Ug99 strains of stem rust. Many Brazilian cultivars had good Fusarium head blight (FHB) resistance, which appears to be derived from Frontana. In contrast FHB resistance in Canadian wheat is largely based on the Chinese variety, Sumai-3. The Brazilian germplasm is a valuable source of semi-dwarf (Rht) genes, and 75% of the Brazilian collection possessed Rht-B1b. Many cultivars in the Brazilian collection were found to be genetically distinct from Canadian wheat, making them a valuable resource to increase the disease resistance and genetic variability in Canada and elsewhere.
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