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Wheat rust in Brazil

Wheat is the best cropping option for the winter season in southern Brazil. According to current predictions the wheat area in 2015 will decline by 5.3% (146 thousand hectares) due to low prices for cereal grain and to high precipitation and disease severities (principally FHB and wheat blast) in 2014 that caused high losses in production. Due to high inoculum pressure leaf rust is controlled every year by resistance genes and fungicide application (an average three applications during the growing season to control all wheat diseases). Of 119 cultivars possibly cultivated in Brazil, 58 are moderately susceptible or susceptible to leaf rust. The objective of this study was to survey the Puccinia triticina population in order to identify the predominant races in Brazil. Infected leaves were collected from wheat crops in different regions in 2014. After isolating pustules and increasing the inoculum, the Thatcher differential lines [Lr1 2a 2c 3a (set 1), Lr9 16 24 26 (set 2), Lr3ka 11 17 30 (set 3), Lr10 18 21 23 (set 4), Lr14a 14b 10+26 20 (set 5), Lr3bg 27+31 and line ORL04002 - Toropi/Ônix) were inoculated. From 186 field samples, 74 isolates were evaluated. Race T(DF)T-MT, first identified in 2007, was predominant in 2013 and 2014. The frequency of race TDP-M(RT), first identified in 2008, increased to second position in 2014. Stripe rust and stem rust are not common diseases in Brazil; however, samples of both diseases were collected in 2013, but not in 2014. Most of the Brazilian OR Sementes lines evaluated in Argentina in 2014 stood out by resistance to stem rust, indicating the importance of incorporating resistance to all three rusts in Brazilian cultivars.

Barcellos
OR Melhoramento de Sementes Ltda., Brazil
Keywords: 
Primary Author Email: 
amarilis@orsementes.com.br
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