Etiologia e quantificação dos agentes causais de manchas foliares na cultura do trigo nas safras 2008 a 2011

Abstract

RESUMOPalavras-chave adicionais: Triticum aestivum, Drechslera, Bipolaris, Stagonospora, ocorrência.T he whea t (Tritic u m a e stiv u m L.) crop is one of the most importa nt options for cultiva tion in the winter sea son. Among the foliar diseases, yellow leaf spot, brown-spot and septoriosis, are cited as the most frequent leaf spot in wheat. This study aimed to identify and quantify the pathogenic fungi associated with leaf spot symptoms in wheat cultivars in Regions of Value for Cultivation and Use (RVCU). One hundred and sixty two samples collected in 2008 to 2011 season, in wheat field in the states of Paraná, Santa Catarina, Minas Gerais, São Paulo and Rio Grande do Sul were analysed. Twenty five aseptic lea f discs per sample were distributed in a moist chamber within a Tonin, R. gerbox a nd incu ba ted a t 2 5 ºC a nd 1 2 hou rs photoperiod. After incubation for eight days the identification and quantification of the fungi incidence present in lea f discs were performed. In the 2 00 8 sea son, there wa s a predominance of Dre c hslera sicc a ns with a n incidence of 0 to 75 %, being the first report of this species in wheat, Bra zil. On the sea sons a vera ge B. so ro k in ia n a showed a 7 .6 % incidence a nd 5 3 .1 % frequ ency, D. tritic i-re p e ntis presented a n incidence of 59.2 % and 90.6 % frequency, D. siccans incidence of 11.0 % a nd 4 8.1 % frequency, and S. nodorum with incidence and frequency of 1.55 % and 2.2 %, respectively.A cultura do trigo é uma das opções mais importantes para cultivo na safra de inverno. Entre as doenças foliares a mancha-amarela da folha, a ma ncha marrom e a septoriose sã o cita da s como a s mais frequ entes em trigo. Este tra ba lho teve como objetivo identificar e quantificar os fungos fitopatogênicos associados a sintomas de manchas foliares em cultivares de trigo, nas tritici-repentis apresentou incidência de 59,2 % e frequência de 90,6 %, D. siccans incidência de 11,0 % e freqüência de 48,1 % e S. nodorum com incidência e frequência de 1,55 % e de 2,2 %, respectivamente.Additional keywords: Triticum aestivum, Drechslera, Bipolaris, Stagonospora, occurrence. ABSTRACTO trigo (Triticum aestivum L.) ocupa papel de destaque dentre os cereais produzidos no Brasil, tendo uma importante função econômica e social. Apesar dessa importância, seu potencial produtivo não tem sido explorado devidamente (1).A produção nacional de trigo na safra 2011/12 foi de 5.788 milhões de toneladas, com rendimento médio de 2.672 Kg/ha e o consumo de 11 milhões de toneladas. A área cultivada foi de 2.166,2 mil hectares, distribuídos nas regiões centro-oeste, sul e sudeste (5).As limitações ocorrentes para produzir trigo são a suscetibilidade dos cultivares, a agressividade dos fungos agentes causais de doenças, o excesso de chuva, o acúmulo de dias nublados e a monocultura em plantio direto favoráveis à ocorrência e ao aumento da intensidade das doenças (11).Devido às condições ambientais adversas, aliadas à suscetibilidade das cultivares e dependendo das práticas culturais, o trigo po...

Widespread distribution of resistance to triazole fungicides in Brazilian populations of the wheat blast pathogen

“…tritici (Tonin et al, 2013), while reductions in sensitivity to strobilurins (QoIs) were reported for the wheat yellow leaf spot pathogens Drechslera siccans and Drechslera tritici-repentis (Tonin et al, 2013).…”

Integrated production systems revealing antagonistic fungi biodiversity in the tropical region

“…These transition areas make up a complex system, which is not yet well understood, which involves the cycling of nutrients between soil-plant-animal. Deforestation and lack of diversity of cultures may result in an unsustainable system, characterised by progressive soil degradation due to the emergence of pests and diseases in agricultural areas (Alves et al, 2011;Santos et al, 2012;Tonin et al, 2013), high production costs and resistance of pathogens to fungicides (Xiao et al, 2013).…”

Addition of mancozeb to the fungicide mixtures DMI + QoI and SDHI + QoI on the control of wheat leaf blights

“…From 2004 season, farmers and farm advisers have complained about the difficulty in controlling wheat leaf blights by using fungicides. Some authors (11,12) have shown that the reduced sensitivity of Drechslera spp. to strobilurins and triazoles, except for pyraclostrobin, may explain the control failure.…”