Detached wheat leaf assay for assessing the sensitivity of Puccinia triticina races to fungicides

• Published in: Summa phytopathologica 2017-09, Vol.43 (3), p.181-185
• Main Authors: Turra, Camila, Reis, Erlei Melo, Barcellos, Amarilis Labes
• Format: Article
• Language: English
• ISSN: 0100-5405; 0100-5405
• DOI: 10.1590/0100-5405/1992

ABSTRACT In experiments conducted in a growth chamber and in laboratory, the preventive, curative and eradicative action of fungicides was assessed for the control of Puccinia triticina races MFT-MT and TFP-HT. The effect of fungicides tebuconazole (triazole) and azoxystrobin (strobilurin) was evaluated separately. Seedlings were inoculated with a suspension of 50 x 103 uredospores/mL distilled water added of 120 μL adjuvant (polyoxyethylene sorbitan monolaurate Tween 20 - Synth). Fungicides were applied 24 hours before inoculation (preventive control), 96 hours after inoculation (curative control) and ten days after inoculation (eradicative control), both in seedlings (in vivo) grown in pots and in leaf segments (in vitro) on Petri dishes. The effect of treatments based on the number of uredia/cm2 and the production of uredospores/uredium were tested in vivo and in vitro. When applied preventively, for both races, the two fungicides controlled 100% leaf rust, and when applied curatively, only azoxystrobin led to 100% control. The tested races remain sensitive to azoxystrobin but maintain the reduction in sensitivity to tebuconazole. Detached wheat leaf assay was efficient in assessing the sensitivity of P. triticina races to fungicides and leaves remained green for 18 days. RESUMO Em experimentos conduzidos em câmara climatizada e laboratório, quantificou-se a ação preventiva, curativa e erradicativa dos fungicidas no controle das raças MFT-MT e TFP-HT de Puccinia triticina. Avaliou-se o efeito dos fungicidas tebuconazol (triazol) e azoxistrobina (estrobilurina), isoladamente. As plântulas foram inoculadas com uma suspensão de 50 x 103 uredosporos/mL de água destilada adicionada de 120 μL/L de adjuvante (polioxietileno sorbitano monolaurato Tween 20 - Synth). Os fungicidas foram aplicados, 24 horas antes da inoculação (controle preventivo), 96 horas após a inoculação (controle curativo) e dez dias após a inoculação (controle erradicativo), tanto nas plântulas (in vivo) cultivadas em vasos como nos segmentos foliares (in vitro) em placas de Petri. Avaliou-se o efeito dos tratamentos em função do número de urédias/cm2 e a produção de uredosporos/urédia, in vivo e in vitro. Os fungicidas aplicados preventivamente, para ambas as raças, controlaram 100% a ferrugem da folha e curativamente somentre a azoxistrobina. As raças testadas permanecem sensíveis à azoxistrobina, porém, mantendo a redução da sensibilidade ao tebuconazole. O método de folhas de trigo dest