Sensitivity of Corynespora cassiicola from soybean to carbendazim and prothioconazole

Abstract

The incidence of target spot disease on soybean has increased in recent years in Brazil even with intensive use of fungicides, and fungal resistance has been reported in recent studies. The objective of this study was to determine the fungicide sensitivity to carbendazim and prothioconazole in a sample of 24 isolates of Corynespora cassiicola from soybean collected from 1996 to 2011 in the states of Paraná, Mato Grosso and São Paulo (Brazil) and Corpus Christi (Paraguay). The 50% effective concentration (EC 50 ) values were estimated by the relative mycelium growth reduction on fungicide-amended medium with the doses of 0, 0.5, 1, 10, 100 and 1000 µg of active ingredient/ mL. For carbendazim, four highly resistant isolates (EC 50 ≥50 μg/mL) were observed from samples collected from Mato Grosso in 2008 and from Paraná and Mato Grosso in 2011. The EC 50 values for prothioconazole ranged from 0.47 µg/mL to 26.44 µg/mL (mean: 5.02 µg/ ml). The results reinforce the occurrence of C. cassiicola resistance to benzimidazole in Paraná and Mato Grosso states.

In vitro sensitivity of Corynespora cassiicola isolated from soybean to fungicides and field chemical control of target spot

“…Most isolates had EC 50 values above the highest tested concentration (1000 µg mL -1 ), indicating resistance of C. cassiicola to carbendazim and thiophanate-methyl in Brazil. Similar results were obtained in other studies (26,31,33).…”

“…In a recent survey, there was evidence of sensitivity of C. cassiicola to carbendazim only in samples collected before 2007, and nonsensitivity in recent isolates obtained after 2008 (33). These authors considered isolates sensitive when EC 50 ≤ 1.0 µg mL -1 , and highly resistant when EC 50 ≥ 50 µg mL -1 .…”

Enantiomeric separation of prothioconazole and prothioconazole‐desthio on chiral stationary phases

“…The results suggested that (R,R)-Whelk-O1 could not separate whether prothioconazole or prothioconazole-desthio, while Chiralcel OD showed the best resolution capability (see Table S1). The maximum Rs could be up to 24 The steric hindrance adjacent to the chiral carbon played an important role in the resolution on (R,R)-Whelk-O1. It was hard to realize the chiral separation of prothioconazole only on Chiracel OJ-H and Chiralcel OD (see Table 1).…”

Evaluation of Fungicides against Target Leaf Spot Caused by (Corynespora cassiicola) in vitro Condition

“…The per cent inhibition of radial growth, sporulation and spore germination over control was calculated as per the following formula (Vincent, 1977 Xavier et al, (2013), studied the incidence of target spot disease on soybean has increased in recent years in Brazil even with intensive use of fungicides, and fungal resistance has been reported in recent studies. They determine the fungicide sensitivity to carbendazim and prothioconazole in a sample of 24 isolates of C. cassiicola from soybean collected from 1996 to 2011 in the states of Parana Mato Grosso and Sao Paulo (Brazil) and Corpus Christi (Paraguay).…”