Abstract
ABSTRACT The objective of this study was to evaluate the genetic control integrated to the chemical control of Asian soybean rust (ASR) and the effects of these measures on crop yield. The experiment was conducted in Erechim, Rio Grande do Sul State, Brazil, in 2016/17 and 2017/18 crop years, under a randomized block design, in a subdivided plot scheme (cultivars in the plots and fungicides in the subplots), with four replicates. The following cultivars were used: BMX Vanguarda (without ASR tolerance); TMG 7062; TMG 7262, and TMG 7161, tolerant to ASR (Inox™ Technology cultivars). The fungicides used were: T1) control (without application of fungicides); T2) azoxystrobin + benzovindiflupyr; T3) difenoconazole + cyproconazole; T4) trifloxystrobin + prothioconazole, and T5) epoxiconazole + fluxapyroxad + pyraclostrobin. Four fungicide applications were carried out at the V6, R1, R5.1 and R6 stages. During the experiment, for the calculation of the area under disease progress curve (AUDPC), disease severity was assessed at 7-day intervals in a random sample of 10 trifolia per plot. After harvest, yield components were determined: number of grains per plant, thousand grain weight (g), and yield (kg ha-1). In 2017/18 crop year, the fungicide difenoconazole + cyproconazole was not efficient for ASR control. The soybean cultivars TMG 7062, TMG 7161 and TMG 7261 delayed the disease progression; however, only TMG 7161 presented tolerance in the presence of the inoculum in 2016/17 and 2017/18 crop years. The association between chemical and genetic control is shown to be efficient for ASR control.
Highlights
The association between chemical and genetic control is shown to be efficient for Asian soybean rust (ASR) control
Due to the importance of soybean and Asian soybean rust, the objective of this study was to evaluate genetic control integrated with chemical control of ASR and the effects of these measures on soybean yield
In 2016/17 crop year, severity was lower than that observed in 2017/18 crop year (Table 1)
Summary
In 2017/18 crop year, the fungicide difenoconazole + cyproconazole was not efficient for ASR control. The soybean cultivars TMG 7062, TMG 7161 and TMG 7261 delayed the disease progression; only TMG 7161 presented tolerance in the presence of the inoculum in 2016/17 and 2017/18 crop years. The association between chemical and genetic control is shown to be efficient for ASR control. O experimento foi conduzido em Erechim/RS, nas safras 2016/17 e 2017/18, sob delineamento de blocos casualizados, em esquema de parcela subdividida (cultivares, nas parcelas; e fungicidas, nas subparcelas), com quatro repetições. Na safra 2017/18 o fungicida difenoconazol + ciproconazol não foi eficiente para o controle da FAS. The use of fungicides is the main form to control Asian soybean rust (ASR). The difficulty in identifying resistant cultivars lies in the several races of P. pachyrrizi showing multiple virulence alleles [17, 18]
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