A comparison of web blight epidemics on common bean cultivars with different growth habits

A comparison of web blight epidemics on common bean cultivars with different growth habits 
Publication Type 
Journal Article 
Costa-Coelho GR, Café Filho AC, Lobo M 
Year of Publication 
Crop Protection 
16 - 20 
Date Published 
Beans, Disease escape, Epidemics, Rhizoctonia solani, Thanatephorus cucumeris, Tropical disease 


  • Web blight epidemics were described on 10 common bean cultivars.
  • Upright growth cultivars showed lowest area under the disease progress curves (AUDPC).
  • In contrast, plants of indeterminate prostrate growth showed highest AUDPCs.
  • Such differences were consistent through three consecutive cropping seasons.
  • Determinate bush upright plants can improve disease management in the field.

The progress of web blight caused by Thanatephorus cucumeris on common bean (Phaseolus vulgaris) “Carioca” cultivars with different growth habits was compared in a three-season study. Field trials were conducted in 2004/2005, 2005/2006 and 2006/2007 in a naturally infested area, with 10 susceptible cultivars from group I (determinate bush, upright plants: cvs. Iapar 81, BRS Horizonte and FT Magnífico); group II (indeterminate bush plants: cvs. BRS Pontal, and Pérola) and group III (plants of indeterminate prostrate growth: cvs. BRSMG Talismã, Aporé, BRS Requinte, Carioca, Carioca Precoce). Severity of web blight was assessed weekly and the resulting progress curves were fit to the monomolecular model. Overall disease impacts were estimated by the area under the disease progress curve (AUDPC), disease progress rate and disease onset. No significant interaction between AUDPC and planting season was detected. Cultivars BRS Horizonte, FT Magnífico and Iapar 81, with upright architecture, short guides, high pods and closer branches presented the lowest AUDPCs. The highest AUDPCs were found among indeterminate lodged plants with long guides and low pods (cvs Aporé and Carioca Precoce), while indeterminate bush cultivars were fitted in an intermediate rank. Differences in disease epidemics among the three groups were confirmed by intercept and disease progress rates of linearized models. Such parameters were significantly lower for upright genotypes, probably because they result in late contact between neighbor plants and consequently delay the establishment of conducive microclimate and mycelial bridges for web blight development. Yields were strongly reduced due to the extremely high disease levels that prevailed at all three seasons. Nevertheless, a negative correlation between grain yield and web blight severity was significant in 2006/2007. Despite the fact that the number of cultivars is too small to generalize responses on escape to web blight, results evidenced that choice of plant architecture is a useful strategy for web blight management.

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