Abstract

DIAZ, CECILIA G. et al. Effect of common bacterial blight in the photosynthetic efficiency and in the yield of common bean. Fitopatol. bras. [online]. 2001, vol.26, n.1, pp. 71-76. ISSN 0100-4158.  http://dx.doi.org/10.1590/S0100-41582001000100012.

The effect of common bacterial blight on photosynthetic efficiency and on common bean (Phaseolus vulgaris) yield was quantified. Two experiments were carried out during the wet season of 1997 at Piracicaba-SP using two cultivars, IAC-Carioca and Rosinha. Different levels of severity were obtained by varying the number of inoculations with the pathogen. Disease severity, assessed with a diagrammatic scale, did not show a significant linear relationship (P>0.01) with yield, while the healthy leaf area duration (HAD) was significantly (P£0.01) linear in relation to yield in both experiments (R² between 0,66 and 0,78). Photosynthesis was related to diseased leaf area by the equation P_x/P₀=(1-x )^b, where P_x is the net photosynthesis of the leaf with severity x, P₀ is the mean net photosynthesis of the healthy leaves, x is the disease severity, and b is the relation between virtual and visual lesion. The values of b, determined by non-linear regression, were 3.08±0.18 and 3.19±0.14 for IAC-Carioca and Rosinha, respectively. In general, the use of b did not significantly improve the HAD-yield relationship.

Keywords : Phaseolus vulgaris; Xanthomonas axonopodis pv. phaseoli; lesão virtual; lesão visual; eficiência fotossintética; avaliação de danos.