Abstract:

In order to study a series of physiological changes in common bean after infestation with bacterial blight, different bean bacterial blight resistant varieties, ‘Shuangfeng No.3’ (SF, resistant variety) and ‘Cat's Eye’ (MY, susceptible variety) were used as test materials to determine the effects of common bean bacterial blight on photosynthetic parameters, photosynthetic pigment content, POD, SOD activity and superoxide anion content-accumulation at different times after inoculation. The results showed that: (1) among different resistant varieties, the net photosynthetic rate, stomatal conductance, stomatal limitation value and water use efficiency of the two varieties showed a downward trend, except for the increase of intercellular CO₂ concentration, and the increase and decrease showed MY>SF. (2) Chlorophyll a, chlorophyll b, total chlorophyll and carotenoid contents of the two varieties decreased due to bacterial blight infestation of common beans, and the overall contents showed SF>MY. This indicated that the photosynthesis and photosynthetic pigment contents of SF were less affected by bacterial blight stress of common beans than MY. (3) The overall POD activity of MY was 3 times higher than that of SF, and the SOD activity showed SF>MY. In terms of superoxide anion content-accumulation, the release of SF decreased 2 d earlier than that of MY, and its defense mechanism appeared earlier than MY. It indicated that maintaining high photosynthetic performance was the physiological basis for strong resistance to the bacterial blight of common bean, and both POD and SOD activities can be used as physiological indicators for the identification of resistance to the bacterial blight of common bean.

Key words: common bean, bacterial blight, photosynthetic pigments, photosynthetic properties, physiological and biochemical indicators