Gas Exchange and Flowering in Verticillium-wilted Pepper Plants

In Navarra, Northern Spain, Verticillium dahliae Kleb. is one of the pathogens that causes drastic reductions in pepper production. The aim of this study therefore was to describe how infection by V. dahliae affects gas exchange during the flowering of pepper in order to determine some possible factors contributing to the significant decrease of plant yield. Verticillium was inoculated when plants had started flowering. The first leaf wilting symptoms appeared on day 18 after inoculation, but leaf water potential rapidly decreased after infection. The inoculated plants produced more flowers than the controls between 15 and 33 days after inoculation, but flower production declined after day 33. Inoculated plants also suffered more defoliation and chlorophyll degradation. Leaf conductance and photosynthesis clearly decreased in both groups of plants as a consequence of senescence, but the values in those inoculated were significantly lower. Results suggest that the decrease in photosynthesis was in part due to defoliation and chlorophyll degradation, as well as premature flower fall. These factors contributed to the negative effects of Verticillium infection on pepper yield.