Gas exchange and flowering in Verticillium-wilted pepper plants

In Navarra, Northern Spain, Verticillium dahliae Kleb. is one of the pathog ens that causes drastic reductions in pepper production. The aim of this st udy therefore was to describe how infection by V. dahliae affects gas excha nge during the flowering of pepper in order to determine some possible fact ors contributing to the significant decrease of plant yield. Verticillium w as inoculated when plants had started flowering. The first leaf wilting sym ptoms appeared on day 18 after inoculation, but leaf water potential rapidl y decreased after infection. The inoculated plants produced more flowers th an the controls between 15 and 33 days after inoculation, but flower produc tion declined after day 33. Inoculated plants also suffered more defoliatio n 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 t he decrease in photosynthesis was in part due to defoliation and chlorophyl l degradation, as well as premature flower fall. These factors contributed to the negative effects of Verticillium infection on pepper yield.