Ecophysiology of susceptible and resistant tomato plants inoculated with Fusarium oxysporum f. sp. lycopersici

Gas exchange and chlorophyll a fluorescence, visible symptoms and hyphal colonization in sensitive ('Craigella') and resistant ('Craigella FR') tomato plants inoculated with Fusarium oxysporum f. sp. lycopersici were studied. One month after the inoculation, measurements were carried out on the first uncolonized and on the youngest fully expanded leaves. The presence of symptoms was always associated with vessel colonization and all leaves over the end point of colonization were apparently healthy. In the first uncolonized leaf of infected sensitive individuals, there was a strong reduction in photosynthetic activity attributable to a severe decline in stomatal conductance. On the other hand, the increase in intercellular CO 2 concentration (+23%) was related to the alteration at mesophyllic level. The photochemical efficiency of PSII did not change even if the non-photochemical quenching increased and the photochemical quenching decreased significantly. Similar results were obtained in the first uncolonized leaf of 'Craigella FR'. Photosynthetic activity did not change in the last fully expanded uncolonized leaf of the resistant plants; in sensitive ones, there are similar alterations to the first uncolonized leaf. Results are discussed to further characterize the mechanism by which Fusarium inhibits photosynthetic process in resistant and susceptible material