Ecophysiological responses of Eucalyptus inoculated with different Ceratocystis fimbriata isolates

Ever-increasing industrial demand means that forest stands and the number of areas with Eucalyptus plantations are growing rapidly in Brazil and worldwide. This has increased the use of genetic materials, increasing the incidences of pests and diseases. Wilt is caused by the Ceratocystis fimbriata fungus, which is one of the most common diseases in Eucalyptus plantations. This study aimed to evaluate the ecophysiological responses of clonal seedlings of Eucalyptus spp. inoculated with different C. fimbriata isolates. The treatments were LPF 1512, 1806, 1607, and 1657 from the states of São Paulo, Minas Gerais, Bahia, and Mato Grosso do Sul, respectively, and a control comprising distilled water. Fungal isolates were inoculated 60 days after seedling planting. After inoculation, the growth, gas, leaf temperature, and chlorophyll a fluorescence were analyzed. Regardless of the isolate, inoculation with C. fimbriata increased water flow resistance in the xylem vessels of Eucalyptus plants, causing water stress. This results in reduced gas exchange and compromised photosynthetic performance, as evidenced by decreased absorption flux per reaction center and low photosynthetic index values. Furthermore, fungal pathogenicity analysis indicated that the LPF 1657 isolate was most virulent to Eucalyptus seedlings, directly affecting the height, photosynthetic CO2 assimilation, stomatal conductance, and transpiration of the inoculated plants.