Phytophthora gummosis in citrus scion/rootstock combinations with seedlings from buds challenged by this pathogen

Abstract

The objective of this work was to evaluate the response of citrus seedlings formed from buds challenged with Phytophthora citrophthora to the infection caused by this pathogen. For this, 'Pera' orange and 'Tahiti' acid lime scions were grafted on 'Rangpur' lime rootstock. The experiment was carried out in a greenhouse, in a completely randomized design in 2×4 factorial arrangement. Seedlings were challenged by a P. citrophthora isolate. Lesion size, plant height, and stem diameter were evaluated, as well as the following physiological attributes: internal CO₂ concentration, transpiration, stomatal conductance, photosynthetic rate, and water use efficiency. In the 'Pera'/'Rangpur' combination, seedlings formed by buds challenged by the pathogen exhibited smaller lesion sizes and higher photosynthetic rates. However, in the 'Tahiti'/'Rangpur' combination, seedlings presented larger lesions, greater stem diameters, lower transpiration rates, and an increased water use efficiency. The challenge with the pathogen and the use of the 'Pera' orange/'Rangpur' lime combination (less sensitive to the disease) shows additive effects in the induction of resistance to gummosis.