Alteração na atividade de peroxidase e concentração de fenóis em microtangerinas (Citrus spp.) infectadas por Phytophthora parasitica

The present research aimed to characterize and evaluate species and varieties of small-fruited mandarins of Tanaka’s group (Citrus spp.) with potential use as rootstocks, in relation to infection to the Phytophthora parasitica, by means of foliar determination of peroxidase activity and total phenolics content. It was used the following species: C. reshni Hort. ex Tan., C. sunki Hort. ex Tan., C. pectinifera Tan., C. crenatifolia Lush., C. amblycarpa Ochese, C. aurantium L, C. reticulata Blanco and C. limonia Osb. The Center of Citrus Germoplasm of Botucatu and Cordeirópolis provide all plant material. Four resistant varieties to the stem rot and root rot infections: Pectinifera, Crenatifolia, Sun Chu Shu (clone Kat 1004) and Cleopatra (clone 1) were evaluated. Susceptible plants infected by P. parasitica presented higher activity of peroxidase, while phenolics contents were lower in susceptible group

<i>Phytophthora</i> Root Rot in Rangpur Lime Cultivated in Soil Managed with Ecological and Conventional Mower

Root rot and gummosis caused by Phytophthora spp. are considered one of the most important citrus diseases in Brazil. Symptoms of Phytophthora spp. infection in citrus plants are associated with lesions on the bark at the base of the plant, roots, and even lower branches. Inappropriately performed cultural practices, such as excessive irrigation and practices that result in reduced aeration and soil drainage, favor the disease. The objective of this study was to evaluate the effect of Urochloa ruziziensis mulching provided by an ecological mower on the severity of Phytophthora nicotianae root rot and the development of citrus plants and their root system. The experiments were carried out under controlled conditions on Rangpur lime seedlings kept in pots containing soil from ‘Hamlin’ orange orchards with the use of an ecological mower or a conventional mower in the management of inter-row vegetation for six years. Urochloa ruziziensis mulching (9 t ha−1) was added or not to the pots. The inoculation of P. nicotianae in the roots occurred through infection of the soil with a solution containing mycelium and sporangia of the pathogen. A 2 × 2 × 2 factorial scheme was used, with the following factors A: soil type, B: inoculation of P. nicotianae and C: mulching of U. ruziziensis. The attributes of plant development, such as root growth, average number of leaves, leaves and dry mass of shoots and roots, in addition to assessments of the severity of disease in the roots, were evaluated. The mulch of U. ruziziensis did not promote an increase in root rot. The soil resulting from this management promoted the better development of Rangpur lime plants. Therefore, vegetation management of inter-row with an ecological mower is not associated with increased symptoms of Phytophthora root rot