Abstract
Studying behaviors of four Italian lemon rootstocks towards Mal Secco leaf infection with the fungus Phoma tracheiphila, isolated in Tunisia in controlled environment, is the aim of this research work. It involves prospection of infected lemons fields in Tunisia, isolation and morphological identification of the fungus, preparation of inoculum and infection of leaves of four rootstocks. Following the artificial inoculation in three assessments after 10, 20 and 30 days post inoculation (dpi) by observing the appearance of disease symptoms, counting the percentage of positive inoculation and determining the average disease intensity according to the leaf empirical scale. All these parameters indicated about the behaviour of the rootstock towards disease in addition to allowing the classification of the four lemon rootstocks according to susceptibility to Mal Secco. Therefore Volkameriana which showed great sensitive behavior was considered as susceptible rootstock. However, Sour Orange showed an intermediate susceptibility to Mal Secco infection and was classified as tolerant rootstock. Nevertheless Flying Dragon and Citrange Troyer were considered as resistant rootstocks after showing a great resistance to the leaf infection by Phoma tracheiphila.
Highlights
Phoma tracheiphila (Petri) Kantsch et Gik. is a mitosporic fungus causing a destructive vascular disease of citrus named ‘mal secco’
The objective of this work was to study the behavior of four Italian lemon rootstocks towards Mal Secco leaf infection, caused by the fungus P. tracheiphila isolated in Tunisia, in controlled environment
Tunisian citrus field by Mal Secco located in El Gobba which is situated in region of Cap Bon in Tunisia
Summary
Phoma tracheiphila (Petri) Kantsch et Gik. is a mitosporic fungus causing a destructive vascular disease of citrus named ‘mal secco’. In infected lemon trees first symptoms appear on younger leaves, with vein discoloration and chlorosis; they become yellow and fall. A progressive basipetal desiccation of shoots, branches, and trunk follows and, the whole plant may die. The infected xylem of young shoots as well as of main and secondary branches and trunk show a yellow or pink-salmon to reddish discoloration [3,1]. The principal host species is lemon (Citrus limon L.), but the fungus has been reported on many other Citrus spp. such as cedar (C. medica L.), lime (C. aurantifolia Christ.), bergamot (C. bergamia Risso), chinotto (C. myrtifolia Raf.), sour orange (C. aurantium L.), rough lemon (C. jambiri Lush) and Volkamerian lemon (C. volkameriana Ten. et Pasq.). The erratic field behavior of the disease, makes its damages difficult to estimate [1]
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