Grafting olive cv. Cornicabra on rootstocks tolerant to Verticillium dahliae reduces their susceptibility

• Published in: Crop protection Vol. 22; no. 2; pp. 369 - 374
• Main Authors: Porras Soriano, A., Soriano Martı́n, M.L., Porras Piedra, A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-03-2003
• Subjects: Bioassay; Olea europea; Olea europea; Bioassay
• ISSN: 0261-2194; 1873-6904
• DOI: 10.1016/S0261-2194(02)00180-1

Verticillium wilt is a widely distributed fungal disease of the vascular system of plants. It has recently appeared in the olive groves of Castilla-La Mancha. The control of this disease is difficult and expensive. The development of new control methods that prevent or at least reduce this disease, represents a new factor of great interest to olive growers and nursery owners.
This work has assayed the influence, as far as susceptibility to V. dahliae is concerned, of the grafting of young plants of Cornicabra olive tree on four cultivars (Arbequina, Frantoio, Lechin and Empeltre) that are tolerant to this disease. Tests were done on plants propagated from softwood stem cuttings, rooted both ungrafted and simultaneously rooted and grafted. Later, the 1-year-old plants were artificially inoculated, by dipping the roots in a conidial suspension of 107 conidia per ml, with a defoliant V. dahliae pathotype. The severity of the disease was evaluated periodically.
The results show that the young plants of Cornicabra olive trees are highly susceptible to the defoliant V. dahliae pathotype. The severity of the disease in these reached an average value of 4.2. The tolerance to this disease of the rootstock cultivars was confirmed, with average values of severity that went from 1.2 in Empeltre to 2.3 in Arbequina. The most interesting and novel part of this work, demonstrated for the first time, is that when Cornicabra was grafted on Frantoio, the severity of the attacks was reduced from 4.2 to 1.8, which indicated that the Frantoio rootstock caused an important reduction in its susceptibility to V. dahliae in the Cornicabra variety, turning it into a plant with a higher tolerance than it showed when ungrafted, going from being highly sensitive to highly tolerant.