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Introduction. The causal agent of Panama disease in banana is Fusarium oxysporum f. sp. cubense (FOC). The authors put forward a hypothesis to account for certain disturbances of the natural defence mechanisms of banana plants against Panama disease as a consequence of very low Zn levels which could alter the mechanism of tylose formation. Materials and methods. A long-term experiment was carried out with 2-month-old banana plants in a growth chamber at 23 °C using three different levels of Zn nutrition. The nutrient solutions were inoculated with FOC 1 and FOC 4. Results and discussion. None of the total plants growing in a nutrient solution inoculated with FOC 1 showed infected rhizomes at the end of the experiment, but 75% of the plants growing in pots inoculated with FOC 4 had infected rhizomes. On the other hand, rhizome infection by FOC 4 was influenced by the nutrient solutions. The data showed that the number of plants with damaged rhizomes was significantly higher in the Zn-deficient treatments (100% of plants) than in the normal Zn solution (25% of plants), these internal symptoms being seen to worsen as the presence of Zn decreased in the nutrient solution. Conclusions. The results obtained seem to confirm the role played by Zn nutrition of banana plants in the appearance of Panama disease and are in accordance with our hypothesis concerning the relationships among plant Zn nutrition, plant IAA level, tylose formation and the incidence of the disease. Likewise, under our experimental conditions, race 1 of FOC is confirmed to be non-pathogenic against this banana cultivar, while race 4 is indeed pathogenic. Spain / Musa / fungal diseases / pathogens / Fusarium oxysporum / plant nutrition / zinc Reponse de plantules de bananiers Dwarf Cavendish, soumises a differents niveaux de nutrition en Zn, vis-a-vis d'une inoculation par les races 1 et 4 du Fusarium oxysporum f. sp. cubense.

3 pages, 1 table.-- Printed version published Dec 2004., The soilborne fungus Fusarium oxysporum f.sp. cubense is the causal agent of banana vascular wilt disease named Panama disease and one of the most serious threats to banana crops worldwide. A water-soluble addition compound of vitamin K3, menadione sodium bisulphite (MSB), first studied as a plant growth regulator, has recently been shown to induce resistance against Panama disease. Effective fungicides are not yet available to control this fatal disease. Here we report on two independent long-term experiments leading to the enhanced resistance response induced by MSB. The results demonstrated that MSB is an effective resistance activator in banana, and a potentially useful agent for the control of Panama disease., The authors would like to thank J.M. Hernández- Hernández fromthe Departamento de Patología Vegetal, Instituto Canario de Investigaciones Agrarias (ICIA), for kindly providing FOC-4 inoculum.

Fusarium wilt of banana (Panama disease), caused by Fusarium oxysporum f.sp. cubense, is a soliborne systemic disease which occludes host vascular system. We report here two experiments on resistance induction with banana plants (cv. Dwarf Cavendish) carried out in glass greehouse with different indoleacetic acid treatments, which are capable of inducing resistance to Panama disease. The results obtained in these experiments suggest that the exogenous application of indoleacetic acid to banana plants induce resistance to Panama disease and that the resistance induction is more effective when performed using low doses and frequent applications. This work seems to confirm the role played by indoleacetic acid according to Beckman's models as, one of the major defence factors of the host plant in vascular wilt diseases., The authors would like to thank J, M, Hermández Hernández from the Departamento de Patología Vegetal, Instituto Canario de Investigaciones Agrarias (ICIA), for kindly providing FOC-4 inoculum. We also acknowledge Mrs. Pauline Agnew who endeavoured to edit the English translation of this paper.

4 pages, 2 figures, 2 tables., [EN] Chitosan and menadione sodium bisulphite (MSB) were applied as agar amendment and seed coating to test the combined effects of them on Fusarium oxysporum f.sp. lycopersicii (FOL) in vitro growth and disease development of tomato plant seeds. In agar amendment, chitosan combined with MSB (chitosan 1.0 mg.m L-1 + MSB 0.1 mg.m L-1) was found to significantly inhibit FOL growth. Only chitosan as agar amendment and seed coating was effective, it diminishing disease occurrence in emerging roots from tomato seeds., [ES] Quitosana y menadiona bisulfito de sodio (MBS) fueron aplicados como enmendantes y recubrimiento de semilla, para probar su efecto combinado sobre el crecimiento in vitro de Fusarium oxysporum f.sp. lycopersicii (FOL) y el desarrollo de la enfermedad en semillas de plantas de tomate. En agar enmendante, la quitosana combinada con el MBS (quitosana 1.0 mg.m L-1 + MBS 0.1 mg.m L-1) inhibió significativamente el crecimiento de FOL. Solamente la quitosana como enmendante y como recubrimiento a la semilla fue efectiva, disminuyendo la incidencia de la enfermedad en las raíces emergentes de las semillas de tomate., The authors thank the fine technical assistance of the Oligosaccharins Laboratory from INCA.