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Late wilt of maize as affected by irrigation management, and tissue effect of the causal fungus Harpophora maydis

AuthorsOrtiz-Bustos, Carmen M.; López-Bernal, Álvaro ; Testi, Luca ; Alcántara, Esteban; Molinero-Ruiz, Leire
Issue DateSep-2016
CitationXVIII Congreso de la Sociedad Española de Fitopatología (2016)
AbstractLate wilt, caused by the soilborne fungus Harpophora maydis, is an emerging disease of maize in Mediterranean growing areas. It is characterized by sudden wilting of the plants during or soon after flowering. Although the most effective control of late wilt is achieved with tolerant germplasm, the occurrence of the disease and progress of symptoms are highly dependent on environmental conditions. The objectives of this work were to: a) assess the effect of irrigation management on the appearance of symptoms and on the disease severity, and b) monitor alterations in the stem tissues through analyses of microscopy images. Maize susceptible plants were grown in pots under shade-house conditions for the whole growing season in a completely randomised factorial experiment with two factors: irrigation and inoculation. Two irrigation levels were established: optimal [120% maximum evapotranspiration (ET), determined by differential weighting of well irrigated plants in two consecutive days every week] and deficit irrigation (50% maximum ET). Half of the plants in each irrigation level were inoculated and the other half were not (controls). A total of 24 plants were used (4 treatments and 6 replications). Late wilt and growth variables were assessed over time. Transversal sections of stems of inoculated and control plants under deficit irrigation were studied under the microscope and analysed with Image J software. Significant differences of disease severity between inoculated and control plants occurred under both irrigation treatments, these differences being markedly higher in the case of deficit irrigation. Growth and harvest index were also significantly reduced in inoculated plants, but only under deficit irrigation. Concerning the evolution of leaf area, the lowest values were obtained under deficit irrigation (irrespective of the inoculation treatment), followed by inoculated and control optimally irrigated plants, respectively. These results show that water deficit increases the disease effects and should be avoided under field conditions. Microscopic analysis of stems from plants with symptoms of wilting revealed no alterations in the xylem vessels, such as the characteristic occlusions observed in the case of some vascular diseases, but an alteration of the parenchyma cells surrounding the vascular bundle that appeared darker, and some abnormally red dark coloured cell walls in the phloem.
DescriptionTrabajo presentado en el XVIII Congreso de la Sociedad Española de Fitopatología (SEF), celebrado en Palencia del 20 al 23 de septiembre de 2016.
Appears in Collections:(IAS) Comunicaciones congresos
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