Magnesium-induced alterations in the photosynthetic performance and resistance of rice plants infected with Bipolaris oryzae

Abstract

Brown spot (BS), caused by the fungus Bipolaris oryzae, is one of the most important diseases contracted by rice. We investigated the effect of magnesium (Mg) on the development of BS, caused by Bipolaris oryzae, and the effects of disease development on the photosynthetic performance of rice (Oryza sativa L.) plants (cv. Metica-1) grown in nutrient solutions containing 0.25 or 4.0 mM of Mg. Assessments of BS severity, leaf Mg and pigment concentrations (total chlorophylls and carotenoids), were carried out at 120 h after inoculation, in addition to gas Across the range of studies involving the mitigation of diseases through the use of agricultural practices with nutrition, there are reports of a nonspecific role for Mg, since its influence may either reduce or enhance the severity of disease. Jones and Huber (2007) reported 22 diseases where severity was decreased by supplying additional Mg, 17 where it was increased and 6 that showed a variable effect, depending on the environment. However, few studies relate the effects of Mg also to the physiological traits of the host species.Given the importance of Mg in plant nutrition and the differential evolution of disease symptoms observed in plants exposed to Mg in other pathosystems, the objective of the authors in the present study was to investigate the effects of Mg on BS development relative to the associated alterations in the photosynthetic performance in rice. It was hypothesized that Mg could influence the physiology of rice plants through B. oryzae, and thus enhance the production of substrates available to the production of defense compounds,which favor the mitigation of disease development. Materials and Methods Plant materialRice plants (cv. Metica-1) were grown in Hoagland and Arnon (1950) in a modified nutrient solution consisting of: 1.0 mM KNO 3 , 0.25 mM NH 4 H 2 PO 4 , 0.1 mM

Sustainable Management of Diseases in Horticulture: Conventional and New Options

“…Calcium appears to be especially effective for post-harvest treatments against gray mould caused by Botrytis cinerea [209,210], whereas magnesium showed inconsistent results in controlling diseases [211]. Further ad hoc studies should be performed to determine the potential beneficial effects [212].…”