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 exchange parameters,. Higher leaf concentration of Mg was observed in plants supplied with 4.0 mM Mg than in those supplied with 0.25 mM. The increase in leaf Mg was accompanied by a decrease in BS severity, higher concentration of total chlorophyll and better photosynthetic performance. Plants supplied with 4.0 mM Mg had higher average values for carbon assimilation, stomatal conductance and internal leaf CO2 concentration when compared with plants supplied with 0.25 mM Mg. Conversely, the concentration of carotenoids was lower in plants supplied with the higher Mg rate. These results suggest that Mg suppresses disease severity and preserves photosynthetic performance by allowing for better stomatal conductance and, consequently, greater availability of CO2 at the carboxylation sites.
Highlights
Brown spot (BS), caused by the fungus Bipolaris oryzae (Breda de Haan) Shoemaker, is one of the most important diseases that affects rice (Oryza sativa L.) (Ou, 1985) and is responsible for much of the yield loss and decrease in grain quality in the world’s rice producing areas (Kohls et al, 1987)
Photosynthetic pigments: Total chlorophyll was higher in plants supplied with 4.0 mM Mg when compared to those with 0.25 mM (Figure 1A), regardless of the inoculation treatment (Figure 1B)
Rice plants supplied with the highest Mg rate contained more foliar Mg which contributed to reducing the area under the brown spot progress curve (AUBSPC)
Summary
Brown spot (BS), caused by the fungus Bipolaris oryzae (Breda de Haan) Shoemaker, is one of the most important diseases that affects rice (Oryza sativa L.) (Ou, 1985) and is responsible for much of the yield loss and decrease in grain quality in the world’s rice producing areas (Kohls et al, 1987). Magnesium (Mg) is one of the most abundant free divalent cations in the cytosol of plants that has multiple functions in plant physiology (Li et al, 2001). This makes it an interesting target for investigation, since nutrients affect disease susceptibility through metabolic changes in plants (Spann and Schumann, 2010). Despite the recognized importance of Mg in plant metabolism, e.g. as the central atom of the chlorophyll molecule and an element required for the aggregation of ribosomes (Wilkinson et al, 1990), little information is available about the effect of this macronutrient in terms of resistance or susceptibility of plants to diseases. Mg is a forgotten element in crop production (Cakmak and Yazici, 2010), and there is less documentation of the interaction between diseases and the Mg supply than for any other nutrient (Huber and Jones, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
