DUARTE, H. S. S.

LOPES, U. P.

RODRIGUES, F. A.

SCHURT, D. A.

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Effect of Magnesium on the Development of Sheath blight in Rice.

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SHORT COMMUNICATIONEffect of Magnesium on the Development of Sheath blight in RiceDaniel A. Schurt1, Ueder P. Lopes1, Henrique S. S. Duarte2 and Fabrıcio A´. Rodrigues11 Laboratory of Host-Parasite Interaction, Department of Plant Pathology, Vicosa Federal University, Vicosa, Minas Gerais State, Zip Code 36570-000,Brazil2 Plant Protection Department, Parana Federal University, SCA-DFF, Curitiba, Parana State, Zip Code 80035-050, BrazilKeywordsfoliar disease, host resistance, macronutrient,Oryza sativa, plant nutrition, RhizoctoniasolaniCorrespondenceF. A. Rodrigues, Vicosa Federal University,Vicosa, Brazil.E-mail: fabricio@ufv.brReceived: September 25, 2013;accepted: January 23, 2014.doi: 10.1111/jph.12240AbstractThis study investigated the effect of magnesium (Mg) on sheath blight,caused by Rhizoctonia solani, development on rice plants from cultivarsBR-IRGA 409 and Labelle grown in nutrient solution containing 0.062,0.125, 0.25 and 0.50 mM of Mg. Sheath blight progress on inoculatedsheaths was evaluated by measuring lesions expansion (mm) at 24, 48, 72and 96 h after inoculation. Data were used to calculate the area underlesion expansion progress curve (AULEPC). The relationship between thefoliar Mg concentration and the Mg rates was quadratic. The Mg concentra-tion on leaf sheaths tissue was highest at the Mg rates of 0.389 and0.400 mM, respectively, for cultivars BR-IRGA 409 and Labelle. A linearmodel best described the relationship between the AULEPC and the Mgrates. The AULEPC decreased by 48.7 and 26.2% for plants of cultivarsBR-IRGA 409 and Labelle, respectively, as the Mg rates in the nutrient solu-tion increased. The results permitted to conclude that high foliar Mg con-centration played a pivotal role to decrease sheath blight lesions expansion.IntroductionSheath blight, caused by Rhizoctonia solani K€uhn [Tha-natephorus cucumeris (AB Frank) Donk] (Hashiba andKobayashi 1996), is one of the major diseases affect-ing rice yield (Ou 1985). Symptoms of sheath blightinclude lesions on the base of the leaf sheath near thewaterline which are elliptical or oval-shaped andgreenish-grey with yellow margins (Ou 1985; Rushand Lee 1992).Control strategies for sheath blight have centredaround the use of fungicides because resistant culti-vars are not commercially available to growers (Leeand Rush 1983). Host resistance against infection bypathogens can be affected by nutrient deficiency ortoxicity (Marschner 1995). Magnesium (Mg) has mul-tiple functions in plant physiology for being the mostabundant free divalent cation in the plants cytosoland the central atom of the chlorophyll molecule(Shaul 2002). Disease intensities can increase ordecrease by supplying Mg to the plants (Jones andHuber 2007). Peanut plants grown under low levels ofMg were more susceptible toMycosphaerella arachidicolathan plants grown under high levels of this macronu-trient (Bledsoe et al. 1946). The severity of bacterialspot, caused by Xanthomonas campestris pv. vesicatoria inpepper (Jones et al. 1983) and the incidence of leafspot, caused by Cochliobolus heterostrophus in maize(Taylor 1952) increased as the foliar concentration ofMg increased. Panicle blast resistance in rice was posi-tively correlated with the high foliar Mg concentration(Filippi and Prabhu 1998).Information related to the effect of Mg on rice resis-tance or susceptibility to sheath blight is, for the bestof our knowledge, lacking in the literature. Therefore,the objective of this study was to investigate the effectof Mg on sheath blight progress in rice to achieve bet-ter disease management.Materials and MethodsRice plants from cultivars BR-IRGA 409 and Labelle,susceptible to R. solani, were grown in Hoagland andArnon’s (1950) modified nutrient solution consistingJ Phytopathol 162 (2014) 617–620  2014 Blackwell Verlag GmbH 617J Phytopatholof: 1.0 mM KNO3, 0.25 mM NH4H2PO4, 0.1 mM NH4Cl,1.0 mM Ca(NO3)2, 0.30 lM CuSO45H2O, 0.33 lMZnSO47H2O, 11.5 lM H3BO3, 3.5 lM MnCl24H2O,0.1 lM (NH4)6Mo7O244H2O, 25 lM FeSO47H2O and25 lM EDTA. The Mg rates used were 0.062, 0.125,0.25 and 0.5 mM. Magnesium sulphate (MgSO47H2O) was used as the Mg source. Sodium sulphate(Na2SO4) was used at the concentrations of 0.43,0.375 and 0.25 mM to prepare the nutrient solutioncontaining the Mg rates of 0.062, 0.125 and 0.25 mM.The Na2SO4 was used because it was necessary toprovide sulphur to the plants without the presence ofMg. Rice seeds were washed in sodium hypochloritesolution (10%) for 1.5 min and then washed indeionized water for 3 min. The seeds were germinatedin rolls of filter paper (15 9 15 cm) soaked with waterand kept at 25°C. Six seedlings were maintained ineach plastic pot (40 925 9 8 cm) (Ecovaso, Jagu-ariuna, SP, Brazil) containing 5 l of nutrient solutionwith the Mg rates. The nutrient solution was replacedevery 4 days or when the electrical conductivity was85% of the initial value. The pH of the nutrientsolution was checked daily and maintained between5.5 and 6.0 with the addition of 1 M solutions of HClor NaOH.Inoculum of R. solani (AG-1 IA) used to inoculatethe plants was obtained according to Rodrigues et al.(2001). Plants (60 days old, maximum tillering stage)were inoculated by placing a 1-cm toothpick colo-nized by R. solani into the lowest inner sheath of themain tiller. Immediately after inoculation, all plantswere transferred to a plastic mist chamber inside agreenhouse. Sheath blight lesions expansion, in mm,on the inoculated sheaths was measured at 24, 48, 72and 96 h after inoculation (hai) with a digital calliper.Data from lesion expansion were used to calculate thearea under lesion expansion progress curve (AULEPC)according to Shaner and Finney (1977).For determination of Mg concentration on leafsheaths tissue, samples from the main culm of eachplant were collected, washed in distilled water, driedin an oven with forced ventilation (70°C) until con-stant weight and subsequently ground in a Thomas–Wiley mill type (Thomas Scientific, Swedesboro, NJ,USA) with 20-mesh sieve. The concentration of Mgon leaf sheaths tissue was determined by nitroperclo-ric digestion according to Bataglia et al. (1983).One 4 9 2 factorial experiment consisting of fourMg rates and two cultivars (BR-IRGA 409 andLabelle) was arranged in a completely randomizeddesign with three replications. The experiment wasrepeated once. A total of 72 plants per each cultivarwere used in each experiment. Cochran’s test forhomogeneity of variance (Gomez and Gomez 1994)indicated that the data from the two experimentscould be pooled for data analysis. Data from Mg con-centration on leaf sheaths tissue and AULEPC wereverified to normality, homogeneity and independenceof experimental error followed by analysis of vari-ance. A regression analysis based on the Mg rates andtwo cultivars was performed. The cultivars BR-IRGA409 and Labelle were coded as 0 and 1, respectively.The highest coefficients of the model used were testedby Student’s t-test (P < 0.05) to the best-fit modelwith all significant terms as follows:Yi ¼ b0 þ b1Ri þ b2R2i þ b3Ci þ b4RiCi þ ei;where Yi = observed value of the variable in theobservation i (i = 1, 2, 3. . ., 48); Ri = Mg rate in theobservation i (0.062, 0.125, 0.250 and 0.50 mM);Ci = cultivars for the observation I (0 = BR-IRGA 409and 1 = Labelle); b0 = constant regression; b1, b2, b3and b4 = regression coefficients; and ei = the regres-sion error associated with the observed value yi. Datafrom foliar Mg concentration were correlated with theAULEPC.Results and DiscussionThe relationship between the foliar Mg concentrationand the Mg rates was quadratic (Fig. 1). The Mg con-centration on leaf sheaths tissue was highest at theMg rates of 0.389 and 0.400 mM, respectively, for cul-tivars BR-IRGA 409 and Labelle (Fig. 1). The expan-sion of sheath blight lesions increased from 24 to 96hai, but in general, the greatest reduction was noticedon the sheaths of plants grown at the highest Mg ratesregardless of cultivar (Fig. 2). A linear model bestdescribed the relationship between the AULEPC andthe Mg rates. The AULEPC decreased by 48.7 and26.2% for cultivars BR-IRGA 409 and Labelle, respec-tively, as the Mg rates in the nutrient solutionincreased (Fig. 3). The correlation between foliar Mgconcentration and AULEPC was negative and signifi-cant for BR-IRGA 409 (r = 0.802, P < 0.05) andLabelle (r = 0.632, P < 0.05). The Mg is a macronu-trient required for the aggregation of ribosomes and asa cofactor for RNA polymerases, ATPases, protein kin-ases, phosphatases, carboxylases and glutathione syn-thase and also important to reduce the intensity ofseveral diseases (Huber and Jones 2013). Data fromthe present study showed that rice resistance tosheath blight increased when the Mg concentrationon leaf sheaths tissue was increased. Brown spotseverity was reduced on rice supplied with high ratesJ Phytopathol 162 (2014) 617–620  2014 Blackwell Verlag GmbH618Magnesium and sheath blight in rice D. A. Schurt et al.of Mg (Jones and Huber 2007). Cotton plants grownunder low levels of Mg were more susceptible to R. so-lani than plants grown under high levels of Mg (Tsaiand Bird 1975). Bean plants grown under low levelsof Mg were more susceptible to R. solani than plantsgrown under high levels of Mg (Bateman 1965). Bled-soe et al. (1946) observed that peanut plants grownunder low levels of Mg were more susceptible to My-cosphaerella arachidicola than plants grown under highlevels of this macronutrient. Peanuts plants were alsomore resistant to R. solani when plants grown underhigh levels of Mg (Csinos and Bell 1989). By contrast,the highest foliar tissue concentration of Mg contrib-uted to increase the intensity of flag smut and take-allon wheat, southern leaf blight on maize, stalk smuton rye and blast on rice (Jones and Huber 2007).Overall, results from the present study showed thathigh foliar Mg concentration played a pivotal role inreducing sheath blight lesions expansion.AcknowledgementsProf. F.A. Rodrigues thanks the CNPq for his fellow-ship. This study was partially financed by CAPES,CNPq and FAPEMIG.ReferencesBataglia OC, Furlani AMC, Teixeira JPF, Furlani PR, GalloJR. (1983) Metodos de analise quımica de plantas.Campinas, SP, InstitutoAgrono^mico (BoletimTecnico,78), pp 48.Bateman DF. (1965) Discussion of the soil environment.In: Baker KF, Snyder WC. (eds) Ecology of Soil-BornePlant Pathogens: Prelude to Biological Control. Berkeley,CA, University of California Press, pp 139.Fig. 1 Concentration of magnesium (Mg) in leaf sheaths of rice plantsfrom cultivars BR-IRGA 409 and Labelle grown in nutrient solution con-taining different Mg rates and inoculated with Rhizoctonia solani. Dataare from two pooled experiments. (n = 6).(a)(b)Fig. 2 Lesion expansion (LE) progress curves on rice plants from culti-vars BR-IRGA 409 (a) and Labelle (b) grown in nutrient solution contain-ing different magnesium rates. The error bars represent the standarderror of the mean. Data are from two pooled experiments. (n = 6).Fig. 3 Area under lesion expansion progress curve (AULEPC) on riceplants from cultivars BR-IRGA 409 (a) and Labelle (b) grown in nutrientsolution containing different magnesium (Mg) rates. In the regressionanalysis, cultivar (c) will be equal to 0 and 1, respectively, for BR-IRGA409 and Labelle. The error bars represent the standard error of themean. Data are from two pooled experiments. (n = 6).J Phytopathol 162 (2014) 617–620  2014 Blackwell Verlag GmbH 619D. A. Schurt et al. Magnesium and sheath blight in riceBledsoe RW, Harris HC, Tisadale WB. (1946) Leaf spot ofpeanut associated with magnesium deficiency. PlantPhysiol 21:237–240.Csinos AS, Bell DK. (1989) Pathology and nutrition in thepeanut pod rot complex. In: Engelhard AW. (ed.) Soil-borne Plant Pathogens: Management of Diseases withMacro- and Microelements. St. Paul, MN, USA, APSPress, pp 124–136.Filippi MC, Prabhu AS. (1998) Relationship between pani-cle blast severity and mineral nutrition content of planttissue in upland rice. J Plant Nutri 21:1577–1587.Gomez KA, Gomez AA. (1994) Statistical Procedures forAgricultural Research, 2nd edn. New York, NY, USA,Wiley.Hashiba T, Kobayashi T. (1996) Rice diseases incited byRhizoctonia species. In: Sneh B, Jabahi-Hare S, NeateS, Dijst G. (eds) Rhizoctonia Species: Taxonomy,Molecular Biology, Ecology, Pathology, and DiseaseControl. Dordrecht, Kluwer Academic Publishers,pp 331–340.Hoagland DR, Arnon DI. (1950) The water-culture methodfor growing plants without soil. Circular. CaliforniaAgricultural Experiment Station 347.Huber DM, Jones JB. (2013) The role of magnesium inplant disease. Plant Soil 368:73–85.Jones JB, Huber DM. (2007) Magnesium and plantdisease. In: Datnoff LE, Elmer WH, Huber DM. (eds)Mineral Nutrition and Plant Disease. St. Paul, MN, USA,APS Press, pp 95–100.Jones JB, Woltz SS, Jones JP. (1983) Effect of foliar andsoil magnesium application on bacterial leaf spot of pep-pers. Plant Dis 67:623–624.Lee FN, Rush M. (1983) Rice sheath blight: a major ricedisease. Plant Dis 67:829–832.Marschner H. (1995) Mineral Nutrition of Higher Plants,2nd edn. London, UK, Academic Press.Ou SH. (1985) Rice Diseases, 2nd edn. Kew, UK, Com-monwealth Mycological Institute.Rodrigues FA, Datnoff L, Kornd€orfer G, Seebold K, RushM. (2001) Effect of silicon and host resistance on sheathblight development in rice. Plant Dis 85:827–832.Rush MC, Lee FN. (1992) Sheath blight. In: Webster RK,Gunnell PS. (eds) Compendium of Rice Diseases.St. Paul, MN, The American Phytopathological Society,pp 22–23.Shaner G, Finney RE. (1977) The effect of nitrogen fertil-ization on the expression of slow-mildewing resistancein knox wheat. Phytopathology 67:1051–1056.Shaul O. (2002) Magnesium transport and function inplants: the tip of the iceberg. Biometals 15:309–323.Taylor GA. (1952) The effects of three levels of magnesiumon the nutrient-element composition of two inbred linesof corn and on their susceptibility to Helminthosporiummaydis. Plant Physiol 29:87–91.Tsai HY, Bird LS. (1975) Microbiology of host pathogeninteractions for resistance to seedling disease and multiadversity resistance in cotton. Proc Beltwide Cotton ProdRes Conf Cotton Dis Counc 35:39.J Phytopathol 162 (2014) 617–620  2014 Blackwell Verlag GmbH620Magnesium and sheath blight in rice D. A. Schurt et al.

Effect of Magnesium on the Development of Sheath blight in Rice.

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