Um experimento de campo, para avaliar a eficiência de serpentinito calcinado como fonte de silício na produtividade da cultura de arroz irrigado, cultivar BRS Formoso, foi utilizado para estudar seu efeito sobre a brusone nas folhas e níveis de açúcares nos tecidos.Nota científica

DIDONET, A. D.

PRABHU, A. S.

SANTOS, A. B. dos

Um experimento de campo, para avaliar a eficiência de serpentinito calcinado como fonte de silício na produtividade da cultura de arroz irrigado, cultivar BRS Formoso, foi utilizado para estudar seu efeito sobre a brusone nas folhas e níveis de açúcares nos tecidos.Made available in DSpace on 2011-06-06T16:57:41Z (GMT). No. of bitstreams: 1
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Soluble tissue sugar content and leaf blast severity in response to the application of calcinated serpentinite as a silicon source in irrigated rice.

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402 Summa Phytopathol., Botucatu, v. 33, n. 4, p. 402-404, 2007NOTAS CIENTÍFICASSoluble tissue sugar content and leaf blast severity in response to the application ofcalcinated serpentinite as a silicon source in irrigated riceAnne Sitarama Prabhu1, Alberto Baêta dos Santos1, Agostinho Dirceu Didonet11Embrapa Arroz e Feijão, Caixa Postal 179, CEP 75375-000, Santo Antônio de Goiás, GO. E-mail: prabhu@cnpaf.embrapa.brData da chegada: 17/03/2006. Aceito para publicação em: 15/03/2007.        1337ABSTRACTA field experiment conducted with the irrigated rice cultivar BRSFormoso, to assess the efficiency of calcinated serpentinite as a siliconsource on grain yield was utilized to study its effect on leaf blastseverity and tissue sugar levels. The treatments consisted of fiverates of calcinated serpentinite (0, 2, 4, 6, 8 Mg.ha-1) incorporatedinto the soil prior to planting. The leaf blast severity was reduced atPrabhu, A.S.; Santos, A.B. dos; Didonet, A.D. Soluble tissue sugar content and leaf blast severity in response to the application of calcinatedserpentinite as a silicon source in irrigated rice. Summa Phytopathologica, v.33, n.4, p.402-404, 2007.RESUMOUm experimento de campo, para avaliar a eficiência de serpentinitocalcinado como fonte de silício na produtividade da cultura de arrozirrigado, cultivar BRS Formoso, foi utilizado para estudar seu efeitosobre a brusone nas folhas e níveis de açúcares nos tecidos. Ostratamentos consistiram de cinco doses de serpentinito calcinado (0,2, 4, 6, 8 Mg.ha-1) incorporadas ao solo antes de plantio. A severidadePrabhu, A.S.; Santos, A.B. dos; Didonet, A.D. A brusone nas folhas e conteúdo de açucares solúveis nos tecidos em resposta a aplicação deserpentinito calcinado como fonte de silício em arroz irrigado.  Summa Phytopathologica, v.33, n.4, p.402-404, 2007.Palavras-chave adicionais: Magnaporthe grisea, Pyricularia grisea, Oryza sativa, fontes de silíciothe rate of 2.96% per ton of calcinated serpentinite. The total tissuesugar content decreased significantly as the rates of serpentinite appliedincreased (R2 = 0.83). The relationship between the tissue sugar contentand leaf blast severity was linear and positive (R2 = 0.81). The decreasein leaf blast severity with increased rates of calcinated serpentinitewas also linear (R2= 0.96) and can be ascribed to reduced sugar level.Additional Keywords:  Magnaporthe grisea, Pyricularia grisea, Oryza sativa, silicon sources.da brusone foi  reduzida numa taxa de 2,96% por tonelada deserpentinito calcinado aplicada (R2 = 0,83). A relação entre o conteúdode açucares no tecido e a severidade da brusone nas folhas foi linear epositiva (R2 = 0,81). A redução da severidade da brusone com o aumentodas doses de serpentinito calcinado também foi linear (R2= 0,96) epode ser atribuída aos reduzidos níveis de açúcares nos tecidos foliares.Rice blast caused by the fungus Pyricularia grisea (Cooke) Sacc.[= Magnaporthe oryzae (T.T.Hebert) Yageshi & Udagawa] is a majoryield limiting factor in the State of Tocantins in Brazil, where irrigatedrice is grown in extensive contiguous areas, in the municipalities ofFormoso, Duaré and Lagoa da Confusão. At present, the widely grownrice cultivars exhibit different degrees of susceptibility to blast. Asthe production costs are high due to chemical control measures whichinclude seed treatment and one or two foliar fungicide sprays, there isan imminent need for exploring alternative disease control methods.Silicon (Si) has been known to control plant diseases with thecorresponding increase in grain yield. The grain yield of upland ricecultivars increased with silicon fertilization and positively correlatedwith Si and Ca contents in the soil (1). The effect of silicon fertilizationin controlling blast and other rice diseases has been demonstrated inexperiments conducted in different countries, including Brazil (2, 3, 7,10, 11). However, the knowledge on the efficiency of Brazilian siliconsources that are available close to the rice production centers is limited.In the State of Goiás, a residual product of asbestos mining industrylocated in Minaçu (SAMA-Mineração de Amianto Ltda.) with a highsilicon and magnesium content (ground serpentinite) is available inlarge quantities. The disposal of this material has become anenvironmental problem. After obtaining the ISO14 001 certificate, theindustry has been exploring the possibilities of utilizing the serpentinitein agriculture as a silicon source, mainly for rice, wheat and sugarcane.The calcination of this product occurs at a temperature of 1200o C toeliminate fibrous crystals of crisotila. The present paper reports theefficiency of calcinated serpentinite on leaf blast severity underconditions of natural field infection and soluble sugar content ofirrigated rice in the State of Tocantins.A field experiment conducted at Embrapa Rice and Bean ResearchStation, located at ‘Formoso do Araguaia’, TO, with the widely grownirrigated rice cultivar BRS Formoso to assess the efficiency ofcalcinated serpentinite as a silicon source on grain yield was utilizedin this study. The main objective was to determine the effect ofcalcinated silicon on leaf blast severity and tissue sugar levels. Thesoil used in this experiment was classified as Inseptisol according toUSA taxonomy classification. The soil analysis showed the followingcharacteristics: pH (H2O) = 5.2; extractable P = 26.9 mg kg-1; extractableSumma Phytopathol., Botucatu, v. 33, n. 4, p. 402-404, 2007 403cations were K = 66.0 mg kg-1; Ca = 15.3 cmo kg-1; Mg = 4.6 cmo kg-1 and Al = 1.0 cmo kg-1; clay = 185g kg-1; silt = 153 g kg-1; sand = 662g kg-1. The lay-out of the experiment was a split plot design with fourreplications. The treatments consisted of five rates of calcinatedserpentinite (0, 2, 4, 6, 8 Mg. ha-1).The calcinated serpentinite has the following chemical composition(g kg-1): SiO2=455.0; Ca (CaO)= 2.8; Al2O3= 3.5; Mg= 185.6; Fe(Fe2O3)= 48.5; Mn (MnO)= 8.9; PPC= 124.4. Calcination was donein furnace at a temperature of 1200oC under atmospheric pressure.The serpentinite was incorporated in the soil with a harrow prior toplanting the experiment. Seeds were drill planted in each 70 m2 subplotsat the rate of 80 seeds per meter and 0.17 m between the rows.Plots were fertilized at planting with 400 kg ha-1 of NPK (4-30-16+Zn) in addition to top dressing with 35 kg ha-1 of N as urea attillering and initiation of floral primordium. Rice plots were floodedabout 30 days after sowing to a depth of 10 to 15 cm of standingwater, remained flooded during the crop growth period, and drainedone week before harvest. The percentage leaf area affected with blastwas determined on fully opened penultimate leaf of main tillers in thefour central rows of each plot. A 10 grade scale (0; 0.5; 1.0; 2.0; 4.0;8.0; 16.0; 32.0; 64.0; 82.0% of leaf area affected) was used to assessthe leaf blast severity according to Notteghem (5), 35 days afterplanting. The extraction and quantification of soluble and total sugarsin leaves was performed according to Passos (6) and expressed on thebasis of dry matter content. For analysis only the leaf blastmeasurements and tissue sugar content data were considered. Theregression analysis was carried out to establish the relationships oftissue sugar content with leaf blast severity and serpentinite rates.Leaf blast severity was reduced significantly with the increase inrates of calcinated serpentinite 32 days after the plant emergence. Therelationship between rates of serpentinite and leaf blast severity aswell as tissue sugar content in the leaves was linear and negative(Figure1).Disease severity, under natural field conditions was reduced at therate of 2.96% per ton of calcinated serpentinite, applied to the soilprior to planting. The results in the present investigation are consistentwith the several earlier reports of leaf blast reduction with increase insilicon rates (2,3,11).The analysis of penultimate leaves showedsignificant reduction of sugar content. The relationships between thesugar content and quantity of serpentinite applied as well as therelationship between tissue sugar content and leaf blast severity werelinear (Figure 2).The role of silicon in blast resistance has been considered mainlymechanical by the formation of physical barrier to penetration by thepathogen (3, 9). Ultrastructural and cytochemical studies showedthat Si may modulate rice defense responses by the synthesis ofantifungal compounds within epidermal cells upon penetration by thefungus P. grisea (8). Rodrigues et al. (9) demonstrated that higherlevels of momilactones A and B were found in leaf extracts of riceplants inoculated with P. grisea and amended with silicon than in non-inoculated and non-amended.ones.The susceptibility of rice plant to leaf blast has been known toincrease at higher nitrogen rates. Nitrogen is an essential element forsynthesis of amino acids, proteins, phenols and phytoalexins involvedin diverse defense mechanisms. Carbohydrate changes occur in thehost tissue when the plants are grown under different nutritionalconditions. High plant sugar content of the tissue favors somepathogens such as P. grisea (5). Plants presumably become resistantwhen tissue sugar content decreases to a certain level and this may beachieved by silicon fertilization. Rice blast is a high sugar disease andthe results in the present work showed that the application ofcalcinated serpentinite decrease cellular sugar levels and increaseresistance to rice blast pathogen under natural conditions for leaf blastprogress. The nature of host defense, related to sugar and nitrogenmetabolism and its relation to specific resistance mechanisms such asphytoalexin production needs further investigation.REFERENCES1. Barbosa filho, M.P.; Snyder, G.H.; Prabhu, A.S.; Datnoff, L.E.;Korndörfer, G.H. Importância do silício para a cultura do arroz.Informações Agronômicas ,  Piracicaba, n.89, 2000.(EncarteTécnico), 8p.2. Berni, R.F.; Prabhu, A.S. Eficiência relativa de fontes de silício nocontrole de brusone nas folhas em arroz. Pesquisa Agropecuá-ria Brasileira, Brasília, v.38, n.2, p.195-201, 2003.3. Datnoff, L.E.; Deren, C.W.; Snyder, G.H. Silicon fertilization fordisease management of rice in Florida. Crop Protection, Lon-don, v.16, n.6, p.525-531, 1997.4. Horsfall, J.G.; Dimond, A.E. Interactions of tissue sugar, growthsubstances and disease susceptibility. Zeitschrift fur Pflan-zenkrankheiten und Pflanzenschutz ,  Stuttgart, v.64, p.415-421, 1957.5. Notteghem, J.L. Cooperative experiment on horizontal resistan-ce to rice blast. In: International Rice Research Institute (LosBaños, Filipinas). Blast and upland rice: report and recom-mendations from the meeting for international collaboration inupland rice improvement. Los Baños, 1981. p.43-51.Figure 1.Relationships of leaf blast severity (LBS) and tissue solublesugar content (TSC) to rates of calcinated serpentinite applied as a siliconsource to irrigated rice. (The leaf blast data were based on assessment,under natural condition of infection in the field).Figure 2.Relationship between soluble tissue sugar levels in rice leavesand leaf blast severity.404 Summa Phytopathol., Botucatu, v. 33, n. 4, p. 402-404, 20076. Passos, L.P. Métodos analíticos e laboratoriais em fisiolo-gia vegetal. Coronel Pacheco: EMBRAPA-CNPGL, 1996. 223p.7. Prabhu, A.S.; Barbosa filho, M.P.; Filippi, M.C.; Datnoff, L.E.;Snyder, G.H. Silicon from disease control perspective in Brazil.In: DATNOFF, L.E.; SNYDER, G.H.; KORNDÖRFER, G.H. Sili-con in agriculture. Amsterdam: Elsevier, 2001. p.293-311.8. Rodrigues, F.; Benhamou, N.; Datnoff, L.E.; Jones, J.B.; Bélan-ger, R.R. Ultrastructural and cytochemical aspects of silicon-me-diated rice blast resistance. Phytopathology, St. Paul, v.93, p.535-546, 2003b.9. RodrigueS, F.; Mcnally, J.D.; Datnoff, L.E.; Jones, J.B.; Labbe, C.;Benhamou, N.; Menzies, J.G.; Bélanger, R.R. Silicon enhances theaccumulation of diterpenoid phytoalexins in rice: A potentialmechanism for blast resistance. Phytopathology, St. Paul, v.94,n.2, p.177-183, 2004.10. Rodrigues, F.; Vale, F.X.R.; Datnoff, L.E.; Prabhu, A.S.; Korndör-fer, G.H. Effect of rice growth stages and silicon on sheath blightdevelopment. Phytopathology, St. Paul, v.93, p.256-361, 2003a.Seebold, K.W.; Datnoff, L.E.; Correa-victoria, F.J.; Kucharek,T.A.; Snyder, G.H. Effect of silicon and fungicides on the controlof leaf and neck blast in upland rice. Plant Disease, St. Paul,v.88, n.3, p.253-258, 2004.

Soluble tissue sugar content and leaf blast severity in response to the application of calcinated serpentinite as a silicon source in irrigated rice.

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