No abstract

Blast, caused by Pyricularia grisea, is one of the most important diseases of wheat. The effects of silicon (Si) on this wheat disease were studied. Plants of wheat cultivars Aliança and BH-1146 were grown in plastic pots containing Si-deficient soil amended with either calcium silicate (+Si) or calcium carbonate (−Si). The content of Si in leaf tissue was significantly increased by 14.8% for the +Si treatment. There were no significant differences between Si treatments for calcium content, so variations in Si only accounted for the observed differences in the level of blast resistance. The incubation period was significantly increased, on average, by 28.2% for the +Si treatment. The area under blast progress curve and the number of lesions per cm 2 of leaf area significantly decreased by 31 and 45%, respectively, for the +Si treatment. There was no significant effect of Si on final disease severity. The concentration of total soluble phenolics observed in both cultivars supplied with Si did not apparently play any role in the increased blast resistance. The highest content of lignin-thioglycolic acid derivatives was found in plants from both cultivars with Si during the time period evaluated. Chitinase activity was high at the intermediate stages of fungal infection in both cultivars supplied with Si. Peroxidase activity was found to be high at the late stage of fungal infection for both cultivars supplied with Si and seemed to play a role in enhancing wheat blast resistance. Polyphenoloxidase activity also apparently had no effect on resistance for any of the treatments. These overall results revealed the potential of Si to decrease wheat susceptibility to blast.

G Gisele isele P Pereira ereira D Domiciano omiciano, , F Fabrıcio abrício A Avila vila R Rodrigues odrigues, , F Francisco rancisco X Xavier avier R Ribeiro ibeiro V Vale ale, , M Maria aria S Santina antina X Xavier avier F Filha ilha, , W Wiler iler R Ribas ibas M Moreira oreira, , C Camila amila C Cristina ristina L Lage age A Abstract Spot blotch, caused by the fungus Bipolaris sorokiniana, is one of the most important diseases on wheat. The effects of silicon (Si) on this wheat disease were studied. Plants of wheat cultivars BR-18 and BRS-208 were grown in plastic pots containing Si-deficient soil amended with either calcium silicate (+Si) or calcium carbonate ()Si). The content of Si in leaf tissue was significantly increased by 90.5% for the +Si treatment. There was no significant difference between Si treatments for calcium content, so variations in Si accounted for differences in the level of resistance to spot blotch. The incubation period was significantly increased by 40% for the +Si treatment. The area under spot blotch progress curve, number of lesions per cm 2 of leaf area, and real disease severity significantly decreased by 62, 36 and 43.5% in +Si treatment. There was no significant effect of Si on lesion size. The role played by total soluble phenolics in the increased resistance to spot blotch of plants from both cultivars supplied with Si was not clear. Plants from cultivar BR-18 supplied with Si showed the highest values for concentration of lignin-thioglycolic acid derivatives during the most advanced stages of fungus infection. Chitinase activity was high at the most advanced stages of fungus infection on leaves from both cultivars supplied with Si and may have had an effect on fungus growth based on the reduction of the components of resistance evaluated. Peroxidase activity was found to be high only at 96 h after inoculation of both cultivars supplied with Si. Polyphenoloxidase activity had no apparent effect on resistance regardless of Si treatments. Results revealed that supplying Si to wheat plants can increase resistance against spot blotch.

Parâmetros genéticos e diversidade em progênies de Macaúba com base em características morfológicas e fisiológicas.Ciência Rural, v.45, n.9, set, 2015. 1599Parâmetros genéticos e diversidade em progênies de Macaúba com base em características morfológicas e fisiológicas

Rice blast, caused by Pyricularia oryzae, is the most important disease in rice worldwide. This study investigated the effects of silicon (Si) on the photosynthetic gas exchange parameters (net CO2 assimilation rate [A], stomatal conductance to water vapor [gs], internal-to-ambient CO2 concentration ratio [Ci/Ca], and transpiration rate [E]); chlorophyll fluorescence a (Chla) parameters (maximum photochemical efficiency of photosystem II [Fv/Fm], photochemical [qP] and nonphotochemical [NPQ] quenching coefficients, and electron transport rate [ETR]); concentrations of pigments, malondialdehyde (MDA), and hydrogen peroxide (H2O2); and activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), and lypoxigenase (LOX) in rice leaves. Rice plants were grown in a nutrient solution containing 0 or 2 mM Si (-Si or +Si, respectively) with and without P. oryzae inoculation. Blast severity decreased with higher foliar Si concentration. The values of A, gs and E were generally higher for the +Si plants in comparison with the -Si plants upon P. oryzae infection. The Fv/Fm, qp, NPQ, and ETR were greater for the +Si plants relative to the -Si plants at 108 and 132 h after inoculation (hai). The values for qp and ETR were significantly higher for the -Si plants in comparison with the +Si plants at 36 hai, and the NPQ was significantly higher for the -Si plants in comparison with the +Si plants at 0 and 36 hai. The concentrations of Chla, Chlb, Chla+b, and carotenoids were significantly greater in the +Si plants relative to the -Si plants. For the -Si plants, the MDA and H2O2 concentrations were significantly higher than those in the +Si plants. The LOX activity was significantly higher in the +Si plants than in the -Si plants. The SOD and GR activities were significantly higher for the -Si plants than in the +Si plants. The CAT and APX activities were significantly higher in the +Si plants than in the -Si plants. The supply of Si contributed to a decrease in blast severity, improved the gas exchange performance, and caused less dysfunction at the photochemical level.

Blast, caused by Pyricularia oryzae, is the most important fungal disease of rice worldwide. This study aimed to compare root and foliar supply of soluble silicon (Si) on rice resistance to blast. The application of soluble Si to the roots increased Si concentration in leaf tissues as compare to plants grown in soil amended with calcium silicate. There was no increase in leaf Si concentration after soluble Si spray, regardless if the leaves were washed or not before analysis. X-ray microanalysis revealed that Si deposition was very similar on the leaf epidermis of plants sprayed with soluble Si, root amended with soluble Si or grown in soil amended with calcium silicate. The lesion size, the number of lesions per cm 2 of leaf and the area under blast progress curve were reduced for rice plants grown in soil that received the application of soluble Si or was amended with calcium silicate. The results of this study showed that the supply of soluble Si to the roots or its spray onto to the rice leaves can decrease blast symptoms.Key words: Pyricularia oryzae, foliar disease, mineral nutrition.Efeito da aplicação radicular e foliar de silício solúvel sobre o desenvolvimento da brusone em arroz Resumo A brusone, causada por Pyricularia oryzae, é a doença fúngica mais importante do arroz no mundo. O objetivo deste estudo foi comparar o suprimento radicular e foliar de silício solúvel (Si) na resistência do arroz à brusone. A aplicação de Si solúvel para as raízes das plantas de arroz aumentou a concentração de Si nos tecidos foliares quando comparados aos de plantas cultivadas em solo suprido com silicato de cálcio. Não houve aumento na concentração foliar de Si após a aplicação de Si solúvel, independentemente de as folhas terem sido lavadas ou não antes da análise. Foi demonstrado por microanálise de raios-X que a deposição de Si foi muito semelhante na epiderme de plantas pulverizadas com Si solúvel, com raiz supridas com Si solúvel ou cultivadas em solo com silicato de cálcio. O tamanho da lesão, o número de lesões por cm 2 de folha e a área abaixo da curva de progresso da brusone foram reduzidos em plantas cultivadas em solos que receberam a aplicação de Si solúvel ou foram supridas com silicato de cálcio. Os resultados deste estudo demonstram que o fornecimento de Si solúvel às raízes ou a sua pulverização sobre as folhas de arroz podem diminuir os sintomas da brusone.Palavras-chave: Pyricularia oryzae, doença foliar, nutrição mineral.

This study aimed to develop and validate a standard area diagram (SAD) set to quantify the severity of spot blotch, caused by Bipolaris sorokiniana, on wheat leaves. The proposed SAD set includes images of leaves with 11 distinct disease severities (0Á1, 1, 5, 10, 20, 30, 40, 50, 60, 70 and 83%). The SAD set was validated by 12 raters without experience in evaluating plant disease. Lin's concordance correlation analysis of estimated versus actual disease severity (based on image analysis) showed that precision and accuracy improved for all raters using the SAD set in contrast to assessments made without it. The SAD set improved accuracy (coefficient of bias, C b = 0Á88 and 0Á99, without and with the SAD set, respectively) and agreement (Lin's concordance correlation coefficient, q c = 0Á81 and 0Á96 without and with the SAD set, respectively) of the estimates of severity. The severity estimates were also more reliable when using the SAD set (coefficient of determination, R 2 = 0Á76 unaided and R 2 = 0Á92 with the SAD set, and intra-class correlation q = 0Á79 without the SAD set and q = 0Á95 using the SAD set). The SAD set proposed in this study will improve the accuracy and reliability of estimates of spot blotch severity on wheat leaves.

The supply of silicon (Si) to wheat plants may potentiate their resistance against infection by Bipolaris sorokiniana. Considering that there is no information regarding how Si affects the infectious process of this fungus on wheat leaves, this study intended to investigate, using light and scanning electron microscopy, the effects of Si supply on the infection process of B. sorokiniana on wheat leaves at tissue level. For that, leaf segments of -Si and +Si plants were prepared. The number of necrotic brown cells and the degree of browning of necrotic cells were determined for each infection site. As results, it was found that the number of brown epidermal cells and the frequency of infection sites showing browning were significantly lower on leaves of +Si plants. On the leaves of -Si plants, an intense dissolution of the wax layer also occurred and hyphae were found inside the disorganized epidermal cells. On leaves of +Si plants, degradation of the wax layer was observed only in areas close to conidia. Within 96 hours after inoculation, a dense network of hyphae had colonized the leaf surface of -Si plants, in striking contrast to +Si plants, for which only sparse hyphae were found.