Efeito do silício no desenvolvimento da mancha marrom do trigo: componentes de resistência e respostas fisiológicas e bioquímicas

• Autor(a) principal: Domiciano, Gisele Pereira
• Data de Publicação: 2008
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4435
• topic: Trigo - Doenças e pragas - Aspectos fisiológicos; Trigo - Doenças e pragas - Aspectos bioquímicos; Trigo - Efeito do silício; Bipolaris sorokiniana; Epidemiologia; Wheat - Diseases and pests - Physiological aspects; Wheat - Diseases and pests - Biochemical aspects; Wheat - Effect of silicon; Bipolaris sorokiniana; Epidemiology; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA

The objective of this work was to evaluate the effect of silicon (Si) in some resistance components of wheat plants against brown leaf spot (BLS), caused by Bipolaris sorokiniana as well as, physiological and biochemical defence responses induced by this element. To do so, plants of two wheat cultivars, BR-18 and BRS- 208, were grown in pots containing 0 and 0.30 g Si/kg of soil and inoculated 45 days after emergency with B. sorokiniana. Incubation period (IP), mean lesion number by cm2 of leaf area (MLN), mean lesion size (MLS) and the area under the disease progress curve (AUDPC) were measured to evaluated silicon effect on resistance components. Photosynthetic rate (PR), total soluble phenolyc compounds concentration (TSPCC), lignin acid tioglycolic derivates concentration (LATDC) and enzymatic activity of quitinases (QUI), peroxidases (POX) and poliphenoloxidase (POD) were measured to evaluate if silicon could induce physiological and biochemical responses. It was verified in this study that silicon concentration was 90,5% higher in plants supplied with this element in comparison with control plants. Moreover, it was observed a higher level of silicon deposition on leafs of both cultivars supplied with this element was revealed by means of X-rays microanalysis. In these plants the IP was prolonged in near 10h in silicon supplied plants, possibly due to physical blocking effect that this element have on fungus penetration. It was also verified that in plant supplied with silicon this element reduced the MLN, the MLS and the AUDPC in 30%, 58% and 68%, respectively, in comparison with control plants. And more, silicon concentrations correlated positively with IP (r = 0.62) and negatively with AUDPC and MLS (r = -0.57 and -0.70, respectively). The resistance components of plants supplied with Si and inoculated with B. sorokiniana were different from those measured in plants inoculated e not supplied with this element. Since silicon was the only source of variation in the experiments it can be conclude that Si enhances resistance of wheat plants against spot brown. The PR was reduced in leafs and flag leafs of plants of both cultivars after 48 hours after inoculation (HAI). However, in plants supplied with silicon, the PR was kept higher during all evaluation, possibly due to low severity of BLS in these plants. Alterations in TSPCC and LATDC due to silicon effect were also observed. Even though TSPCC oscillated a bit, it was significantly lower in leafs of silicon supplied plants during the evaluation time, although it ́s unlike that it contributed for enhancing wheat resistance to BLS. However, in the presence of silicon the decrease in TSPCC was accompanied with increase of LATDC and decrease in BLS severity. Higher concentrations of LATD in plants supplied with silicon and inoculated with B. sorokiniana, may have contributed to enhancement of cultivars resistance against BLS. QUI activity was significantly enhanced in plants of both cultivars supplied with silicon after 48 HAI. POX activity was increased only in plants of cultivar BRS- 208 supplied with silicon. Since plants supplied with silicon showed low BSP severity the high activity of QUI and POX may indicate that these enzymes participates in wheat defense against BLS. PFO activity, however, did not significantly changed between plants supplied or not with silicon. The results of this study are first evidences that silicon affects BLS severity by altering wheat resistance components to BLS and by the potentialization of physiological and biochemical responses. Silicon has then, a great potential to be used as a BLS management measure in near future.