Silício no manejo de doenças do arroz e elaboração e validação de uma escala diagramática para mancha ocular

Abstract

Rice (Oryza sativa) is a crop of economic importance for many countries because it is considered as a strategic food for food security, making it paramount for humankind. Among the several factors that limit rice productivity are diseases that when unmanaged can lead to damages up to 100%. The objective of this research was: i) to evaluate the effect of silicate fertilization (Si) on the resistance components [incubation period (IP), relative efficiency of infection (REI), lesion expansion rate (r), lesion length (LL), latent period (LP), area under disease progress curve (AUDPC) and final severity (FS)] to the eye leaf spot (Drechslera gigantea) in cultivars BRS Querência (EMBRAPA), BRS Atalanta (EMBRAPA) ) and Puitá INTA CL (BASF S / A); and evaluate the effect of silicon fertilization in field on brown spot (Bipolaris oryzae), blast (Magnaporthe oryzae) and scald (Monographella albescens), grains yield and its industrial quality; ii) to develop and validate a diagrammatic scale for quantification of eye leaf spot severity using the Quant software. In greenhouse results, the factors Si and cultivar were significant, but not their interactions. The supply of Si to the plants reduced IP, LP, REI, LL, FS and AUDPC, respectively at 8.4, 23.4, 33.11, 28.12, 62.23, 61.86%, compared to plants without Si. In field, the AUDPC of the brown spot and scald was reduced by 25.7 and 16.4%, respectively, in Si-treated plants. No significant difference was observed in grains yield or its quality due cultivars or Si treatment. The proposed diagrammatic scale contains seven levels of severity (0.3, 1.0, 3.0, 5.0, 10, 15, and 21%) and it increased the precision and accurate for estimation of the eye leaf spot severity. In conclusion, the results presented in this work show that the application of calcium silicate in the soil resulted in Si accumulation in the rice leaves, which increased the resistance to Drechslera gigantea. However, in field the effect of silicon fertilization was less expressive.