Centro de Ciências Agrárias

URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/11727

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Influence of leaf position that correspond to whole plant severity and diagrammatic scale for white spot of corn
(Crop Protection, 2010-09) Capucho, A. S.; Zambolim, L.; Duarte, H. S. S.; Parreira, D. F.; Ferreira, P. A.; Lanza, F. E.; Costa, R. V.; Casela, C. R.; Cota, L. V.
The main objective of this research is to determine the influence of leaf position on corn plants with white spot caused by Pantoea ananatis, which better represents the infection on the whole plant. A diagrammatic scale to quantify the severity of the disease was elaborated and validated. For scale elaboration, the minimal and maximal limits of the disease severity observed in the field were considered, and intermediate levels followed logarithmic increments according to the Weber–Fechner stimulation law. The scale has nine classes: 0.1, 1, 2, 4, 8, 16, 24, 32 and 64%. For scale evaluation, a severity evaluation for white spot was performed by 10 raters with no experience in disease evaluation. Initially, severity estimation was performed without a scale for 41 leaves with different levels of severity. Afterward, the same raters used the proposed diagrammatic scale. Through linear regression to compare the actual and estimate severity values, the raters’ accuracy and precision were analyzed. Satisfactory accuracy and precision were achieved when estimation was performed with a diagrammatic scale. To determine the best leaf disease severity evaluation, correlation and regression analyses were performed with 25 plants of five genotypes, for a total of 284 leaves analyzed. Results analysis leads us to conclude that the severity of white spot on corn plants significantly correlates with the disease mean severity of leaves 0 and -1, i.e., a leaf of the corn ear and the one immediately below it. This scale provided good levels of accuracy and precision (a mean R2 of 94%), with errors concentrating around 10%. Raters presented increased reproducibility (R2 > 90% in 82% of cases) of severity estimates. The proposed diagrammatic scale is considered adequate to estimate the severity of white spot in corn for germplasm evaluations, for epidemiological studies and for evaluation of control strategies for this disease.
Quality of maize grains treated with allyl isothiocyanate stored in hermetic bags
(Journal of Stored Products Research, 2010-04) Santos, Silmara Bispo; Martins, Marcio Arêdes; Faroni, Lêda Rita D’Antonino; Rodrigues Junior, Valfrido; Dhingra, Onkar Dev
This purpose of this study was to evaluate the quality of maize grain treated with allyl isothiocyanate (AITC) and stored under hermetic conditions. Maize grains with moisture contents of 14.8 or 17.9% wet basis (w.b.) initial moisture content were packaged in high density polyethylene bags and submitted to treatment with AITC at a concentration of 300 μL kg−1. The bags were stored in controlled temperature chambers at 15, 25 or 35 °C. At 30-day intervals, for a period of 150 days, three bags were removed from the chambers and the grains were submitted to commercial classification, moisture content, bulk density, germination potential and electrical conductivity analyses. It was verified that AITC at 300 μL kg−1 has no significant effect on the physiological quality of maize grains stored in hermetic bags. The microbiological analyses indicate the control of fungi and yeasts on the grains stored with 17.9% w.b. and treated with AITC. The maize grains stored with 14.8% w.b. moisture content in hermetic systems suffered no deterioration and retained their quality for a longer period than grains stored with 17.9% w.b. moisture content, independent of AITC treatment.