Tropical Melhoramento and Genetica LTDA

Cambé, Brazil

Tropical Melhoramento and Genetica LTDA

Cambé, Brazil
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Koga L.J.,State University Londrina | Canteri M.G.,State University Londrina | Calvo E.S.,Tropical Melhoramento and Genetica LTDA | Xavier S.A.,State University Londrina | And 3 more authors.
Tropical Plant Pathology | Year: 2011

This work compared development of soybean rust (SR) on the susceptible cultivar BRS 133 and on the resistant line CB06-953/963 (Rpp4 gene) following different fungicide treatments applied in different developmental stages. The assessed variables were percent plant defoliation, coefficient of damage (CD) and economic threshold level (ETL), the latter two calculated from disease severity ratings and yield. Experiments were conducted in the field during the 2006-2007 growing season with one sowing date (Experiment I) and in 2007- 2008 with two sowing dates (Experiments II and III). The experimental design was a randomized complete block with ten treatments and four replications. Overall, the Rpp4 gene in the resistant line was effective in reducing development of SR in all three experiments. The values of CD and ETL were higher for the resistant line than for the susceptible cultivar. The resistant line needed 13.3 days longer than the susceptible cultivar to reach the ETL in Experiment II. Fungicide applications were more effective in protecting yield and minimizing defoliation in the susceptible cultivar than in the resistant line. Under high inoculum pressure (Experiment III), three and four fungicide sprays applied during the season resulted in significantly higher yields (P<0.05) in both soybean genotypes compared with the untreated controls. Late season fungicide applications reduced rust severity and increased the yield of the resistant cultivar.


Koga L.J.,State University Londrina | Canteri M.G.,State University Londrina | Calvo E.S.,Tropical Melhoramento and Genetica LTDA | Martins D.C.,State University Londrina | And 3 more authors.
Tropical Plant Pathology | Year: 2014

The objectives of this study were to evaluate the influence of soybean cultivar of two maturity groups, early/semi-early (E) or intermediate (I), on the management of Asian soybean rust (ASR) with fungicides and yield. Field trials were conducted during the 2006/07 and 2007/08 growing seasons. Seven cultivars of the two groups were tested in the first season and eight in the second season. All cultivars had plots that were treated (T) or non-treated (NT) with a commercial mixture of pyraclostrobin + epoxiconazole. ASR severity (%) was visually assessed several times during the crop cycle and yield (kg ha-1) was determined at harvest. Values of the standardized area under the disease progress curve (AUDPC) calculated from the severity assessments was higher in 2007/08 than in 2006/07, but no differences were found between cultivars of the E and I maturity groups. Differences in yield between between T and NT plots were lower in cultivars of the E group than those of the I group in both the 2006/07 (37.6% and 52.8% respectively) and the 2007/08 season (56.9% and 85.0%, respectively). A higher stability in yield was found for cultivars of the E maturity group compared to those of the I group.

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