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| Author(s): |
Evandro Binotto Fagan
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2008-01-18 |
| Examining board members: |
Durval Dourado Neto;
Jose Laercio Favarin;
Paulo Augusto Manfron;
Sandro Luis Petter Medeiros;
Joao Domingos Rodrigues
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| Advisor: | Durval Dourado Neto |
| Abstract | |
In Brazil, the soybean is one of the most cultivated crop. However, problems related to fungal diseases caused losses in yield up to 95%. The use of pyraclostrobin had provided increase in yield and diseases control, as Asian rust mainly, considered one of the main soybean disease actually. With the purpose of studying the physiological effect of the pyraclostrobin (strobilurin) application on soybean crop, three experiments were carried out at Piracicaba, State of São Paulo, Brazil (University of São Paulo, Escola Superior \"Luiz of Queiroz\"), using different cultivars (two field experiments, from November 2005 to May 2006, with \'M-SOY 8008 RR\' and \'BRS 245 RR\' cultivar and one greenhouse experiment, from January to May 2007, with \'BRS Conquista\' cultivar). Physiological (net photosynthesis, respiration, ethylene production and the nitrate reductase - enzyme - activity) and phenometric analysis (total - shoot + root - leaves and stem dry mass and leaf area) and soybean yield were evaluated. The statistical field experiment design was complete randomized block design with three treatments (T1: no fungicide application; T2: two applications of pyraclostrobin and T3: two applications of tebuconazole - triazol - at R1 and R5.1 soybean phenological stages) and four replications. The statistical greenhouse experiment design also was complete randomised block design with two treatments (T1: pyraclostrobin application and T2: no fungicide application) and five replications. The field experiment observed data had been used according to the Van Keuler and Wolf (1986) models. The nitrate reductase enzyme activity was increased when the fungicide was applied at R1 stage. The respiratory rate decreases soon after the pyraclostrobin application (stage R5.1). The pyraclostrobin (strobilurin) increased: (i) the plant CO2 gross assimilation rate; (ii) the pod CO2 net assimilation rate; (iii) the mass of 1000 seeds and (iv) yield (13 and 4 bags ha-1 in relation to T1 and T3, respectively). In relation to \'BRS 245 RR\' cultivar, the pyraclostrobin increased leaves, stem and total (shoot + root) dry mass and leaf area from 14 days after first application to end of the crop cycle. The greenhouse observed data demonstrated that the pyraclostrobin application increased the photosynthesis rate (maximum values occurred 7 days after application - DAA) and the nitrate reductase enzyme activity (maximum values occurred 0 DAA) until 7 DAA. The physiological effect of pyraclostrobin application on the stomatal conductance and transpiration rate occured until 3 DAA, period of maximum effect. The respiratory rate decreased until 7 DAA, however the ethylene biosynthesis was inhibited gradually until 18 DAA. The observed data allows to conclud that the pyraclostrobin application increased the soybean physiological activity and the yield, being that the highest activity in the carbon assimilation and nitrogen rate occurred until the 7 DAA. (AU) | |