Epidemiologia comparativa da ferrugem asiática (Phakopsora pachyrhizi Sydow) em cultivares de soja de diferentes grupos de maturação

• Autor(a) principal: Moreira, Eder Novaes
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1053
• topic: Phakopsora pachyrhizi; Epidemiologia; Época de plantio; Phakopsora pachyrhizi; Epidemiology; Planting time; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA

Since the first report in South America in 2001, Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrhizi, has caused significant loss in all regions of soybean production in Brazil. The potential of ASR in causing losses spurred research aimed aspects of the use of fungicides such as efficacy, number of applications, ideal time to apply, but these criteria do not consider the epidemiological aspects of ASR and attributes the growth of plants of different cultivars may thus compromising disease management under conditions of severe epidemics. Little is known about the epidemiological behavior of ASR for different maturity groups of cultivars available to soybean farmers, the rising interest in developing this work, which aimed to: 1. Compare the temporal dynamics of ASR in three soybean cultivars with different maturity groups, seeded four times, to better understand the behavior of epidemics and thus establish alternatives for the best management of ASR. 2. Evaluate the association of leaf area index (LAI) between different soybean cultivars under the temporal dynamics of ASR. Eight experiments were performed at the site of the Foundation for Research Support and Integrated Development of Rio Verde, located in the city of Lucas do Rio Verde - MT. We used three soybean cultivars with different maturity cycles, all susceptible to ASR, which were: P98Y11RR (early maturity, 95-110 days), MSoy-8527RR (medium cycle; 111-120 days) and MSoy-9144RR ( late cycle; greater than 121 days). The results show that the ASR progress curves for different cultivars showed different epidemiological behavior. With the exception of the fourth season of sowing, the area under the curve of progress on the rust (AUCPRR), was higher for plants early cultivar than in other cultivars. For medium maturity cultivar, the AUCPRR was lower than for early-maturing cultivar in all sowing dates in two seasons. The highest values of progress rate (rgomp) were observed for the early cultivars, irrespective of sowing dates, with values of 0.0654, 0.0659, 0.0782 and 0.0891, respectively, for the sowing dates. October, November, December and January. On the other hand, the lowest values were observed for rGomp late-maturing cultivar, irrespective of sowing dates, with values of 0.0368, 0.0431, 0.0473 and 0.0563, respectively, for sowing times October, November, December and January. Both values ymax and TAMIF reinforce that early cultivars have higher values. Regarding TAMIF the early cultivars reach faster the leaf area index LAI absoluta. The association LAI and temporal dynamics of ASR was observed shortening of the cycle of cultivars in different seasons. The LAI P98Y11RR varied among cultivars (early cycle) MSoy-8527RR (cycle medium) and MSoy-9144RR (late cycle) at different sowing times, affecting the temporal dynamics of ASR. The highest values of LAI occurred for plants relating to sowing dates 1. The area under the curve of growth on LAI (AUCGLAIR) was higher for plants that grow later in other cultivars. The fact that AUCGLAIR remained constant between sowing dates for late cultivars suggests that the LAI had a strong influence on the progress of ASR in early cultivars of plants than the plants of medium and late cultivars. Confirming that the earliness of the proportion of diseased leaf area compared to healthy leaf area is reduced rapidly, because of the ASR achieve leaf area and hence the LAI when compared to middle and late cultivars that have higher LAI. Therefore, assuming the same intensity ASR, in the three cultivars (early, mid and late), the cultivar early achieve faster healthy leaf area, ie, these cultivars have a higher dependence on green leaf tissue, when compared to the middle and late cultivars because of the differences in the proportions of healthy leaf area and leaf area comprising the sick LAI total.