Monocyclic components, photosynthetic efficiency and grain yield in the Corynespora cassiicola - Soybean pathosystem

Abstract

In Brazil the 2009-2010 soybean crop took up an area of 23.06 million hectares. That result constitutes in the second largest sown area. Total production was estimated in 69.7 million tons and productivity in 2,941 kg / ha. Diseases are among the factors that can reduce soybean productivity. Approximate 40 diseases caused by fungi, bacteria, nematodes and viruses had been identified in Brazil. That number keep increasing because of the expansion of soybean production into new areas and a result of monoculture as well. The soybean target spot caused by Corynespora cassiicola is a common disease in soybean crops and in their growing areas in Brazil. From soybean crop in 2005-2006 the same disease has caused increasing damages in susceptible cultivars especially. Information about grain yield in crop production is the basis for any economic analysis of quantification of disease. In order to determine crop losses, some models had been proposed for grain yield quantification which comprises the result of physiological concepts and effects of disease on the foliage of the host plant. The parameters used in these models are the healthy area duration (HAD) and healthy leaf area absorption (HAA). Those parameters have proven effective for use as predictors of crop yield by replacing the severity of the disease. Those models are being used in several pathosystems. Thus, this research will study the effect of temperature on the mycelial growth of C. cassiicola isolates; conducting an epidemiological study on the C.cassiicola - soybean pathosystem under controlled conditions; evaluate the effect of disease on photosynthetic efficiency of soybean and determine Bastiaans coefficient for this pathosystem; quantify grain yields in BMX Potencia, Nidera 5909 and BRS 295 in field conditions.