Spore Density and Arbuscular Mycorrhizal Colonization in Sunflower Grown in Campo Verde (Brazil)

The objective of this study was to evaluate the number of spores and the mycorrhizal root colonization in a Cerrado soil (Red-Yellow Latosol) cultivated with different sunflower genotypes. The sampling of the rhizospheric soil was performed at three growth stages: Sowing, flowering, and harvest. The experimental design was in completely randomized blocks with four replications. Three different sunflower hybrids were tested in the 2009 and 2010 cropping seasons. The collected data comprised the total number of spores per 50 g of soil at the three growth stages, along with arbuscular mycorrhizal fungi (AMF) colonization. It was verified that the mycorrhizal colonization was not influenced by the sunflower genotypes, and the mean spore densities were equivalent to 4.94 and 4.64 g soil-1 in 2009 and 2010, respectively. More importantly, AMF colonization was enhanced by lower soil phosphorus levels. The maximum spore production was obtained at flowering, with mycorrhizal colonization rates ranging from 21 to 28% and from 28 to 48% in 2009 and 2010, respectively. The number of spores also varied from 153 to 342 and from 147 to 320 in 2009 and 2010, respectively.