Herança transgeracional da disponibilidade de fósforo na produção de sementes e rendimento de grãos em soja

Abstract

The effect of phosphate fertilization on seeds from several species has been extensively studied as the Brazilian seed market reaches an advanced degree of maturity. Although several studies have evaluated the effect of phosphate fertilization on soybean seed physical and physiological quality, only a few studies observed marked differences on seed viability and vigor tests performed, however, marked responses on yield on the subsequent generation were observed in some of these studies. Thus, the aim of this research was to identify the underlying mechanisms responsible for the superior performance of soybean seeds produced under elevated availability of phosphorus. On chapter I, contrasting cultivars were selected for tolerance to phosphate starvation. Six cultivars presented superior performance while four were more severely affected by phosphate starvation. On chapter II, seeds from the cultivars DM 66i68 RSF IPRO (more tolerant or more stable) and SYN 15630 IPRO (more sensitive or responsive) were produced under doses proportional to 0, 50, 100, 150 and 200% of the recommended P dosage for a yield expectation of 5 Mg ha-1. Phosphate fertilization promotes growth and dry matter production, improves all yield components, increases the ratio between total dry matter and yield, promotes greater concentration of the minerals P, Ca, Mg, Fe and Zn on seeds. Seeds produced under greater availability of phosphorus present less solute loss during imbibition on the electrical conductivity and potassium leakage tests and produce seedlings with greater speed of emergence index, greater dry matter of components and leaf area. On chapter III, seeds from both cultivars evaluated on chapter II and produced under the doses of 0%, 50% and 200% of phosphorus were used for grain production using the doses 0 and 200% of phosphorus. Greater doses of phosphorus during seed production led to increased plant height, node number, shoot diameter, grain yield and 1000-seeds weight during grain production. On chapter IV, the results from a study performed during the Doctoral Exchange Program at the University of Georgia are presented where a genome-wide association (GWA) study for the characteristic maturity group on soybean varieties from the USDA germplasm was carried out. 16879 genotypes from maturity groups 000 through IX were used. Using paired associations between every two adjacent maturity groups, 58 QTLs were detected from which 54 were confirmed in the GWA with all the accessions. The results generated can help soybean breeders manipulate the maturity loci for genetic improvement of soybean yield.