Manganês via foliar em soja convencional e transgênica RR: efeitos na qualidade de sementes, atividade enzimática, lignina e produtividade

Abstract

The Mn is associated with enzymes activation, which include the ones related to the formation of lignin, and the latter may influence seed quality. There are reports that glyphosate-resistant (GR) soybean plants are less efficient than conventional ones in accumulation of Mn and that GR soybean has greater lignin content than conventional. However, studies on these areas still are contrasting. The aim of this study was to evaluate the influence of foliar Mn application in the production process and in the quality of soybean seeds, in conventional cultivars and its derived GR. The experiment was carried out at the Federal University of Lavras, MG state, using a randomized block design with three replications and a 4 x 4 x 2 factorial structure, with four soybean cultivars, two conventional and its derived GR (Celeste and Baliza RR, Jataí and Silvânia RR), four rates of foliar Mn (0; 200; 400 and 600 g Mn ha-1) and two stages of application (R1 or R3). It was evaluated the agronomic traits (lodging, number of pods per plant, thousand seed weight and yield), the chemical composition (lignin content in the seed coat and the Mn content in the seed), the enzyme activity (esterase, EST; isocitrate lyase, ICL; alcohol dehydrogenase, ADH; malate dehydrogenase, MDH; superoxide dismutase, SOD; peroxidase, PRX) and physiological (germination, accelerated aging, emergency, electrical conductivity and tetrazolium) and sanitary quality of seeds, before and after storage. In regards to the agronomic traits, it was found that the response to the application of Mn might be conditioned to the genotype rather than to the GR genetic modification, with increase in seed yield of Baliza RR and Celeste with of foliar Mn application, maximum values obtained with 150 g Mn ha-1. There was a trend of better results when applied Mn in R1. In relations to seed quality, Celeste and Baliza RR seed have better physiological quality when compared to Jataí and Silvânia RR. The foliar Mn application provides better physiological and sanitary quality of seeds. For the chemical composition it was observed that Mn applied by foliar translocates to the seeds, but doesn’t modify the lignin content in the seed coat. The lignin content in the GR soybeans seeds coat are superior to their conventional ones. Soybean cultivars whose seeds have higher lignin contents in the seed coat not necessarily present better physiological quality. In what concerns the enzymes, it was observed that the expression of SOD, PRX, EST and ICL in soybean seeds are affected due to the foliar Mn application, regardless the stage of application. In the seeds of cultivars that have better physiological quality, Celeste and Baliza RR, it is found higher expression of ADH and ICL, but lower expression of MDH and PRX