Teor de lignina e qualidade de sementes de soja em relação ao retardamento da colheita

Abstract

The unfavorable weather conditions in the pre-harvest soybean seeds after physiological maturity, can cause damage and negatively affect the quality of the seeds. Therefore, the aim of this work was to evaluate the soybean cultivars seed behavior with different lignin as the postponement of harvest with artificial incidence of rain and storage. The trial was conducted in Iraí de Minas, Brazil, in a randomized block design with three replications and factorial 5x3x3, five soybean cultivars (NK 7059 RR, SYN 1163 RR, RR SYM 9070, AS 7307 and SYN 1283 RR RR) three harvest seasons (R8, R8 + a rain simulation in the pre-harvest and R8 + two rainfall simulations in pre-harvest) and three storage times (0, 90 and 180 days). The rainfall simulations in pre-harvest were performed using irrigation from central pivot, the intensity of 30 mm of water, until the pods stay wet, and were subsequently harvested when they reached 18% water content. The interval between harvests was approximately six days. The seeds were evaluated for chemical composition (lignin content), the percentage of moisture damage (tetrazolium), physiological quality (germination, accelerated aging, conductivity, emergency, emergency speed index), sanitary quality ("Blotter test") and enzyme activity (catalase, esterase, alcohol dehydrogenase, malate dehydrogenase and isocitrate lyase). The cultivar AS 7307 RR showed higher lignin content in the seed coat, a lower percentage of damage by moisture and higher vigor. The cultivars NK 7059 RR and SYN 1163 RR have lower lignin content in seed coats and higher percentages of moisture damage evaluated by the tetrazolium test, and to cultivate SYN 1163 RR is among the cultivars with lower physiological performance. The electrical conductivity values increase with storage for all cultivars. The percentage of normal seedlings emergency and the emergency speed index vary with storage. There incidence of Fusarium spp. (23.04%), Aspergillus sp. (13.16%), Penicillium sp. (8.37%), Phomopsis sp. (3.16%) and Colletotrichum truncatum (1.71%). There is variation in the electrophoretic pattern of catalase, esterase, alcohol dehydrogenase; malate dehydrogenase and isocitrate lyase for seeds submitted to the harvest delay, stored and not stored.