Retardamento de colheita e estudo da diversidade genética em soja para seleção de genitores com qualidade de semente

Abstract

Soybeans are a grain-producing species of high international demand and occupy a prominent position in the Brazilian economy. The success of this culture in Brazil is due to the public and private investment in production technologies and genetic breeding programs. It is through the seed that the genetic advances reach the producer. In this context, the success of a cultivar and high productivities depends on the quality of the seed. Therefore, studies aiming at the identification of superior genotypes and the characterization of cultivars in terms of seed quality are important for breeding programs, also allowing the study of genetic diversity for selection purposes. The objective of the study was to evaluate the physiological quality of seeds of soybean cultivars at different harvest times and to study the genetic diversity from the characteristics related to the physiological quality of soybean seeds in order to identify superior parents. The experiment was conducted in an experimental area located at Capim Branco Farm, belonging to the Federal University of Uberlândia, in the 2016/2017 season. Ten soybean cultivars were evaluated (CD 2737 RR, UFUS 7415, UFUS 7910, UFUS Milionária, UFUS 7801, NA 5909 RG, UFUS 8301, TMG 7062 IPRO, UFUS Xavante and UFUS 6901) in four harvest periods (R7, R8, R8+15, R8+30), constituting a 10 x 4 factorial. The experiment was carried out in a randomized complete block design with four replicates. The agronomic and seed quality data were analyzed by uni and multivariate statistics. Twelve agronomic characters were evaluated and for the physiological quality the following tests were performed: germination, electrical conductivity and fresh and dry matter of seedlings. The genetic dissimilarity was estimated by the generalized distance of Mahalanobis and genotypes grouped by the UPGMA methods, farthest neighbor, nearest neighbor, Tocher and canonical variables. The genotypes NA 5909 RG, TMG 7062 IPRO and UFUS 6901 were the earliest, with the cycle ranging from 90 to 105 days. Averages of productivity close to the Brazilian average in the 2016/2017 harvest, which is of 3364.00 kg ha-1, in the cultivars NA 5909 RG and UFUS 6901, were observed, even delaying the harvest in 30 days. In the tests for physiological quality of seeds, highlight the NA 5909 RG, which presented the best averages for the evaluated characters. The genotypes formed four identical groups in the methods of Tocher, UPGMA, more distant neighbor and canonical variables. The total number of pods was the major contributor to genetic diversity. The hybridizations of UFUS 7415 and UFUS 7801 genotypes with cultivar NA 5909 RG are promising to obtain segregating populations with high genetic variability for physiological seed quality.