Evaluation of Marker-Assisted Introgression of Yield QTL Alleles into Adapted Soybean

Genetic diversity is limited in southern elite soybean [Glycine max (L.) Merrill]. Introgression of diverse alleles for yield may increase the rate of yield improvement. Beneficial yield alleles at three quantitative trait loci (QTL) from the northern cultivar Archer have been tagged with molecular markers. The objective of this research was to assess the value of the three Archer alleles for increased yield in southern environments and genetic backgrounds. Four sets of near isogenic lines (NIL) for each quantitative trait locus (QTL) were derived from heterozygous F6 plants identified from the crosses of Archer X Asgrow A5403 and Archer X Pioneer 9641. The NIL sets were tested at four environments across 2 yr. Data was collected on yield, height, and maturity. None of the marker effects were significant for any of the three QTL for any trait, when averaged over all sets or for individual sets. The results suggest that the Archer alleles are not superior to the southern alleles when tested in southern environments. Archer has low relative yield in the South, while in the original mapping study ARcher was the high-yield adapted parent. The superior genetic value assigned to the Archer yield QTL to may not be readily transported to populations or environments where Archer is inferior. Recombination and epistasis may also have affected the ability of the Archer markers and QTL to improve yield. Our results indicate that it may be difficult to capture the value assigned to QTL alleles derived from diverse parents with variable relative genetic value when the alleles are introgressed into populations with different genetic backgrounds, or when tested in different environments

Genetic characterization of ninety elite soybean cultivars using coefficient of parentage Caracterização genética de noventa cultivares elites de soja por meio do coeficiente de parentesco

The objective of this work was to estimate the coefficient of parentage and to understand the genetic structure of 90 elite soybean cultivars, which are adapted to different Brazilian environments. A total of 4,005 coefficients of parentage (f) were obtained and used to group the cultivars by UPGMA method. The constructed dendrogram showed several related cultivar groups which shared similar ancestors and clearly showed the genetic structure of the main Brazilian cultivars. Effective population sizes (Ne) were also estimated for cultivars in different generations. The average f = 0.2124 value, obtained from cultivars classified into four decades according to the release year, suggested effective soybean population sizes of 11 and 13 calculated using arithmetic and weighted means, respectively. The relatively small Ne and the high parentage coefficient support the conclusion that there is a high similarity degree among the main soybean cultivars in Brazil.<br>O objetivo deste trabalho foi estimar o coeficiente de parentesco e conhecer a estrutura genética de 90 cultivares elites de soja adaptadas aos diferentes ambientes brasileiros. Foram obtidos 4.005 coeficientes de parentesco (f), os quais foram utilizados para realizar o agrupamento das cultivares, pelo método UPGMA. O dendrograma formado permitiu observar vários grupos de cultivares que se aproximaram por possuírem ancestrais comuns, e mostra a estrutura genética das principais cultivares indicadas para o Brasil. Foi estimado também o tamanho efetivo populacional (Ne) de cultivares em diferentes gerações. O valor de f calculado (f = 0,2124) comparado com as médias ponderada e aritmética das cultivares organizadas segundo os períodos de lançamento durante quatro décadas revela que o Ne para a soja é de 11 e 13, para a média aritmética e ponderada, respectivamente. O Ne relativamente pequeno e o alto coeficiente de parentesco sustenta a conclusão de que existe alto grau de similaridade entre as principais cultivares de soja indicadas para o Brasil

Genetic diversity among Brazilian soybean cultivars based on SSR loci and pedigree data

In this study, simple sequence repeats (SSR) loci and pedigree data were used to investigate the genetic relationship in a group of 168 Brazilian soybean cultivars. Eighteen SSR loci produced an average of 5.06 alleles and a mean gene diversity of 0.58 for the cultivars studied. Genetic distance (GD) was determined using the modified Roger's Wright distance, and a final dendrogram was in agreement with the cultivar pedigree. A distance matrix based on the coefficient of parentage scores was also generated for the cultivars, which ranged from 0 to 1, with a mean of 0.18, whereas SSR-based genetic similarity (1- GD) ranged from 0.01 to 0.90, with a mean of 0.25. Mantel's Z test showed that the similarity matrices generated from both the data sets were low, but significantly correlated (r = 0.31, p<0.001). The results showed that SSR data and pedigree analyses could help to quantify more accurately the degree of relationship among the soybean cultivars.<br>Locos microssatélites e dados de genealogia foram utilizados para avaliar a diversidade genética de um grupo de 168 cultivares brasileiras de soja. Os dezoito locos utilizados apresentaram em média 5,06 alelos por loco e coeficiente de diversidade genética médio de 0,58. O dendrograma final resultante da matriz de distância genética de Roger modificado por Wright, apresentou boa concordância com a ancestralidade dos grupos formados. Também foi estimado os coeficientes de parentesco entre as cultivares, sendo observada variação de 0 a 1 com média de 0,18, enquanto que as similaridades para os locos microssatélites (1- GD) variou de 0,01 a 0,90 com média de 0,25. A correlação entre as duas matrizes obtidas determinada pelo teste Z de Mantel apresentou valor baixo, 0,31, mas significativo (p<0,001). Os resultados obtidos sugerem que os locos microssatélites aliados às informações de genealogia proporcionam melhor análise da diversidade genética de cultivares de soja