Identificação de QTL associados à simbiose entre Bradyrhizobium japonicum, B. elkanii e soja

Abstract

Resumo -O objetivo deste trabalho foi identificar QTL (locos de caráter quantitativo), utilizando marcadores do tipo microssatélites (SSR), relacionados à fixação biológica de nitrogênio (FBN), em uma população F 2:7 de cultivares de soja (Glycine max) com diferentes capacidades de FBN, Bossier (alta) e Embrapa 20 (média). Foram mapeados 16 marcadores, distribuídos em seis grupos de ligação, cobrindo uma região de 5% do genoma (151,6 cM). A análise de regressão identificou 12 associações significativas em quatro grupos de ligação (B1, C2, D1b e H): três para a massa da parte aérea seca, quatro para número de nódulos, duas para a massa de nódulos e três para a massa média de nódulos. Todos os QTL detectados foram de efeitos menores. Contudo, sete marcadores foram confirmados nas duas populações, indicativo de uso potencial em programas de melhoramento visando à FBN.Termos para indexação: fixação biológica do nitrogênio, marcadores moleculares, mapa genético, microssatélites, nodulação, SSR. Identification of QTL associated with the symbiosis of Bradyrhizobium japonicum, B. elkanii and soybeanAbstract -The objective of this work was to identify QTL (Quantitative Trait Loci) related to biological nitrogen fixation (BNF) using microsatellites (SSR) markers, in an F 2:7 population of soybean (Glycine max) cultivars with contrasting capacities of BNF, Bossier (high) and Embrapa 20 (medium). 16 markers located in six linkage groups have been mapped, covering about 5% of the genome (151.6 cM). The regression analysis identified 12 significant associations in four linkage groups (B1, C2, D1b and H): three for shoot dry weight, four for nodule number, four for nodule weight and three for the medium value of nodule weight. All QTL had minor effects. However, seven QTL were confirmed in both populations, indicating that they might be effective in increasing BNF in soybean breeding programs.

Use of the QTL approach to the study of soybean trait relationships in two populations of recombinant inbred lines at the F7 and F8 generations

“…On the other hand, Wiebold et al (1981) observed a low to moderate (36% to 56%) heritability in the broad sense, for net photosynthesis of individual leaves, in the initial F 3 and F 4 generations using an infrared gas analysis system at temperatures varying from 29 to 31 o C. Table 1 shows heritability values for W ST , n N e W N of 87.47%, 18.70% e 32.02%, respectively. These values are in agreement with the observations of Santos et al (2006) who estimated heritability values of 49% for stem dry mass, 30% for nodule number, and 33% for nodule dry mass, in a segregating population composed of 157 recombinant inbred lines derived from the cross between two soybean cultivars identified as contrasting for biological nitrogen fixation capacity. Therefore, it can be concluded that the evaluated traits are under environment effects, as well as that the present population can be used in studies aimed at evaluating heritability of such traits.…”

“…Mansur et al (1993) that the LGs C1, C2 and D1 have loci associated with the traits leaf area and maturity of the soybean. The identification of a QTL associated with W ST in the LG L confirms the observation that in this LG there is a QTL associated with WST (Santos et al, 2006) and plant height of G. max (Lee et al, 1996).…”

Nodulation Capacity of Argentinean Soybean (<i>Glycine max</i> L. Merr) Cultivars Inoculated with Commercial Strains of <i>Bradyrhizobium japonicum</i>

“…While the rj 1 allele [15] conditions a restriction of nodulation with a broad range of rhizobia, other genes like Rj 2 [15], Rj 3 [16], Rj 4 [17] , Rj 5 and Rj 6 [18] restrict nodulation only with defined members of bradyrhizobia serogroups. Furthermore, Nicolás et al [19,20], Santos et al [21] found that nodulation of soybean cultivars is also under the control of QTL (quantitative traits) such that soybean cultivars can be grouped in high and low nodulating ones.…”

Análise de agrupamento de diferentes densidades de marcadores no mapeamento genético por varredura genômica

“…Santos et al (2006) relacionaram o efeito do QTL à herdabilidade da característica. Assim, a identificação de QTL de pequeno efeito requer grande quantidade de marcadores estrategicamente ordenados.…”