03779naa a2200193 a 450000100080000000500110000800800410001910000160006024500970007626000090017330000120018249000370019450001800023152028670041170000180327870000230329670000200331977302460333914667862007-07-27       2004    bl uuuu     u00u1 u    #d1 aDIAS, W. P.  aGenetics of resistance in soybeans to race 4+ of soybean cyst nematode, Heterodera glycines.  c2004  ap. 168.  a(Embrapa Soja. Documentos, 228).  aEditado por Flávio Moscardi, Clara Beatriz Hoffmann-Campo, Odilon Ferreira Saraiva, Paulo Roberto Galerani, Francisco Carlos Krzyzanowski, Mercedes Concordia Carrão-Panizzi.  aThe work had as objectives to study the inheritance of resistance to race 4+ of soybean cyst nematode (SCN) and to identify markers, of microsatelites and loco i (the seed coat color), associated to the loci of resistance. Race 4+ refers to population of SCN, identified for the first time in Brazil, and wich differs from traditional race 4 for its ability to infect Hartwig cultivar, but not its ancestral PI 437654. The experiments were carried out at Embrapa Soybean, in Londrina, PR, Brazil. The inheritance of resistance of genotypes E97-2502-1 and E97-2502-5 (types PI 437654), crossed with the susceptible parent E96-776 (type 'Hartwig'), was studied using 120 F2:3 families, 120 F2 individuals and 20 F1 individuals and each of parental. Generations of each crossing were evaluated at greenhouse, during October, November and December of 2000. Seedlings of each generation and of the diferencials of race were transplanted (one by pot) in clay pots and inoculated with 4000 nematode eggs. In both crossings, the inoculations resulted in high numbers of females in the susceptible genotypes, confirming the presence of race 4+. There was no effect of the reciprocal. The estimates of heritability were of medium to high magnitude. Transgressive segregation and partial dominance to resistance were observed. For the crossing E96-776 x E97-2502-1 were detected additive, dominant and epistatics of additive x additive type effects, with at least two genes controlling the resistance. In the crossing E96-776 x E97-2502-5, only one gene was enough to explain the observed segregation. An additive-dominant model adjusted well to the data. The studies for identification of microsatelites markers were realized in the first semester of 2003, using leave DNAs extracted from parentals, F1s and of 122 F2 plants of crossing E96-776 x E97-2502-1. The Satt 177 and Satt 341, located in the A2 group, next to loco i, were the only associated with resistance. The three marks codominants were enclosed in one same group of linkage. The loco i was located between the two microsatelites, at 28.2 cM of Satt 177 and at 18.4 cM of Satt 341. The analysis on the three markers indicated the presence of a resistance QTL situated 4 cM of loco i, 24 cM of Satt 177 and 14.4 cM of Satt 341. The identified genomic region matches with that one of the A2 group, where the Rhg4 gene for resistance to some races of SCN is located. The three markers are significantly associated with the resistance. Although additivity and dominance in the direction of the resistance for the three markers were detected, additive effects always predominated. Variations in females number, explained with loco i, Satt 341 and Satt 177, were of 64.1%, 55.1% and 30.7%, respectively. Considering only the resistant plants, selection efficiencies were, respectively, of 100.0%, 67.8% and 62.5%.1 aCAMPOS, V. P.1 aKIIHL, R. A. de S.1 aARIAS, C. A. A.  tIn: WORLD SOYBEAN RESEARCH CONFERENCE, 7.; INTERNATIONAL SOYBEAN PROCESSING AND UTILIZATION CONFERENCE, 4.; CONGRESSO BRASILEIRO DE SOJA, 3., 2004, Foz do Iguassu. Abstracts of contributed papers and posters. Londrina: Embrapa Soybean, 2004.