Identificação de novos locos de resistência à ferrugem asiática (Phakopsora pachyrhizi) em soja (Glycine max)

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

12/12/2008

RESUMO

In Brazil, the soybean rust, caused by Phakopsora pachyrhizi, has caused yield losses and increased the cost of production by the intensive use of fungicides in soybean fields. The use of resistant varieties is an important tool to control the disease. Currently five different loci have been reported containing genes for resistance to disease, called rpp1 to rpp5. A new race of the fungus broke the resistance conferred by some genes present in the loci rpp1 and rpp3 in Brazil. This study aimed to perform allelism tests between sources of resistance identified in the germplasm bank of Embrapa Soybean, whose genes do not belong to rpp4 and rpp2 loci. To accomplish this objective, 20 sources of resistance genes mapping out of the loci rpp2 and rpp4 (Laperuta, 2007) were divided into a group with four testers, which were crossed between them, and with the other 16 sources. The parentals and F2 generations from these crosses were inoculated and evaluated in a greenhouse. Each plant was classified according to the reaction of resistance (RB lesion) or susceptibility (TAN lesion). Based on the segregation observed in the F2 generation, it was possible to conclude that among the four sources used as testers, three of them (PI 200487 or "Kinoshita," PI 200526 or "Shira Nui" and GC 84058 18-4) have at least one gene of resistance in the same linkage group (LG), while the other tester (PI203398 or "Abura") has a gene of resistance in an independent locus. Among the other sources tested, three of them (PI 416764 and PI 423966) belong to the group "Kinoshita," three (PI 416810, PI 417421 and PI 398777) belong to the group "Abura", and five (PI 397618TC1, PI 417074, PI 417503, Nova Santa Rosa and Hyuuga) segregated independently in relation to the groups "Kinoshita" and "Abura," which indicates that they have at least one gene of resistance mapping out of the loci 17 tested. The sources GC 84058-21-4 and GC 84051-9-1 didn’t segregat in crosses with the tester GC 84058-18-4 and must contain at least one gene next to the LG of "Kinoshita." Three other sources (PI 471904, PI 200455 and PI 417115) not segregated in crosses with "Abura," but it was not possible to conclude about their LG, because the PI 471904 also do not segregate with "Kinoshita”, while the PI 200455 do not segregate with the testers PI 200526 and PI 200487 of the group "Kinoshita" and, finally, the PI417115 also do not segregate with PI 200487 of the group "Kinoshita." According to these results, it is possible that we are dealing with a new cluster of genes for disease resistance in LG-N.

ASSUNTO(S)

genética vegetal soja - biologia molecular fungos fitopatogênicos plant genetics soybean molecular biology phytopathogenic fungi

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