| Title: | Resistance to soybean sudden death syndrome and root colonization by Fusarium solani f. sp. glycine in near-isogenic lines. |
| Authors: | Njiti, V.N., Doubler, T.W., Suttner, R.J., Gray, L.E., Gibson, P.T., Lightfoot, D.A. |
| Source: | Crop Sci. 1998, 38(2):472-477 |
| Abstract: | One genomic region in soybean [Glycine max (L.) Merr.] 'Essex' and three in 'Forrest' underlie field resistance to sudden death syndrome (SDS) leaf scorch in their recombinant inbred line (RIL) progeny. Root infection by Fusarium soloni (Mart.) Sacc. f. sp. glycine precedes the leaf scorch caused by SDS. Forrest shows rate-reducing resistance to both root colonization by F. solani and leaf scorch, whereas Essex does not. Our objective was to determine whether genomic regions that underlie resistance to the SDS leaf scorch also caused resistance to root colonization by F. solani in near-isogeneic lines (NILs). The NILs were derived from individual plants selected from within one recombinant-inbred line (ExF34). ExF34 was heterogenous within regions of linkage group C2 and G, each of which encompassed quantitative trait loci (QTL) for resistance to SDS. Using DNA markers, four genotypic classes could be identified. The QTL effects were compared with two SDS disease parameters, leaf scorch measured as SDS disease index (DX) at the R6 growth stage and root colonization by F. solani measured as infection severity (IS) at the R5.5 and RS growth stages. The Forrest allele of the genomic region on linkage group G was consistently associated with decreased DX (P < 0.05-0.0004) and IS (P < 0.05-0.0017). The Essex allele of the genomic region on linkage group C2 caused a decrease in DX (P > 0.05) and IS in the susceptible pair of the four NIL classes at R5.5 but not R8. Therefore, the QTL on linkage group G and C2 confer separate components of resistance to SDS that are suitable for selection in a resistance gene pyramid. |