Genetic analysis of soybean resistance to Fusarium solani f.sp. glycines

Abstract

In order to study the genetic control of soybean resistance to sudden death syndrome (SDS), a 5 x 5 diallel with the F 2 generation, without the reciprocals, was carried out in a greenhouse. The following parents were used: Forrest, MG/BR-46 (Conquista), IAC-4, FT-Cristalina, and FT-Estrela. The first two cultivars are more resistant to SDS than IAC-4, which is considered to be moderately resistant to SDS, and the last two cultivars are highly susceptible. The fungus was inoculated with three colonized sorghum grains placed at the bottom of the holes with two soybean seeds. Single plants were evaluated between 14 and 37 days after emergency based on foliar severity symptoms (1-5) of SDS. The disease incidence and a disease index were also calculated for each plot (clay pots with five plants each). The analysis for severity and disease index was performed only with the data of the 37 th day after emergence. Additive and dominant genetic effects were detected by Jinks-Hayman's analysis, but the dominant genetic effects were higher. The genetic parameters estimated indicated that the average degree of dominance showed the presence of overdominance; at least three loci or genic blocks that exhibited dominance were responsible for the genetic control of SDS resistance; the estimates of narrow-sense heritabilities were moderate (0.48 to 0.62), but in the broad-sense they were higher (0.90 to 0.95), thus reinforcing the presence of dominance effects; and the resistance to SDS was controlled mostly by dominant alleles. Five microsatellite markers (Satt163, Satt309, Satt354, Satt371 and Satt570), reported as linked to five QRLs of the SDS, were used to genotype the parents and showed the possibility of occurrence of multiallelism in those loci, but this evidence did not invalidate the fitting of the data to the Jinks-Hayman's model.

Diallel among soybean genotypes with high oil content and resistance to sudden death syndrome

“…Therefore, the use of resistant cultivars is a fundamental component in the integrated management of SDS. Due to the probable polygenic nature of genetic resistance to this disease and the large environmental influence in the manifestation of symptoms, coupled with the fact that there are no efficient chemical or cultural methods of control, SDS has become a major concern to soybean farmers and researchers in the regions where it occurs (Fronza et al 2004). Because of the demand from the oil-chemistry industry and, recently, with the possibility of using soybean oil as a biofuel, it has become fundamental to develop new genetic material with a higher oil yield and also tolerance to the main root diseases.…”

Molecular Breeding to Overcome Biotic Stresses in Soybean: Update

“…Ref. [ 103 ] testified QTLs conferring nine LGs (A2, C2, D2, F, G, I, J, L and N) for resistance to root infection (Rfs1) on linkage group G. Soybase [ 104 ] includes more than 56 recordsof QTLs for Fusarium wilt in soybean.…”

“…Resistance to Fusarium wilt seems to partially result from a locus on linkage group G causing a proportional decrease in resistance to colonization of the tap root by Fusarium as well as linkage groups C2, G and N that reduced foliar symptoms but not root infection [ 102 , 103 ]. SDS QTLs on linkage group G displayed a robust allelic difference in NIL populaces resulting from cultivars Essex and Forrest [ 100 , 104 ].…”

“…The 7.5 ± 0.5 cM area of chromosome 18 (linkage group G) was revealed to comprehend several resistance loci employing recombination actions from four near-isogenic lines population and nine DNA markers [ 103 ]. Three to four genes, viz., QRfs -, QRfs 1-, QRfs 2- and QRfs 3-rich islands, were inferred to conveyresistance in linkage group G [ 108 ].…”

Validation of microsatellite markers for assisted selection of soybean genotypes resistant to powdery mildew

“…Several studies have tried to identify SSR markers linked to diseases: resistance to sudden death, cyst nematode, brown spot, and Asian soybean rust (Fronza et al 2004, Silva et al 2007, Brogin 2005; resistance to witches' broom in cacao (Santos et al 2007), angular leaf spot and powdery mildew in common bean (Teixeira et al 2005); and powdery mildew in wheat (Liu et al 2001).…”