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PubMed2006

Pseudomonas syringae effector avrB confers soybean cultivar-specific avirulence on Soybean mosaic virus adapted for transgene expression but effector avrPto does not.

Soybean mosaic virus (SMV) was adapted for transgene expression in soybean and used to examine the function of avirulence genes avrB and avrPto of Pseudomonas syringae pvs. glycinea and tomato, respectively. A cloning site was introduced between the P1 and HC-Pro genes in 35S-driven infectious cDNAs of strains SMV-N and SMV-G7. Insertion of the uidA gene or the green fluorescent protein gene into either modified cDNA and bombardment into primary leaves resulted in systemic expression that reflected the pattern of viral movement into uninoculated leaves. Insertion of avrB blocked symptom development and detectable viral movement in cv. Harosoy, which carries the Rpg1-b resistance gene corresponding to avrB, but not in cvs. Keburi or Hurrelbrink, which lack Rpg1-b. In Keburi and Hurrelbrink, symptoms caused by SMV carrying avrB appeared more quickly and were more severe than those caused by the virus without avrB. Insertion of avrPto enhanced symptoms in Harosoy, Hurrelbrink, and Keburi. This result was unexpected because avrPto was reported to confer avirulence on P. syringae pv. glycinea inoculated to Harosoy. We inoculated Harosoy with P syringae pv. glycinea expressing avrPto, but observed no hypersensitive reaction, avrPto-dependent induction of pathogenesis-related protein la, or limitation of bacterial population growth. In Hurrelbrink, avrPto enhanced bacterial multiplication and exacerbated symptoms. Our results establish SMV as an expression vector for soybean. They demonstrate that resistance triggered by avrB is effective against SMV, and that avrB and avrPto have general virulence effects in soybean. The results also led to a reevaluation of the reported avirulence activity of avrPto in this plant.

Bacterial Proteins↗
PubMed2000

Bradyrhizobium spp. (TGx) isolates nodulating the new soybean cultivars in Africa are diverse and distinct from bradyrhizobia that nodulate North American soybeans.

The newly developed cultivars of soybean in Africa, known as Tropical Glycine cross (TGx), are nodulated by bradyrhizobia indigenous to African soils, here designated Bradyrhizobium spp. (TGx). Isolates of Bradyrhizobium spp. (TGx) obtained from nodules of TGx soybeans that were inoculated with soils from 65 locations in six African countries were characterized and grouped into 11 phylogenetic clusters on the basis of RFLP of the 16S rRNA gene. Five restriction enzymes (RsaI, HinfI, MspI, CfoI and HaeIII) established RFLP groups within these Bradyrhizobium spp. (TGx) isolates, which were used to construct a phylogenetic tree showing their genetic relationship with other Bradyrhizobium species. RFLP analysis indicated that Bradyrhizobium spp. (TGx) is a heterogeneous group with some isolates related to Bradyrhizobium japonicum and Bradyrhizobium elkanii strains and some to Bradyrhizobium spp. (misc.) reference strains isolated from a variety of tropical legumes. The heterogeneity within the large phylogenetic clusters was further examined through analysis of randomly amplified polymorphic DNA (RAPD) using GC-rich PCR primers. The RAPD analysis showed additional heterogeneity in the Bradyrhizobium spp. (TGx) phylogenetic clusters, which was not revealed by separations based on RFLP analysis. The Bradyrhizobium spp. (TGx) isolates were classified into effective and ineffective types based on their symbiotic performance on TGx soybean. The isolates were randomly distributed throughout the phylogenetic clusters regardless of their symbiotic effectiveness on TGx soybean.

Africa↗
PubMed1993

Identification of the soybean allergenic protein, Gly m Bd 30K, with the soybean seed 34-kDa oil-body-associated protein.

The soybean allergenic protein, Gly m Bd 30K [Ogawa et al., J. Nutr. Sci. Vitaminol., 37, 555-565 (1991)] which is most strongly and frequently recognized by the IgE antibodies in sera of soybean-sensitive patients with atopic dermatitis, has been characterized. The allergen was isolated from the crude 7S-globulin fraction as an oligomeric form with a molecular weight of more than 3000,000 by gel-filtration chromatography. On two-dimensional gel electrophoresis, the native oligomeric allergen had an isoelectric point of about pH 4.5 and was dissociated into a monomeric form with a molecular weight of about 32,000 by the treatment with sodium dodecyl sulfate and 2-mercaptoethanol. The monomeric allergen had an N-terminal amino acid sequence and amino acid composition identical with those of the soybean seed 34-kDa oil-body-associated protein or the soybean vacuolar protein P34 with close homology to papain-like thiol proteinases [Kalinski et al., J. Biol. Chem., 267, 12068 (1992)]. The identity was further confirmed by the immunological cross-reactivity to the antibodies produced against each of the purified allargen and the 34-kDa oil-body-associated protein. By this observation, Gly m Bd 30K was shown to have about 30% sequence homology with Der pI, a house dust mite allergen that is a thiol proteinase from Dermatophagoides pteronyssius.

Allergens↗
PubMed2004

Recombination within a nucleotide-binding-site/leucine-rich-repeat gene cluster produces new variants conditioning resistance to soybean mosaic virus in soybeans.

The soybean Rsv1 gene for resistance to soybean mosaic virus (SMV; Potyvirus) has previously been described as a single-locus multi-allelic gene mapping to molecular linkage group (MLG) F. Various Rsv1 alleles condition different responses to the seven (G1-G7) described strains of SMV, including extreme resistance, localized and systemic necrosis, and mosaic symptoms. We describe the cloning of a cluster of NBS-LRR resistance gene candidates from MLG F of the virus-resistant soybean line PI96983 and demonstrate that multiple genes within this cluster interact to condition unique responses to SMV strains. In addition to cloning 3gG2, a strong candidate for the major Rsv1 resistance gene from PI96983, we describe various unique resistant and necrotic reactions coincident with the presence or absence of other members of this gene cluster. Responses of recombinant lines from a high-resolution mapping population of PI96983 (resistant) x Lee 68 (susceptible) demonstrate that more than one gene in this region of the PI96983 chromosome conditions resistance and/or necrosis to SMV. In addition, the soybean cultivars Marshall and Ogden, which carry other previously described Rsv1 alleles, are shown to possess the 3gG2 gene in a NBS-LRR gene cluster background distinct from PI96983. These observations suggest that two or more related non-TIR-NBS-LRR gene products are likely involved in the allelic response of several Rsv1-containing lines to SMV.

Base Sequence↗
PubMed2004

Soybean: feed quality and safety. Part 2: pathology of soybean feeding in animals. A review.

Various animal models in farm and laboratory animals indicate the possible pathological effect of soybean feeding. Immunity and tolerance to oral soybean intake and a generalised meta-model of effects are discussed. It seems that FAO/WHO recommendations will have to be considered in assessing the biological value of soybean feed sources. Determination of hull content, antigenic potential, conglycinin and trypsin inhibitor content is warranted in view of the future component pricing of soybean meals.

Allergens↗
PubMed2000

Field evaluation of soybean engineered with a synthetic cry1Ac transgene for resistance to corn earworm, soybean looper, velvetbean caterpillar (Lepidoptera: Noctuidae), and lesser cornstalk borer (Lepidoptera: Pyralidae).

A transgenic line of the soybean 'Jack', Glycine max (L.) Merrill, expressing a synthetic cry1Ac gene from Bacillus thuringiensis variety kurstaki (Jack-Bt), was evaluated for resistance to four lepidopteran pests in the field. Jack-Bt and genotypes serving as susceptible and resistant controls were planted in field cages and artificially infested with larvae of corn earworm, Helicoverpa zea (Boddie), and velvetbean caterpillar, Anticarsia gemmatalis (Hübner), in 1996, 1997, and 1998, and also with soybean looper, Pseudoplusia includens (Walker), in 1996. Susceptible controls included Jack (1996-1998), 'Cobb' (1996), and Jack-HPH (1996). GatIR 81-296 was used as the resistant control in all 3 yr. Compared with untransformed Jack, Jack-Bt showed three to five times less defoliation from corn earworm and eight to nine times less damage from velvetbean caterpillar. Defoliation of GatIR 81-296 was intermediate between that of Jack and Jack-Bt for corn earworm, and similar to that of Jack for velveltbean caterpillar. Jack-Bt exhibited significant, but lower resistance to soybean looper. Jack-Bt also showed four times greater resistance than Jack to natural infestations of lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), in conventional field plots at two locations in 1998. Data from these experiments suggest that expression of this cry1Ac construct in soybean should provide adequate levels of resistance to several lepidopteran pests under field conditions.

Animals↗
PubMed2006

Characterization of antibiosis and antixenosis to the soybean aphid (Hemiptera: Aphididae) in several soybean genotypes.

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is an introduced pest of soybean, Glycine max (L.) Merr., in North America, and it can reduce yields by 50%. Since 2000, when A. glycines was first detected in the United States, studies of this insect and possible control methods have been initiated. Plant resistance to this aphid species is one important component of integrated control. Reproduction of A. glycines was compared on 240 soybean entries in a pesticide-free greenhouse. Eleven entries had fewer nymphs produced, compared with the susceptible checks, and these entries were used in follow-up experiments to assess antibiosis and antixenosis. Antibiosis was estimated in true no-choice tests, in which adults were confined individually in double-sided sticky cages stuck to the upper side of leaves. Antixenosis was assessed in choice tests, in which all entries were planted in a single pot. Adult aphids were placed in the center of the pot, and 24 h later the number of adults on each plant was counted. Of the 11 entries evaluated, nine showed a moderate antibiotic effect to A. glycines, and the other two entries (K1639 and Pioneer 95B97) showed not only a strong antibiotic effect but also exhibited antixenosis as a category of resistance to A. glycines. The resistant soybean entries found in this work are potential sources for A. glycines control.

Animals↗
PubMed1987

Induced non-enzymatic browning of soybean meal. II. Ruminal escape and net portal absorption of soybean protein treated with xylose.

Non-enzymatic browning was tested as a means of increasing ruminal escape of soybean meal N. Soybean meal was treated with xylose (3 mol/mol SBM-lysine), sodium hydroxide (pH 8.5) and enough water to achieve an 83% dry matter mixture and then heated at 150 C for 30 min (XTS-30). Trial 1 evaluated ruminal escape of N from XTS-30 compared with commercial soybean meal (CS) or urea (U) in a replicated 3 X 3 Latin square design using six duodenally cannulated Angus X Hereford steers (24.7 kg). Duodenal flow of dietary N was higher (P less than for steers fed XTS-30 (47.9 g/d) than for steers fed CS (39.5 g/d). The ruminal escape estimate for XTS-30 (33.7%) was higher (P less than .10) than CS (13.1%), whereas total tract apparent N digestibility was not different among treatments. In trial 2, net portal absorption of alpha-amino N was measured in Finnsheep X Suffolk ram lambs (24.7 kg) fed U, CS or XTS-30 in a 3 X 3 Latin square design. Portal blood flow was measured by primed, continuous infusion of para-aminohippuric acid. Portal blood flow was lower (P less than .05) for U.fed lambs than for lambs fed CS or XTS-30, and tended to be lower for lambs fed CS than those fed XTS-30. Net portal absorption of alpha-amino N tended to be lowest for lambs fed U (281 mmol/d) and highest for lambs fed XTS-30 (578 mmol/d). The results are interpreted to show that non-enzymatic browning increased flow of soybean meal N to the intestine.

Animal Feed↗
PubMed2005

Entity evidence for differentiation between Tia and Tib types of soybean Kunitz trypsin inhibitor: detection of a novel transitional variant type between Tia and Tib in wild soybean (Glycine soja Sieb. & Zucc.).

Soybean Kunit trypsin inhibitor (SKTI) has several polymorphic types. Of these SKTI, there are large differences of nine amino acid substitutions between Tia and Tib. So far no transitional type between them has been found. A novel transitional intermediate variant between Tia and Tib was detected in 11 lines from 720 Japanese wild soybeans (Glycine soja Sieb. & Zucc.). This variant showed identical electrophoretic mobility to Tib in the Davis system polyacrylamide gel electrophoresis (PAGE), but higher electric points than other SKTI proteins (Tia, Tib, Tic) in isoelectric focusing PAGE. The genetic analysis of SKTI in F(2) seeds from a cross between the novel variant type and Tib showed that this variant type is inherited as codominant alleles in a multiple allelic system at an SKTI locus. This variant also showed inhibitory activity to trypsin. We propose the genetic symbol Ti b ( i5) for this novel variant. The sequence analysis of Tib ( i5) revealed that six nucleotides were different between Tib ( i5) and Tia, and the nucleotides of these mutated positions were identical to Tib. This causes substitution of five amino acids at the residue position 62 (Tyr-->Phe), 74 (Ser-->Arg), 114 (Met-->Val), 120 (Leu-->Ile) and 137 (Pro-->Thr). These substitutive amino acids are completely in accord with the amino acids of Tib, showing that Tib ( i5) is an intermediate between Tia and Tib types. Tib ( i5) type is widely distributed throughout seven separate areas from northeast to southwest Japan with a 1.5% frequency of total materials examined. This indicated that Tib ( i5) type did not originate from a recent mutation event, but had spread in wild soybean from ancient times.

Base Sequence↗
PubMed2001

Cloning of a cDNA for a constitutive NRT1 transporter from soybean and comparison of gene expression of soybean NRT1 transporters.

We have isolated a cDNA for a putative transporter, named GmNRT1-3, in the NRT1 family from soybean. It was predicted to have a similar topological structure not only to both GmNRT1-1 and GmNRT1-2 reported previously, but also to other members of the family. Two other cDNAs isolated have parts of the sequence for putative NRT1 transporters, GmNRT1-4 and GmNRT1-5, suggesting that at least five NRT1 transporters occur in soybean. These GmNRT1 genes and the GmNRT2 gene, encoding a soybean NRT2 nitrate transporter, showed different expression patterns to each other under various nitrogen conditions. Specifically, GmNRT1-3 was constitutively expressed in both roots and leaves, while GmNRT1-2 was gradually expressed as the roots developed in the presence of ammonium as a nitrogen source, but not in the presence of both ammonium and nitrate. Based on these results, we discussed the possible regulation in the expression and role of these transporters in nitrate uptake.

Anion Transport Proteins↗
PubMed1984

Induction of phytoalexin synthesis in soybean. Stereospecific 3,9-dihydroxypterocarpan 6a-hydroxylase from elicitor-induced soybean cell cultures.

A microsomal preparation from elicitor-challenged soybean cell suspension cultures catalyzes an NADPH-dependent and dioxygen-dependent 6a-hydroxylation of 3,9-dihydroxypterocarpan to 3,6a,9-trihydroxypterocarpan. The latter is a precursor for the soybean phytoalexin glyceollin. No reaction is observed with NADH. The 6a-hydroxylase is inhibited by cytochrome c. Optical rotatory dispersion spectra of the enzymatic product formed from racemic dihydroxypterocarpan and of the remaining unreacted substrate proved that the product has the natural (6aS, 11aS)-configuration and that hydroxylation proceeds with retention of configuration. The 6a-hydroxylase was also found in elicitor-challenged soybean seedlings. The results indicate that the 6a-hydroxylase is specifically involved in the biosynthesis of glyceollin.

Benzopyrans↗
PubMed1995

Measurement of Gly m Bd 30K, a major soybean allergen, in soybean products by a sandwich enzyme-linked immunosorbent assay.

By a sandwich enzyme-linked immunosorbent assay, a soybean major allergen, Gly m Bd 30K, in soybean products was measured. The allergen occurred at high concentrations in soy milk, tofu, kori-dofu, and yuba, but its content in kinako was small. No allergen was found in fermented foods such as miso, shoyu, and natto. The allergen was clearly shown to occur in meat balls, beef croquettes, and fried chicken that contained soybean protein isolate.

Allergens↗
PubMed2006

Development of resistant transgenic soybeans with inverted repeat-coat protein genes of soybean dwarf virus.

In an attempt to generate soybean plants resistant to soybean dwarf virus (SbDV), we transformed a construct containing inverted repeat-SbDV coat protein (CP) genes spaced by beta-glucuronidase (GUS) sequences into soybean somatic embryos via microprojectile bombardment. Three T(0) plants with an introduced CP gene were obtained, and one generated T(1) seeds. The presence of the transgene in T(1) plants was confirmed by PCR and Southern blot hybridization analysis, but expression of CP was not detected by northern blot hybridization analysis. Two months after inoculation of SbDV by aphid, T(2) plants contained little SbDV-specific RNA and remained symptomless. These plants contained SbDV-CP-specific siRNA. These results suggest that the T(2) plants achieved resistance to SbDV by an RNA-silencing-mediated process.

Capsid Proteins↗
PubMed2006

Timecourse microarray analyses reveal global changes in gene expression of susceptible Glycine max (soybean) roots during infection by Heterodera glycines (soybean cyst nematode).

Changes in gene expression within roots of Glycine max (soybean), cv. Kent, susceptible to infection by Heterodera glycines (the soybean cyst nematode [SCN]), at 6, 12, and 24 h, and 2, 4, 6, and 8 days post-inoculation were monitored using microarrays containing more than 6,000 cDNA inserts. Replicate, independent biological samples were examined at each time point. Gene expression was analyzed statistically using T-tests, ANOVA, clustering algorithms, and online analytical processing (OLAP). These analyses allow the user to query the data in several ways without importing the data into third-party software. RT-PCR confirmed that WRKY6 transcription factor, trehalose phosphate synthase, EIF4a, Skp1, and CLB1 were differentially induced across most time-points. Other genes induced across most timepoints included lipoxygenase, calmodulin, phospholipase C, metallothionein-like protein, and chalcone reductase. RT-PCR demonstrated enhanced expression during the first 12 h of infection for Kunitz trypsin inhibitor and sucrose synthase. The stress-related gene, SAM-22, phospholipase D and 12-oxophytodienoate reductase were also induced at the early time-points. At 6 and 8 dpi there was an abundance of transcripts expressed that encoded genes involved in transcription and protein synthesis. Some of those genes included ribosomal proteins, and initiation and elongation factors. Several genes involved in carbon metabolism and transport were also more abundant. Those genes included glyceraldehyde 3-phosphate dehydrogenase, fructose-bisphosphate aldolase and sucrose synthase. These results identified specific changes in gene transcript levels triggered by infection of susceptible soybean roots by SCN.

Animals↗
PubMed2005

Soybean mosaic virus helper component-protease enhances somatic embryo production and stabilizes transgene expression in soybean.

Soybean mosaic virus (SMV) helper component protease (HC-Pro), a suppressor of post-transcriptional gene silencing, was evaluated for its ability to enhance production of soybean hygromycin-resistant somatic embryos (HR-SEs), and stabilize transgene expression. Immature soybean cotyledonary explants were co-cultured with Agrobacterium tumefaciens strain KYRT1 harboring either pCAMBIA1302, carrying a hygromycin phosphotransferase gene (hpt) and a gene encoding green fluorescent protein; pCAMBIA1305.1, carrying hpt and beta-glucuronidase (uidA) genes; pG2-HC-Pro, a derivative of pCAMBIA1305.1 containing SMV G2 HC-Pro; or pG5-HC-Pro, a derivative of pCAMBIA1305.1 containing SMV G5 HC-Pro, but lacking uidA. Significantly (rho<0.02) higher numbers of HR-SEs were obtained from explants transformed with Agrobacterium harboring either pG2-HC-Pro or pG5-HC-Pro than with either of the vector controls (pCAMBIA1302 or pCAMBIA1305.1). Beta-glucuronidase (GUS) expression was significantly (rho<0.003) higher in 50-day-old transgenic plants expressing GUS along with SMV-HC-Pro and in SMV-infected GUS transgenic plants than in transgenic plants expressing GUS alone. Together, these data suggest that SMV-HC-Pro enhanced recovery of HR-SEs by suppressing silencing of the hygromycin phosphotransferase gene.

Base Sequence↗
PubMed2005

Emergence of Rsv-resistance breaking Soybean mosaic virus isolates from Korean soybean cultivars.

Twelve Rsv resistance-breaking (RB) isolates of Soybean mosaic virus (SMV) were obtained from field-grown soybean plants showing mosaic symptoms and subsequently examined biologically and molecularly. All of these RB isolates were identified as SMV based on serological and infectivity assays, and the amplification of P1 gene products by reverse transcription-polymerase chain reaction (RT-PCR). Differential soybean cultivars, lines or accessions Lee 68 (rsv), PI 96983, York, Marshall, Ogden, Kwanggyo, Suweon 97 (Rsv1 alleles), L29 (Rsv3), and V94-5152 (Rsv4), following inoculation with each RB isolate, showed similar systemic symptoms suggesting that these RB isolates can overcome Rsv resistance at three loci. To differentiate the 12 RB isolates molecularly, the P1 coding region for each isolate was amplified, cloned, sequenced and compared to known SMV strains. The P1 region from the RB isolates shared 86-90% and 90-99% similarities in amino acid (aa) and nucleotide sequence, respectively, with known SMV strains. Comparison of aa sequences indicated that these RB isolates are newly emerging isolates capable of breaking Rsv resistance. Phylogenetic analysis further suggested that the RB isolates can be classified as three major types. However, recombination was not observed within the coding region of P1 protein among the types. This is the first report on the emergence of SMV isolates capable of overcoming all of the known resistance alleles at the Rsv1 locus, as well as distinct resistance genes at Rsv3 and Rsv4.

Amino Acid Sequence↗
PubMedDate not supplied

Inheritance and allelism tests of Raiden soybean for resistance to soybean mosaic virus.

The gene symbol Rsv2 was previously assigned to the gene in the soybean [Glycine max (L.) Merr.] line OX670 for resistance to soybean mosaic virus (SMV). The Rsv2 gene was reported to be derived from the Raiden soybean (PI 360844) and to be independent of Rsv1. Accumulated data from our genetic experiments were in disagreement with this conclusion. In this study, Raiden and L88-8431, a Williams BC5 isoline with SMV resistance derived from Raiden, were crossed with two SMV-susceptible cultivars to investigate the mode of inheritance of SMV resistance in Raiden. They were also crossed with five resistant cultivars to examine the allelomorphic relationships of the Raiden gene with other reported genes at the Rsv1 locus. F1 plants, F2 populations, and F2-derived F3 (F2:3) lines were tested with SMV strains G1 or G7 in the greenhouse or in the field. The individual plant reactions were classified as resistant (R, symptomless), necrotic (N, systemic necrosis), or susceptible (S, mosaic). The F2 populations from R x S crosses segregated in a ratio of 3 (R + N):1 S and the F2:3 lines from Lee 68 (S) x Raiden (R) exhibited a segregation pattern of 1 (all R):2 segregating:1 (all S). The F2 populations and F2:3 progenies from all R x R crosses did not show any segregation for susceptibility. These results demonstrate that the resistance to SMV in Raiden and L88-8431 is controlled by a single dominant gene and the gene is allelic to Rsv1. The heterozygous plants from R x S and R x N crosses exhibited systemic necrosis when inoculated with SMV G7, indicating a partial dominance nature of the resistance gene. Raiden and L88-8431 are both resistant to SMV G1-G4 and G7, but necrotic to G5, G6, and G7A. Since the resistance gene in Raiden is clearly an allele at the Rsv1 locus and it exhibits a unique reaction to the SMV strain groups, assignment of a new gene symbol, Rsv1-r, to replace Rsv2 would seem appropriate. Further research is ongoing to investigate the possible existence of the Rsv2 locus in OX670 and its relatives.

Crosses, Genetic↗
PubMedDate not supplied

Complementary action of two independent dominant genes in Columbia soybean for resistance to Soybean mosaic virus.

A stem-tip necrosis disease was observed in the soybean [Glycine max (L.) Merr.] cultivar Columbia and its derivative OX686 when infected with a necrosis-causing strain of Soybean mosaic virus (SMV) in Canada. A dominant gene named Rsv3 was found in OX686 for the necrotic reaction. In the present research we have found that Columbia is resistant to all known SMV strains G1-G7, except G4. Genetic studies were conducted to investigate the inheritance of resistance in Columbia and interactions of resistance gene(s) with SMV strains. Columbia was crossed with a susceptible cultivar, Lee 68, and with resistant lines PI96983, Ogden, and LR1, each possessing a resistance gene at the Rsv1 locus. F(1) individuals, F(2) populations, and F(2:3) lines from these crosses were inoculated with G7 or G1 in the greenhouse. Our inheritance data confirmed the presence of two independent dominant genes for SMV resistance in Columbia. Results from allelism tests further demonstrate that the two genes (referred to as R3 and R4 in this article) in Columbia were independent of the Rsv1 locus. R3 appears to be the same gene previously reported as Rsv3 in OX686, which was derived from Columbia. The R3 gene confers resistance to G7, but necrosis to G1. The other gene, R4, conditions resistance to G1 and G7 at the early seedling stage and then a delayed mild mosaic reaction (late susceptible) 3 weeks later. Plants carrying both the R3 and R4 genes were completely resistant to both G1 and G7, indicating that the two genes interact in a complementary fashion. Plants heterozygous for R3 or R4 exhibited systemic necrosis or late susceptibility, suggesting that the resistance is allele dosage dependent. The R4 gene appeared epistatic to R3 since it masked expression of necrosis associated with the response of R3. The complementary interaction of two resistance genes, as exhibited in Columbia, can be useful in development of soybean cultivars with multiple and durable resistance to SMV.

Colombia↗