Soybean Strains Research Articles

Verification of strain identity in Brazilian soybean inoculants by using the Polymerase Chain Reaction

The standards for meeting inoculant quality in Brazil include a requirement of strain verification as well as the necessity for a minimal number of viable bacterial cells. This requirement stimulated us to develop a rapid and simple PCR-based method to distinguish the four Brazilian strains of Bradyrhizobium, SEMIA 587, SEMIA 5019 (29W), SEMIA 5079 (CPAC-15) and SEMIA 5080 (CPAC-7), recommended for the inoculation of soybean. PCR reactions using the random amplified polymorphic DNA (RAPD) PCR primer CRL-7 together with a modified buffer resulted in four different fingerprint patterns, which permitted the Brazilian soybean strains to be distinguished from each other. The fingerprint patterns obtained were reproducible irrespective of the source of templates. Comparisons with fingerprint patterns obtained with soybean bradyrhizobia from the USDA Culture Collection led to the conclusion that two of the Brazilian inoculant strains (SEMIA 587 and SEMIA 5019) were characteristic for B. elkanii, while the other two (SEMIA 5079 and SEMIA 5080) were more typical of B. japonicum. Also, we obtained evidence that the RAPD analysis with primer CRL-7 may be useful for distinguishing variants of the same strain.

Relationships between nuclear DNA content and seed and leaf size in soybean

A correlation between genome size and agronomically important traits has been observed in many plant species. The goal of the present research was to determine the relationship between genome size, seed size, and leaf width and length in soybean [Glycine max (L.) Merr.] Twelve soybean strains, representing three distinct seed size groups, were analyzed. Flow cytometry was used to estimate their 2C nuclear DNA contents. Data on seed size and leaf size of the 12 strains were obtained from 1994 and 1995 field experiments. Variation of 2C nuclear DNA among the 12 soybean strains was 4.6%, ranging from 2.37 pg for a small-seed strain to 2.48 pg for a large-seed strain. Strain seed size was positively associated with leaf width (r=0.92) and leaf length (r=0.93). Genome size was highly correlated with seed size (r=0.97), leaf width (r=0.90) , and leaf length (r=0.93). The results of our study indicate that there is a significant correlation between genome size and leaf and seed size in soybean. It is possible that selection for greater seed size either leads to, or results from, greater genome size. If so, this relationship might be worth exploring at a more fundamental level.

Variation in Root Nodule Formation between Soybean Strains and Rhizobium Strains Native to Japan

Variation in Root Nodule Formation between Soybean Strains and <i>Rhizobium</i> Strains Native to Japan

Alterations in Clinically Important Phytoestrogens in Genetically Modified, Herbicide-Tolerant Soybeans

The growing clinical interest in and use of soybean-based food products or extracts to increase dietary phytoestrogen intake makes the precise composition of the key biologically active ingredients of soybeans, notably genistin and daidzin, of substantial medical interest. Conventional soybeans are increasingly being replaced by genetically modified varieties. We analyzed the phytoestrogen concentrations in two varieties of genetically modified, herbicide-tolerant soybeans and their isogenic conventional counterparts grown under similar conditions. An overall reduction in phytoestrogen levels of 12-14% was observed in the genetically altered soybean strains, mostly attributable to reductions in the concentrations of genistin and, to a lesser extent, in daidzin. Significant sample-to-sample variability in these two phytoestrogens, but not in glycitin, was evident in the genetically altered soybeans. Given the high biological potency of isoflavones and their metabolic conversion products, these data suggest...

Growth and survival of root-nodule bacteria in legume inoculants stored at high temperatures

The maximum temperatures to which legume inoculants were exposed when despatched to five destinations in Australia (36–39°C) and nine in Indonesia (29–42°C) were used to define experimental storage conditions to study survival of root-nodule bacteria in peat culture. Cultures of three strains of Bradyrhizobium and two strains of Rhizobium were prepared in sterilised peat at a moisture potential of −log 10 4.5 Pa and incubated at 25°C for 14 days. They were then stored at either 25, 30, 35 or 40°C for 28 days. There was no significant effect of temperature in the first 5 days. By day 7, the numbers of the clover strain declined significantly at temperatures between 30 and 40°C and those of the medic, lupin and both soybean strains at 40°C. Numbers of all strains exceeded log 10 8.3 g −1 peat when stored at 35°C for 28 days; the two strains for soybeans exceeded log 10 9.0 g −1. Although when stored at 40°C for 2 weeks, the numbers of the five strains declined, they all multiplied rapidly when returned to 25°C. This response was repeated when the same packets were subjected to this regimen a second time. After a third cycle, recovery when returned to 25°C was slower than before but numbers still exceeded log 10 7.6 g −1 peat. Storage at 40°C for 42 days did not affect the infectivity of the strains. These results indicate that peat-based cultures may be distributed with safety in the tropics from a centralised production centre. Regional reincubation at a favourable temperature (25°C) for growth is recommended when temperatures inside the packaging are likely to have exceeded 35°C for 7 days.

Partial Characterization of a Soybean Strain of Tobacco Mosaic Virus

Properties of a strain of tobacco mosaic virus (TMV-S) originally isolated from soybean (Glycine max) were compared with those of two isolates of the common strain of TMV (ATCC PV-135 and PV-220), one TMV strain infecting bean (Phaseolus vulgaris) (TMV-B, ATCC PV-742), and sunnhemp mosaic virus (SHMV, ATCC PV-744). The virion capsid protein subunits of the common and soybean strains were 21 kDa. Reduced and alkylated capsid proteins of TMV-B and SHMV migrated as two bands and more rapidly than capsid proteins of the common and soybean strains in acrylamide gels containing sodium dodecyl sulfate. Host symptomatology, serological assays, particle morphology, and gel electrophoresis of the monopartite genome (6.4 kb) and whole virions demonstrated that TMV-S is closely related to the common strain of TMV but only distantly related to SHMV and TMV-B, which should be regarded as an SHMV isolate

Inheritance of a Lipoxygenase‐1 Allozyme in Soybean

Three soybean [Glycine max (L) Merr.] seed lipoxygenase isozymes, involved in generating products which contribute to undesirable flavors in processed protein products, have been characterized genetically. The objective of this study was to determine the inheritance of an alternate lipoxygenase‐1 allozyme, which has a more acidic isoelectric point than the normal allozyme (pI 5.79 vs. pI 5.85 for the normal allozyme). This alternate allozyme was originally seen in soybean strains L2‐3 and PI 86023, which are null for lipoxygenase‐2, genotype lx2 lx2. A similar alternate allozyme was subsequently seen in ‘McCall’. The 1:2:1 F2 segregation ratios from several crosses of “normal” allozyme × alternate allozyme parents indicated codominant inheritance of the two allozymes. The gene symbol Lxb1 is assigned to the allozyme with pI 5.79, and the gene symbol for the allozyme with pI 5.85 becomes Lxa1 This gives an allelic series at the lipoxygenase‐1 locus Lxa1, Lxb1, and lx1. The lx1 and lx2 loci are very tightly linked. Crosses between Lxa1 Lxa1 Lx2Lx2 and Lxb1 Lxb1 lx2lx2 genotypes would be designed to incorporate the lx2lx2 genotype into cultivars with improved protein flavor attributes for soyfood products. while phenotypes of Lx2Lx2 and lx2lx2 genotypes are indistinguishable in terms of lipoxygenase‐2, the presence of two electrophoretic bands for lipoxygenase‐1 (Lxa1 Lxb1) when the lipoxygenase‐2 locus is also heterozygous makes it possible to identify individuals with the recessive lx2 allele. The selection of heterozygotes can reduce the time needed to backcross the lx2 allele.

Normal and Low Linolenic Acid Soybean Strains: Response to Planting Date

Enzymes controlling biosynthesis of fatty acids in the oil of soybean [Glycine max (L.) Merr.] seeds are sensitive to temperature during the time of oil deposition. Soybean strains have been developed with low levels of linolenic acid (18:3) in an effort to improve oil flavor and stability. This study was conducted to determine the response of fatty acid composition in normal and low linolenic acid soybean strains to planting date, a production variable that may result in different temperatures during oil deposition. ‘Century’, C1640, and 9509 (three genotypes differing in linolenic acid due to alleles at the fan locus) were planted at four or five dates in each of 5 yr near West Lafayette, IN. Dates when 95% of the pods were mature and the fatty acid composition of the oil were determined for each plot. Fatty acid composition was not affected by planting date in either 1986 or 1990. In 1987 and 1988, levels of palmitic acid tended to decrease slightly and levels of stearic acid tended to increase slightly with successively later planting dates. From 1987 through 1989, linolenic acid was affected more than the other fatty acids by planting date. Regression of linolenic acid content on average maximum daily air temperature from 0 to 20 d prior to maturity demonstrated that 18:3 decreased 4.9 and 3.0 g kg−1 for each 1 °C increase in temperature for Century and C1640, respectively. The data demonstrate that late planting in Indiana should not result in substantially increased levels of linolenic acid in strains containing the fan allele.

Tracing development of soybean leaf primordia by marking progenitor cells with mutant markers.

Marking cells with genetic marker is a useful way to study plant development. A heterozygous (Y11y11) strain of soybean was exposed to X rays or 14 MeV neutrons before, or 1-7 days after, sowing. Clones of dark-green (due to reversion of the Xantha-like allele y11) or yellow (due to loss of the wild-type allele y11) cells were produced in the first and second compound leaves. Of these clones, none extended beyond the mid-vein. In the first leaf, about half the clones produced by marking before sowing were delimited by the mid-vein but extended beyond the main lateral veins; whereas, about 20% were bounded by small lateral veins, indicative that in the first-leaf primordium of the dormant embryo the mid-vein is already differentiated, but that only about half of the main lateral veins are. After marking on day 7, 99% of the marked clones in the first leaf were bounded by small lateral veins. This and the preceding results indicate that most small lateral veins develop during the first seven days after sowing, together with development of the leaf lamina. Primordia of the 6th or later leaves in dormant seeds exposed to neutrons produced two marked clones that extended over the mid-vein, showing that the mid-vein and lamina are not completely differentiated at this early stage.

Tolerance to Phytophthora Rot in Soybean: II. Evaluation of Three Tolerance Screening Methods

Five screening methods for tolerance to Phytophthora megasperma f. sp. g1ycinea (Drechs.) T. Kuan &amp; D.C. Erwin (Pmg) in soybean [Glycine max (L.) Merr.] have been published. This study compares three of these methods. The 45 soybean strains used were reported susceptible to Race 4 of Pmg. Field tests were grown in 1985 and 1986 near Vickery, OH, on Fulton silty‐clay (fine, illitic, mesic Aeric Ochraqualt) known to be infested with Race 4 and other races of Pmg. Inoculum‐layer and slant‐board tests were conducted in a greenhouse and growth chamber, respectively, in 1986 and 1987. Height and maturity data were obtained from replicated yield tests with low Pmg pressure. The inoculum‐layer test gives tolerant lines high scores, whereas the slant board and field tests give low values to tolerant lines. The inoculum‐layer and slant board data correlated well (r = ‐0.77, P &lt; 0.01) but neither correlated as well with the field data (r = ‐0.41, P &lt; 0.05; and r = 0.49, P &lt; 0.01, respectively). Field tolerance scores were correlated with maturity (r 0.46, P &lt; 0.01); however, the field scores of the 15 latest maturing strains were not correlated with maturity and correlated well with the inoculum‐layer and slant board scores (r = ‐0.74, P &lt; 0.01; and r = 0.76, P &lt; 0.01, respectively). Apparently, field scores must be taken prior to onset of pod yellowing (R7). Both laboratory methods are suitable substitutes for the field test, but they evaluate seedling tolerance only. The inoculum‐layer method is easier, less expensive, and allows both root rot ratings and tolerance scores based on shoot growth.

Genetic Relationships between Loci Controlling Palmitic and Linolenic Acids in Soybean

Three mutagen‐derived soybean [Glycine max (L.) Merr.] lines have been identified with unique levels of fatty acids. Levels of linolenic acid (18:3) in C1640 and palmitic acid (16:0) in C1726 C1727 are controlled by alleles with additive effects at three loci. If these loci are independent, soybean strains could be developed with unique and useful combinations of both linolenic and palmitic acids. The primary objective of this study was to determine the genetic relationships between loci controlling levels of palmitic acid and the locus controlling linolenic acid. Additionally, effects of altered levels of linolenic and palmitic acids on total fatty acid composition were determined. Fatty acid composition of F2 seeds from crosses of C1640 (low 18:3) with both C1726 (low 16:0) and C1727 (high 16:10) were determined by gas chromatography. Chi‐square analyses of the data demonstrated that the fan locus controlling low 18:3 was inherited independently from both the fap1 and fap2 loci controlling low and high levels of 16:0, respectively. There was no indication of an interaction among alleles at these loci. The decreases in palmitic acid due to fap1 and increases due to fap2 were associated primarily with changes in oleic and linoleic acids. Decreases in linolenic acid due to fan were associated primarily with increases in linoleic acid.

Analysis of populations and physiological characterization of microorganisms in rhizospheres of plants with antagonistic properties to phytopathogenic nematodes

Populations of rhizosphere microflora of plants which have demonstrated an antagonism toward phytopathogenic nematodes, including velvet bean (Mucuna deeringiana), castor bean (Ricinus communis), sword bean (Cannavalia ensiformis), and Abruzzi rye (Secale cereale)., were compared to the rhizosphere microflora of soybean. Population densities of total bacteria were significantly lower for young Abruzzi rye, mature velvet bean, and mature castor bean, and fungi from mature velvet bean than for soybean. Population densities of spore-forming bacilli were significantly higher for Abruzzi rye than for soybean. Population densities of coryneform bacteria for mature sword bean and velvet bean were significantly higher than for soybean. All seedling test poants supported significantly higher population densities of chitinolytic fungi than soybean. On mature plants, chitinolytic bacteria were significantly higher on all test plants except velvet bean. Populations of endophytic root bacteria for three of the four test plants were significantly higher than for soybean. Fifty randomly, selected bacterial strains from seedlings and mature plants of soybean and each test plant were characterized for various physiological traits associated with rhizosphere competence, including chitinolytic activity, gelatin hydrolysis, production of hydrogen cyanide, starch hydrolysis, phenol oxidation, siderophore production, and production of antifungal compounds (inhibition ofPythium ultimum and/orRhizoctonia solani). There was a strong trend to increased frequency in each of the physiological tests with bacteria from test plants in comparison to those from soybean. The frequency of starch hydrolysis was up to 24 times greater for strains from test plants than for soybean strains, and siderophore production was up to 22 times more frequent for test plants. These results demonstrate that, compared to soybean, plants with properties antagonistic to phytopathogenic nematodes have a distinct rhizosphere microflora.

Implications of selecting improved strains of soybeans for dry-matter accumulation and grain yield

Three maturity groups of soybeans (Glycine max L.) were used to investigate the relationship between dry-matter accumulation (DMA) and grain yield (GY), and the prospects for selection of high seed yielding strains among the existing soybean cultivars in a tropical environment. The positive and significant association between DMA and GY (r=0.888***) indicated that selection for high DMA could give gains in GY. However, the higher harvest index (HI=37.5%) for the low seed yielding early maturing genotypes than the more vegetatively endowed and higher seed producing late maturity group, is an indication that excessive DMA could be disadvantageous. Total seed yield per land area for the three maturity groups of soybeans showed that the genotypes with high harvest index and low seed yield could be as good as those ones with high seed and dry-matter yields with low harvest index. The high coefficient of variation which ranged between 18.1 and 59.8% and the heritability estimations which also ranged from 34.4 to 82.2% are indicative of the presence of substantial genetic diversity and there are good prospects for the improvement of the crop through selection.

Biochemical and serological characteristics of two similar soybean rhizobia

Abstract Two slow-growing soybean rhizobial strains (Bradyrhizobium japonicum), OUG 115 and OUG 117, were compared in biochemical and serological experiments. A slight difference was detected in the growth curve in liquid media containing arabinose as a sole carbon substrate, but for the other carbon sources there were no differences between the two strains. Both strains reacted strongly with the corresponding antisera but weakly cross reacted with each other.

Inheritance of Chlorimuron Ethyl Sensitivity in the Soybean Strains BSR 101 and M74‐462

Initial work with the sulfonylurea herbicide chiorimuron ethyl (ethyl 2‐[[[[(4‐chloro‐6‐methoxypyrimidin‐2‐yl) amino] carbonyl] amino] sulfonyl] benzoate) indicated that certain soybean [Glycine max (L.) Merr.] strains exhibited high levels of sensitivity to recommended field application rates. Knowledge of the mode of inheritance of chiorimuron ethyl sensitivity would allow for generation of cultivars toleranto chlorimuron ethyl. In addition, cross tolerance to other members of the suifonylureas has been observed and tolerance to chlorimuron ethyl may be expressed as tolerance to other sulfonylureas. Sensitive and tolerant strains of soybean were identified and two crosses of a tolerant strain ‘Elgin’ by the sensitive strains ‘BSR 101’ and M74‐462 were evaluated in the F2 and F3 generations to determine the mode of inheritance of chlorimuron ethyl sensitivity. The F2 plants and F2‐derived families in the F3 generation from each of the crosses were evaluated in the greenhouse using a hydroponic culture. Three days after transplanting seedlings into Hoagland's solution, chlorimnron ethyl was added giving a concentration of 2 mg a.i. L−1. Ten days after treatment, the plants were rated based upon reddening of the leaves. This evaluation indicated that chlorimuron ethyl sensitivity in both BSR 101 and M74‐462 is conferred by a single recessive gene.

A Procedure to Identify Genes Affecting Maturity Using Soybean Isoline Testers1

Maturity genes in soybean [Glycine max (L.) Merr.] have been discovered through accidental cotransfer during backcrossing of other traits. This study evaluated a test for identification of maturity genes in soybean strains that does not require backcrossing such genes into a common genetic background. All eight maturity isolines with homozygous combinations of the genes E1 el, E2 e2, and E3 e3 have been developed by backcrossing with the cultivar ‘Clark’. These isolines were used in testcrosses with Clark, ‘Harosoy’, or ‘Mukden’. Maturity dates (R8) for single field‐grown plants of parental and populations were taken in 1982. In 1983, flowering dates (RI) were also recorded, and pod‐picked bulk F3 populations were included for the Harosoy testcrosses and Clark isolines. Genotypes were proposed after examining the changes in ranges and variances between testcrosses, and by comparison with the Harosoy and Clark testcross progenies in which the segregating loci were known. Harosoy and Clark were confirmed to have the alleles el e2 E3 and el E2 E3, respectively. The genes El and E2 could be detected singly or together using either flowering or maturity data. The gene E3 could not be reliably detected unless a photoperiod sensitivity follow‐up test was utilized. Mukden had the genotype e1e2e3. This test will allow the maturity genotype of unrelated soybean strains to be determined, and make discovery of other genes possible without backcrossing into a common genetic background.

Studies of symbiotic plasmids in Rhizobium trifolii and fast‐growing bacteria that nodulate soybeans

The Rhizobium trifolii symbiotic plasmid pRt5a was transferred to the fast‐growing soybean strain USDA 194. Transconjugants carrying pRt5a were not able to nodulate clovers and one of the transconjugants had lost its smallest resident plasmid and did not fix nitrogen in soybean. Transconjugants of USDA 194 carrying pRt5a were able to transfer pRt5a back to a non‐nodulating R. trifolii which inherited the symbiotic properties of the R. trifolii strain from which the plasmid was derived.

Nitrogen fixation in soybeans as influenced by cultivar and Rhizobium strain differences

The effect of soybean variety and Rhizobium strain, as well as the level of nitrogen fertilizer, were tested in a field experiment in Greece. Three nodulating varieties were used and one non-nodulating variety as control, with two Rhizobium strains, one commercially available and one isolated from the soil of the experimental site. Nitrogen fertilizer labeled with 15N enabled the nitrogen derived from the atmosphere (Ndfa), from the soil (Ndfs), and from the fertilizer (Ndff) to be estimated. Statistical analyses showed that the combined variety-strain effect was responsible for most of the variation observed in all parameters, either measured directly or calculated, while the nitrogen level had no effect. The locally isolated strain generally performed equally as well as the commercial one. With the highest yielding variety in particular, the nitrogen-fixing efficiency of soybean nodules, expressed as plant total nitrogen in excess of that in the non-nodulated control in relation to nodule dry weight, was even superior. Taking into account the low fertilizer recovery by plants, it is suggested that adapted cultivars properly inoculated can fix most of the nitrogen they need for high yields. This is of great economic importance for crops with high nitrogen-fixing efficiency, like the soybeans used in this work, which can fix more than 200 kg N/ha, as 15N dilution and nitrogen difference evaluations have confirmed. The local cultivars in this connection were superior to the United States cultivar, while the difference between cultivars in symbiotic performance were not due to the ability to nodulate, but rather to a much higher nodule-specific efficiency. The commercially available strain was found to produce generally more nodules and the locally isolated strain produced less but larger and more efficient nodules. Finally, the grains from the nodulated plants contained significantly smaller quantities of Fe, Ni, Cu, Zn, and especially Mo compared with non-nodulated plants, as determined by X-ray fluorescence techniques.

Isolation of mutants of fast‐growing soybean strains that are effective on commercial soybean cultivars

Fast‐growing rhizobia that nodulate soybeans (Glycine max L. cvs Peking and Malayan) have been isolated. Initial inoculation of commercial cultivars of soybean with these strains results in the formation of a few pink nodules. Isoiates from these nodules form fully effective symbiosis with the soybean cultivar from which they were isolated. These results demonstrate that is is possible to isolate effective mutants of fast‐growing soybean strains by allowing the plants to select for effective mutants. These mutants are potentially valuable because, if their symbiotic properties can be improved, they could possibly be used as commercial soybean inoculants.

Bowman-Birk proteinase isoinhibitor complements of soybean strains

Bowman-Birk proteinase isoinhibitor complements of soybean strains