USDA Soybean Germplasm Collection Research Articles

Nulls for the Major Soybean Bowman‐Birk Protease Inhibitor in the Genus Glycine

The Bowman‐Bilk protease inhibitor (BBI) is a major antinutritional factor in soybean [Glycine max (L.) Merr.]. This study was conducted to determine nulls for the major soybean BBI in the genus Glycine. A monoclonal antibody‐based competitive enzyme‐linked immunosorbent assay (ELISA) was used to rapidly detect the relative levels of the major soybean BBI in unpurified seed extracts. A total of 12 690 accessions from 13 species were tested. All of the G. max and G. soja Siebold & Zucc. accessions from the USDA Soybean Germplasm Collection contained BBI. The BBI nulls were found hi several of the wild perennial species: G. curvata Tind., G. cyrtoloba Tind., G. latifolia (Benth.) Newell & Hymowitz, G. microphylla (Benth.) Tind, G. tabacina (Labill.) Benth., and G. tomentella Hayata. The absence of BBI was confirmed by additional immunochemical methods and by enzymatic determination of trypsin and chymotrypsin inhibition. The BBI nulls identified in this study could potentially be utilized in the production of a soybean cultivar lacking the major soybean BBI.

Geographical Patterns of Variation in the USDA Soybean Germplasm Collection: II. Allozyme Frequencies

Allozyme frequencies can be used as quick and inexpensive measures for determining patterns of diversity in germplasm collections. Our objective was to describe the extent of geographical diversity present in five enzymes controlled by seven variable protein loci (13 alleles) for 2236 accessions of Glycine max (L.) Merr. in the USDA soybean germplasm collection. These accessions represent the entire range of geographical origins in the collection. Countries of origin were grouped into 15 regions based on geography and number of accessions. Assays were performed for leucine aminopeptidase, malate dehydrogenase, superoxide dismutase, phosphoglucoisomerase, and 6‐phosphogluconate dehydrogenase. Each locus had two alleles, except that Sod2 had three and MDH was monomorphic. Total gene diversity was low for all loci except Pg12 and Pgd1. The proportion of the total diversity between regions was relatively high for Sod2. Canonical discriminant and cluster analyses resulted in five clusters, each containing a single region (Africa, Central China, Southwest Central Asia, India, or the New World) and one cluster that contained I0 regions (Chungchong, Korea; Cholla, Korea; Europe; Japan, Jilin, China; Kyonggi, Korea; Kyongsang, Korea; Korea; North China; and Southeast Asia) and 85% of all accessions. This indicates that allele frequencies at these loci were poor discriminators of phenotypic diversity. Additional enzyme loci and other morphological and physiological characters should be used to assist in the further description of this collection.

Evaluating Soybean Germ Plasm for Brown Stem Rot Resistance

Over 3.400 accessions from the USDA Soybean Germplasm Collection in maturity groups 000 to IV were evaluated between 1981 and 1984 for resistance to brown stem rot (BSR) caused by Phialophora gregata. Lines were evaluated in naturally infested fields at latitudes to which they were adapted. In 1985 and 1986, 13 early maturity, and 25 late maturity, putatively resistant lines were evaluated in replicated tests. (…)

Evaluating Soybean Germplasm for Specific Leaf Weight

Specific leaf weight (SLW) defined as the mass of tissue per unit leaf area has been positively correlated with leaf photosynthesis in several species and has therefore been suggested as a potentially useful selection criterion. Little research has been done to assess the range in genetic variability of SLW in soybean [Glycine max (L.) Merr.] as a first step in evaluating the potential of selection for SLW. In previous reports, comparisons of SLW among lines of differing maturity have been confounded with environmental conditions associated with the various sampling times. The objectives of this research were to determine the phenotypic variability of SLW that exists in a portion of the Maturity Group I soybean germplasm of comparable maturity, and to estimate the genetic component of that variability. Four leaf discs, 8.7 mm in diam., were cut from each of two leaflets of five plants for 231 Maturity Group I accessions in the USDA soybean germplasm collection. One leaflet each was collected from the most recently fully expanded leaf and the next youngest leaf on each plant between R5 and R6 growth stages. All selected leaves were in an unshaded position in the canopy and sampled near solar noon on clear sky days. Plots were grown at Urbana, IL in 1983 and 1984 and at West Lafayette, IN in 1984 with one replication in each environment. Averaged across all locations and years accession means for SLW ranged from 47 to 86 g m−2. ‘Hodgson 78’ replicated nine times in each 1984 environment, had a mean SLW of 62 g m−2. Repeatability for SLW was 0.48 indicating that effective selection for this trait should be possible.

Soybean Plant Introductions with Resistance to Races 4 or 5 of Soybean Cyst Nematode

Soybean cyst nematode (1Heterodera glycines Ichinohe) (SCN) is a serious pest of soybean [Glycine max (L.) Merr.) in the southern USA. A major portion of the U.S. soybean collection has not been screened for races of SCN. Approximately 9000 soybean plant introductions (PIs) were screened for their reaction to SCN races 4 and 5 in the greenhouse. The seedlings were grown in soil infested with SCN, and white females on the roots were counted. We found 21 PIs with some level of resistance to either race 4 or 5. A total of seven resistant, three moderately resistant, and two moderately susceptible PIs for race 4 were identified. Two PI's were heterogeneous for resistant and moderately resistant reactions. For race 5, seven PIs were resistant, two showed moderate resistance, two were moderately susceptible, whereas one segregated for resistant and moderately resistant reactions. All PIs showing resistance to races 4 or 5 were earlier reported to be resistant to race 3 and are in either Maturity Group II, III, or IV. PI 437654 was resistant to both races 4 and 5. In additional tests, it was found to be resistant to five races (races 1 through 5) of SCN. PI 437654 is the only PI resistant to all five recognized races of SCN and would be a good source in resistant cultivar development. These PIs are available to the researchers from the USDA soybean germplasm collection.

Frequency and Comparative Anatomy of the Extended Endothelium among Soybean Plant Introductions and Weathering Resistant Genotypes1

In some genotypes of soybean [“Glycine max” (L.) Merr.], the endothelium of the testa forms a dome‐shaped extension in the region of the pit in the abaxial surface of the cotyledons. The importance and functions of this tissue are not fully understood. Using scanning electron microscopy we observed a high frequency (0.91) of the extended endothelium in experimental weathering resistant genotypes received from the International Institute of Tropical Agriculture. Similar examination of 378 random genotypes from the USDA soybean germplasm collection revealed the frequency of this trait to be 0.34. The dimensions of this tissue in these latter genotypes varied from <0.4 to >2.1 mm2 in area, and from 80 to 220 pm in thickness. The cells of the extended endothelium are generally large, vertically elongated, and have large cell wall thickenings.

Defining the Seed‐filling Period in Soybeans to Predict Yield1

The duration of seed fill has been shown to be related to seed yield in soybean [Glycine max (L.) Merr.]. However, several different growth stages have been used to delimit the seed‐filling period (SFP). This study was conducted to determine which growth stages delimit the SFP most highly correlated with yield. Twenty‐eight indeterminate accessions, 14 from each of Maturity Groups II and III, were selected from the USDA Soybean Germplasm Collection. These lines were selected for differences in length of SFP and similarities in other agronomic traits. Field experiments were grown in a Flanagan silt loam (Aquicarguidoll) and a Catlin silt loam (Typic Argiudoll) in 1980 and 1981, respectively. Data collected included the date of all reproductive (R) stages and seed yield. Genotypic and phenotypic correlation coefficients were determined for various reproductive or seedfilling periods and seed yield.Phenotypic correlation coefficients demonstrated a positive relationship between the duration of seed fill and seed yield but could not define the most appropriate seed‐filling period to predict yield. The genotypic correlations between various SFPs and seed yield provide evidence that supports the use of R4 or R5 as estimates of the beginning of seed fill and R7 as the termination. These data suggest that the currently defined R‐stages of soybean reproductive growth can provide reasonable estimates of the duration of seed fill and the seed‐filling periods so defined had a high correlation with seed yield among the lines in this experiment.

Evolutionary studies of the soybean: the frequency and distribution of alleles among collections of Glycine Max and G. Soja of various origin

Allelic frequencies at 10 loci common throughout the genus Glycine subgenus Soja were determined for 27 geographical area-species samples. The samples included 366 accessions of Glycine soja, the ‘wild’ soybean, and 193 accessions of G. max, the domesticated soybean, from the USDA Soybean Germplasm Collection. The data indicate that the alleles for grey pubescence (t1), low seed coat peroxidase level (ep), and blunt pubescence tip (pb) probably arose as mutations during the domestication of G. max. The remaining seven loci studied(Fr, Pa1, Pa2, Fg1, Fg2, Fg3and Fg4)are polymorphic throughout the subgenus Soja; differences among collections of G. max and G. soja seem to be the result of differing selection pressures. A cluster analysis of allelic frequencies reveals two distinct groups within the subgenus corresponding to G. soja and G. max, Semi-wild accessions of G. max, while morphologically more similar to cultivated plants, clustered with samples of G. soja. The semi-wild accessions examined are thought to have arisen via hybridization between G. soja and G. max.

Expanding the genetic potential of the soybean

AbstractThe primary center of genetic dispersion of the soybean probably is in northeastern China. The soybean plant traveled from its area of origin to Korea and Japan in ancient times and to Europe and America more recently. Although soybeans were confined to the Far East for many centuries, the western world now produces more than 80% of the total, and the United States and Brazil are the main producers. The increased expansion of soybeans in Latin America is largely a result of the advances of genetic and agronomic technology, which have permitted the development of adapted cultivars and improved management systems for the subtropical and tropical areas of this region. The USDA soybean germplasm collection—particularly the gene bank maintained in Mississippi—has been the most important genetic resource for the developing commercial cultivars in Brazil, Columbia, Ecuador and Peru. Germplasm from other countries, e.g., Japan, Korea, Taiwan, Indonesia, India, the Philippines and some African countries, also has contributed to the enrichment of the soybean gene pools in Latin America, mainly through the International Soybean Program (INTSOY). The International Soybean Variety Evaluation Experiment (ISVEX) of INTSOY has been planted in more than 1,200 locations and in more than 107 countries since 1973. In Latin America in 1978, this experiment was planted in 29 locations of 11 countries. The experiment was designed to (a) test the adaptation of cultivars, (b) compare local and introduced cultivars, (c) provide new germplasm for local breeding programs, (d) identify potential areas for soybean production, and (e) evaluate cultivar performance in different environments.

A cluster analysis of wild and domesticated soybean phenotypes

Cluster analysis techniques were used to examine phenotypic variation within the USDA Soybean Germplasm Collection. This study included ten Plant Introductions each of the domesticated soybean, Glycine max (L). Merr., the ‘wild’ soybean, G. soja Sieb. & Zucc., and a disputed species, G. gracilis Skvortz. G. max and G. soja were found to be morphologically distinct entities and G. gracilis was found to be conspecific with G. max. Because G. gracilis probably represents weedy races associated with the cultivated soybean and because ‘gracilis’ phenotypes can be distinguished from G. max, the designation, G. max forma gracilis, is recommended.