Walter R. Fehr

RFLP analysis of soybean seed protein and oil content

SummaryThe objectives of this study were to present an expanded soybean RFLP map and to identify quantitative trait loci (QTL) in soybean [Glycine max (L.) Merr.] for seed protein and oil content. The study population was formed from a cross between a G. max experimental line (A81-356022) and a G. soja Sieb. and Zucc. plant introduction (PI 468916). A total of 252 markers was mapped in the population, forming 31 linkage groups. Protein and oil content were measured on seed harvested from a replicated trial of 60 F2-derived lines in the F3 generation (F2∶3 lines). Each F2∶3 line was genotyped with 243 RFLP, five isozyme, one storage protein, and three morphological markers. Significant (P<0.01) associations were found between the segregation of markers and seed protein and oil content. Segregation of individual markers explained up to 43% of the total variation for specific traits. All G. max alleles at significant loci for oil content were associated with greater oil content than G. soja alleles. All G. soja alleles at significant loci for protein content were associated with greater protein content than G. max alleles.

Effect of altered fatty acid composition on soybean oil stability

During the last 15 years, hybridization and induced mutation breeding of soybeans have been successful in producing an altered fatty acid composition in the extracted oil. The objective of those investigations was to produce a low-linolenic acid soybena oil. Crude oils extracted from the seeds of three such genotypes were processed in laboratory simulations of commercial procedures to finished deodorized oils. Analysis of the fatty acid composition of the three oils showed the linolenic acid content to be 3.3%, 4.2% and 4.8%. The stability of these finished oils was compared to that of oil from a soybean variety having a linolenic acid content of 7.7% and of a commercial hydrogenated-winterized soybean oil (3.0% linolenic acid). Test and control oils were evaluated by a trained sensory panel initially, after accelerated storage at 60 C and during use at 190 C in room tests. Peroxide values were determined at the time of sensory evaluation. Results indicated there was no significant difference in flavor stability during storage between test and control oils. There was no significant difference, between the oils, in peroxide development during accelerated storage. Compared to control oils, the test oils had improved overall room odor intensity scores and lacked the fishy odors of non-hydrogenated soybean oil and the hydrogenated odors of commercial cooking oil.

Control of iron‐deficiency chlorosis in soybeans by plant breeding

Abstract A series of research studies has been conducted at Iowa State University to determine the possibilities and problems associated with the development of soybean (Glycine max (L.) Merrill) cultivars with improved resistance to iron‐deficiency chlorosis on calcareous soils. An evaluation was made of the amount of yield reduction associated with different levels of chlorosis symptoms. Cultivars ranging from highly resistant to highly susceptible to iron chlorosis were tested on calcareous and noncalcareous soils. Chlorosis symptoms were rated visually with scores ranging from 1, no yellowing, to 5, severe yellowing with some necrosis. The average percentage yield loss increased linearly by 20% for each unit increase in chlorosis score. There was yield reduction whenever yellowing was observed, even if the symptoms were slight. To completely avoid yield loss from iron chlorosis, cultivars must be developed that have no symptoms any time during plant development. Tests of soybean cultivars and plant in...

Soybean Aphid (Hemiptera: Aphididae) Development on Soybean with Rag1 Alone, Rag2 Alone, and Both Genes Combined

ABSTRACT Aphis glycines Matsumura (Hemiptera: Aphididae) can reduce the yield of aphidsusceptible soybean (Glycine max (L.) Merrill) cultivars. The Rag1 and Rag2 genes confer resistance to some biotypes of A. glycines. These genes individually can limit population growth of A. glycines and prevent yield loss. The impact of these genes when combined is not known. We compared the development of A. glycines on soybean with Rag1 alone (R1/S2), Rag2 alone (S1/R2), both genes combined (R1/R2), or neither gene (S1/S2). In addition, we determined the impact of different levels of aphid infestation on seed yield. The genotypes were grown in cages and artificially infested with A. glycines to achieve five treatment levels: aphid-free, 675 aphids per plant, 25,000 cumulative aphid days (CAD) (25K), 50,000 CAD (50K), and 75,000 CAD (75K). The S1/S2 line reached the 50K treatment, but did not reach the 75K treatment. Aphid development on R1/S2 and S1/R2 soybeans after two infestations reached a maximum of 25K. The maximum treatment reached on R1/R2 was only 675 aphids per plant after two infestations, at which there was no significant yield reduction when compared with the aphid-free treatment. The maximum yield reduction of S1/S2 was 27% at 50K treatment compared with 2% for R1/S2 and 12% for S1/R2 at the 25K treatment. Our results indicated that for A. glycines used in our study, cultivars with both Rag1 and Rag2 had less aphid exposure and less yield reduction than soybeans with only one resistant gene.

Improving the fatty acid composition of soybean oil

Efforts to improve the composition of soybean oil by breeding the beans for low linolenic acid in the oil have continued since 1968. This paper reports recent work using hybrid crosses and induced mutations. No lines are yet available that contain oil having less than 3% linolenic acid.

Improving soybean quality by plant breeding

Treatment of soybean seeds with x-rays has been successful in increasing the incidence of low-linolenic-acid soybean strains both in pure breeding lines and crosses of low-linolenic-acid lines. The incidence of strains high in oleic acid also is increased by x-ray treatment. A procedure for measuring the lipoxygenase content of seed is described. There is a 2- to 3-fold variation in the lipoxygenase activity of the soybean lines tested. The lipoxygenase activity of soybean seed is influenced by the genotype of the maternal parent.

Fatty Acid Development in a Soybean Mutant with High Stearic Acid

The fatty acid composition of developing soybean (Glycine max [L.] Merrill) seeds was evaluated in the mutant line, A6, and its parent, FA8077. Seeds of both lines were harvested at 2-day intervals from 15 to 39 days after flowering (DAF) and at 4-day intervals from 39 DAF until maturity. Significant differences between the two lines were observed for stearic and oleic acid percentages at 19 DAF. The maximum difference between the lines was at 25 DAF, when A6 had 45.4% and FA8077 had 4.1% stearic acid. The increase in stearic acid percentage in A6 was accompanied by a decrease in oleic acid to 16.8% at 25 DAF, compared with 53.7% oleic acid for FA8077. The two lines did not differ in development of palmitic, linoleic and linolenic acids. The protein and oil content of mature seeds were similar for the two lines.

Current practices for correcting iron deficiency in plants with emphasis on genetics

Abstract There are important genetic differences in some crop species for the amount of loss in production caused by iron‐deficiency chlorosis. Progress has been made in the correction of iron deficiency by the development and use of iron‐efficient genotypes. Breeders of oat (Avena byzantina C. Koch), dry bean (Phaseolus vulgaris L.), sorghum [Sorghum bicolor (L.) Moench], and soybean [Glycine max (L.) Merrill] are engaged in the selection of cultivars with improved iron efficiency. Genotypes of soybean have been developed with iron efficiency superior to that previously identified in the species. Information on the iron chlorosis resistance of soybean cultivars is provided to farmers to facilitate their selection of appropriate seed. Seed mixtures of efficient and inefficient soybean cultivars are used to maximize production and minimize the risk of crop loss from iron deficiency under appropriate conditions.

Alternative breeding strategies for the improvement of iron efficiency in soybean

Abstract The potential production loss attributable to Fe‐deficiency chlorosis in soybean [Glycine max (L.) Merr.] grown on calcareous soil is sufficient to justify the development of high‐yielding, Fe‐efficient soybean cultivars in several states. Alternative breeding methods and screening techniques for the development of high‐yielding, Fe‐efficient cultivars and parental germplasm were studied. In the breeding methodology studies, populations derived from crosses of lower yielding, Fe‐efficient X high‐yielding, Fe‐inefficient parents had lower mean yields but greater average Fe‐efficiency than populations derived by backcrossing to the high‐yielding parent. Phenotypic correlations between the yield of breeding lines on noncalcareous soil and their Fe‐efficiency on calcareous soil were positive or not significant, indicating that selection of high‐yielding, Fe‐efficient cultivars should be possible. In a recurrent selection program to improve the Fe‐efficiency of a population, a nutrient solution system...

Alternatives to conventional field evaluation for genetic selection for Fe‐efficiency of soybean

Abstract Breeding for improved Fe‐efficiency of soybean [Glycine max (L.) Merrill] has resulted in the identification of genotypes that exhibit little or no chlorosis when grown on calcareous soils in Iowa. Continued selection for even greater levels of Fe‐efficiency would be desirable to obtain parent lines that could facilitate the incorporation of Fe‐efficiency into high‐yielding cultivars. Two methods have been identified for inducing chlorosis in genotypes that do not have adequate symptoms in conventional field tests on calcareous soils. One method is used with soybeans grown on calcareous soil in the field. The main stems of plants to be evaluated are cut off above the cotyledonary or unifoliolate nodes during early vegetative development. The symptoms on the new leaves produced by plants after they have been cut off are more severe than on the leaves that develop on plants that are not cut off. The second method is a nutrient solution system designed to allow the evaluation of Fe‐efficiency. A goo...