Transformation of soybean [Glycine max (L.) Merr.] with a gene encoding a glyphosate‐tolerance 5‐enolpyruvylshikimate‐3‐phosphate synthase enzyme from Agrobacterium sp. strain CP4 resulted in the development of glyphosate‐tolerant line 40‐3‐2. Glyphosate (N‐phosphonomethyl glycine) is the active ingredient of Roundup herbicide. Line 40‐3‐2 was yield tested at 17 locations in 1992,23 locations in 1993, and 18 locations in 1994. At those locations, broadcast applications of glyphosate at various rates were made over 40‐3‐2 or its derivatives from early vegetative growth to pod fill. No significant yield reduction was observed as a result of the glyphosate treatment at any of the locations. Development of glyphosate‐tolerant soybean promises to provide the farmer with access to a new weed control system that should result in lower production costs and reliable weed control under a wide range of conditions.

No abstract

Soybean accessions from China were screened in an attempt to identify unique sources of resistance to Phialophora gregata, the cause of brown stem rot. In 1994, over 500 accessions from the USDA Soybean Germplasm Collection, University of Illinois, Urbana-Champaign, were evaluated in the field at Urbana, IL, for reaction to brown stem rot. The accessions originated from nine provinces in central China and ranged in maturity from groups II to IV. Disease assessment was based on incidence of foliar symptoms and severity of stem symptoms produced by infection with natural inoculum. Based on field results, 64 putatively resistant lines were selected and evaluated in the greenhouse by a root-dip inoculation method. Thirteen accessions with levels of resistance equal to those of resistant standards were identified from five provinces. These lines may have value as donors of unique sources of resistance to brown stem rot.

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.

Normal levels of linolenic acid (70‐80 g kg‐1) in soybean [Glycine max (L.) Merr.] oil adversely affect oil flavor and stability. The mutation‐induced line C1640 has half the normal level of linolenic acid (37 g kg‐1), but is 24% lower yielding than ‘Century’, from which it was selected. This study was conducted to determine if there are genetic relationships betweena gronomictr aits and the fan allele for low linolenic acid identified in C1640. Century and ‘Harper’, both with the FanFan alleles for normal 18:3, were crossed with C1640 containing the fanfan alleles for low 18:3. Both FanFan and fanfan segregates from the two crosses were evaluated for agronomic traits and linolenic acid in replicated tests over a 2‐yr period on a Chalmers soil (fine‐silty, mixed, mesic Typic Haplaquoll) at the Purdue University Agronomy Research Center near West Lafayette, IN. The fanfan segregates in the Century × C1640 cross averaged slightly higher in seed yield and taller in plant height than the FanFans egregates. In the Harper × C1640 cross, fanfan segregates averaged 1 d later in maturity than FanFan segregates. Mean values for FanFan and fanfan segregates for other traits in both crosses were essentially the same. These data indicate that there are no associations between the fanfan alleles and those agronomic traits needed in commercial soybean cultivars with low levels of linolenic acid. Apparently the low yield of C1640 is controlled by genetic changes independent of the mutation for low 18:3. Regression of linolenic acid level on maturity dates for both FanFan and fanfan segregates in the Harper × C1640 cross show that segregates of both genotypes tended to have increased linolenic acid at later maturity dates. This could be attributed to the cooler temperatures during seed maturation to which the later maturing segregates were exposed.