Linolenic acid and seed lipoxygenases are associated with off flavours in soybean products. F5 recombinant inbred lines (RILs) from a cross between a low linolenic acid line (RG10) and a seed lipoxygenase-free line (OX948) were genotyped for simple sequence repeats (SSR), random amplified polymorphic DNA (RAPD), sequence-tagged sites (STS), and cleaved amplified polymorphic sequence (CAPS) markers and evaluated for seed and agronomic traits at 3 Ontario locations in 2 years. One hundred twenty markers covering 1247.5 cM were mapped to 18 linkage groups (LGs) in the soybean composite genetic map. Seed lipoxygenases L-1 and L-2 mapped as single major genes to the same location on LG G13-F. L-3 mapped to LG G11-E. This is the first report of a map position for L-3. A major quantitative trait locus (QTL) associated with reduced linolenic acid content was identified on LG G3-B2. QTLs for 12 additional seed and agronomic traits were detected. Linolenic acid content, linoleic acid content, yield, seed mass, protein content, and plant height QTL were present in at least 4 of 6 environments. Three to 8 QTLs per trait were detected that accounted for up to 78% of total variation. Linolenic acid and lipoxygenase loci did not overlap yield QTL, suggesting that it should be possible to develop high-yielding lines resistant to oxidative degradation by marker-assisted selection (MAS).

A possible solution to stability problems is to genetically reduce the content of linolenic acid in soybean seed. RG10 is a low linolenic acid line (<25 g/kg) produced by ethyl methane sulfonate (EMS) treatment of the low linolenic acid EMS mutant line C1640. The objective of this study was to determine the molecular basis of the low linolenic acid trait in RG10. Sequence analyses of mutant RG10 and wild-type OX948 x-fatty acid desaturase (Fad3) genes showed that the low level of linolenic acid in RG10 is likely a result of mutations in two Fad3 genes. A mutation in the Fad3A gene introduces a stop codon in exon 6 that would prematurely terminate translation and a second mutation in the 5¢ splice site of intron 5 of the Fad3B gene may result in abnormal mRNA splicing products. Both mutations would result in a non-functional enzyme. Molecular markers developed for these mutations should simplify and accelerate introgression of the RG10-based low linolenic acid trait into elite soybean cultivars.

Legumes contain a variety of phytochemicals derived from the phenylpropanoid pathway that have important effects on human health as well as seed coat color, plant disease resistance and nodulation. However, the information about the genes involved in this important pathway is fragmentary in common bean (Phaseolus vulgaris L.). The objectives of this research were to isolate genes that function in and control the phenylpropanoid pathway in common bean, determine their genomic locations in silico in common bean and soybean, and analyze sequences of the 4CL gene family in two common bean genotypes. Sequences of phenylpropanoid pathway genes available for common bean or other plant species were aligned, and the conserved regions were used to design sequence-specific primers. The PCR products were cloned and sequenced and the gene sequences along with common bean gene-based (g) markers were BLASTed against the Glycine max v.1.0 genome and the P. vulgaris v.1.0 (Andean) early release genome. In addition, gene sequences were BLASTed against the OAC Rex (Mesoamerican) genome sequence assembly. In total, fragments of 46 structural and regulatory phenylpropanoid pathway genes were characterized in this way and placed in silico on common bean and soybean sequence maps. The maps contain over 250 common bean g and SSR (simple sequence repeat) markers and identify the positions of more than 60 additional phenylpropanoid pathway gene sequences, plus the putative locations of seed coat color genes. The majority of cloned phenylpropanoid pathway gene sequences were mapped to one location in the common bean genome but had two positions in soybean. The comparison of the genomic maps confirmed previous studies, which show that common bean and soybean share genomic regions, including those containing phenylpropanoid pathway gene sequences, with conserved synteny. Indels identified in the comparison of Andean and Mesoamerican common bean 4CL gene sequences might be used to develop inter-pool phenylpropanoid pathway gene-based markers. We anticipate that the information obtained by this study will simplify and accelerate selections of common bean with specific phenylpropanoid pathway alleles to increase the contents of beneficial phenylpropanoids in common bean and other legumes.

The nitrogen fixing ability of common bean (Phaseolus vulgaris L.) in association with rhizobia is often characterized as poor compared to other legumes, and nitrogen fertilizers are commonly used in bean production to achieve high yields, which in general inhibits nitrogen fixation. In addition, plants cannot take up all the nitrogen applied to the soil as a fertilizer leading to runoff and groundwater contamination. The overall objective of this work is to reduce use of nitrogen fertilizer in common bean production. This would be a major advance in profitability for the common bean industry in Canada and would significantly improve the ecological footprint of the crop. In the current work, 22 bean genotypes [including recombinant inbred lines (RILs) from the Mist × Sanilac population and a non-nodulating mutant (R99)] were screened for their capacity to fix atmospheric nitrogen under four nitrogen regimes. The genotypes were evaluated in replicated field trials on N-poor soils over three years for the percent nitrogen derived from atmosphere (%Ndfa), yield, and a number of yield-related traits. Bean genotypes differed for all analyzed traits, and the level of nitrogen significantly affected most of the traits, including %Ndfa and yield in all three years. In contrast, application of rhizobia significantly affected only few traits, and the effect was inconsistent among the years. Nitrogen application reduced symbiotic nitrogen fixation (SNF) to various degrees in different bean genotypes. This variation suggests that SNF in common bean can be improved through breeding and selection for the ability of bean genotypes to fix nitrogen in the presence of reduced fertilizer levels. Moreover, genotypes like RIL_38, RIL_119, and RIL_131, being both high yielding and good nitrogen fixers, have potential for simultaneous improvement of both traits. However, breeding advancement might be slow due to an inconsistent correlation between these traits.