@article{xue_upchurch_kwanyuen_2008, title={Relationships between oleic and linoleic acid content and seed colonization by Cercospora kikuchii and Diaporthe phaseolorum}, volume={92}, ISSN={["1943-7692"]}, DOI={10.1094/PDIS-92-7-1038}, abstractNote={ Compared with standard cultivars, seed of mid-oleic soybean genotypes sometimes have shown increased colonization by Cercospora kikuchii in the field as judged by increased levels of purple-stained seed. To examine relationships between oleic and linoleic acid levels in soybean seed and postharvest seed colonization by two fungal seed pathogens, we inoculated seed with differing oleic:linoleic acid (O/L) ratios. Seed with defined O/L ratios were produced by allowing seed development of two isogenic soybean lines to occur in three different air temperature environments. Seed produced in these environments were harvested, individually analyzed for fatty acid composition, and inoculated with mycelium preparations of the fungal seed pathogens C. kikuchii or Diaporthe phaseolorum var. sojae. Fungal biomass of infected seed was quantified by measuring in vitro ergosterol content. For both soybean lines, colonization by C. kikuchii was positively correlated with the O/L ratio (r = 0.55, P < 0.03) and oleic acid content (r = 0.61, P < 0.02), and negatively correlated with linoleic (r = –0.60, P < 0.02) and linolenic (r = –0.58, P < 0.03) acid content. No association was found between the extent of seed colonization by D. phaseolorum and the seed O/L ratio. Our data suggest that the O/L ratio may be related to soybean seed colonization by C. kikuchii, but there is no evidence of a relationship with D. phaseolorum var. sojae colonization. }, number={7}, journal={PLANT DISEASE}, author={Xue, H. Q. and Upchurch, R. G. and Kwanyuen, P.}, year={2008}, month={Jul}, pages={1038–1042} }
 @article{xue_upchurch_kwanyuen_2006, title={Ergosterol as a quantifiable biomass marker for Diaporthe phaseolorum and Cercospora kikuchii}, volume={90}, ISSN={["1943-7692"]}, DOI={10.1094/PD-90-1395}, abstractNote={ The relationship between ergosterol content and biomass was determined for the soybean fungal pathogens Diaporthe phaseolorum (Cooke & Ellis) Sacc. var. sojae, causal agent of Phomopsis seed decay, and Cercospora kikuchii (Matsumoto & Tomoy.), causal agent of leaf blight and purple seed stain. Biomass was manipulated by varying incubation period, and ergosterol was quantified by high-pressure liquid chromatography. Fungal dry mass was linearly correlated with ergosterol content (r2 = 0.90, P < 0.05 for D. phaseolorum, and r2 = 0.95, P < 0.01 for C. kikuchii). In vitro ergosterol content of fungi was 3.16 μg/mg for D. phaseolorum and 2.85 μg/mg for C. kikuchii. Ergosterol content of inoculated seed was qualitatively correlated with observed seed colonization by both pathogens. Soybean variety had a significant effect on fungal colonization by D. phaseolorum and ergosterol content. Results show that ergosterol content can be used to quantify colonization of soybean seed by both pathogens. }, number={11}, journal={PLANT DISEASE}, author={Xue, H. Q. and Upchurch, R. G. and Kwanyuen, P.}, year={2006}, month={Nov}, pages={1395–1398} }
 @article{byfield_xue_upchurch_2006, title={Two genes from soybean encoding soluble Delta 9 stearoyl-ACP desaturases}, volume={46}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2005.06-0172}, abstractNote={The Δ9 stearoyl acyl‐carrier protein desaturase (SACPD) gene of soybean [Glycine max (L.) Merrill] encodes a soluble enzyme that converts stearic to oleic acid. Understanding the regulation of SACPD expression and enzyme activity are thus important steps toward developing soybean lines with altered stearic or oleic acid content. Using primers designed to a G. max SACPD cDNA sequence, a 3648‐bp product was cloned and sequenced from the genome of cultivar Dare. Comparison of the third SACPD exon protein sequence with other available Glycine SACPD sequences revealed unique amino acid variability at positions 310 and 313. Sequence‐specific primers were designed for Real‐time RT‐PCR (reverse transcriptase‐polymerase chain reaction) for this region of exon 3. Diagnostic and specific products were recovered with these primers using Dare cDNA template and Dare genomic DNA. Sequencing of a second genomic clone from Dare confirmed that there were two SACPD genes, designated A and B, in this cultivar. Survey of the genomes of 51 soybean lines and cultivars with PCR and the gene‐specific primers indicated that all 51 had both A and B Differences between SACPD‐A and ‐B transcript abundance in soybean tissues, while quantifiable, were not dramatic. SACPD‐A and ‐B transcript accumulation for three seed developmental stages between R5 and R6 was essentially equal. Biochemical analysis of the proteins encoded by these two SACPD genes may reveal whether the amino acid variability uncovered in this study has any relation to enzyme activity.}, number={2}, journal={CROP SCIENCE}, author={Byfield, GE and Xue, H and Upchurch, RG}, year={2006}, pages={840–846} }
 @article{xue_isleib_payne_novitzky_obrian_2005, title={Aflatoxin production in peanut lines selected to represent a range of linoleic acid concentrations}, volume={68}, ISSN={["1944-9097"]}, DOI={10.4315/0362-028X-68.1.126}, abstractNote={To determine whether concentrations of linoleate in peanut (Arachis hypogaea L.) seed oil could be used to predict an ability to support aflatoxin production, seeds of genotypes representing a range of linoleate content were inoculated with Aspergillus flavus Link ex Fries and assayed for aflatoxin content. Seeds were blanched and quartered, inoculated with conidia of A. flavus, placed on moistened filter paper in petri dishes, and incubated for 8 days at 28 degrees C. Multiple regression analysis was used to account for the variation among lines with the use of fatty acid concentrations as independent variables. In test 1, linoleate accounted for 39 to 44% of the variation among lines for aflatoxin B1 and B2 and total aflatoxin (26 to 27% after log transformation). Oleate accounted for substantial additional variation (27 to 29%) among lines (20 to 23% after log transformation). Other fatty acids accounted for small fractions of among-line variation. In test 2, linoleate accounted for about 35 to 44% of the variation among entries across traits (29 to 37% for log-transformed data); arachidate accounted for 19 to 29% (27 to 33% after log transformation). Eicosenoate accounted for a small part of the total entry variation. In both experiments, residual variation among entries was significant. Low-linoleate lines consistently contained more aflatoxin, whereas normal- to high-linoleate lines contained variable amounts. Although fatty acid concentrations accounted for significant portions of genetic variation, it is not practical to use them as predictors for susceptibility to aflatoxin contamination, especially for lines in the normal range for oleate and linoleate.}, number={1}, journal={JOURNAL OF FOOD PROTECTION}, author={Xue, HQ and Isleib, TG and Payne, GA and Novitzky, WF and Obrian, G}, year={2005}, month={Jan}, pages={126–132} }
 @article{xue_isleib_payne_wilson_novitzky_g o'brian_2003, title={Comparison of aflatoxin production in normal- and high-oleic backeross-derived peanut lines}, volume={87}, ISSN={["1943-7692"]}, DOI={10.1094/PDIS.2003.87.11.1360}, abstractNote={ The effect of the high-oleate trait of peanut on aflatoxin production was tested by comparing normal oleic lines with high-oleic backcross-derived lines. Seeds were blanched, quartered, and inoculated with Aspergillus flavus conidia, placed on moistened filter paper in petri dishes, and incubated for 8 days. In one experiment, dishes were stacked in plastic bags in a Latin square design with bags and positions in stacks as blocking variables. High-oleic lines averaged nearly twice as much aflatoxin as normal lines. Background genotype had no significant effect on aflatoxin content, and interaction between background genotype and oleate level was not detected. In a second experiment, dishes were arranged on plastic trays enclosed in plastic bags and stacked with PVC spacers between trays. Fungal growth and aflatoxin production were greater than in the first experiment. Background genotype, oleate level, and their interaction were significant. The mean of high-oleic lines was almost twice that of normal lines, but the magnitude of the difference varied with background genotype. Special care should be taken with high-oleic lines to prevent growth of Aspergillus spp. and concomitant development of aflatoxin contamination. }, number={11}, journal={PLANT DISEASE}, author={Xue, HQ and Isleib, TG and Payne, GA and Wilson, RF and Novitzky, WP and G O'Brian}, year={2003}, month={Nov}, pages={1360–1365} }