@article{guiguitant_marrou_vile_sinclair_pradhan_ramirez_ghanem_2021, title={An exploration of the variability of physiological responses to soil drying in relation with C/N balance across three species of the under-utilized genus Vigna}, volume={172}, ISSN={["1399-3054"]}, DOI={10.1111/ppl.13224}, abstractNote={Abstract}, number={2}, journal={PHYSIOLOGIA PLANTARUM}, author={Guiguitant, Julie and Marrou, Helene and Vile, Denis and Sinclair, Thomas R. and Pradhan, Deepti and Ramirez, Martha and Ghanem, Michel Edmond}, year={2021}, month={Jun}, pages={477–486} }
 @article{pradhan_dunne_ramirez_sinclair_2020, title={Nitrogen-fixation drought tolerance in virginia-type peanut}, volume={34}, ISSN={["1542-7536"]}, DOI={10.1080/15427528.2020.1740903}, abstractNote={ABSTRACT Symbiotic nitrogen-fixation activity of grain legumes commonly does not exhibit tolerance to soil drying, including in peanut (Arachis hypogaea L.). Since the demand for nitrogen of peanut is large in the synthesis of seeds with high protein concentration, loss of nitrogen-fixation activity can result in major yield decreases. The objective of this study was to search the germplasm of virginia-type peanut for sources of nitrogen-fixation drought tolerance. The first phase was a field screen in one growing season of 100 lines from which leaves were harvested and nitrogen concentration measured. Research in soybean had shown that low leaf-nitrogen concentration was associated with nitrogen-fixation drought tolerance. A wide range of leaf nitrogen concentrations was observed, and 10 lines of low leaf nitrogen (23.1 to 26.4 mg N g−1) were identified for the second phase of study. The second phase of study was done in a greenhouse with 5-week old plants sealed in pots subjected to a 2-week dry down. Each day, the plants were briefly exposed to acetylene to measure acetylene reduction activity as an indicator of nitrogen-fixation activity. The soil water content, at which a decline in nitrogen fixation was initiated, was not different among seven lines. Three of the lines exhibited high sensitivity of nitrogen fixation to soil drying. None of the lines, however, exhibited substantial tolerance of nitrogen fixation to soil drying, indicating a need to search an even more diverse population of peanut to identify a genetic source for tolerance.}, number={4}, journal={JOURNAL OF CROP IMPROVEMENT}, author={Pradhan, Deepti and Dunne, Jeffrey and Ramirez, Martha and Sinclair, Thomas R.}, year={2020}, month={Jul}, pages={540–548} }
 @article{upchurch_ramirez_2011, title={Effects of temperature during soybean seed development on defense-related gene expression and fungal pathogen accumulation}, volume={33}, ISSN={["0141-5492"]}, DOI={10.1007/s10529-011-0722-5}, abstractNote={Soybean [Glycine max (L.) Merr] plants were exposed to three temperature regimens during seed development to investigate the effect of temperature on the expression of eight defense-related genes and the accumulation of two fungal pathogens in inoculated seeds. In seeds prior to inoculation, either a day/night warm (34/26 °C) or a cool temperature (22/18 °C) relative to normal (26/22 °C) resulted in altered patterns of gene expression including substantially lower expression of PR1, PR3 and PR10. After seed inoculation with Cercospora kikuchii, pathogen accumulation was lowest in seeds produced at 22/18 °C in which of all defense genes, MMP2 was uniquely most highly induced. For seeds inoculated with Diaporthe phaseolorum, pathogen accumulation was lowest in seeds produced at 34/26 °C in which of all defense genes, PR10 was uniquely most highly induced. Our detached seed assays clearly demonstrated that the temperature regimens we applied during seed development produced significant changes in seed defense-related gene expression both pre- and post inoculation and our findings support the hypothesis that global climate change may alter plant-pathogen interactions and thereby potentially crop productivity.}, number={12}, journal={BIOTECHNOLOGY LETTERS}, author={Upchurch, Robert G. and Ramirez, Martha E.}, year={2011}, month={Dec}, pages={2397–2404} }
 @article{upchurch_ramirez_2011, title={Soybean Plastidal Omega-3 Fatty Acid Desaturase Genes GmFAD7 and GmFAD8: Structure and Expression}, volume={51}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2010.09.0537}, abstractNote={ABSTRACTWe characterized soybean [Glycine max (L.) Merr.] FAD7 and FAD8 gene structure and expression responses to temperature and pathogen stress to compare and contrast these features to those reported for higher plant plastidal omega‐3 (ω‐3) desaturases. We found that the genomic structure and deduced amino acid sequence of soybean FAD7 and FAD8 are similar to other higher plant plastidal ω‐3 desaturases: eight exons and seven introns, predicted proteins of 453 amino acid residues containing three conserved histidine motifs, amino terminal chloroplast transit peptides, and molecular masses of 51.3 and 51.4 kDa, respectively. GmFAD7 has 76% amino acid sequence identity to GmFAD8. Two complete copies of GmFAD7, one on chromosome 18 and one on chromosome 7, and two complete copies of GmFAD8, one on chromosome 3 and one on chromosome 1 of the ‘Williams 82’ soybean genome, were found with strong sequence similarity to GmFAD7 and GmFAD8 of cultivar Dare. Dare GmFAD7 transcript expression in leaves remained at a relatively low level and was unaffected by any of the temperature treatments we imposed, but GmFAD8 transcript accumulation was sharply upregulated by a cool temperature (20/16°C day/night) after a 12 h exposure and total linolenic acid as a percent of total leaf fatty acids increased from 60 to about 68% after 48 h at the cool temperature. Inoculation of soybean leaves with the fungal pathogen Cercospora kikuchii differentially upregulated the level of GmFAD7 transcripts to twice that of GmFAD8 by 12 h postinoculation. The response of soybean foliar FAD8 expression and linolenic acid levels to cool temperature was similar to observations in other plants. On the other hand, despite increased soybean FAD7 expression in response to foliar pathogen stress the expected associated increase in foliar linolenic acid was not detected.}, number={4}, journal={CROP SCIENCE}, author={Upchurch, Robert G. and Ramirez, Martha E.}, year={2011}, month={Jul}, pages={1673–1682} }
 @article{upchurch_ramirez_2010, title={Gene Expression Profiles of Soybeans with Mid-Oleic Acid Seed Phenotype}, volume={87}, ISSN={["0003-021X"]}, DOI={10.1007/s11746-010-1576-z}, abstractNote={Abstract}, number={8}, journal={JOURNAL OF THE AMERICAN OIL CHEMISTS SOCIETY}, author={Upchurch, Robert G. and Ramirez, Martha E.}, year={2010}, month={Aug}, pages={857–864} }
 @article{ramirez_hebbar_zhou_wolk_curtis_2005, title={Anabaena sp strain PCC 7120 gene devH is required for synthesis of the heterocyst glycolipid layer}, volume={187}, ISSN={["1098-5530"]}, DOI={10.1128/JB.187.7.2326-2331.2005}, abstractNote={ABSTRACT}, number={7}, journal={JOURNAL OF BACTERIOLOGY}, author={Ramirez, ME and Hebbar, PB and Zhou, RB and Wolk, CP and Curtis, SE}, year={2005}, month={Apr}, pages={2326–2331} }
 @article{ramirez_israel_wollum_1998, title={Using spontaneous antibiotic-resistant mutants to assess competitiveness of bradyrhizobial inoculants for nodulation of soybean}, volume={44}, ISSN={["0008-4166"]}, DOI={10.1139/cjm-44-8-753}, abstractNote={Spontaneous mutants (3/parental strain) of soybean bradyrhizobia resistant to streptomycin and erythromycin were selected from strains isolated from bradyrhizobial populations indigenous to Cape Fear and Dothan soils. These were used to evaluate (i) the validity of using antibiotic-resistant mutants to make inferences about the competitiveness of parental strains in soil environments and (ii) the recovery of strains in nodules after inoculation of soybeans grown in soils with indigenous bradyrhizobial populations. Streptomycin and erythromycin resistances of all mutants were stable after approximately 27 generations of growth in yeast extract - mannitol medium, but 33% of the mutants lost resistance to erythromycin upon passage through nodules. Only 17% of the mutants were as competitive as their parental strain when inoculated in a ratio near 1:1 in vermiculite. Four of 10 mutants, which differed in competitiveness from their parental strain in vermiculite, had competitiveness against the soil populations equal to that of their parental strain. Therefore, assessment of competitiveness of mutants and parental strains in non-soil media may not accurately reflect their competitiveness in soil systems. For both the Cape Fear and Dothan soils, recovery of a given mutant from nodules of field-grown plants was always lower than from nodules of plants grown in the greenhouse. Inoculation of the entire rooting zone in the greenhouse experiment and of only a portion of the rooting zone in the field experiments may account for this difference in recovery. Techniques that increase the volume of soil inoculated may enhance nodulation by inoculant strains.Key words: Bradyrizobium, antibiotic resistance, competition.}, number={8}, journal={CANADIAN JOURNAL OF MICROBIOLOGY}, author={Ramirez, ME and Israel, DW and Wollum, AG}, year={1998}, month={Aug}, pages={753–758} }
 @article{ramirez_israel_wollum_1997, title={Phenotypic and genotypic diversity of similar serotypes of soybean bradyrhizobia from two soil populations}, volume={29}, ISSN={["0038-0717"]}, DOI={10.1016/S0038-0717(97)00009-6}, abstractNote={The physiological and genetic diversity within two major serotypic groups of bradyrhizobial isolates obtained from soybean (Glycine max L. Merr.) plants grown on a Dothan and a Cape Fear soil was examined. All isolates serotyped as 3194 had large colonies with smooth borders and high resistances to erythromycin, streptomycin and spectinomycin with minimal inhibitory concentration values (MIC) ranging from 200 to 400 μg ml−1. Pulsed-field gel-electrophoresis (PFGE) separation of DNA fragments generated with the rarely cutting restriction endonuclease, Xba I, revealed six genotypes among 28 different 3194 isolates. Four of these genotypes were common to both soils and only 21% of the isolates were classified as having high N2-fixation capacity. Leaf chlorosis was induced by 46% of the 3194 isolates. Among the 122124 isolates, MIC values were lower than for 3194 isolates ranging from < 13 to 200 μg ml−1. These 122124 isolates produced small colonies (50%) and large colonies with rough borders (50%) when plated on YEM. The genetic diversity of serotype 122124 isolates differed with soil type as PFGE patterns revealed nine genotypes among the 16 isolates from the mineral organic (Cape Fear) soil and only three genotypes among the 14 isolates from the sandy mineral (Dothan) soil. Only two of the 12 genotypes were common to both soils. Sixty percent of the 122124 isolates were classified as having high N2-fixation capacity and none induced foliar chlorosis. Pulsed-field gel-electrophoresis pattern was the only trait that generated groups of isolates that were similar with respect to other measured traits.}, number={9-10}, journal={SOIL BIOLOGY & BIOCHEMISTRY}, author={Ramirez, ME and Israel, DW and Wollum, AG}, year={1997}, pages={1539–1545} }
 @article{ramirez_israel_wollum_1997, title={Phenotypic characterization of soybean bradyrhizobia in two soils of North Carolina}, volume={29}, DOI={10.1016/S0038-0717(97)00008-4}, abstractNote={Serotypic composition of nodules (480 per soil type) from five soybean cultivars grown on two (Dothan and Cape Fear) soils of the Atlantic Coastal Plain of North Carolina was characterized. Symbiotic N2-fixation efficiency, capacity for induction of foliar chlorosis symptomatic of rhizobitoxine production and antibiotic resistances of isolates purified from these nodules were also determined. While host plant cultivar had no significant effect on the serotype distribution, soil type had a large effect on the distribution and diversity of serotypes. Forty-six serotypes were identified among nodules from the Cape Fear soil, but only serotype 4676 (8%), 76 (11%), 94 (9%) and 122124 (12%) occurred in more than 5% of the nodules. Thirty percent of nodule occupants were not identified with the eleven antisera used. Twenty-four serotypes were identified among nodules from the Dothan soil. Of these serotypes 3194 (32%), 4676 (16%), and 76 (23%) occurred in more than 15% of the nodules. Five percent of the nodule occupants were not identified. Major serotypes did not change, but their frequency changed when fields were sampled at different growth stages in the same season and at the same growth stage in different seasons. Isolates serotyped as 3194, 4676, and most of the isolates serotyped as 76 generally exhibited higher levels of resistance to streptomycin and erythromycin than isolates serotyped as 24, 94 and 122124. Five percent of the isolates from the Cape Fear soil (all serotyped as 3194) and 18% of the isolates from the Dothan soil (serotyped as 3194 or 76) induced foliar chlorosis when cultivar Brim was the host. Only 12–14% of the isolates from the two populations had N2-fixation capacity equal to or greater than that of the efficient reference strain MN110. However, four improved soybean cultivars grown in the same fields and year that isolates were obtained did not exhibit a significant seed yield response to application of 150 kg N ha−1 when yields in the minus N treatment ranged from 3.2 to 3.7 Mg ha−1. A significant seed yield response by a non-nodulated cultivar indicated that these soils were N limited. Therefore, the symbiotic N2-fixation capacity of these bradyrhizobial populations did not limit soybean seed yields despite the low percentage of isolates with high N2-fixation efficiency and the presence of isolates with the capacity to induce leaf chlorosis symptomatic of rhizobitoxine production.}, number={9-10}, journal={Soil Biology & Biochemistry}, author={Ramirez, M. E. and Israel, D. W. and Wollum, A. G.}, year={1997}, pages={1547–1555} }