@article{maidana-ojeda_fernandez-gamarra_enciso-maldonado_chavez_talavera-stefani_caballero-mairesse_mongelos-franco_sanabria-velazquez_vargas_burgos-cantoni_et al._2023, title={First Report of <i>Zymoseptoria tritici</i> Causing <i>Septoria tritici</i> Blotch in Wheat in Paraguay}, ISSN={["1943-7692"]}, DOI={10.1094/PDIS-06-23-1150-PDN}, abstractNote={Wheat (Triticum aestivum) is the third most cultivated field crop in Paraguay; it is grown on over 450,000 hectares with an annual production of 927,776 tons (fao.org/faostat). In 1952, Septoria tritici blotch (STB) was associated with the fungus Septoria tritici solely based on microscopic observation of conidia (Viedma and Delgado 1987). However, no morphometric or molecular studies have been performed in Paraguay up to date. Over the following decades, STB epidemic outbreaks were recorded, with a reduction in wheat production of up to 70% (Viedma and Delgado 1987). During winter 2021, leaf blotch symptoms were observed with an incidence above 50% in wheat fields in Capitán Miranda, Itapúa, Paraguay. Scattered, spherical, buried, and light brown necrotic spots with dark edges were observed on the leaves. Pycnidia with prominent central ostiole were observed. Leaves with symptoms were washed with 1% sodium hypochlorite for 1 min, rinsed with sterile distilled water, and incubated in wet chambers to induce sporulation of the fungus. Pycnidia produced greyish to white cirri. Isolated conidia were thin, elongated, and hyaline, ranging from 26.9-72.7 × 1.5-2.9 μm with one to three septa. Monosporic colonies on potato dextrose agar (PDA, ; Difco laboratories, Detroit, MI) media varied in color from white to pink, dark gray to black, or black with stroma-like structures. Based on morphology, the fungus was characterized as Zymoseptoria tritici (Hoorne et al. 2002; Gilchrist-Saavedra et al. 2005). Fungal DNA was extracted from mycelia, and the internal transcribed spacer (ITS), translation elongation factor 1-α (TEF1-α), 28S rRNA gene (LSU), actin gene (act), calmodulin (CaM) were amplified using ITS1/ITS4, EF1-728F/EF-2, LSU1Fd/ LR5, ACT-512F/ACT-783R, CAL-228F/CAL737R primers, respectively. PCR amplicons were sequenced at Macrogen (Seoul, Republic of Korea) and deposited in the NCBI GenBank database (ITS: OQ360718; TEF1-α: OQ999044, LSU: OQ996413, act: OQ999046, CaM: OQ999045). Sequences were aligned with several isolates of Septoria spp. previously reported (Verkley et al. 2013; Stukenbrock et al. 2012) using ClustalW. The alignments were concatenated with Bioedit (Hall 1999). The UPGMA method with 1,000 bootstrap replications, was used to construct the phylogenetic tree using MEGA11 with Readeriella mirabilis as the outgroup. The isolate from Paraguay grouped into the Zymoseptoria tritici clade with 96% bootstrap support. To confirm pathogenicity, ten wheat plants cv. Itapúa 80 were grown in pots for three weeks in growth chambers (22 ± 2°C; 16 h photoperiod). Subsequently, these plants were inoculated with 1×107 conidia ml-1 suspension, and ten non-inoculated plants served as control. Seven days after inoculation (DAI), symptoms were observed displaying oval necrotic lesions and approximately 14 DAI abundant pycnidia were observed on and around the lesions. Segments of symptomatic leaves were placed in moisture chambers overnight to enhance cirri development. Conidia were mounted on a slide and observed under the compound microscope. Individual cirrhus were transferred to plates containing PDA and produced colonies like those used in the inoculation (Hoorne et al. 2002). We confirmed that the causal agent of STB from wheat fields in Paraguay was Zymoseptoria tritici. This pathogen causes annual wheat disease epidemics in Paraguay; therefore, optimizing surveillance for early detection and understanding its distribution will improve integrated management.}, journal={PLANT DISEASE}, author={Maidana-Ojeda, Marco and Fernandez-Gamarra, Marta A. and Enciso-Maldonado, Guillermo A. and Chavez, Pedro and Talavera-Stefani, Liliana N. and Caballero-Mairesse, Gabriela G. and Mongelos-Franco, Yeruti and Sanabria-Velazquez, Andres D. and Vargas, Maria Jose and Burgos-Cantoni, Cinthia and et al.}, year={2023}, month={Aug} }
 @article{sanabria-velazquez_cubilla_flores-giubi_barua_romero-rodriguez_enciso-maldonado_thiessen_shew_2023, title={First Report of Macrophomina euphorbiicola Causing Charcoal Rot of Stevia in Paraguay}, volume={107}, ISSN={["1943-7692"]}, DOI={10.1094/PDIS-06-21-1279-PDN}, abstractNote={Stevia (Stevia rebaudiana [Bertoni] Bertoni) is a perennial plant originating in Paraguay. Stevia is primarily cultivated for the production of non-caloric sweeteners. In December 2018, wilted stevia cv. 'PC4' were recovered from two separate fields of 0.3 ha (24.66 S 56.46 W) and 0.5 ha (24.69 S 56.44 W), both with 3 years history of stevia production in San Estanislao County, San Pedro, Paraguay. The wilted plants were randomly distributed in beds covered with plastic mulch and a 30% disease incidence was recorded. Dark brown septate hyphae and microsclerotia were observed on stem bases and black necrotic roots of the wilted plants. Root and crown regions were washed, cut into 0.5 to 1.0 cm pieces, and then surface-disinfested with 0.6% NaOCl before placing them in Petri dishes containing acidified potato-dextrose-agar. Plates were incubated for one week at 25 ± 5°C under fluorescent light with a 12 h photoperiod yielding five isolates SP1PY, SP2PY, SP3PY, SP4PY and SP5PY with gray-black colonies without conidia but showing numerous microsclerotia. Twenty microsclerotia from pure cultures of five isolates were measured, with mean width 38.8 ± 4.7 µm and length 68.8 ± 15.5 µm. Fungal DNA was extracted from mycelia of five isolates for PCR amplification of the internal transcribed spacer (ITS) and translation elongation factor 1-alpha (TEF1-α) using ITS4/ITS5 and EF1-728F/EF-2 primers (Machado et al. 2019). The resultant amplicons were sequenced at Eton Bioscience (Research Triangle Park, NC) and deposited in the NCBI GenBank database (ITS: MT645815, OM956150, OM956151, OM956152, OM956153; and TEF1-α: MT659121, OM959505, OM959506, OM959507, OM959508). Sequences were aligned with several isolates of Macrophomina spp. previously reported (Huda-Shakirah et al. 2019; Machado et al. 2019; Santos et al. 2020; Poudel et al. 2021) using ClustalW. Alignments (ITS and TEF-1α) were concatenated to generate a maximum likelihood tree using MEGA7. The novel isolates grouped into the M. euphorbiicola clade with 95% of bootstrap support. Stevia plants cv. 'Katupyry' were grown in 10 cm-diameter nursery bags containing autoclaved sandy soil and kept under greenhouse conditions (28 ± 5°C; 16 h photoperiod). Fifteen plants per isolate (n=75) were inoculated by adding 20 g of rice infested with M. euphorbiicola to each plant. Infested grains were distributed around the crown of the plant at a depth of 0.5 cm; non-infested rice was added to four control plants. Lower-stem lesions and microsclerotia of M. euphorbiicola developed on all inoculated plants. No lesions or microsclerotia were observed on control plants. The M. euphoribiicola fungus was re-isolated from inoculated stevia plants but not from the non-infested rice treated plants. Koch's postulates were repeated twice with similar results. Previously, M. phaseolina was reported causing charcoal rot on stevia in Egypt (Hilal and Baiuomy 2000), and in North Carolina, USA (Koehler and Shew 2017). However, Paraguayan isolates grouped with isolates of M. euphorbiicola based on the combined sequences of the ITS and TEF-1α regions. Machado et al. (2019) reported M. euphorbiicola causing charcoal rot on castor bean (Ricinus communis) and bellyache bush (Jatropha gossypifolia) in Brazil, which borders northeast Paraguay, a major stevia production area. This pathogen has a significant impact on stevia production during hot, dry weather by reducing the number of harvestable plants and increasing replanting costs in perennial production systems.}, number={1}, journal={PLANT DISEASE}, author={Sanabria-Velazquez, Andres D. D. and Cubilla, Alberto and Flores-Giubi, Maria Eugenia and Barua, Javier E. E. and Romero-Rodriguez, Cristina and Enciso-Maldonado, Guillermo A. A. and Thiessen, LindseyD D. and Shew, H. David}, year={2023}, month={Jan} }
 @article{sanabria-velazquez_enciso-maldonado_maidana-ojeda_diaz-najera_ayvar-serna_thiessen_shew_2023, title={Integrated Pathogen Management in Stevia Using Anaerobic Soil Disinfestation Combined with Different Fungicide Programs in USA, Mexico, and Paraguay}, volume={13}, ISSN={["2073-4395"]}, DOI={10.3390/agronomy13051358}, abstractNote={Stevia is a semi-perennial crop grown to obtain the diterpene glycosides in its leaves, which are processed to manufacture non-caloric sweeteners. Anaerobic soil disinfestation (ASD) and fungicide application were evaluated for the management of stevia stem rot (SSR) and Septoria leaf spot (SLS) in lab and field experiments. In 2019 and 2021, experiments using carbon sources for ASD were carried out in microplots at NCSU (Clayton, NC, USA). In 2020/21 and 2021/22 seasons, field experiments were conducted at CSAEGRO, Mexico (MX) and CEDIT, Paraguay (PY) using a 2 × 3 factorial design with two ASD treatments and three fungicide treatments. ASD treatments included soil amended with cornmeal (MX) or wheat bran (PY) at a rate of 20.2 Mg ha−1, molasses at 10.1 Mg ha−1, and non-amended controls. Fungicide applications included chemical (azoxystrobin), organic (pyroligneous acid, PA), and a non-treated control. ASD was effective in reducing sclerotia viability of Sclerotium rolfsii in laboratory assays (p < 0.0001) and microplot trials (p < 0.0001) in NC. During field trials, the viability of sclerotia was significantly reduced (p < 0.0001) in soils amended with cornmeal + molasses or wheat bran + molasses as carbon sources for ASD. While there was no significant effectiveness of ASD in reducing SLS in 2020 and 2021 or SSR in MX 2020 field trials (p = 0.83), it did exhibit efficacy on SSR in 2021 (p < 0.001). The application of fungicides was significantly effective in reducing SSR (p = 0.01) and SLS (p = 0.001), with azoxystrobin being the most consistent and PA not being statistically different from the control or azoxystrobin. The effects of ASD on fresh yield were inconsistent, exhibiting significant effects in Mexican fields in 2020 but not in 2021. During Paraguayan field trials, ASD only significantly interacted with fungicide applications in the dry yield in 2022. In the 2020/21 MX and 2020 PY field trials, fungicides were significantly effective in enhancing dry leaf yields, with azoxystrobin showing the highest consistency among treatments and PA variable control. In conclusion, utilizing ASD alongside organic fungicides can be a valuable tool for stevia farmers when the use of chemical fungicides is limited. Further research is required to enhance consistency and reduce the costs associated with these treatments under diverse edaphoclimatic conditions.}, number={5}, journal={AGRONOMY-BASEL}, author={Sanabria-Velazquez, Andres D. and Enciso-Maldonado, Guillermo A. and Maidana-Ojeda, Marco and Diaz-Najera, Jose F. and Ayvar-Serna, Sergio and Thiessen, Lindsey D. and Shew, H. David}, year={2023}, month={May} }
 @article{andres enciso-maldonado_lozoya-saldana_teresa colinas-leon_axayacatl cuevas-sanchez_dejesus sanabria-velazquez_bamberg_raman_2022, title={Assessment of Wild Solanum Species for Resistance to Phytophthora infestans (Mont.) de Bary in the Toluca Valley, Mexico}, ISSN={["1874-9380"]}, DOI={10.1007/s12230-021-09856-x}, journal={AMERICAN JOURNAL OF POTATO RESEARCH}, author={Andres Enciso-Maldonado, Guillermo and Lozoya-Saldana, Hector and Teresa Colinas-Leon, Maria and Axayacatl Cuevas-Sanchez, Jesus and Dejesus Sanabria-Velazquez, Andres and Bamberg, John and Raman, K.}, year={2022}, month={Jan} }
 @article{lopez-nicora_andres enciso-maldonado_giuliana caballero-mairesse_dejesus sanabria-velazquez_jose armandans-rojas_concepcion soilan-duarte_javier grabowski-ocampos_arminda resquin-romero_agustin colman_margarita pedrozo-fleitas_et al._2022, title={Distribution and Abundance of Nematodes in Horticultural Production in Paraguay}, ISSN={["1535-1025"]}, DOI={10.1094/PHP-01-22-0001-S}, abstractNote={ In Paraguay, there is no information describing the distribution and abundance of plant-parasitic nematodes and other free-living nematodes from vegetable farms. The objectives of this study were to determine the prevalence and abundance of plant-parasitic nematodes on vegetable farms, to evaluate the relationship between plant-parasitic nematodes and ecological diversity, and to evaluate the relationship between edaphic factors and nematode communities. Vegetable farms ( n = 217) across nine departments in Paraguay were included in this survey, and soil samples were collected between March and September 2021. More than 10 plant-parasitic nematode genera were identified in this survey and are presented as follows in decreasing order of prevalence: Helicotylenchus (0 to 2,000 nematodes/100 cm3 of soil), Meloidogyne (0 to 4,120), Criconemella (0 to 400), root-related genera in Tylenchidae (0 to 400), Pratylenchus (0 to 280), Tylenchorhynchus (0 to 200), Trichodorus (0 to 40), Rotylenchulus (0 to 1,800), Hoplolaimus (0 to 20), Xiphinema (0 to 80), Scutellonema (0 to 1,000), Criconema (0 to 24), and Hemicycliophora (0 to 20). Meloidogyne was the most abundant nematode on vegetable farms, highlighting the potential threat of this pathogen to horticultural production in Paraguay. Nematodes were separated into five trophic groups depending on their feeding habits. Diversity of trophic groups was estimated using Shannon's diversity index, which was inversely related to plant-parasitic nematodes. Additionally, the relationship between edaphic factors (physical-chemical soil properties) and nematode abundance was evaluated. Soil texture was significantly associated with nematode abundance. This study is a first step to aid local growers in developing sustainable and economic agricultural systems. }, journal={PLANT HEALTH PROGRESS}, author={Lopez-Nicora, Horacio D. and Andres Enciso-Maldonado, Guillermo and Giuliana Caballero-Mairesse, Gabriela and Dejesus Sanabria-Velazquez, Andres and Jose Armandans-Rojas, Andres and Concepcion Soilan-Duarte, Laura and Javier Grabowski-Ocampos, Cristian and Arminda Resquin-Romero, Gloria and Agustin Colman, Adans and Margarita Pedrozo-Fleitas, Lidia and et al.}, year={2022}, month={Jun} }
 @article{khadka_sanabria-velazquez_cardina_miller_2022, title={Evaluation of Anaerobic Soil Disinfestation for Environmentally Sustainable Weed Management}, volume={12}, ISSN={["2073-4395"]}, DOI={10.3390/agronomy12123147}, abstractNote={In anaerobic soil disinfestation (ASD), soil amended with a carbon source undergoes anaerobic conditions accompanied by changes in microbial community composition and an increase in the concentration of organic acids, primarily acetic and butyric acids, and gases that are deleterious to plant pathogens, insects, and potentially to weeds. The purpose of this study was to explore the efficacy of ASD with different carbon sources on inactivation of propagules of a variety of weed species. Germination and viability of propagules of common lambsquarters (Chenopodium album L.), black nightshade (Solanum nigrum L.), yellow nutsedge (Cyperus esculentus L.), common pokeweed (Phytolacca decandra L.), barnyardgrass (Echinochloa crus-galli L.), dandelion (Taraxacum officinale (Weber)), and redroot pigweed (Amaranthus retroflexus L.) were tested using different rates of four carbon sources: molasses, wheat bran, mustard greens biomass, and raw chicken manure. Wheat bran was the most effective carbon source for inactivation of all weed propagules, followed by molasses and mustard greens biomass. Carbon sources were mixed with soil, which was irrigated to saturation and covered with plastic to promote anaerobic conditions for three weeks. Chicken manure inactivated all the tested species except A. retroflexus compared to the anaerobic control. Rates of carbon sources applied in soil were weakly but significantly correlated (r > 0.42 and p < 0.04) with weed seed mortality or germination inhibition (E. crus-galli) for all the tested carbon sources and weed species except for chicken manure for C. album, A. retroflexus, and S. nigrum. Laboratory tests to confirm organic acid toxicity showed that 1000 µL L−1 acetic plus 1000 µL L−1 butyric acids for at least 60 h inhibited of sprouting of C. esculentus tubers and E. crusgalli seeds, whereas 120 h or exposure was required to inhibit C. album seed germination. Anaerobic soil disinfestation effectively suppressed weed seed germination and viability when wheat bran, molasses and mustard greens biomass were used as carbon sources. This approach could be adopted for weed management in organic systems or any farming system where priority is given to environmentally sustainable practices.}, number={12}, journal={AGRONOMY-BASEL}, author={Khadka, Ram B. and Sanabria-Velazquez, Andres D. and Cardina, John and Miller, Sally A.}, year={2022}, month={Dec} }
 @article{sanabria-velazquez_enciso-maldonado_maidana-ojeda_diaz-najera_thiessen_shew_2022, title={Validation of Standard Area Diagrams to Estimate the Severity of Septoria Leaf Spot on Stevia in Paraguay, Mexico, and the United States}, ISSN={["1943-7692"]}, DOI={10.1094/PDIS-07-22-1609-RE}, abstractNote={ Septoria leaf spot (SLS) affects stevia leaves, reducing their quality. Estimates of SLS severity on different genotypes are made to identify resistance and as a basis to compare management approaches. The use of standard area diagrams (SADs) can improve the accuracy and reliability of severity estimates. In this study, we developed new SADs with six illustrations (0.5, 1, 10, 25, 40, and 75% severity). The SADs were validated by raters with and without experience in estimating SLS. Raters evaluated 40 leaf photos with SLS severities ranging from 0 to 100% without and with the SADs. Agreement (ρc), bias (Cb), precision (r), and intracluster correlation (ρ) coefficients were significantly closer to “true” severity values when the SADs was used by inexperienced (ρc = 0.89; Cb = 0.97; r = 0.90, ρ = 0.81) and experienced (ρc = 0.94; Cb = 0.99; r = 0.95, ρ = 0.91) raters. The SADs were tested under field conditions in Paraguay, Mexico, and the United States, with inexperienced raters assigned to two groups, one SADs trained and the other not trained, that estimated SLS severity three times: first, all raters without SADs and no time limit for the estimates; second, only the SADs-trained group used SADs and no time limit; and third, only the SADs-trained group used SADs, with a time limit of 10 s imposed per specimen assessment. Agreement and reliability of SLS severity estimates significantly improved when raters used the SADs without a time limit. The use of the new SADs improved the accuracy, precision, and reliability of SLS severity estimates, enhancing the uniformity in assessment across different stevia programs. }, journal={PLANT DISEASE}, author={Sanabria-Velazquez, Andres D. and Enciso-Maldonado, Guillermo A. and Maidana-Ojeda, Marco and Diaz-Najera, Jose F. and Thiessen, Lindsey D. and Shew, H. David}, year={2022}, month={Nov} }
 @article{enciso-maldonado_morales-vazquez_sanabria-velazquez_diaz-najera_zapata-maldonado_fuentes-aragon_2020, title={First report of powdery mildew caused by Golovinomyces ambrosiae on Cosmos atrosanguineus (Hook.) Voss}, volume={102}, ISSN={["2239-7264"]}, DOI={10.1007/s42161-020-00630-2}, number={4}, journal={JOURNAL OF PLANT PATHOLOGY}, author={Enciso-Maldonado, Guillermo A. and Morales-Vazquez, Bulmaro and Sanabria-Velazquez, Andres D. and Diaz-Najera, Jose F. and Zapata-Maldonado, Christian I. and Fuentes-Aragon, Dionicio}, year={2020}, month={Nov}, pages={1345–1346} }