First report of foliar nematode (Aphelenchoides pseudobesseyi) on soybean in Colombia.

Soybean (Glycine max L.) is produced in over 70,000 ha in the Altillanura Region, eastern Colombia (Agronet 2023). From 2018 to 2020, foliar symptoms like green stem and foliar retention of soybean, which in Brazil can cause up to 100% soybean yield losses (Meyer et al. 2017), were observed in soybean fields in Colombia. During 2020, samples from symptomatic plants in reproductive stages (R1-R8) were collected from different commercial soybean fields in the Altillanura Region. Over 200 samples were processed, using an incubation method described in Coyne et al. (2014). Nematodes were recovered from photosynthetic leaf tissues and enlarged nodes/buds with population densities ranging from 13 to 132 and 36 to 936 nematodes/10g, respectively. Adult females were morphologically and molecularly characterized as Aphelenchoides pseudobesseyi (Oliveira et al. 2019; Subbotin et al. 2020). Female body length (n = 20) ranged from 653.3 to 806.3 µm (mean = 723 µm ± 52.7), stylet length from 11.0 to 12.3 µm (11.8 µm ± 0.3), body diameter from 14.8 to 17.9 µm (16.3 µm ± 1.1), post-uterine sac length from 38.7 to 51.9 µm (44.6 µm ± 5.1), vulva to anus from 145.5 to 223.2 µm (172.2 µm ± 22.4), and 26% of the vulva-anus distance. Genomic DNA was extracted (QIAGEN DNeasy® Blood & Tissue kit) from a pool of nematodes. The D2A/D3B (Tenente et al. 2004) primers were used to amplify and sequence the D2/D3 expansion region of the 28S rRNA gene. PCR product (~759 bp) was purified, sequenced, deposited in GenBank (OQ930285), and compared to previously deposited sequences (e.g., KX356756, KY510840, KY510839, KY510841, KT692694, KY510842, MH187565) by means of the BLAST algorithm. Similarly, 988F and 18SR-Burs (De Jesus et al. 2016) primers were used to amplify and sequence the near full-length 18S RNA gene (SSU). PCR product was purified, sequenced, deposited in GenBank (OQ954344), and compared to previously deposited sequences (e.g., KT454962, KT943534, KT943535, KY510835, KY510836, KY510837, KY510838, MH187565). Phylogenetic Bayesian analysis (Ronquist et al. 2012) of the of the D2/D3 and 18S regions placed this nematode from Colombia in the A. pseudobesseyi clade (PP = 100). To fulfill a modified Koch's postulates, the A. pseudobesseyi population described above was used in a greenhouse assay. In total, 120 soybean plants (cv. Flor Blanca) were infected with 200 A. pseudobesseyi (females + males)/plant. Briefly, at cotyledon stage (VC), 50 µl aliquot containing 50 A. pseudobesseyi was delivered onto each cotyledon and unifoliolate leaves (200 nematodes/plant). Sterile water was delivered to 80 plants which served as control. Plants were kept in the greenhouse at approximately 25°C and covered with clear plastic bag for 72 h to maintain over 90% relative humidity. After 15, 30, 45, and 60 days, soybean plants (n = 20) were processed, A. pseudobesseyi quantified, and the average reproduction factor (final population/initial population) was 0.1, 2.9, 14.0, and 1.8, respectively. Infected plants showed symptoms of blistering leaves with malformation (midrib vein twist), and A. pseudobesseyi was not observed in control plants. To our knowledge, this is the first report of A. pseudobesseyi parasitizing soybean buds and leaves in Colombia. Soybean is an important commodity for the Altillanura Region, and it is important to monitor the risk posed by this nematode. Furthermore, a better understanding of the nematode-host interaction and epidemiology in Colombia soybean producing regions is needed.

Lower methane emissions were associated with higher abundance of ruminal Prevotella in a cohort of Colombian buffalos.

BACKGROUND: Ruminants burp massive amounts of methane into the atmosphere and significantly contribute to the deposition of greenhouse gases and the consequent global warming. It is therefore urgent to devise strategies to mitigate ruminant's methane emissions to alleviate climate change. Ruminal methanogenesis is accomplished by a series of methanogen archaea in the phylum Euryarchaeota, which piggyback into carbohydrate fermentation by utilizing residual hydrogen to produce methane. Abundance of methanogens, therefore, is expected to affect methane production. Furthermore, availability of hydrogen produced by cellulolytic bacteria acting upstream of methanogens is a rate-limiting factor for methane production. The aim of our study was to identify microbes associated with the production of methane which would constitute the basis for the design of mitigation strategies. RESULTS: Moderate differences in the abundance of methanogens were observed between groups. In addition, we present three lines of evidence suggesting an apparent higher abundance of a consortium of Prevotella species in animals with lower methane emissions. First, taxonomic classification revealed increased abundance of at least 29 species of Prevotella. Second, metagenome assembly identified increased abundance of Prevotella ruminicola and another species of Prevotella. Third, metabolic profiling of predicted proteins uncovered 25 enzymes with homology to Prevotella proteins more abundant in the low methane emissions group. CONCLUSIONS: We propose that higher abundance of ruminal Prevotella increases the production of propionic acid and, in doing so, reduces the amount of hydrogen available for methanogenesis. However, further experimentation is required to ascertain the role of Prevotella on methane production and its potential to act as a methane production mitigator.

Prevotella: A Key Player in Ruminal Metabolism.

Ruminants are foregut fermenters that have the remarkable ability of converting plant polymers that are indigestible to humans into assimilable comestibles like meat and milk, which are cornerstones of human nutrition. Ruminants establish a symbiotic relationship with their microbiome, and the latter is the workhorse of carbohydrate fermentation. On the other hand, during carbohydrate fermentation, synthesis of propionate sequesters H, thus reducing its availability for the ultimate production of methane (CH4) by methanogenic archaea. Biochemically, methane is the simplest alkane and represents a downturn in energetic efficiency in ruminants; environmentally, it constitutes a potent greenhouse gas that negatively affects climate change. Prevotella is a very versatile microbe capable of processing a wide range of proteins and polysaccharides, and one of its fermentation products is propionate, a trait that appears conspicuous in P. ruminicola strain 23. Since propionate, but not acetate or butyrate, constitutes an H sink, propionate-producing microbes have the potential to reduce methane production. Accordingly, numerous studies suggest that members of the genus Prevotella have the ability to divert the hydrogen flow in glycolysis away from methanogenesis and in favor of propionic acid production. Intended for a broad audience in microbiology, our review summarizes the biochemistry of carbohydrate fermentation and subsequently discusses the evidence supporting the essential role of Prevotella in lignocellulose processing and its association with reduced methane emissions. We hope this article will serve as an introduction to novice Prevotella researchers and as an update to others more conversant with the topic.

CARACTERIZACIÓN MOLECULAR DE CLONES DE Theobroma cacao L, POR MEDIO DE MARCADORES MOLECULARES MICROSATÉLITES / Theobroma cacao L. CLONES MOLECULAR CHARACTERIZATION USING MOLECULAR MICROSATELLITE MARKERS

Theobroma cacao L. es la única especie del género Theobroma que se explota comercialmente en grandes extensiones, registrando en la actualidad una amplia distribución mundial, a través de programas de desarrollo directamente influenciados por factores vinculados al mercado y por los intereses de productores, comerciantes, industriales y consumidores. En este estudio se evaluaron 12 clones de cacao por medio de marcadores moleculares utilizando 10 secuencias microsatélites (SSRs), como un estudio piloto antes de un ensayo a mayor escala. Los datos se procesaron mediante el programa Power Marker Versión 3.25. Se estimaron las frecuencias alélicas y luego se generó una matriz de distancias genéticas basada en el coeficiente de Nei. Utilizando el algoritmo de agrupamiento UPGMA se generó el dendrograma correspondiente. El análisis de diversidad mostró un índice de diversidad genética total de 0,6944 considerado intermedio para los materiales evaluados. La estimación de la heterocigosidad promedio fue de 0,58579 y de promedio del contenido de información polimórfica de 0,6523. En este estudio los marcadores mTcCIR6, mTcCIR25, mTcCIR26 y mTcCIR12 son los más informativos y polimórficos. Se recomienda relacionar los resultados de diversidad genética con caracteres morfo-agronómicos y de patogenicidad en los distintos clones de cacao a fin de consolidar estrategias eficaces de mejoramiento y control de enfermedades.

Theobroma cacao L. is the only Theobroma species that is commercially exploited in enormous extensions, registering presently wide distribution worldwide through development programs directly influenced by factors linked to the market and the producers, traders, industrials, and consumers’ interests. In this study 12 cacao clones were evaluated by means of molecular markers using 10 microsatellite sequences (SSRs) as a pilot study before a test at a greater scale. The data were processed using the Power Maker Version 3.25 program. The allelic frequencies were stimated and a genetic distance matrix was developed based on the Nei coefficient. Using the UPGMA grouping algorithm the corresponding dendrogram was generated. The diversity analysis showed a total genetic diversity index of 0.6944 considered intermediate for the materials evaluated. The average heterozygocity estimate was 0.58579 and the average polymorphic information content was 0.6523. In this study markers mTcCIR6, mTcCIR25, mTcCIR26 and mTcCIR12 are the most informative and polymorphic ones. It is recommended to relate the genetic diversity results with morpho-agronomic and pathogenicity characters in the different cacao clones in order to consolidate efficient strategies for disease improvement and control.