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Genome-wide association analyses of agronomic traits and Striga hermonthica resistance in pearl millet

Hussein Shimelis Chris Ojiewo Abhishek Rathore (2023, [Artículo])

Pearl millet (Pennisetum glaucum [L.] R. Br.) is a nutrient-dense, relatively drought-tolerant cereal crop cultivated in dry regions worldwide. The crop is under-researched, and its grain yield is low (< 0.8 tons ha−1) and stagnant in the major production regions, including Burkina Faso. The low productivity of pearl millet is mainly attributable to a lack of improved varieties, Striga hermonthica [Sh] infestation, downy mildew infection, and recurrent heat and drought stress. Developing high-yielding and Striga-resistant pearl millet varieties that satisfy the farmers’ and market needs requires the identification of yield-promoting genes linked to economic traits to facilitate marker-assisted selection and gene pyramiding. The objective of this study was to undertake genome-wide association analyses of agronomic traits and Sh resistance among 150 pearl millet genotypes to identify genetic markers for marker-assisted breeding and trait introgression. The pearl millet genotypes were phenotyped in Sh hotspot fields and screen house conditions. Twenty-nine million single nucleotide polymorphisms (SNPs) initially generated from 345 pearl millet genotypes were filtered, and 256 K SNPs were selected and used in the present study. Phenotypic data were collected on days to flowering, plant height, number of tillers, panicle length, panicle weight, thousand-grain weight, grain weight, number of emerged Striga and area under the Striga number progress curve (ASNPC). Agronomic and Sh parameters were subjected to combined analysis of variance, while genome-wide association analysis was performed on phenotypic and SNPs data. Significant differences (P < 0.001) were detected among the assessed pearl millet genotypes for Sh parameters and agronomic traits. Further, there were significant genotype by Sh interaction for the number of Sh and ASNPC. Twenty-eight SNPs were significantly associated with a low number of emerged Sh located on chromosomes 1, 2, 3, 4, 6, and 7. Four SNPs were associated with days-to-50%-flowering on chromosomes 3, 5, 6, and 7, while five were associated with panicle length on chromosomes 2, 3, and 4. Seven SNPs were linked to thousand-grain weight on chromosomes 2, 3, and 6. The putative SNP markers associated with a low number of emerged Sh and agronomic traits in the assessed genotypes are valuable genomic resources for accelerated breeding and variety deployment of pearl millet with Sh resistance and farmer- and market-preferred agronomic traits.

High-Yielding Varieties Striga-Resistant Agronomic Parameters CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA GENOME-WIDE ASSOCIATION STUDIES STRIGA HERMONTHICA PEARL MILLET

Presencia de Perkinsus marinus en el ambiente y en los moluscos Anadara tuberculosa, Mytella strigata y Crassostrea corteziensis de la costa de Nayarit

Presence of Perkinsus marinus in the environment and in the mollusks Anadara tuberculosa, Mytella strigata and Crassostrea corteziensis from the coast of Nayarit

Naoki Abraham Kawamoto Camacho (2023, [Tesis de maestría])

El parásito Perkinsus marinus cuyo ciclo de vida le permite subsistir en el ambiente y cumplir su ciclo dentro del hospedero es el agente causal de la perkinsosis, letal para Crasssotrea virginica y enlistado por la Organización Mundial de Salud Animal (OMSA). El comercio de ostiones entre el Golfo de México y el Pacífico mexicano ha generado preocupaciones sanitarias al introducir estos moluscos en comunidades costeras del Pacífico. P. marinus formaría parte de la microbiota ambiental y estar en los moluscos bivalvos de estos ambientes. En el presente estudio se emplearon las técnicas PCR, qPCR, secuenciación de amplicones y de próxima generación, así como análisis de microbioma para determinar la presencia de P. marinus en el ambiente y en los moluscos Anadara tuberculosa, Mytella strigata y Crassostrea corteziensis que coexisten en el estero Pozo Chino, Nayarit. Además, se analizaron muestras embebidas en parafina de Tabasco, Veracruz (C. virginica), Nayarit y Sinaloa (C. corteziensis) para realizar comparaciones genotípicas. La prevalencia de infección mediante PCR fue de 86% en ostiones de la zona baja y media del estero, y de 66% en la zona alta, mientras que para M. strigata fue de 2.2% por qPCR. No se detectó a P. marinus en el ambiente ni en A. tuberculosa. La identidad del parásito fue de 86.1 al 100% mediante secuenciación dirigida. Los primers que amplifican productos de 130 pb fueron más eficaces. La no detección del parásito en el entorno se debe a su baja presencia, consecuencia de la baja salinidad, ausencia de infecciones graves y la falta de eventos inusuales de mortalidad, evitando la liberación masiva del parásito en el ambiente. Además, la baja detección en M. strigata y ausencia en A. tuberculosa puede relacionarse con su susceptibilidad. El análisis del microbioma eucariótico mostró a P. marinus como parte de la microbiota en C. corteziensis. En el ambiente los grupos más abundantes fueron copépodos, moluscos, poliquetos y diatomeas. Se requiere profundizar en su estudio en el ambiente y hospederos a lo largo del año para dimensionar mejor el riesgo sanitario que se enfrenta en una zona donde se ha establecido el parásito.

The parasite Perkinsus marinus, whose life cycle allows it to survive in the environment and complete its cycle within the host, is the causative agent of perkinsosis, lethal to Crassostrea virginica, and listed by the World Organisation for Animal Health (WOAH). The trade of oysters between the Gulf of Mexico and the Mexican Pacific coast has raised sanitary concerns by introducing these mollusks into coastal communities on the Pacific. In areas where detection has occurred, P. marinus would be part of the environmental microbiota (plankton/sediments) and in coexisting bivalve mollusks. In this study, PCR, Real-Time PCR (qPCR), amplicon sequencing and next-generation sequencing techniques, as well as microbiome analysis, were employed to determine the presence of P. marinus in the environment (plankton and sediments) and in the mollusks Anadara tuberculosa, Mytella strigata, and Crassostrea corteziensis coexisting in the Pozo Chino estuary, Nayarit. Paraffin-embedded samples from Tabasco, Veracruz (C. virginica), Nayarit, and Sinaloa (C. corteziensis) were also analyzed for genotypic comparisons. The infection prevalence through PCR was 86% in oysters from the lower and middle zones of the estuary and 66% in the upper zone, while for M. strigata, it was 2.2% by RT-PCR. P. marinus was not detected in the environment or in A. tuberculosa. Directed sequencing revealed a parasite identity of 86.1 to 100%. Primers amplifying 130 bp products were more effective. The lack of detection of the parasite in the environment is due to its low presence, resulting from low salinity, the absence of records of severe infections, and the lack of unusual mortality events, preventing massive release of the parasite into the environment. Additionally, the isolated detection in M. strigata and absence in A. tuberculosa may be related to their susceptibility. Analysis of eukaryotic microbiomes identified P. marinus as part of the microbiota in C. corteziensis. In the environment, the most abundant groups were copepods, mollusks, polychaetes, and diatoms. Further studies in the environment and hosts throughout the year are required to better understand the health risks in an area where the parasite has become established.

Perkinsus marinus, Anadara tuberculosa, Mytella strigata, Crassostrea, protista, Pozo Chino, susceptibilidad Perkinsus marinus, Anadara tuberculosa, Mytella strigata, Crassostrea, protist, Pozo Chino, susceptibility CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA CIENCIAS DE LA TIERRA Y DEL ESPACIO OCEANOGRAFÍA OCEANOGRAFÍA ACUICULTURA MARINA OCEANOGRAFÍA ACUICULTURA MARINA