Insights into the genetic architecture of complex traits in Napier grass (Cenchrus purpureus) and QTL regions governing forage biomass yield, water use efficiency and feed quality traits

Abstract

Napier grass is the most important perennial tropical grass native to Sub-Saharan Africa and widely grown in tropical and subtropical regions around the world, primarily as a forage crop for animal feed, but with potential as an energy crop and in a wide range of other areas. Genomic resources have recently been developed for Napier grass that need to be deployed for genetic improvement and molecular dissection of important agro-morphological and feed quality traits. From a diverse set of Napier grass genotypes assembled from two independent collections, a subset of 84 genotypes that best represents the genetic diversity of the collections were selected and evaluated for two years in dry (DS) and wet (WS) seasons under three soil moisture conditions: moderate water stress in DS (DS-MWS); severe water stress in DS (DS-SWS) and, under rainfed (RF) conditions in WS (WS-RF). Data for agro-morphological and feed quality traits, adjusted for the spatial heterogeneity in the experimental blocks, were collected over a two-year period from 2018 to 2020. A total of 135,706 molecular markers were filtered, after removing markers with missing values > 10% and a minor allele frequency (MAF) < 5 %, from the high-density genome-wide markers generated previously using the genotyping by sequencing (GBS) method of the DArTseq platform. A genome-wide association study (GWAS), using two different mixed linear model algorithms, identified more than 58 QTL regions and markers associated with agronomic, morphological and water-use efficiency traits. QTL regions governing purple pigmentation and feed quality traits were also identified. The identified markers will be useful in the genetic improvement of Napier grass through the application of marker-assisted selection and for further characterization and map-based cloning of the QTLs.

Genetic Diversity and Population Structure of a Rhodes Grass (Chloris gayana) Collection

“…In Napier grass, initially only 17% and 33% of the SilicoDArT and SNP markers, respectively, were mapped using the pearl millet genome [43]. However, more than 80% of the markers were subsequently mapped onto the Napier grass genome when it became available [44]. In addition, except for Setaria italica, the reference genomes were not assembled at the chromosome level.…”

Morphological characterization of Elephant grass (Pennisetum purpureum Schumach) ecotypes collected in Chiapas, Mexico

“…Taking into consideration the forage potential of the Napier grass (Rusdy, 2016;Wangchuk et al, 2015), the ILRI conducted a study of 345 genotypes, in order to analyze and compare genetic diversity between and within world collections. The results provide useful information for the management, conservation, improvement strategy, and improvement of the genetic diversity within the said collections (Muktar et al, 2021). In addition, evaluations of agronomic traits have been carried out (Kebede et al, 2016a) selecting cultivars with high biomass production (Cunha, 2011), as a result of their chemical composition and in vitro digestibility (Kebede et al, 2016b).…”