Plant Gene and Trait 2024, Vol.15, No.6, 295-304 http://genbreedpublisher.com/index.php/pgt 297 3.2 Progress in genotypic evaluation Genotypic evaluation has advanced significantly with the use of molecular markers and genome sequencing technologies. For example, genotyping-by-sequencing (GBS) was used to analyze 1628 Ethiopian sorghum accessions, identifying distinct cluster groups and candidate genes associated with adaptation to abiotic factors (Girma et al., 2020). The USDA-NPGS Ethiopian sorghum germplasm collection was characterized using 148 476 SNP markers, revealing high genetic diversity and unique genetic profiles for each accession (Cuevas et al., 2016). Whole-genome sequencing (WGS) of the sorghum Association Panel (SAP) identified over 43 million variants, enhancing the understanding of genomic diversity and enabling the identification of novel genomic associations for important traits (Figure 1) (Boatwright et al., 2022). Figure 1 Genome-wide associations for plant height (Adopted from Boatwright et al., 2022) Image caption: (a) and tannin content (b) using linear mixed models in GEMMA. Horizontal lines with solid, dotted, and dashed patterns represent the Bonferroni-adjusted threshold of 0.05 for SNPs, indels, and CNVs, respectively. Vertical dotted lines indicate the positions of known genes and loci for height (Dw), maturity (Ma), and tannin (Tan) (Adopted from Boatwright et al., 2022) 3.3 Application cases of evaluation to illustrate the contribution to sorghum germplasm improvement The evaluation of sorghum germplasm has led to significant improvements in breeding programs. For instance, the development of a core subset of 387 lines from the Ethiopian sorghum germplasm has facilitated the identification of candidate genes for abiotic stress tolerance, which can be exploited for breeding more resilient sorghum varieties (Girma et al., 2020). The mini core collection developed by ICRISAT has been extensively evaluated for agronomic traits, aiding in the identification of accessions with desirable characteristics for crop improvement (Upadhyaya et al., 2009). Additionally, the genomic characterization of the USDA-NPGS Ethiopian sorghum germplasm has provided valuable resources for sorghum breeders, enabling the effective screening and selection of specific populations for breeding programs (Cuevas et al., 2016). These efforts demonstrate the critical role of phenotypic and genotypic evaluations in enhancing the utilization and improvement of sorghum germplasm resources. 4 Classification and Organization of Sorghum Germplasm Resources 4.1 Classification of germplasm resources based on phenotypic and genotypic data The classification of sorghum germplasm resources involves both phenotypic and genotypic data to ensure a comprehensive understanding of the genetic diversity and potential of the crop. Phenotypic characterization includes the assessment of various morphological and agronomic traits such as plant height, panicle length, grain yield, and resistance to biotic and abiotic stresses. For instance, a study on Ethiopian sorghum germplasm revealed significant phenotypic diversity across different agro-climatic regions, highlighting the association of important traits with specific environments (Girma et al., 2020). Similarly, the evaluation of sorghum germplasm from the Eastern Highlands of Ethiopia showed a wide range of morpho-agronomical diversity, which is crucial for conservation and improvement efforts (Mulima et al., 2018).
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