Genetic Diversity Assessment for Nutritional Traits of Ex-situ Finger Millet Collections

Technical Summary: Genetic Diversity Assessment for Nutritional Traits of Ex-situ Finger Millet Collections

Problem Statement
Finger millet (Eleusine coracana) is a critical subsistence crop in arid and semi-arid regions of Africa and Asia, valued for its high carbohydrate, energy, protein, and mineral content. It plays a vital role in addressing malnutrition, particularly deficiencies in iron (Fe), zinc (Zn), and protein among vulnerable populations. Despite its nutritional potential and status as a center of origin in Ethiopia, the crop remains underutilized for genetic improvement in breeding programs, which have historically prioritized agronomic traits like yield and drought tolerance over nutritional quality. There is a lack of comprehensive characterization regarding the genetic diversity of nutritional traits within ex-situ finger millet collections from various African countries, limiting the ability of breeders to select superior genotypes for biofortification.

Methodology
The study evaluated 200 finger millet accessions (genotypes) obtained from the Ethiopian Institute of Biodiversity, representing collections from Ethiopia, Zimbabwe, Eritrea, and Zambia. The experimental design utilized a 10 × 20 alpha lattice design with two replications across three locations (Maiaini, Zana, and Rama) in the Tigray region of Ethiopia over two growing seasons (2019/2020).

• Data Collection: Grain nutrient content was assessed for all genotypes. To ensure accuracy, pooled grain samples were cleaned to prevent contamination and analyzed using a near-infrared spectrophotometer (DA 720). The traits measured included moisture content, protein, starch, calcium (Ca), magnesium (Mg), iron (Fe), and zinc (Zn).
• Statistical Analysis: Data were analyzed using IBM-SPSS for t-tests and Pearson's correlation coefficients. Cluster analysis was performed using Ward's Linkage method and Squared Euclidean Distance in MINITAB v19, validated by Discriminant Analysis. Principal Component Analysis (PCA) was conducted using Past4.0 software to identify patterns of variation among the nutritional traits.

Key Results

• Genetic Variability: Significant variation (P < 0.001) was observed among the 200 genotypes for all nutritional traits.
  • Protein: Ranged from 5.15% to 9.33% (mean 6.43%). Genotype 203574 (from Zimbabwe) exhibited the highest protein content.
  • Minerals: Calcium ranged from 139 to 431 mg/100g; Magnesium from 120.85 to 525.50 mg/100g; Iron from 4.06 to 30.68 mg/100g; and Zinc from 0.11 to 4.89 mg/100g.
  • Top Performers: Genotypes 203574, 234160, 203259, 203257, and 203262 were identified as the highest performers for protein, calcium, magnesium, iron, and zinc, respectively. Notably, all top-ranking genotypes for these specific traits originated from Ethiopia, with the exception of the top protein genotype (203574) from Zimbabwe.
• Correlations: Iron content showed significant positive correlations with calcium, magnesium, and zinc. Calcium was strongly positively correlated with zinc (r = 0.62, P < 0.01). Protein content showed weak, non-significant negative correlations with most mineral traits.
• Cluster Analysis: The genotypes were grouped into six distinct clusters. Cluster I contained the most genotypes (73), including all 49 Zimbabwean accessions. Clusters V and VI contained genotypes with the highest mineral concentrations. Cluster V was characterized by high magnesium and iron, while Cluster VI showed elevated calcium, magnesium, zinc, and iron. The largest genetic distances were observed between clusters IV and VI, and II and VI.
• Principal Component Analysis (PCA): The first two principal components accounted for approximately 60.7% of the total variation. PC1 (40.27%) was primarily driven by magnesium, zinc, calcium, and moisture. PC2 (17.51%) was influenced by protein, starch, and iron.
• Geographical and Phenotypic Factors: Nutrient profiles varied by country of origin; Ethiopian genotypes generally had lower zinc and iron compared to Eritrean and Zimbabwean genotypes, though Ethiopian accessions showed high magnesium. Seed color also influenced nutrient content: brown and orange seeds had higher calcium and iron but lower magnesium, while brown and white seeds exhibited higher zinc compared to black and red seeds. Moisture, protein, and starch did not vary significantly by seed color.

Significance and Contributions
The study provides a foundational assessment of the genetic diversity of nutritional traits in African finger millet collections. By identifying specific genotypes with superior nutritional profiles (e.g., high calcium, iron, zinc, and protein), the research offers a direct resource for breeders to select parental lines for hybridization programs. The clustering of genotypes based on nutritional traits simplifies the selection process, allowing breeders to target specific clusters (such as V and VI) to combine desirable mineral traits.

The findings underscore the potential of finger millet as a vehicle for alleviating micronutrient malnutrition. The study concludes that integrating these high-nutrient genotypes into breeding programs, potentially through both conventional and molecular techniques, can accelerate the development of varieties that address the dual challenges of food security and nutritional health. Furthermore, the correlation between geographical origin and nutrient content suggests that germplasm collection strategies can be refined to target specific nutrient profiles. The authors emphasize that while the crop is a significant source of minerals, particularly calcium, future efforts should focus on enhancing local varieties rich in grain nutrients and exploring their application in composite flour technologies.