Phenotypic variation and genetic diversity assessment of proso millet (Panicum miliaceum L.) germplasm resources in northern Xinjiang

Characterizing genetic diversity in proso millet ( Panicum miliaceum L.) is essential for crop improvement and breeding programs. This study evaluated the genetic diversity, phenotypic variation, and population structure of 46 proso millet accessions using five qualitative and twelve quantitative traits across two growing seasons (2023-2024) in northern Xinjiang. Grain color showed the highest genetic diversity index (H′ = 2.064), while panicle type showed the lowest (H′ = 1.383). Green panicle color (84.78%), long panicle branch length (63.04%), lateral panicle type (71.74%), and yellow grain color (86.96%) were predominant. Grain yield (Y) and grain weight per panicle (GWP) exhibited the highest coefficients of variation (15.00% and 14.61%, respectively) and substantial genetic diversity indices (Y: H′ = 2.11; GWP: H′ = 2.12), indicating considerable selection potential. Grain yield was significantly positively correlated with grain weight per panicle (r = 0.901, P < 0.01 ) and main panicle length (r = 0.863, P < 0.01 ). Combined analysis of variance revealed highly significant genotypic effects for all agronomic traits, while genotype × environment interaction effects were non-significant for all traits, indicating stable genotype rankings across years. Broad-sense heritability estimates were very high for yield-related traits, with grain yield (H² = 0.998) and grain weight per panicle (H² = 0.996) demonstrating strong genetic control. Stepwise regression analysis identified grain weight per panicle and main panicle length as the primary yield predictors (R² = 0.91). Principal component analysis showed PC1 and PC2 explained 70.13% of total variation, representing vegetative vigor and yield capacity, respectively. Cluster analysis identified three groups with distinct trait profiles suitable for dual-purpose breeding, early-maturing cultivar development, and forage breeding, respectively. The evaluated germplasm possesses substantial genetic diversity, providing valuable resources for breeding parent selection in northern Xinjiang proso millet improvement programs.