Root and Shoot Growth Dynamics as Determinants of Seedling Vigour in Rice (Oryza sativa L.)

Abstract

Early seedling vigour is a critical trait for successful crop establishment in rice, particularly under direct-seeded conditions where rapid and uniform emergence determines crop performance. The current research aimed to examine the influence of root and shoot growth on seedling vigour in 40 rice varieties (Oryza sativa L.). It was done in the laboratory of Institute of Agricultural Science, Department of Genetics and Plant Breeding, University of Calcutta, West Bengal. Germination percentage, root length, shoot length, seedling length, fresh weight, and dry weight of seedlings were recorded under controlled conditions, and vigour indices I and II were computed. Significant variability was observed among genotypes. The genotype Thubi had a maximum germination percentage of 97.5%, whereas the highest seedling length (23.52 cm) and vigour index I (2205) were obtained in the genotype CSR-38. The genotype Kanakchur showed the highest vigour index II (1.475) due to high dry matter accumulation. Positive correlations between seedling length and shoot length (r = 0.914) and seedling length and root length (r = 0.750) showed that coordinated elongation growth is one of the factors that contribute greatly to vigour at an early stage. On the other hand, biomass-related parameters is showed lower or even negative correlations with length-related parameters (dry weight vs seedling length, r = -0.389), indicating a trade-off between these two components. Multivariate analysis, including principal component analysis (PC1 = 47.23%, PC2 = 20.27%; % variance accounted for = 67.50%) and clustering analysis, additionally reinforced the presence of substantial genetic variation among the genotypes and the dominance of root-shoot growth characteristics in contributing towards seedling vigour. The CSR-38, Kakrisal, and Sabita genotypes have been recognized as superior genotypes with respect to early growth characteristics. The study illustrates the importance of a balance between root and shoot growth in contributing towards seedling vigour.