Assessment of Genetic Variability and Path Analysis for Early Seedling Vigour Traits in Rice (Oryza sativa L.) under Laboratory and Dry Direct-Seeded Conditions
Saileela Maila
Department of Molecular Biology and Biotechnology, Sri Venkateswara Agricultural College, Acharya N.G. Ranga Agricultural University, Tirupati, India.
Sheshu Madhav Maganti *
ICAR- National Institute for Research on Commercial Agriculture (NIRCA), Rajahmundry, India.
Ramana Rao P.V.
Department of Genetics and Plant Breeding, Regional Agricultural Research Station, Maruteru, India.
Amaravathi Y.
Department of Molecular Biology and Biotechnology, Institute of Frontier Technology, Regional Agricultural Research Station, Tirupati, India.
Raghavendra T.
Department of Crop Physiology, Regional Agricultural Research Station, Nandyal, India.
*Author to whom correspondence should be addressed.
Abstract
Early seedling vigour (ESV) is a critical trait for successful crop establishment in direct-seeded rice systems. The present study evaluated 86 rice genotypes under laboratory and dry direct-seeded rice (DDSR) conditions to assess genetic variability and trait contributions to ESV through genetic parameter estimation and path coefficient analysis of seedling traits and vigour indices. Analysis of variance revealed significant differences among genotypes for all traits across both environments, reflecting the availability of substantial genetic diversity confirming a broad genetic base amenable to selection. The phenotypic coefficient of variation (PCV) was only marginally greater than the genotypic coefficient of variation (GCV), suggesting minimal environmental influence on trait expression. Broad-sense heritability estimates were uniformly high (>80%) and most traits displayed moderate to high genetic advance as percent of mean (GAM), indicating the predominance of additive gene action and scope for effective selection. The path coefficient analysis identified critical factors influencing the vigour indices root length was the primary driver of Seedling Vigour Index I in laboratory conditions, while shoot elongation traits dominated under dry direct-seeded rice environments. Seedling dry weight was the main direct contributor to Seedling Vigour Index II across both environments. Overall seedling dry weight, shoot length, root length and total seedling length emerged as reliable selection indices for improving ESV. The findings highlight the importance of multi-environment phenotyping in prioritizing traits and by identifying key contributors to early seedling vigour, this study provide key trait-based selection criteria for breeding rice genotypes adapted to direct-seeded cultivation systems.
Keywords: Early seedling vigour, Heritabilty(h2), GAM, path coefficient analysis, seedling vigour indices, dry direct-seeded rice