Genetic variability and selection prospects among upland rice genotypes under Kharif conditions in peninsular India

Introduction

Upland rice is cultivated without standing water and therefore experiences greater dependence on rainfall distribution, soil-water storage and the duration of the effective growing season than irrigated lowland rice. In such environments, breeding progress depends on identifying germplasm with sufficient genetic variation and on distinguishing traits whose phenotypic expression reliably reflects inherited differences. Genetic variability, broad-sense heritability and expected genetic advance are consequently used together to assess the likely response to selection rather than relying on mean performance alone (Seyoum et al., 2012; Demeke et al., 2023) [3,6] . Grain yield is a complex quantitative character influenced by several component traits and by genotype × environment interaction. A diverse germplasm set can provide alternative combinations of flowering duration, plant stature, panicle architecture and grain attributes from which selection indices may be constructed. Studies in upland and transplanted rice have similarly demonstrated that significant genotype effects and coordinated estimates of variance, heritability and genetic advance are useful for identifying selection targets (Seyoum et al., 2012; Faysal et al., 2022) [4,6] . The present paper therefore isolates the genetic-variability objective of the thesis and asks: how much variation exists among the 40 entries, which traits are predominantly genetic in expression, and which genotypes merit further validation?

Materials and methods

The experiment was conducted during Kharif 2025 at the Experimental Farm of the Department of Genetics and Plant Breeding, College of Agriculture, VNMKV, Parbhani, Maharashtra, India. Forty upland rice genotypes obtained from CRRUS, Hazaribagh, and ICAR-IRRI, Hyderabad, were evaluated in a randomized block design with three replications. Each entry occupied two rows in a 4.5 m × 1.20 m plot, with 30 cm × 5 cm row-to-plant spacing. Recommended agronomic practices were followed throughout the crop season. Five competitive plants per genotype per replication were sampled for observations. This manuscript analyzes the 11 traits for which complete numerical summary tables were available: days to 50% flowering, days to maturity, plant height, tillers plant-1, panicle length, total spikelets panicle-1, test weight, grain length, grain breadth, length/breadth ratio and grain yield plant-1. The thesis methods chapter also describes filled and unfilled spikelets; because complete numerical estimates for those traits were not supplied in the summary tables, they were not reconstructed or included here. The randomizedblock model was used to test genotype effects. Genotypic variance (σ²g), phenotypic variance (σ²p), genotypic and phenotypic coefficients of variation (GCV and PCV), broad-sense heritability (h²b) and genetic advance as percent of mean (GA%) were interpreted using the frameworks of Burton and DeVane (1953) [2] and Johnson et al. (1955) [5] . In broad-sense form, h²b = σ²g/σ²p. GCV and PCV were calculated as 100√σ²g/mean and 100√σ²p/mean, respectively. The estimates reported here are transcribed from the thesis summary tables; no raw-plot reanalysis was performed.

Results and discussion

Genotypic differentiation and experimental precision

Genotype mean squares were highly significant for all 11 traits, establishing broad differentiation within the evaluated germplasm. The largest F-ratio occurred for plant height (192.979), followed by grain length (172.910), while tiller number showed the smallest but still highly significant Fratio (3.943). Grain yield plant-1 had an F-ratio of 93.824. Replication effects were reported as non-significant, supporting the interpretation that the observed differences were primarily associated with genotype rather than block heterogeneity. Similar genotype-level differentiation has been reported in upland rice collections by Seyoum et al. (2012) and Demeke et al. (2023) [3,6] .

Magnitude and nature of variability

The PCV exceeded the GCV for every trait, as expected when environmental variance contributes to phenotypic expression. The GCV-PCV difference was smallest for grain yield, plant height, grain length, flowering time and maturity, suggesting comparatively limited environmental masking at the genotype-mean level. The largest gap occurred for tillers plant-1, for which GCV was 14.416% and PCV was 21.382%; this pattern is consistent with the thesis interpretation that tillering should be selected using replicated progeny means rather than a single observed value. Grain yield plant-1 had the largest GCV (25.084%), followed by test weight (20.950%) and grain length (20.765%). In practical breeding terms, high GCV indicates substantial relative dispersion, but it does not by itself prove that selection will be effective. The more informative combination is high heritability with high expected gain. In the present population, grain yield, grain length, test weight, plant height, grain breadth and length/breadth ratio met that combined criterion, whereas tiller number combined high GA% with only moderate heritability.

Genotype performance and breeding utility

The genotype means indicated meaningful contrasts for phenology, architecture, grain attributes and yield. Gangavati Ageti was earliest for flowering (71.00 days) and maturity (87.67 days), whereas Sanchuriya Mutant-15 was latest for flowering (97.33 days) and CR Dhan-415 was latest for maturity (121.67 days). R-IR17A2891 had the highest total spikelet number (124.00) and grain yield (5.94 g plant-1). Hazaridhan combined high yield (5.84 g plant-1) with the longest and broadest grain, while CRR-433-1-1 was among the high-yielding entries and shared the highest mean tiller number with Hazaridhan.

Conclusions and breeding implications

The 40-genotype upland rice set contained substantial exploitable variability for all 11 analyzed traits. Grain yield plant-1 was especially promising as a direct selection target because it combined the highest GCV (25.084%), high broad-sense heritability (0.969) and the highest GA% (50.857%). Plant height, grain length, test weight, grain breadth and length/breadth ratio also showed high heritability with high expected gain, although each must be balanced against agronomic and market requirements. Tiller number requires a different selection strategy: its high GA% should not be interpreted as evidence of stable singleplant expression because heritability was only 0.455 and the PCV-GCV difference was large. In the next breeding cycle, selection should prioritize productive panicles and yieldrelated sink traits, with tiller number evaluated across replications and environments. R-IR17A2891, Hazaridhan and CRR-433-1-1 should be advanced to multi-location upland trials, but none should be recommended for release or broad cultivation solely on the basis of this one-season experiment.

References

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