Evaluation of morphological and yield-related traits in rice (Oryza sativa L.) germplasm under irrigated conditions

Introduction

Rice (Oryza sativa L.) is one of the most important cereal crops and belongs to the tribe Oryzeae, sub-family Pooideae, under the family Poaceae (Gramineae). According to modern biosystematic classification, the genus Oryza is divided into several sections, and O. sativa is belonging in the series Sativa of section Sativae. It is an Asian species with a diploid chromosome number of 2n = 24 and possesses the AA genome. The genus Oryza comprises approximately 24 species, which are naturally distributed across tropical and subtropical regions of the world [1] . Rice is one of the most important food crops in the world and serves as a major pillar of global food security. It is the staple diet for more than half of the world's population, with nearly four billion people relying on rice as their primary source of food. Owing to its high nutritional value, rice contributes approximately 20% of the daily caloric intake and 15% of the protein requirement for the global population [2] . Morphological characteristics are important determinants of plant growth, development, and final grain yield in rice. Traits such as plant height, number of tillers, leaf size, leaf orientation, internode length, and biomass production influence the plant's capacity to capture solar radiation, efficiently utilize available water and nutrients, and sustain effective grain filling. Consequently, the assessment of these morphological attributes is essential for evaluating the yield potential of different rice genotypes. Rice cultivars with high yield potential are generally characterized by higher chlorophyll content and enhanced photosynthetic capacity, which contribute to greater biomass accumulation and improved grain production [3] . Increased photosynthetic efficiency enhances plant growth and overall productivity [4] , whereas higher biomass production provides a strong foundation for achieving superior grain yield [5] . The spatial arrangement of the upper leaves and the positioning of panicles within the plant canopy play a vital role in maintaining an efficient source-sink balance in rice. Panicles bearing nearly 150 spikelets are considered desirable because they enhance the sink capacity and thereby contribute to higher yield potential [6] . Among all leaves, the flag leaf is the most important photosynthetic organ during the grain-filling stage and makes a major contribution to grain development, resulting in increased grain weight. Rice plants possessing broad and erect flag leaves are generally associated with superior grain yield. Besides supporting the translocation of photosynthates from vegetative tissues to developing grains, an optimum flag leaf angle together with a higher leaf area index during the grain-filling period improves spikelet fertility and facilitates the efficient movement of assimilates, ultimately enhancing grain production [7] .

Materials and Methods

A field experiment was conducted during the kharif season of 2025 at Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.), India, using 33 rice (Oryza sativa L.) germplasm under irrigated conditions. The experiment was laid out in an alpha lattice design with two replications. Twenty-three-day-old seedlings were transplanted at a spacing of 20 × 15 cm (row-to-row × plant-toplant). Recommended fertilizer doses of N, P₂O₅ and K₂O were applied at 120:60:40 kg ha⁻¹. All recommended agronomic practices were followed during the crop growth period, and no prominent disease incidence was observed. Data were recorded on plant height (cm), number of tillers plant⁻¹, number of leaves plant⁻¹, leaf area (cm²), flag leaf angle (°), 1000-grain weight (g), economic yield (g m⁻²), biological yield (g m⁻²) and harvest index (%). Weather data on temperature, relative humidity, rainfall and rainy days during the crop growing season from June to November 2025 are presented in Table 1. A total rainfall of 1165.4 mm was received during the experimental period.

Results and Discussion

Data on morphological and yield-related attributes of the crop are presented in Table 2. Significant differences were observed among the 33-rice germplasm for these characters at their respective growth stages. Plant height in the majority of commercial rice varieties generally ranged from 1 to 2 m. However, excessive plant height may increase the risk of lodging, particularly under heavy rainfall during the early crop season. Therefore, reduction in plant height is considered desirable for improving lodging resistance. A negative association between plant height and grain yield has also been reported, which may be attributed to competition among sink components for the limited photosynthates produced by the source organs [8] .

Number of tillers plant [-1] at flowering

Number of tillers per plant was recorded at the flowering stage, and significant differences were observed among the tested germplasm. The recorded value ranged from 16.33 to 7.67. Highest number of tillers per plant was attained by germplasm IR24MD2916 (16.33), followed by IR24MD3059 (16.17) and IR24MD3928 (15.50). Lowest number of tillers per plant was attained by germplasm IR24MD2982 (7.67), followed by IR153967 (8.16) and IR24MD3137 (8.34).

Excessive tillering may lead to a higher rate of tiller abortion, smaller panicles and poor grain filling, whereas inadequate tillering can result in fewer productive panicles and consequently reduce grain yield. This indicates that an optimum number of tillers is essential for achieving better yield performance in rice [9] .

Number of leaves plant -1 at flowering

Number of leaves per plant was recorded at the flowering stage, and significant differences were observed among the tested germplasm. The recorded value ranged from 34.50 to 66.50. Highest number of leaves per plant was attained by germplasm IR24MD3059 (66.50), followed by IR24MD2916 (65.33) and IR24MD2990 (64.50). Rice plants generally retain about five functional leaves from panicle initiation to heading, highlighting the importance of maintaining physiologically active leaves during the reproductive phase [10] .

Leaf area per plant was recorded at the flowering stage, and significant differences were observed among the tested germplasm. The recorded value ranged from 2931.51 cm 2 to 1511.75 cm 2 . Highest leaf area was measured by germplasm IR24MD3928 (2931.51 cm 2 ), followed by IR24MD2916 (2691.81 cm 2 ) and IR24MD2911 (2575.80 cm 2 ). Lowest leaf area was measured by germplasm IR24MD2982 (1511.75 cm 2 ), followed by IRRI104 (Check) (1560.13 cm 2 ) and IR24MD3957 (1579.86 cm 2 ). Excessive leaf area may result in increased mutual shading within the canopy, thereby reducing canopy photosynthesis and limiting sink development. Thus, an optimum leaf area is important for maintaining efficient light interception and photosynthetic activity [11] .

Flag leaf angle ([o]) at flowering

Flag leaf angle was recorded at the flowering stage, and significant differences were observed among the tested germplasm. Flag leaf angle plays an important role in determining grain yield, as it is closely associated with leaf length and may influence canopy architecture and light interception [12] .

Test weight (1000 seeds)

Test weight was recorded at the physiological maturity stage, and significant differences were observed among the tested germplasm. The recorded value ranged from 27.17 g. to 13.79 g. Highest test weight was measured by germplasm IR16A3891(Check) (27.17 g.), followed by IR24MD3135 (26.47 g.), IR24MD2830 (23.15 g.). Lowest test weight was measured by germplasm IRRI168 (Check) (13.79 g.), followed by IR24MD2911 (15.00 g.), DDR Dhan 44 (Check) (15.10 g.).

It represents the weight of an individual seed; however, direct measurement is difficult due to the small size of individual seeds [13] .

Economical yield(g/m 2 ) Economic yield was recorded at the physiological maturity stage, and significant differences were observed among the tested germplasm. The recorded value ranged from 1071.62 g/m 2 to 470.24 g/m 2 . Highest economic yield was measured by germplasm IR24MD3928 (1071.62 g/m 2 ), followed by IR24MD2916 (1062.27 g/m 2 ), and IR24MD2911 (1021.97 g/m 2 ). Lowest economic yield was measured by germplasm IR24MD3951 (470.24 g/m 2 ), followed by IR24MD2982 (488.90 g /m²), and IR24MD2927 (519.59 g /m²). Swarna exhibited higher yield potential, as reflected by its greater yield and higher values for yield-related traits, particularly the number of tillers and panicles, across all three environmental conditions [14] .

Biological yield(g/m 2 ) Biological yield was recorded at the physiological maturity stage, and significant differences were observed among the tested germplasm. The recorded value ranged from 2496.76 g /m² to 1034.06 g /m². Highest biological yield was measured by germplasm IR24MD2830 (2496.76 g /m²), followed by IR24MD2916 (2368.88 g /m²), and IR24MD3928 (2360.25 g /m²). Lowest biological yield was measured by germplasm IR24MD3951 (1034.06 g /m²), followed by IR24MD2927 (1238.68 g /m²), and IR24MD2989 (1354.78 g /m²). A linear relationship was observed between plant biomass production and water use efficiency [15] .

Harvest index was recorded at the physiological maturity stage, and significant differences were observed among the tested germplasm. The recorded value ranged from 46.11% to 25.74%. Highest harvest index was measured by germplasm IR24MD2972 (46.11%), followed by R24MD2911 (46.04%), and IR24MD3059 (45.97%). Lowest harvest index was measured by germplasm IR24MD2830 (25.74%), followed by IR24MD2982 (29.86%), and IR24MD1858 (32.98%).

The number of fertile grains per panicle and harvest index showed a significant and positive association with grain yield. Furthermore, both traits exhibited a high direct effect on grain yield, indicating their importance as potential selection criteria for improving yield in rice [16] . Correlation analysis revealed significant associations among several morphological and yield-related traits of the rice germplasm (Table 3). Number of tillers per plant exhibited a highly significant and positive correlation with number of leaves per plant (r = 0.963**) and leaf area (r = 0.663**), indicating that genotypes producing more tillers also tended to maintain a greater number of leaves and larger leaf area. Similarly, number of leaves per plant showed a highly significant positive association with leaf area (r = 0.648**), suggesting that increased leaf production contributed to greater total leaf area. Economic yield exhibited a significant positive correlation with number of tillers per plant (r = 0.419*) and number of leaves per plant (r = 0.406*), while its association with leaf area was highly significant and positive (r = 0.587**). This indicates that greater tillering, leaf production and leaf area may contribute to enhanced assimilatory capacity and ultimately higher economic yield in rice. Biological yield was significantly and positively correlated with leaf area (r = 0.427*) and showed a highly significant positive association with economic yield (r = 0.749**), indicating the important contribution of vegetative biomass accumulation towards final economic productivity. Harvest index exhibited a significant negative correlation with plant height (r = -0.382*) and a significant positive correlation with economic yield (r = 0.416*), suggesting that comparatively efficient partitioning of biomass towards economic yield was associated with higher harvest index. In contrast, plant height showed a non-significant negative association with economic yield (r = -0.232). Test weight showed non-significant correlations with most of the studied traits, including economic yield (r = -0.233). Overall, the correlation analysis indicated that number of tillers per plant, number of leaves per plant and leaf area were important traits associated with economic yield, while leaf area and economic yield also contributed substantially to biological yield. These relationships may be useful in identifying desirable traits as selection criteria in rice breeding programmes.

Conclusion

The study revealed considerable variation among the rice germplasm for plant height, tiller number, number of leaves, leaf area, flag leaf angle, test weight, economic yield, biological yield and harvest index. The observed differences indicated substantial scope for selection of superior genotypes based on yield and associated morpho-physiological traits. Among the studied traits, higher tiller number, leaf number, leaf area, biological yield and harvest index were important contributors to productivity. The superior performance of selected germplasm for economic and biological yield suggests their potential for utilization in rice improvement programmes. Therefore, these morphophysiological and yield-related traits can be considered important selection criteria for developing high-yielding rice genotypes under irrigated conditions.

Acknowledgement

AcknowledgementThe authors sincerely acknowledge the support and cooperation of the Department of Plant Physiology, College of Agriculture, Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.), India, for assistance in field management, observations, and data collection. The authors also express their gratitude to the reviewers and editor for their valuable suggestions and constructive comments in improving the manuscript.

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