Correlation assessment of morphophysiological and biochemical traits with seed yield in linseed (Linum usitatissimum L.) under irrigated and utera conditions

Introduction

Linum usitatissimum L., commonly known as flax or linseed, belongs to the Linaceae family and has a chromosome number of 2𝑛 = 30. It is an annual plant growing 30-100 cm tall, with a main stem and shallow, branching taproot that can extend 90-120 cm into light soils. In dense planting for fiber production, it tends to produce a single stem, while sparse planting encourages branching. The fruit is a five-celled capsule containing around ten seeds (Bisen et al., 2025) [1] . It is an important rabi oilseed crop valued for its nutrientrich oil and industrially useful fibre. In India, it is predominantly grown under rainfed conditions (accounting for about 63% of the area) and in rice-fallows under the utera or paira system (25%), while only a minor fraction (17%) receives assured irrigation. The utera cropping system relies entirely on the receding residual moisture left after the rice harvest (Bhowmick et al., 2005) [2] . Under such moisture-limited conditions, the crop frequently faces terminal drought and heat stress, which negatively impacts plant growth, physiological functioning, and ultimately, the seed yield (Anastasiu et al., 2016) [3] . Seed yield itself is a highly complex, polygenic trait that is heavily influenced by environmental variations. Direct selection for higher yield is often difficult because of strong genotype-by-environment interactions. Therefore, plant breeders rely on indirect selection by identifying secondary morpho-physiological and biochemical traits that are genetically linked to yield. Understanding the degree and direction of association between yield and these component traits is essential for designing an effective breeding program. By assessing these correlations under both irrigated and utera conditions, researchers can identify the specific plant characteristics that contribute to drought adaptation and yield stability. The objective of this study was to examine the correlation of individual morpho-physiological and biochemical parameters with seed yield to help for linseed improvement.

Materials and Methods

The experimental material comprised twenty diverse linseed genotypes, including two checks, PKV NL-260 and LSL-93, obtained from AICRP on Linseed, College of Agriculture, Nagpur. The field experiment was conducted during rabi 2024-25 at the AICRP on Linseed farm, College of Agriculture, Nagpur. The experiment was laid out in a factorial randomized block design with three replications under irrigated and utera conditions. A spacing of 30 cm × 10 cm was maintained, with a gross plot size of 3.00 m × 2.20 m. Recommended cultural practices were followed to raise a healthy crop under both conditions. Five plants were randomly selected from each plot for recording plant-based observations. Plant height (cm) at 60 DAS, Number of leaves at 60 DAS, total dry weight (g plant -1 ) at 90 DAS were recorded. Biochemical traits like total chlorophyll content in leaves (mg g -1 ) by colorimetric method were recorded at 60 DAS and seed oil content (%) was estimated by soxhlet's procedure. At harvest, test weight (g), harvest index (%), and seed yield per hectare (qt) were recorded. Pearson's correlation coefficients were calculated using the mean data of the different characters to evaluate their association with seed yield, with significance tested at the 5% and 1% levels of probability according to standard statistical methodology. The experimental data were statistically analysed according to the procedure described by Panse et al. (1967) [4] .

Results and discussion

The correlation analysis provided deep insights into how individual growth and biochemical parameters influence seed yield. The perhectare seed yield showed a positive relationship with all the evaluated morpho-physiological and biochemical traits. A detailed, trait-bytrait discussion of these correlations is presented below. (Table No.1).

Plant height at 60 DAS

Among all the studied parameters, plant height at 60 DAS exhibited the strongest and most highly significant positive correlation with seed yield per hectare (r 2 = 0.68**). Plant height also displayed a significant positive correlation with total dry weight (r 2 = 0.49*). The 60 DAS stage marks a crucial phase where the plant transitions from vegetative growth to reproductive development. A taller and more robust main stem offers a larger structural framework, allowing the plant to accommodate more primary and secondary branches. This directly translates into a higher capsule-bearing capacity. Furthermore, strong vertical growth under utera conditions indicates better earlystage vigor, helping the plant establish itself before residual soil moisture depletes. Similar findings were reported by Kumar (2016) [5] and Patel et al. (2025) [6] .

Number of leaves at 60 DAS

The number of leaves per plant at 60 DAS showed a significant positive association with seed yield (r 2 = 0.46*). It also possessed a strong positive inter-correlation with total dry weight (r 2 = 0.67**) and total chlorophyll content (r 2 = 0.55*). Leaves are the primary photosynthetic organs of the plant. A higher number of leaves results in a denser canopy and an optimal leaf area index, maximizing the interception of sunlight. In moisture-limited utera conditions, a well-developed canopy is highly beneficial because it provides ground cover, shading the soil and reducing direct moisture evaporation. This ensures that the plant can sustain carbon assimilation and produce more photosynthates to feed the developing seeds. These results are consistent with the findings of Khatun et al. (2023) [7] .

Total dry weight at 90 DAS

The accumulation of dry matter at 90 DAS recorded a highly significant positive correlation with seed yield per hectare (r 2 = 0.65**). Total dry weight serves as a direct indicator of the plant's overall physiological efficiency, growth vigor, and net assimilation over its lifespan. While adequate irrigation naturally favors continuous dry matter production, maintaining high biomass under utera conditions requires significant drought tolerance. Genotypes that accumulate higher total dry weight possess a greater source capacity. During the grain-filling stage, these stored reserves are effectively mobilized to the capsules, leading to higher seed yields. Similar findings were reported by Dabalo et al. (2020) [8] and Kunte et al. (2024) [9] .

Total chlorophyll content at 60 DAS

Total leaf chlorophyll content at the 60 DAS stage exhibited a significant positive correlation with seed yield (r 2 = 0.48*) and a highly significant correlation with total dry weight (r 2 = 0.62**). Chlorophyll is the fundamental pigment driving photosynthesis. As the crop enters the reproductive phase around 60 DAS, sustained photosynthetic activity is crucial for capsule formation and seed filling. Under moisture stress, plants often experience early leaf yellowing and pigment degradation. A positive correlation suggests that genotypes displaying a "stay-green" trait retaining their chlorophyll content for a longer duration can continue to produce assimilates during critical reproductive stages, thereby safeguarding the final yield. These results are consistent with the findings of Khatun et al. (2023) [7] .

Seed oil content %

Seed oil content exhibited a weak positive and non-significant correlation with seed yield per hectare (r 2 = 0.14). The absence of a significant correlation signifies that the biological processes governing lipid synthesis (oil content) function independently of the pathways that drive total seed biomass accumulation. From a crop improvement standpoint, this is highly advantageous. It implies that researchers can confidently select for high-yielding varieties without worrying about a negative trade-off causing a decline in seed oil quality. These observations are consistent with those of Singh et al. (2018) [10] .

Days to maturity

The duration required for the crop to reach maturity displayed a positive but non-significant association with seed yield (r 2 = 0.25). The crop matured faster under utera conditions (111.72 days) compared to irrigated conditions (118.97 days), acting as a natural mechanism to escape terminal drought. However, the weak correlation with yield suggests that crop duration was not the primary deciding factor for productivity in this experiment. High-yielding genotypes achieved their performance through superior physiological mechanisms like high biomass and chlorophyll retention rather than strictly by altering their growth cycle. The evaluation of crop duration and its varying impact on productivity under different environmental stresses has been documented in the variability assessments by Triveni et al. (2024) [11] .

Test weight

The test weight showed a positive but non-significant correlation with seed yield per hectare (r 2 = 0.42). While test weight decreased from 7.61 g under irrigated conditions to 7.07 g under utera conditions due to moisture limitations, this trait is generally under strong genetic control and remains relatively stable. The lack of statistical significance indicates that variations in overall seed yield among these twenty genotypes were primarily driven by differences in the total number of capsules per plant, rather than the individual size or weight of the seeds. The relative stability of test weight and its complex interaction with overall seed yield have been similarly explored by Akbar et al. (2003) [12] .

Harvest index

Harvest index (HI), which measures the efficiency of a plant in converting its total biological yield into economic seed yield, exhibited a significant positive correlation with productivity (r 2 = 0.55*). Additionally, it was positively correlated with test weight (r 2 = 0.47*) and dry weight (r 2 = 0.54*). This relationship highlights that merely producing a large vegetative mass is not enough; the plant must also efficiently partition those resources into the seeds. Under utera conditions, moisture stress often limits the development of reproductive parts. Therefore, genotypes with a high harvest index are highly desirable, as they demonstrate an efficient source-to-sink translocation mechanism even under stress. These observations are consistent with those of by Kunte et al. (2024) [9] and Patel et al. (2025) [6] .

Conclusion

The correlation analysis of twenty diverse linseed genotypes underscores the critical importance of vigorous vegetative growth and physiological efficiency for realizing high seed yield. The highly significant positive correlations of yield with plant height at 60 DAS (r 2 = 0.68**) and total dry weight at 90 DAS (r 2 = 0.65**) indicate that early establishment and sustained biomass production are the primary drivers of productivity. Additionally, positive associations with harvest index (r 2 = 0.55*), total chlorophyll content at 60 DAS (r 2 = 0.48*), and leaf number at 60 DAS (r 2 = 0.46*) highlight the necessity of an active photosynthetic canopy and efficient dry matter partitioning to the seeds, especially under moisture-limited utera conditions. Because test weight (r 2 = 0.42), days to maturity (r 2 = 0.25), and seed oil content (r 2 = 0.14) showed non-significant correlations with yield, improvement programs can effectively target vegetative and partitioning traits to enhance total seed yield without negatively impacting oil quality. These findings provide valuable selection criteria for developing climate-resilient linseed cultivars suited for varied moisture environments.

Acknowledgement

AcknowledgmentsI extend my heartfelt gratitude to all those who have been instrumental in the successful completion of this research endeavor. I would like to acknowledge the support of my research guide who shared their expertise and perspectives. My sincere thanks to Professor, agricultural botany section for providing the necessary resources and facilities.

References

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