Correlation studies on growth, flowering and yield attributes of cucumber (Cucumis sativus L.) cv. Malini under plant growth regulator treatments

Introduction

Cucumber (Cucumis sativus L.) is one of the most important and widely cultivated vegetable crops of the family Cucurbitaceae with a chromosome number of 2n = 14. It is a monoecious, trailing or climbing annual vine (Baily, 1969) with triangular-ovate leaves, lateral tendrils, and flowers developing at leaf axils, producing cylindrical fruits. Being day-neutral, cucumber can be grown throughout the year, and under protected cultivation such as shade nets, multiple crops can be harvested annually, increasing its economic importance. Yield in cucumber is a complex trait influenced by vegetative growth, flowering behavior, and reproductive development. Parameters such as vine length, leaf area, branching pattern, flower sex ratio, and timing of flowering not only determine plant vigor but also directly affect fruit set, fruit number, and fruit weight. Therefore, understanding the relationships among these traits is crucial for designing effective crop management strategies. Plant growth regulators (PGRs), including gibberellic acid (GA₃), Ethrel, and salicylic acid, are widely used to modify vegetative and reproductive traits in cucumber. PGRs can enhance vine elongation, leaf expansion, branch development, femaleness, and flowering efficiency, ultimately improving yield and quality. However, the effect of PGRs is often dose-and stagedependent, and their influence on trait interactions remains underexplored. Correlation analysis provides a quantitative measure of associations among vegetative, flowering, and yield traits, allowing identification of traits that directly or indirectly influence yield. Such analyses are essential for selecting key growth and reproductive traits that contribute most to productivity, especially in monoecious crops like cucumber where flower sex expression plays a critical role. In view of this, the present study aim to provide insights into trait interrelationships and potential targets for improving yield through PGR application.

Materials and Methods

Experimental Site and Duration

The present study was conducted at the College of Horticulture, Mojerla. The experiment was carried out under shade net conditions to evaluate the effects of different concentrations of plant growth regulators (PGRs) on vegetative growth, flowering, and yield of cucumber (Cucumis sativus L.) cv. Malini.

Experimental Design and Treatments

The experiment was laid out in a Completely Randomized Design (CRD) with three replications. The study consisted of 10 treatments, including:

• GA₃: 75, 150, and 250 ppm • Ethrel: 100, 200, and 300 ppm • Salicylic acid: 75, 150, and 250 ppm • Control: water spray

Crop Establishment and Spacing

Seeds were sown on well-prepared raised beds with dimensions of 100 × 40 × 50 cm (width × height × distance between beds) during the first week of December. Two seeds per hill were sown, maintaining a plant spacing of 180 × 30 cm. Standard agronomic practices, including irrigation, nutrient application, and pest management, were applied uniformly across all treatments.

Application of Plant Growth Regulators

PGR treatments were applied as foliar sprays at 20 and 35 days after sowing (DAS), ensuring uniform coverage of the canopy.

Data Collection

Data were recorded from five randomly selected plants per plot. Observations included:

• Vegetative growth parameters: vine length (cm), number of primary branches per vine, length of primary branches (cm), number of leaves per vine, number of nodes per vine, internodal length (cm), and leaf area (cm²). • Phenological and flowering traits: days to initiation of flowering, days to first female flower appearance, node number of first female flower, days to 50% flowering, sex ratio (male:female), and days to first harvest.

Phenological data were collected at 30, 60, and 90 DAS, while growth and yield traits were recorded at appropriate growth stages.

Statistical Analysis

The mean values of all measured traits were calculated and subjected to statistical analysis following the methods of Panse and Sukhatme (1985) [11] . To assess relationships among traits, Pearson's correlation coefficients were computed between vegetative, flowering, and yield parameters. Significance of correlation was tested at 5% and 1% levels. The analysis allowed interpretation of associations between growth attributes, flowering behavior, and fruit yield. [13] in squash and Murthy et al. (2007) [9] in gherkin.

Results and Discussion

The number of leaves per vine showed a strong positive correlation with leaf area (r = 0.81**), indicating that increased leaf production directly contributed to enhanced photosynthetic surface area. Comparable results were reported by Chaurasiya et al. (2016) [4] in muskmelon and Ansari and Chowdhary (2018) [2] in bottle gourd.

Similarly, number of primary branches per vine was positively associated with vine length, leaf number, and leaf area, confirming that lateral branching plays a vital role in improving overall vegetative vigour, as also reported by Mir (2007) [8] in cucumber.

These positive associations clearly indicate that plant growth regulators inducing vigorous vegetative growth enhanced multiple growth attributes simultaneously, which ultimately contributed to improved yield potential.

Relationship between Growth, Flowering Traits and Fruit Yield

The correlation coefficients between growth, flowering, yield attributes and fruit yield are presented in Table 2. Fruit yield exhibited strong positive correlations with most vegetative and yield-contributing traits, while flowering delay parameters showed negative associations. Influence of vegetative traits on fruit yield Fruit yield showed a highly significant positive correlation with vine length (r = 0.90**), number of leaves per vine (r = 0.90**), leaf area (r = 0.80**), and number of primary branches per vine (r = 0.87**), indicating that vigorous vegetative growth enhanced assimilate production and translocation towards developing fruits. Similar relationships between vegetative growth and yield have been reported by Ajay et al. (2018) [1] in cucumber and Shafeek et al. (2016) [13] in squash.

The length of primary branches recorded the strongest positive association with fruit yield (r = 0.91**), suggesting that longer lateral branches provided more sites for female flower initiation and fruit set, thereby increasing yield. This finding corroborates the observations of Mir ( 2007) [8] and Mehdi et al. (2012) [7] , who reported that enhanced branching favoured yield improvement in cucumber.

Influence of flowering behaviour on fruit yield (early vs delayed interpretation)

Days taken to initiation of flowering exhibited a significant negative correlation (r = -0.69**) with fruit yield, clearly indicating that early initiation of flowering (fewer days) resulted in higher fruit yield, whereas delayed flowering (more days) adversely affected yield. Early flowering allows plants to enter the reproductive phase sooner, extending the effective fruiting period, as also reported by Ajay et al. ( 2018) [1] and Pandey et al. (2016) [10] in cucumber. Similarly, days taken to first female flower appearance showed a negative correlation (r = -0.35*), indicating that early appearance of female flowers enhanced yield, while delay in female flower emergence reduced productivity. Comparable results were reported by Mir (2007) [8] and Mehdi et al. (2012) [7] , who observed that early femaleness was crucial for higher yield in cucumber. The node number of first female flower appearance exhibited a negative association (r = -0.26), suggesting that appearance of female flowers at lower node numbers (early nodes) was more favorable for fruit yield than appearance at higher nodes. Similar findings were reported by Ansari and Chowdhary (2018) [2] in bottle gourd.

The sex ratio (male:female) was negatively correlated with fruit yield (r = -0.28), indicating that a lower sex ratio (higher proportion of female flowers) resulted in increased yield, while higher male dominance reduced fruit production. These observations are in agreement with Mir (2007) [8] and Mehdi et al. (2012) [6] in cucumber.

Influence of yield components on fruit yield

Fruit yield showed a highly significant positive correlation with number of fruits per vine (r = 0.90**) and fruit weight (r = 0.85**), suggesting that yield improvement was primarily governed by fruit number, followed by fruit size. Similar associations between yield components and total yield were reported by Ghani et al. (2018) [5] , and Sapkota et al. (2020) [12] in cucurbitaceous crops.

Conclusion

The present investigation clearly demonstrated that fruit yield in cucumber is a complex trait influenced by multiple interrelated growth and flowering parameters. Early flowering, early appearance of female flowers at lower nodes, and a lower male:female ratio, combined with vigorous vegetative growth and enhanced branching, played a decisive role in maximizing fruit yield under shade net conditions.