Optimizing Gibberellic Acid Application to Enhance Seed Yield and Quality in Kenaf (Hibiscus cannabinus L.) under Top-Cutting Management

• Arju Miah

  Genetic Resources and Seed Division, Bangladesh Jute Research Institute, Manik Mia Avenue,

  Author

• Md Abdur Razzak Taohidi

  Genetic Resources and Seed Division, Bangladesh Jute Research Institute, Manik Mia Avenue, Dhaka-1207, Bangladesh.

  Author

• Md Al-Mamun

  Genetic Resources and Seed Division, Bangladesh Jute Research Institute, Manik Mia Avenue, Dhaka-1207, Bangladesh.

  Author

• Md Kamrujjaman

  Agronomy Division, Bangladesh Jute Research Institute, Manik Mia Avenue, Dhaka-1207, Bangladesh.

  Author

• Mohammad Shahadat Hossain

  Agronomy Division, Bangladesh Jute Research Institute, Manik Mia Avenue, Dhaka-1207, Bangladesh.

  Author

• Md Siddikur Rahman

  Training, Planning and Communication Division, Bangladesh Jute Research Institute, Manik Mia Avenue, Dhaka-1207, Bangladesh.

  Author

• Atik Hasan

  Breeding Division, Bangladesh Jute Research Institute, Manik Mia Avenue, Dhaka-1207, Bangladesh.

  Author

• Marium Khatun

  Department of Genetics and Plant Breeding, Gazipur Agricultural University, Gazipur-1706, Bangladesh.

  Author

• Muhammad Iqbal Hossain

  Plant Pathology Department, Patuakhali Science and Technology University, Patuakhali, Bangladesh.

  Author

Kenaf (H. cannabinus L.) is an economically important bast fibre crop whose seed production is often constrained by poor flowering, pod set and inconsistent seed quality under late-season cultivation in Bangladesh. This study aimed to evaluate the effect of foliar gibberellic acid (GA₃) applications on growth, yield and seed quality of two improved varieties (BJRI Kenaf 4 and BJRI Kenaf 5) under a standardized top-cutting regime. A two-factor factorial field experiment was conducted in a randomized complete block design with three replications during the kharif-late season. Treatments comprised five GA3 concentrations (25, 50, 75, 100 and 125 ppm) with an untreated control (0), applied twice at 7 and 14 days after top-cutting (30 DAT). Results indicated significant varietal, GA₃ and interaction effects on plant growth, reproductive traits and seed quality. Plant height increased progressively up to 75 ppm GA₃ (224–226 cm) before declining at higher concentrations. Branch number per plant peaked at 75–100 ppm (8.0–8.2 branches), with similar trends observed for pods per plant (50–52 pods), seeds per pod (28–29) and thousand-seed weight (32–32.5 g). Seed yield was maximized at 75 ppm GA3, reaching 1450–1470 kg ha^-¹, representing a 70% increase over the untreated control. Seed quality attributes improved with GA₃, with germination percentage (96–97%) and vigor index (≈2050) peaking at 100 ppm, while electrical conductivity of seed leachates was lowest at 75 ppm, indicating superior membrane integrity. Correlation analysis revealed strong positive associations between seed yield and plant height (r = 0.87), thousand-seed weight (r = 0.82), and vigor index (r = 0.76), highlighting their utility as selection criteria for yield improvement. Overall, moderate GA₃ concentrations (50–75 ppm) were most effective for enhancing seed yield and quality in kenaf under top-topping management. These findings provide a practical, low-cost strategy for improvement of kenaf seed production and offer a physiological basis for integration of GA3 into varietal improvement and seed technology programs.

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