Reproductive Biology and Genetic Parameters of Blue Pine: Insights into Germination, Growth and Breeding Potential

Background Pinus wallichiana often referred to as Bhutan pine, Himalayan pine or blue pine, A.B. Jackson is a five-needle pine belonging to the Pinaceae family that is indigenous to the Hindu Kush, Karakoram and Himalayan regions. Results Male and female strobili phenophases lasted 10–11 and 77–78 weeks, respectively. Cones were collected from 18 phenotypically superior trees across six locations to assess variability in morphological traits. Trees from Akhal exhibited the highest values for all measured traits, including tree height (28.9 m), DBH (47.7 cm), cone length (22.44 cm), cone weight (123.42 g), and seed weight (87.98 g). Seeds underwent cold stratification at 25-day intervals (0–125 days) at 4 ± 1°C to evaluate germination and seedling performance. Maximum germination (72.67%) and seedling vigor were observed at 100 days of stratification, while the Akhal genotype showed superior overall performance (germination 86.77%, vigor index 1048.18). High genetic variability was observed, with the highest GCV and PCV for dry root weight (51.40, 52.65 respectively). Heritability was highest for cone specific gravity (0.78) and seed morphological traits. Principal component analysis (PCA) revealed that the first two components explained 96.23% of the total variation, with cone weight and seed thickness as major contributors. Cluster analysis grouped genotypes into five clusters, with Cluster I exhibiting superior cone, seed, and seedling traits, indicating potential for selective breeding and genetic improvement programs.