Diversity and Plant Growth-Promoting Activities of Culturable Seed Endophytes in Abies pindrow (Royle ex D. Don) Royle: Their Role in Seed Germination and Seedling Growth.

Abies pindrow, a vital conifer in the Kashmir Himalayan forests, faces threats from low regeneration rates, deforestation, grazing, and climate change, highlighting the urgency for restoration efforts. In this context, we investigated the diversity of potential culturable seed endophytes in A. pindrow, assessed their plant growth-promoting (PGP) activities, and their impact on seed germination and seedling growth. We cultured 729 microbial isolates that were resolved into 30 bacterial and 18 fungal species across various phyla. All 48 isolates exhibited various PGP activities. Specifically, all the cultured isolates showed IAA activity with concentrations ranging from 2.07 to 8.453 μg/ml, while ammonia production ranged from 0.936 to 3.436 mM/ml. Only 18 isolates, predominantly fungi, tested positive for phosphate solubilisation. Additionally, 20 isolates exhibited the ability to inhibit the growth of Fusarium oxysporum f.sp. pini. We selected four bacterial and six fungal isolates, which showed positive results for all PGP activities, to evaluate their effects on seed germination and seedling growth. Notably, seed germination rates increased by 750.9% under bacterial and consortium treatments and by 550.45% under fungal treatment. The consortium treatment also led to a 96% increase in needle count, while bacterial treatment enhanced stem length by 55.4%. Furthermore, shoot biomass also showed a significant increase with both bacterial and fungal treatments, underscoring the potential of harnessing seed endophytes to boost A. pindrow seedling health and resilience. This study underscores the crucial role of seed endophytic diversity in enhancing seed germination, seedling growth, and forest restoration efforts.