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Seed priming is the process of controlled hydration of seeds to a level that permits pre-germinative metabolic activity to proceed, but prevents actual emergence of the radicle. Seed priming with living bacterial inoculums is known as biopriming, which involves the application of plant growth promoting rhizobacteria (PGPR), resulting in enhanced germination, plant growth and disease résistance. Santalum album, L is a semi-root parasitic tree distributed in South India and is one of the most valuable and world renounced timber species. The poor germination rate combined with the long germination period is a major limitation in the regeneration of sandal. The present study was formulated to evaluate the effect of seed biopriming procedures on the germination and seedling performance of Santalum album. The biopriming agent’s viz. Pseudomonas fluorescens, Trichoderma viride, PGPR II at concentrations 25, 50, 75 and 100% and durations 1, 2,3,4,6 and 8 days and hydropriming for the same duration constituted the treatments of the study. The primed seeds were sown after the post priming storage for one day and one week. The results indicated that, for the post priming storage of one day, biopriming with T. viride at 100 % for 1 day (73.3%) followed by T viride at 75% for 1 day (35.96%) recorded the highest germination and the lowest was on biopriming with P. fluorescens at 50% for 2 days (0 %). Whereas, for post priming storage of one week, the highest germination was obtained on biopriming with T. viride at 100% for 3 days (82.72%), followed by P. fluorescens at 100% for 6 days (81.27%) and the lowest germination was obtained for the seeds bioprimed with PGPR II at 25% for 1 day and PGPR II at 100% for 3 days (0%). The shortest imbibition period was observed for the seeds bioprimed with P. fluorescens at 100% for 8 days (13 days) for one day storage and for the seed subjected to post priming storage of one week, for majority of the treatments, the imbibition period was reduced to 15 days.
The electrical conductivity of the seed leachates, was the maximum for the seeds hydroprimed for 3 days (1.469 dScm-1) and the lowest was in hydropriming for 6 days (0.172dScm-1) and for the seeds subjected to biopriming the range of electrical conductivity varies from 0.266 dS cm-1 (PGPR II at 100% for 1 day) to 1.32 dScm-1(T. viride at 75% for 6 days). Biochemical analysis of the seeds after priming indicated that the total carbohydrate was maximum on biopriming with T. viride at 25% for 3 days (0.772 mg g-1) and the lowest value was on biopriming with P. Fluorescens at 50% for 6 days (0.088 mg g-1). The total protein was maximum for the seeds treated with PGPR II at 25% for 4 days (0.077 mg g-1) and the lowest was for those treated with T. viride at 50% for 2 days (0.016 mg g-1).Crude fat content of the primed seeds was maximum for the seeds treated with P. fluorescens at 100% for 3 days (73.2%) and the minimum for those treated with T. viride at 75% for 1 day (34%). Seedling growth and biomass production were recorded at 30 and 180 days after transplanting. In the context of seedling attributes, the maximum seedling height is observed for the seeds bioprimed with PGPR II at 100% for 2 days (27.2 cm), the largest collar diameter was for T viride at 25% for 4 days (4.08mm) and the maximum number of leaves is obtained for T viride at 75% for 8 days (26.7) for the seeds subjected to post priming storage of one day. For one week storage, the largest value for seedling height is obtained for seeds bioprimed with P. fluorescens at 100% for 8 days (28.10 cm), the collar diameter was obtained maximum for biopriming with P. fluorescens at 100% for 8 days (5.63 mm) and the largest number of leaves is obtained for T. viride at 100% for 1 day (23.7). Hierarchical cluster analysis indicated that the best seedling performance was on biopriming with T. viride at 25% for 4 days for one day storage and P. fluorescens at 100% for 8 days, for the seeds subjected to post priming storage of one week at 30 and 180 days after transplanting. The present investigation confirms the superiority of biopriming treatments in improving the germination and seedling performance of the sandal and biopriming being an eco-friendly treatment that can be recommended for the quality planting stock production of sandal.