In vitro seed germination behaviour of different citrus varieties in MS basal media

An experiment was conducted from 2021 to 2023 at the tissue culture laboratory, micro-propagation unit, Uttar Banga Krishi Viswavidyalaya, Pundibari, West Bengal, to observe the seed germination behaviour and standardise the seedling rootstock for in vitro shoot-tip grafting. The experiment was laid out in a completely randomised design with three replications, comprising eight different citrus rootstocks (viz., NRCC 1, 2, 3, 4, Rough lemon, Rangpur lime, Pummelo, and Mandarin) as a control treatment, which were cultured in Murashige and Skoog basal media. Seeds were treated with Tween 80 for 15 minutes, followed by bavistin 500 mg for 1 hour, plantomycin 50 mg for 10 minutes, and mercuric chloride 100 mg for 2 minutes before inoculation to remove toxic residues from the seeds and also to prevent fungal and bacterial contamination. Seeds were thoroughly washed with double-distilled water three times after each treatment. In each treatment, 100 seeds were inoculated, with five seeds per jam bottle. The results showed that Rough lemon had the highest seed germination rate (81.84%), followed by NRCC 4 (81.41%). The first sprouting of seed was observed in pummelo (5.49 days) followed by rangpur lime (5.59 days). The minimum days required for 50% seed sprouting were observed in NRCC 4 (7.47 days) and Mandarin (7.93 days). The minimum average number of days required for seed germination was observed in NRCC 3 (13.13), followed by NRCC 2. The germination index was found to be highest in NRCC 4 (59.00%), followed by NRCC 2 (44.16%). The polyembryony rate was observed to be highest in Mandarin (24.19%) and Rangpur lime (16.29%). The highest number of leaves was observed in rough lemon, pummelo and NRCC 4 (2.67). Rootstocks such as rough lemon, NRCC 4, pummelo, and rangpur lime have shown potential for in vitro shoot-tip grafting.