ISHS Acta Horticulturae 402: International Symposium on Cultivar Improvement of Horticultural Crops. Part 1: Vegetable Crops
IN VITRO CULTURE OF WATERMELON AND CANTALOUPE WITH AND WITHOUT BENEFICIAL BACTERIUM |
| Authors: | Z. Liu, V. Pillay, J. Nowak |
| Abstract:
Restricted root growth is the most critical factor in a commercial production of watermelon and cantaloupe. The plants are very susceptile to water stress and low temperature and require relatively long growing season to produce good fruit yields. In Nova Scotia, due to the poor climatic conditions, watermelon and cantaloupe are grown almost exclusively by hobby gradeners. A growth promoting pseudomonad bacterium, Stain PsJN, which significantly enhances in vitro growth and root development in potato and tomato and enhances transplant stress tolerance in micropropagated potato plantlets was used to inoculate seeds and/or seedlings of watermelon cv. Sugar Baby and cantaloupe cv. Hybrid Alaska. Seeds were washed twice with 2 % soap and surface sterilized with 33 % solution of a commercial bleach, for 15 min, rinsed with sterile distilled water (SDW) and allowed to imbibe for 24 hours. Seed coats were then removed and seeds were surface sterilized again, in 10 % Javex for 10 min, rinsed (3X) with SDW, and treated either with phosphate buffer saline solution (PBS) containing approximately 2 x 108 CFU/ml of bacterium suspenion (bacteri - zed treatments) or with PBS alone (controls), for half an hour. The seeds were germinated in GA - 7 Magenta vessels containing 40 ml half strength hormone free MS medium at 21°C, 16 h photoperild, 120 – 140 uE m-2s-1 fluorescent light. When cotyledons completely opened, root tips were trimmed and the seedlings were dipped again either in the bacterial suspension (BB and CB treatments) or in PBS (BC and CC treatments). Summary of the treatments is presented below: Graphic available in full text only The plantlets were then individually transferred to test tubes containing 10 ml medium. The number of nodes per plant, shoot length, shoot weight, root length and weight were determined after 4 weeks of growth. Bacteria populations wee determined in the middle sections of surface sterilized stems and on the root surface of 5 - week - old plantlets. Stems were surface sterilized in 10 % Javex for 5 min, rinsed 3X with SDW and blotted with sterile filter paper. Samples of 0.1 g per shoot were taker, form the middle sections and ground in a mortar with 10 ml 0.1 M phosphate buffer, containing 2.464 g/l MgSO4, pH 6.5 (Buffer A). The homogenates were transferred to 250 ml flasks using 10 ml 0.2 % Tween - 20 in Buffer A and shaken for 10 min, 110 rpm. Root samples (0.1 g) were washed in the similar way, using SDW. Bacterium populations were determined by dilution plating with four dilution and five replicates per each dilution, per treatment. A completely randomized design with 4 treatments and 12 replicates per treatment was used in all experiments. Data were analyzed with SAS computer program, using Duncan's Multiple Range Test (DMRT). | |
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