2017 Sweet Potato Slip Production Research Update

Transcription

1 2017 Sweet Potato Slip Production Research Update This research update shares findings from the 2017 slip propagation season. Canadian sweet potato growers rely on planting material from the U.S. Slips availability at planting is a major bottleneck limiting further expansion of sweet potato acreage in Canada. Vineland s new sweet potato variety VSP445 is scheduled for release in spring This past year, researchers at Vineland have been working to develop a commercially viable slip propagation system. Two methods of slip propagation were investigated to determine the most efficient way to produce slips in greenhouses. System 1: Vegetative propagation Vegetative propagation focuses on slip propagation from rooted vegetative plant material. Single node cuttings were harvested from tissue culture of mother plants and transplanted into germination trays containing 50 or 144 cells throughout the 2017 winter months. Beds were prepared with potting soil and slips from the trays were planted at 80, 100, 120 and 140 plants/m 2 densities from both 144 and 50-cell trays in Vineland s greenhouse (see Picture 1). Plants were trimmed several times to create thick compact mother plants from which slips could grow. Picture 1: Slip density trial (April 20, 2017). 01

2 The number of marketable slips produced at each density were compared to determine the most effective way to maximize the number of slips produced per square metre in a greenhouse without using sweet potato roots. This trial was replicated at Baker s Nursery in Bayfield, ON Results The number of slips harvested ranged from 247 to 278/m 2 with the highest number of slips found for the 140 plants/m 2 density (see Graph 1). Since tray size has no effect on the number of slips harvested, using 144-cell trays would be more efficient as they require less space in a greenhouse. Graph 2: Number of slips produced by each plant. The largest number of slips produced per plant was found at 80 slips/m 2 density, with an average of 4.5 slips per plant (see Graph 2). The largest number of slips were observed at 100 plants/m 2 density at Baker s Nursery (see Graph 3). Graph 3: Total number of slips at each density from data collected at Baker s Nursery. Results from both trials were statistically insignificant, suggesting plant density is not a factor in the number of harvestable slips. Graph 1: Total number of slips produced at each density from two harvests at Vineland. Given the low yield potential for slips using this method of propagation, it is unlikely it will be developed as a commercial propagation technique. 02

3 System 2: Storage root propagation U.S. growers use storage roots to produce slips by placing them in beds in fields or in unheated greenhouses. In Canada, weather conditions during March and April prevent direct planting of storage roots in the field. Greenhouse space is required to produce slips in Canada. In Vineland s greenhouse, sweet potato storage roots were spaced 1 cm apart onto a 8-cm bed of Sunshine Mix 1 with 2.5 cm of potting soil placed over the roots (see Picture 3). Graph 4: Total number of slips produced by each sweet potato grade over two harvests. Picture 2: Sweet potato roots planted in the greenhouse (March 23, 2017). Results The total number of slips produced over two harvest seasons from U.S. grade No. 1 and U.S. grade No. 2 sweet potatoes are compared in Graph 4. There was no difference in the number of slips produced between both grades. It is likely small potato roots (U.S. grade No. 2) will be used in commercial slip production. Picture 3: Growing slips from storage roots in Vineland s greenhouse (May 3, 2017). 03

4 According to Graph 4 on page 3, the slip yield per square metre was comparable between U.S. No. 1 and U.S. No. 2 sweet potatoes. It is therefore recommended to use U.S. grade No. 2 sweet potato for propagation as they have similar yield and lower input costs than U.S. No. 1. At Baker s Nursery, U.S. No. 2 sweet potatoes were planted into daisy trays containing a 1-cm layer of Promix HP Mycorrhizae potting soil, then covered totally with potting soil. Takeaway messages The tray size used to propagate individual nodes does not influence slip yield If using vegetative cuttings, slip density does not seem to influence the number of slips produced per square metre Storage roots produced an average of 848 marketable slips/m 2 The yield of marketable slips is far greater using sweet potato roots than vegetative cuttings (see Graph 6) An average of 848 marketable slips/m 2 were harvested in two cuttings, two weeks apart (see Graph 5). Commercial grade sweet potato roots were used in our experiments. In future years, G2 seed potato roots will be utilized in slip production to ensure disease and virus-free plantings for high yield and quality. Graph 6: Total number of marketable slips per square metre harvested from vegetative cuttings and sweet potato roots. Graph 5: Total number of marketable slips per square metre obtained from two harvests at Baker s Nursery. Certified seed production - scaling up from tissue culture Tissue-cultured plants were received from New Liskeard Research Station in April The plantlets were transplanted into 50-cell trays (75 ml of Sunshine Mix 1). Once new roots were established, they were transplanted at 180 plants/m 2 density into beds prepared with 10 cm of soil. 04

5 Once plants were established in beds, apical tips were harvested and transplanted into additional beds prepared with 10 cm of potting soil (see Picture 4). This procedure was repeated once again until slips were ready to be transplanted into the field. Trial 1: Full slip field production On June 19, slips were harvested from the tissue-cultured material and transplanted in the field the next day (see Picture 5). Over the course of eight weeks, 1,900 slips were transplanted using this technique. Another 1,850 slips from the greenhouse were transplanted mid-july. Picture 4: Tissue-cultured plant beds (May 3, 2017). Assuming an average of four U.S. No. 2 sweet potatoes per slip, a yield of 13,200 G1 sweet potatoes for G2 slip production could be expected in Picture 5: Researchers transplanting tissue-cultured slips onto hills at the Vineland Research Farm (June 20, 2017). 05

6 Vineland Research and Innovation Centre 4890 Victoria Avenue North, Box 4000 Vineland Station, ON L0R 2E0 tel: VinelandResearch vinelandresearch.com About Vineland s Global Reach, Local Touch: New Vegetable Varieties Research Program This program encompasses breeding new vegetable varieties adapted to Canadian growing conditions and meeting consumer preferences. Researchers at Vineland are establishing a pipeline for locally-adapted sweet potatoes that would give Canadian growers a larger share of the more than $40 million market. Researchers are developing a cost-effective sweet potato slip production system and breeding high yielding early sweet potato varieties for release in Picture 6: Sweet potato single node cuttings trial at Vineland s Research Farm (September 26, 2017). Trial 2: Single node field production On July 5, slips were harvested from tissuecultured plants and single nodes were cut and planted into 144-cell trays (15 ml of Sunshine Mix 1). A week post-transplanting, roots had developed sufficiently to be transplanted into the field, where a trial was set up at 15-cm, 20-cm and 30.5-cm spacing. Using this method, 8,750 cuttings were transplanted into the field with the intent of obtaining at least three U.S. No. 2 sweet potatoes from each cutting for a total of 24,250 G1 potatoes for G2 slip production in 2018 (see Picture 6). Seed production summary Data on total yield of U.S. No. 2 sweet potatoes will be collected in the fall of Dr. Viliam Zvalo, Research Scientist, Vegetable Production joined Vineland in 2014 to investigate various crop production systems for Canadian growers. If the information contained in this research update is of interest to you or if you have any questions, please contact Viliam at: x808 or viliam.zvalo@vinelandresearch.com 06