USVI Public Records

Document text

Influence of Variety and Harvest Date on Sweet Potato Weevil Damage UVI AES Biotechnology & Agroforestry Thomas W. Zimmerman, Stafford M.A. Crossman, Carlos Montilla, Noel Burnett, Chinaemere Igwebuike, Kenya Emanuel Student project to identify viruses in Sweet Potato From the six growing areas, all had 1-3 viruses Yellow represent Potyvirus, Blue represent Cucumber Mosaic Virus and Red represent Zucchini Yellow Mosaic Virus Sweet Potato Varieties USDA* Francia Gonime Liberty Mojave Okinawa Ruddy Toquecita White Jewel Yellow Sunflower Caribbean Craneal PR 406 PR 8023 Pujol St Kitts Sweet James LSU* B-14 Evangeline Murasaki Virus-Free material arrived as 1-2 two test tubes and needed to be micropropagated in vitro Sweet Potato grown in vitro with multiple sucrose concentrations 0 1 2 3 4 5 6 0 5 10 15 20 25 30 35 40 45 Days Leaves 0% 3% 6% 9% 12% 0 1 2 3 4 5 6 0 5 10 15 20 25 30 35 40 45 Leaves Days 0% 0.1% 0.3% 1% 180 Days In vitro plants were grown under a 16 hr photoperiod at 25C Rooted shoots were transferred to sterilized potting mix, covered for a week to assist in acclimatization. After two weeks, they were transferred to a greenhouse. Replicated trial 1 ft between plants 4.5 ft between rows, 9 varieties/row, 17 plants/variety/row, 3 rows/block, 3 blocks Six weevil traps placed throughout the field and monitored weekly Sweet potatoes ready for vine removal and harvest Harvesting 0 4 8 12 16 20 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Weevils Week Average number of male weevils captured weekly per trap 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 100 Days 115 Days 130 Days Average Kg Marketable Tuberous Sweet Potato Roots per Plant Variety Kg Average Number of Marketable Tuberous Sweet Potato Roots per Plant Variety 0 1 2 3 4 5 6 100 Days 115 Days 130 Days R O O T S 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Weevil small Mkt 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Weevil small Mkt Comparison between 100 and 130 day for Marketable, Small and Weevil damaged Sweet Potatoes 130 Days 100 Days Taste Evaluation Refrigerated Storage At harvest soluble solids (sugars) 6-8% After 2 weeks soluble solids increases to 8-13% After 4 weeks soluble solids range 10-16% Future studies on postharvest to determine refrigeration vs room temperature storage influence on sugar content Conclusions Sweet potato viruses are present throughout St Croix 0.1-0.3% sucrose can used for extended culture life 1 year Weevils are present throughout sweet potato production Harvest at 100 days minimizes weevil damage Varieties B-14, Francia, Mojave, Pujol, PR 8023 and Toquecita produce over 1 Kg/plant in 100 days Varieties with the greatest weevil resistance at 130 days were Gonime, Liberty, St Kitts, Sweet James, Toquecita and Yellow Sunflower  Refrigeration increases soluble sugar content Acknowledgements This research was supported through a grant from the VI Department of Agriculture Specialty Crops Block Grant Program and USDA-Hatch. Special thanks to my students and Biotechnology & Agoforestry field staff: James Gordon Henry Harris Raheem Smart Mike Morgan Anna Bastien-Gilbert Kalunda Cuffy Tyrone Pascal Jomanni Bernier Khalid Matthew Coauthors: Stafford M.A. Crossman Carlos Montilla Noel Burnett Kenya Emanuel Chinaemere Igwebuike