2018 ASHS Annual Conference

In Alaska, more than 95% of the $2 billion spent on food purchases each year is imported via boat or plane, and grocery stores have a maximum of two weeks supply. Prices for fresh produce are very high in rural communities, and this limits consumption. Climate modifying structures such as high tunnels can enable growers to produce fruits and vegetables locally, and the USDA estimates it has awarded $4 million in contracts and grants for high tunnels in Alaska. High tunnels in Alaska require extra construction considerations to withstand heavy snow loads (10 ft at Flattop Farm, the site of this experiment in Anchorage) and deep ground freezing. Additionally, crops such as watermelon require additional strategies for successful production. We grafted two watermelon cultivars, Blacktail Mountain and Marmaladny, on Tetsukabuto rootstock and evaluated fruit production. Seeding was 10 June 2017, and grafting was with the hole-insertion method on 17 June 2017. This was the third planting as the first and second plantings were lost due to seed-borne disease on cultivars that were locally sourced and that spread to experimental plants. Seedling production, grafting, and hardening were in grow rooms in the house basement, with fluorescent or halide grow lights and temperature maintained at 75-83 ^oF. Grafted plants were healed for 9 days in a grow tent (50 in. X 50 in. X 79 in.), also inside the house; an ultrasonic humidifier and humidistat provided 90% RH, temperature was 74-75 ^oF, and lighting was a fluorescent grow tube. Transplanting into the high tunnel was on 29 June. The experimental design was a randomized complete block with 6 plants per plot. Raised beds were covered with IRT olive-colored mulch (1 mil). Plants were hand pollinated within a cultivar. Soil temperature in the plots was 60 ^oF on 24 Aug. Fruit were harvested on 28 Sept., and all fruit were immature (TSS 5-6%). Grafted Marmaladny produced almost 2 times the number of fruit and 3 times the total fruit weight per plot than grafted Blacktail Mountain, and 4 times the number of fruit and 9 times the total fruit weight than non-grafted Blacktail Mountain and non-grafted Marmaladny (P < 0.0001). Average weight per fruit was 5.73 lb for grafted Marmaladny, which was 1.7 times greater than other entries (P = 0.02). Grafting of watermelon increased fruit production with cold soil temperature in southcentral Alaska. The experiment will be repeated in 2018.