Postharvest Comparison of Raspberry Cultivars and Selections Grown Under Tunnels or Field Systems in the North Carolina Piedmont

Raspberry production in the southeastern U.S. has been a challenge for many years, as the high humidity and high temperatures tend to reduce fruit size, accelerate ripening, and exacerbate Botrytis cinerea.  There is considerable interest in North Carolina to grow local raspberries as a specialty crop.  Raspberry plants from multiple breeding programs were grown in field and tunnel systems in Salisbury, NC representing the Piedmont area of NC and treated conventionally with a recommended fertilizer and fungicide regime.  Air temperatures during the floricane season (May-July)  are 23-32 and 13-19 C (max/min),  and 28-17 and 16-4 (max/min)  in the primocane season (August-November).  Humidity is 70 to 95% during the production season.  Fruit were harvested when detachable from the receptacle into 160 g clamshell boxes and held at 5 C, 95% RH for 4-6 days, until mold was visible on berries.  Color was determined subjectively  on a 1 (light red) to 3 (too dark) scale.  Fruit were determined to be soft or firm when taken individually out of the clamshell, and 10 soft and 10 firm were also tested using a firm tester with fruit set calyx end down.  Most of the cultivars tested were rated as too dark (3) after storage for 4-6 days at 5 C.  For most of the stored fruit, more than 50% were considered soft after removal.  Firm and soft fruit measured 2 and 0.5 N, respectively.    Of the selections and cultivars tested, NC344 and Nantahala, both developed under local conditions, had lighter red and firmer berries.  Tunnel berries were slightly better in postharvest quality than the field grown fruit.