Theses and Dissertations

Issuing Body

Mississippi State University


Reddy, K. Raja

Committee Member

Silva, Juan L.

Committee Member

Matta, Frank B.

Committee Member

Shankle, Mark W.

Committee Member

Denny, Geoffrey C.

Date of Degree


Document Type

Dissertation - Open Access



Degree Name

Doctor of Philosophy


College of Agriculture and Life Sciences


Department of Plant and Soil Sciences


Sweetpotato is an important staple crop, and a supplementary source of nutrients; minerals, carbohydrates, and vitamins, for the food industry. Quality of sweetpotatoes depends on cultivar, preharvest management practices, and harvest equipment causing skinning. Information on morph-physiological characteristics of storage roots is needed for preharvest management decisions, cultivar selection, and application of harvest aids and harvesting procedures for postharvest storage durability of sweetpotatoes. Also, devices to measure skinning properties of storage roots are needed. This research was conducted to measure skin toughness of various sweetpotato cultivars. The number of skin layers was determined using fluorescent microscopy, and lignin content was determined with the Near Infrared System. Preharvest cultural practices, such as devining to enhance skin set and lignin content, were applied 1, 3, 7 days preharvest, and Ethephon at the rate of 1.68 ha-and 0.84 kg ha-1 applied at 1, 3, and 7 days preharvest. In addition, curing to enhance skin healing and lignin content was evaluated. This research was conducted in the field and in the greenhouse environments. The force gauge and the torquometer were the most accurate and precise devices to measure the force needed to break the skin of the various sweetpotato cultivars. The cultivars, “L07-6R”, “L07-146”, and “Beauregard-14” had the toughest skin compared to the other cultivars. However, “Covington” and “Hatteras” had the highest lignin content. Fluorescent microscopy showed that the cultivars “L07-6R” and “L07-146” had 12 and 10 cell layers, respectively, and the treatment of Ethephon at 1.68 Kg∙ha-1 3 days and 7 days before harvest resulted in the highest lignin content in the skin. Divining 3 days preharvest, and applying Ethephon at 0.84 kg∙ha-1 at 1day and 3days preharvest resulted in the highest lignin content. In addition, the treatments with Ethephon at 1.68 Kg∙ha-1 applied at 3 days and 7 days preharvest resulted in the hardest skin as indicated by torquometer and the force gauge. Curing for 7 days resulted in higher lignin content compared to the others pretreatments. When wounded and cured for 7 days, the healing process was enhanced greatly, resulting in rapid skin set of sweetpotato storage roots.



skinning storage roots||skin toughness||lignin determination