Location: Vegetable Crops Research Unit
Title: Storage research roundup Author
Submitted to: Common Tater
Publication Type: Trade Journal
Publication Acceptance Date: August 17, 2013
Publication Date: September 1, 2013
Citation: Bethke, P.C. 2013. Storage research roundup. Common Tater. 65(9):12-13. Technical Abstract: With so much research being done in the areas of potato production, variety development, genetics, disease resistance and pest management it is easy to miss some of the research being done on potato storage. Below are highlights from a few of the noteworthy papers published recently that relate to the general field of potato storage. (Chung et al., 2013). Bacterial soft rot is a major contributor to storage losses. Variation in tuber resistance to soft rot caused by Pectobacterium carotovorum subsp. carotovorum was assessed for 65 cultivars and 13 breeding lines of potato after storage for up to 6 months. (Gao et al., 2013). The late blight pathogen Phytophthora infestans can infect tubers in storage as well as leaves and stems. The RB gene, which was isolated from wild relatives of potato, confers broad-spectrum foliar resistance against late blight. Tuber resistance to late blight was demonstrated using transgenic potatoes expressing unusually high amounts of RB gene transcript. (Castleberry and Jayanty, 2012). Pressure bruise is a quality concern for all market classes of potato. An experimental apparatus was constructed that simulated the weight of a potato pile on stored tubers. A pre-storage dehydration treatment increased the extent of pressure flattening and pressure bruising, but this effect was only seen after 14 weeks of storage. Cultivars differed in susceptibility to bruising and the impact of the pre-storage dehydration treatment on bruise formation. (Külen et al., 2013). Potato tubers contain vitamin C and phenolic compounds. These compounds may provide health benefits by functioning as antioxidants. The vitamin C and total phenolic contents of 16 potato clones grown in Colorado were estimated at harvest and after 2, 4, 6 and 7 months of storage at 4°C. Vitamin C content of all clones dropped as storage time increased, with an average reduction of approximately 50%. Tuber phenolic contents changed less with time in storage. (McKenzie et al., 2013). Vacuolar acid invertase is the primary enzyme responsible for cold-induced sweetening of potato tubers. The activity of this enzyme depends on its abundance and on the abundance of an invertase inhibitor protein. Transgenic potato lines were generated in which transcription from the invertase inhibitor gene INH2 was increased or decreased relative to that in untransformed controls. Resulting changes in tuber acid invertase activity and reducing sugar accumulation clearly demonstrated that the invertase inhibitor encoded by the INH2 gene is an important component of resistance to cold-induced sweetening. (Wang and Bethke, 2013). Stem-end chip defect is a post-harvest disorder of chipping potatoes that results in localized darkening along the vasculature and adjacent tissues at the stem end of fried chips. Potato plants that were more infected with the fungal pathogen Verticillium dahliae were shown to have a higher incidence of severe stem-end chip defects than plants that were less infected. Verticillium dahliae infection of plants was correlated with an up regulation of acid invertase activity and an accumulation of reducing sugars at the stem end of tubers. The increase in reducing sugars is likely the immediate cause of dark color formation during frying. (Halford et al., 2012). Reducing sugars and asparagine are the precursors for acrylamide in fried potato products. Tuber contents of these acrylamide precursors were monitored from November to July in nine varieties of potato grown commercially in the South East of England. Free asparagine contents changed during the storage period, but the direction and magnitude of change depended on variety and time of storage. (Suttle et al., 2012). Potato tuber dormancy is advantageous during storage but must be lost in order for seed tubers to sprout. Previous studies have suggested that the plant growth regulator abscisic acid (ABA) may play a key role in the maintenance of tuber dormancy. By using compounds that perturb or prevent the breakdown of ABA, it was shown that a decline in ABA content is not a prerequisite for tuber dormancy loss. (Li et al., 2013). In order to learn more about the potential benefits and pitfalls of molecular breeding for potato tuber quality, DNA markers for genetic loci contributing positively and negatively to chip color, tuber starch content and starch yield were used to genotype a range of potato varieties and breeding clones. Markers associated with better tuber quality were identified and 6 of these were used to genotype the progeny of a single cross between two varieties. The expected relationships between marker composition and tuber quality were not observed. It was postulated that this might reflect the small number of markers used. Alternatively, it was suggested that the utility of a given marker might vary with environmental conditions during tuber growth.