A P R I L 2 0 1 8 12 POTATO GROWER Most cultivars peak performance will be in the 1.5 to 3.0 stem range. If a smaller tuber size profile is desired, growers can manipulate stem numbers by green sprouting (chitting) or using products such as gibberellic acid, plant in beds using a higher plant population number, or plant in rows tightening up the row spacing, within-row spacing or both. Shape of tubers varied from round, to elongate for All Blue. Color ranged from yellow for Yukon Gold, to purple for All Blue and sev- eral advancing selections. Predominantly, our program focuss- es on bright red skinned genotypes and many had superior color com- pared to industry standards Red Norland, Red LaSoda and Red Pontiac. The general rating score is a reflection of many characteristics including total yield, tuber size pro- file, tuber shape and color. General rating scores ranged from 2.6 for All Blue and Sangre, to 4.8 for Dakota Ruby. Total yields were significantly differ- ent, ranging from 158 cwt./acre for ND081557C-1P to 443 cwt./acre for Red Pontiac (Table 2). Yield of A sized tubers (US No. 1s) ranged from 6 cwt/acre for ND081557C-1P, to 263 cwt/acre for Chieftain. Percentage A size ranged from 3% for ND081557C-1P to 70% for Red Norland. Due to a more normal growing season and an industry desire to identify and produce clones with a higher tuber set and smaller tuber size profile, clone per- formance tended to mirror that market attribute. The percentage of 0 to 4-ounce size tubers ranged from 5% for Red Pontiac to 97% for ND081557C-1P. The percentage tubers 4-6 ounce ranged from 2% for ND081557C-1P to 51% for ND6961-21PY, again reflecting an overall smaller size profile. Oversize tubers (>10 oz.) were most prevalent for industry standards such as Red LaSoda, Red Pontiac, and Sangre. Tubers were generally graded as US No. 2s or culls due to misshapen tubers. Tubers per plant varied from 4.1 for ND7132-1R to 15.3 for ND113091B- 2RY, with a mean of 8.1 (Table 3). Specific gravity ranged from 1.0760 for ND113207-1R, a clone having a waxy texture, to 1.1212 for ND081557C-1P, a clone with a dry, mealy texture. Hollow heart and brown center incidence were low for all clones with the exceptions of Red Pontiac, ND7132-1R and ND1243-1PY. Trial entries were also evaluated for blackspot and shatter bruise potential. Blackspot bruise results when polyphenol oxidase and tyrosine combine within dam- aged cells due to tubers bumping around during harvest and han- dling operations. Typically, the skin is not broken and bruises are diffi- cult to detect without peeling. Based on our ratings (range of 1.3 to 3.3), producers should use manage- ment practices to maximize the marketing of bruise-free tubers, including a pre-harvest irrigation if possible, maintain belts and con- veyors full of tubers and soil as the potatoes move through the har- vester, limit drops, and utilize padding on harvesters, in trucks, and on conveyors going into stor- age. Shatter bruise potential was evaluated following storage at 45F. Ratings for entrants ranged from 2.1 to 4.0; proper tuber hydration and using bruise-free management tech- niques limit shatters. Shatter bruis- es may serve as entrance points for pathogens such as Fusarium species. Standouts in the trial included ND081571-2R, ND081571-3R, ND102663B-3R, ND102775C-5RR (a round to oval selection with red flesh), ND113091B-2RY (bright red NDSU fresh market trials south east of Crystal, North Dakota, the first week of August 2017. The 2017 trials were hosted by Dave and Andy Moquist.