Fine screening potato (Solanum) species germplasm for tuber calcium

A representative sample of the US potato germplasm collection was screened in the greenhouse for ability to accumulate tuber calcium. Germplasm with very high and very low calcium accumulation capacity has been identified by progressively screening for extremes among species, among populations (accessions), and finally among genotypes (i.e., fine screening). Among accessions, the bestS. gourlayi andmicrodontum populations averaged more than six-fold greater tuber calcium than the poorestS. kurtzianum population. When screening was performed at the genotype level, the best individuals ofgourlayi andmicrodontum had over eight-fold greater calcium than the poorestkurtzianum individual. When grown in the field, calcium levels ofS. microdontum selections were confirmed to be significantly higher thantuberosum cultivars. When selected genotypes were intercrossed and their progeny were compared to their original populations, mean tuber calcium was significantly changed in the intended direction of selection forS. kurtzianum (made lower) andS. microdontum (made higher). These stocks are expected to be useful tools for study of the genetic and physiological bases of tuber calcium accumulation, refining screening methods, and breeding improved cultivars.