Tuber Yield, Quality and Infestation Levels of Potato Genotypes, Resistant to the Root-Knot Nematode, Meloidogyne chitwoodi

As part of developing a routine potato cultivars resistance test to Meloidogyne chitwoodi, both the effect of nematode density (Pi) and pot size on growth, tuber yield, quality and tuber infestation level were studied in glasshouse conditions. The study was carried out in four experiments using cv. Desiree as control and seven genotypes with a single resistance gene to M. chitwoodi and 1 genotype, with resistance to Globodera pallida. Plants were inoculated with ranges of Pi from 0.0625 to 256 J2 (g dry soil)−1 in log series. Haulm height, tuber yield, starch dry matter content (SDC) and tuber quality were recorded. Additionally, harvested tubers of experiment 2 were stored for 240–300 days to estimate actual tuber infestation at planting when used as seed in a subsequent season. Haulm height was positively affected with increasing Pi’s and negatively with decreasing pot size. The yield was not affected in four out of seven genotypes with resistance to M. chitwoodi; they can be considered as tolerant, having a relative minimum yield, m = 1. Three genotypes and cv. Desiree showed relative minimum yield, m 20 and are not accepted for processing. The fraction of clean tubers of the resistant genotypes had significantly increased to 91% compared to < 8% for cv. Desiree and MDG2. Tuber infestation, expressed to number of juveniles per gram dry soil of cv. Desiree after storage, showed no regression with the Pi and averaged 0.35 J2 (g dry soil)−1, while all tested genotypes provided ca. 0.002 J2 (g dry soil)−1