Quantifying Solanum chacoense root morphology responses to limited nitrogen supply using in vitro , hydroponic, and field monolith methods

Solanum chacoense Bitt. (chc) is a short-day adapted wild diploid (2n = 2x = 24) species, relative of the commercial potato S. tuberosum L. (tbr), that has demonstrated higher below-ground biomass when cultivated under limited nitrogen (N) supply, suggesting it possesses greater potential for N recovery by increasing root length density (RLD). The objectives of this study were to compare screening methodologies for evaluating RLD responses of chc genotypes and tbr cultivars under limited N supply for the identification of superior rooting chc genotypes. Seventeen genotypes of chc and three commercial tbr varieties were exposed to 0.5 and 1.0 N rates across three root screening methodologies: in vitro, hydroponic, and field evaluated at tuber initiation and plant maturity stages. Although the development of a reliable high throughput root screening system was unachievable due to differences in environment and root sampling protocols across methodologies, there were significant positive correlations amongst RLD for a majority of methods in both chc and tbr. This suggests that RLD can be utilized for evaluating both Solanum species and genotypes within species and environments. RLD for chc 0048-34 and 0053-7 genotypes were significantly higher than tbr cultivars in all tested methods indicating that chc possesses the potential for increasing N recovery in future breeding with tbr.