Net nitrate uptake by the roots of different potato haploids

Seventy haploids were obtained by crossing the pollinator Solanum tuberosum L. Group Phureja (P.I.1.22) (2n = 2x) with tetraploid clones of Solanum tuberosum L., 'Spunta' and 'Desiree,' two adapted Italian varieties. By tuber morphology screening, they were grouped into six classes and six haploids were selected as representative for each class. Esterase isozyme analysis on leaves of the selected haploids indicated the presence of a considerable degree of genetic variability. Six potato haploids were evaluated for differences in nitrate acquisition efficiency. A wide variability of net nitrate uptake rate, ranging from 2.36 to 4.23 mumoles/h/g FW, was observed among the potato genotypes. Furthermore, the time needed for the expression of the nitrate uptake induction showed large differences (from 6.93 to 46.2 h). Relative growth rate of potato haploids correlated with the accumulated nitrate (At) while any correlation with the parameters relative to the induction phase of nitrate uptake was observed. Results indicated that, besides morphological variability, potato haploid populations showed a high variability in nitrate acquisition efficiency. This variability must be gauged in order to select potato varieties with improved capacity for nitrate uptake.