Evaluation of tuber-bearing Solanum species for nitrogen use efficiency and biomass partitioning

Modern potato cultivars (Solanum tuberosum L.) require high rates of fertil izer nitrogen (N). This practice is costly and can pose a serious threat to surface and groundwater. Previous evaluation of wild potato germplasm demo nstrated the existence of species capable of producing high total biomass u nder low N conditions, with the ability to make maximum use of added N. The refore, a two-year field experiment was conducted in 1994 and 1995 to inves tigate the response of selected wild potato accessions and their hybrids wi th the haploid USW551 (USW) to low and high N environments. The haploid USW and cultivars Russet Burbank, Red Norland, and Russet Norkotah were also i ncluded in the study. Uniform propagules and seedlings from the various Sol anum species were transplanted to a Hubbard loamy sand (Udic Haploboroll) a t Becker, Minn. and were subjected to two N treatments: 0 and 225 kg N ha(- 1). At harvest, total dry biomass of wild and hybrid potato germplasm was e qual to or higher than that of the cultivars. However, cultivar biomass par titioning was 1% to roots, 15% to shoots, 0% to fruits, and 84% to tubers, whereas wild potato species partitioned 18% to roots plus nontuberized stol ons, 52% to shoots, 23% to fruits, and only 7% to tubers. Hybrids were inte rmediate, allocating 9% of their biomass to roots plus nontuberized stolons , 39% to shoots, 14% to fruits, and 38% to tubers. Nitrogen use efficiencie s for many of the species and crosses were comparable to that for Russet Bu rbank and greater than those for Red Norland and Russet Norkotah. Of the wi ld species tested, S. chacoense accessions had the highest biomass accumula tion and N uptake efficiencies and may be the best source of germplasm for improving NUE in a potato breeding program.