Evaluation of wild Solanum species for drought resistance: 1. Solanum gandarillasii Cardenas

Since drought is a major factor limiting global potato production, identification of Solanum germplasm with drought resistance features is essential. The current study compared responses of Solanum tuberosum L. ‘Kennebec’ to those of the wild tuber bearing species, Solanum gandarillasii Cardenas, with respect to drought and heat stress. The cultivar Kennebec exhibited more leaf water loss as well as increased osmotic adjustment compared to S. gandarillasii during the imposition of progressively severe drought. In Kennebec, this stress led to severe leaf wilting and eventual canopy loss. However, S. gandarillasii was less sensitive to prolonged drought in terms of reduced loss of above ground biomass. The conservative “water saving” responses of S. gandarillasii included drought sensitive stomata resulting in low transpiration rates. Coupled with this apparent loss of an effective cooling mechanism, S. gandarillasii demonstrated superior thermal tolerance. Decreased intrinsic water use efficiency (WUE) at the leaf level was evident in Kennebec compared to S. gandarillasii when exposed to increasing levels of soil moisture stress and regardless of radiation level. This difference in WUE could be attributed to differences in transpiration rate and not to photosynthetic rate. S. gandarillasii may be appropriate for growth areas exhibiting drought conditions where reduced desiccation and thermal damage to leaf tissues are assets. Kennebec, however, was a ‘water spender’ that would be more appropriately grown under temperate growing conditions with an adequate water supply.