Cold sensitivity gradient in tuber-bearing Solanum based on physiological and transcript profiles

Tuber-bearing Solanum species exhibit a wide variation with respect to cold sensitivity. Physiological evaluation based on the leakage of cellular electrolytes showed a continuous gradient of sensitivity among cultivated and wild species, which ranged from chilling sensitivity to freezing tolerance by cold acclimation (CA). Solanum trifidum Correll, a chilling-sensitive species, defines the baseline of cold tolerance within the genus, while S. commersonii Dunal, a cold-acclimating species, represents the hardiest end of the spectrum. Solanum species at the extreme ends of the sensitivity gradient exhibited distinct expression signatures for selected CA-associated genes (CBF1, ZAT12, COR47, and GolS3). Transcription factor (CBF1 and ZAT12) expression was positively correlated with CA but not with the sensitivity gradient among nonacclimating species. Variation across the sensitivity gradient was reflected by the differences in induction profiles of nonregulatory genes (COR47 and GolS3).