Analysis of the cold tolerance and physiological response differences of amur grape (Vitis amurensis) germplasms during overwintering

Abstract Vitis amurensis is a cold-resistant species, but information on the cold tolerance of germplasms is lacking. In this study, a pictorial assessment of 2,3,5-triphenyltetrazolium chloride (TTC) staining images was used to evaluate germplasm responses to cold stress. The low semi-lethal temperature (LT50) estimated from the staining images of 32 amur grape germplasms, during their dormant stage over two consecutive years ranged from −40.4℃ to −26.8℃, and the cold tolerance of the germplasms was classified into four zones based on these LT50 values; these zones might be associated with regions of resource collection. Then, a different germplasm was selected from different hardiness zones. V. amurensis ‘ZuoShan-2′ is a highly cold-resistant germplasm belonging to Zone 1, while ‘Shuangfeng’ and ‘201230′ are from Zone 2 and 3, respectively. The changes in the cold tolerance of V. amurensis ‘ZuoShan-2′, ‘Shuangfeng’ and ‘201230′ from October to January were similar, and their lowest LT50 occurred in November after a period of naturally low temperatures. However, there were differences in the cold acclimation capabilities during overwintering, with ‘Zuoshan-2′ exhibiting the greatest cold tolerance and ‘201230′ exhibiting the weakest. Their overwintering capabilities were the most correlated with the total soluble sugar contents of shoots based on the correlation analysis and gray correlation degree across physical factors compared with LT50. Further determination by high performance liquid chromatography (HPLC) and analysis found that the fructose, glucose and trehalose levels in soluble sugar mainly contributed to overwintering.