Comparative On Frost Hardiness Of Several Varieties Of Pear And Apple Trees

The samples were one-year-old branches and leaves in three varieties of pear trees:Pyrus sp ‘Huang-guan’, Pyrus pyrifolia (Burm.f.) Nakai, and Pyrus spp‘HongXiangSu’, and two varieties of apple trees: Malus pumila millapple ‘GoldenDelicious’, and Malus pumila millapple ‘gongqi Fuji’. They were collected fromQinhuangdao Changli Institute of Pomology. We measured the frost hardiness (FH) ofdifferent varieties in pears and apples during cold hardening and deharding by meansof the electrolyte leakage (EL) and electrical impedance spectroscopy (EIS) methods.We verified the changes of the moisture content, soluble sugar and starch, andanalysed the electrical impedance spectra and parameters with non-frost exposedbranches and leaves, and compared these parameters among different pears and apples.The correlation between the EIS parameters and the FH was studied, and the order ofFH in different pear and apple varieties was found.The study shows that:During cold hardening, the FH of each varieties increasedsharply. After entering the dehardening process, the FH became decresase. The FH ofshoots and leaves measured by EIS and EL presented similar tendency;The order ofFH in different pear varieties was: Pyrus spp ‘HongXiangSu’> Pyrus sp‘Huang-guan’> Pyrus pyrifolia (Burm.f.) Nakai, and that of different apple varietieswas: Malus pumila millapple ‘Golden Delicious’> Malus pumila millapple ‘gongqiFuji’; Distribution coefficient of relaxation time and specific intracellular resistancewere the better EIS parameters for assessing FH under artifical frost exposedmaterials; The contents of water, soluble sugar and starch in leaves and shoots ofdifferent varieties of fruit trees related with FH, R2>0.5,a part of the R2reach0.94.suggesting that these parameters could be used to estimate FH.