Effects Of Cultivar And Harvest Maturity On Postharvest Chilling Injury In Peach Fruit

In this study,a total of 12 peach cultivars（‘Baifeng’,‘Hujingmilu’,‘Baili’,‘Jinxiu’,‘Jinhua’,‘Jinhuanghou’,‘Zhonghuashoutao’,‘Yingshuanghong’,‘Jinqiuhongmi’,‘Zhongyou13’,‘Zhongyou8’,‘Hongshanhu’）from 4 peach variety groups,i.e.,melting peach,yellow peach,non-melting peach,and nectarine were used as materials to study the effects of harvest maturity on the occurrence of chilling injury in fruit storage,the differences among cultivars and the related physicochemical mechanisms.The following main results were obtained.It was found that different cultivars of peach with different maturity had different sensitivity to low temperature.Among them,the harvest maturity of‘Baifeng’,‘Hujingmilu’,‘Jinxiu’,‘Zhonghuashoutao’and‘Yingshuanghong’peach had negative correlation with chilling injury,while the harvest maturity of‘Zhongyou8’nectarine had positive correlation with chilling injury.Harvesting maturity of‘Baili’and‘Jinhua’,‘Jinhuanghou’,‘Jinqiuhongmi’,‘Zhongyou13’and‘Hongshanhu’had little effect on chilling injury.In each group,there are cultivars with high and low sensitivity to cold injury,and there are great differences in sensitivity to cold injury among cultivars.‘Hujingmilu’,‘Jinxiu’,‘Jinhuanghou’,‘Zhonghuashoutao’,‘Yingshuanghong’and‘Zhongyou8’had high sensitivity to chilling injury,while‘Baili’,‘Jinqiuhongmi’,‘Zhongyou13’and‘Hongshanhu’had low sensitivity to chilling injury,which was not easy to occur.According to the relationship of each variety degree of chilling injury and recovery maturity curve,determine the slight chilling injury（Browning index of 0.2）at the time of harvest maturity（fruit ethylene release rate as index）threshold,and then according to the fruit of ethylene release rate and the relationship between the fruit firmness,of each cultivar is determined from the point of control the chilling harvest maturity（for the fruit firmness index）threshold.The picking firmness of‘Baifeng’and‘Hujingmilu’peach should not exceed 24 N and 11 N,respectively.The picking firmness of‘Jinxiu’and‘Jinhua’peach should not exceed 19 N and 28 N,respectively.The sensitivity of‘Baili’,‘Jinqiuhongmi’,‘Zhongyou13’and‘Hongshanhu’to chilling injury was low,and the picking firmness had little effect on chilling injury after storage,so there was no harvest maturity threshold.‘Jinhuanghou’has high sensitivity to chilling injury,and harvest maturity has little effect on chilling injury after storage,so there is no harvest maturity threshold.‘Zhonghuashoutao’and‘Yingshuanghong’have high sensitivity to cold injury and cannot meet the standard of average IB index not higher than 0.2,so it is advisable to improve the harvest maturity as much as possible,and the smaller the corresponding harvesting firmness,the better.For‘zhongyou8’nectarine whose ethylene release rate was positively correlated with IB index,as far as the chilling injury itself is concerned,it is better to harvest at a lower maturity.The correlation between chilling injury and MDA content,H₂O₂ content and TP content was analyzed by different cultivars.It was found that the IB index of‘Hujingmilu’peach was significantly negatively correlated with MDA content,while the IB index of‘Baifeng’and‘Yingshuanghong’peach was significantly positively correlated with MDA content.The IB index of‘Hujingmilu’was significantly negatively correlated with H₂O₂content,while that of‘Jinhua’peach was significantly negatively correlated.The IB index of‘Hujingmilu’peach was positively correlated with the content of TP content,The IB index of‘Yingshuanghong’was negatively correlated with the content of TP content,while that of‘Zhongyou8’nectarine was significantly negatively correlated.The IB index of‘Jinxiu’yellow peach had no significant correlation with the content of MDA,H₂O₂ and TP content.These results showed that MDA,H₂O₂ and TP content were not suitable for the common index of chilling injury of peach fruit,and there were great differences among cultivars.