Analysis Of Salt Tolerance Of ’Meihong’ Apple And Its Parent ’Gala’ Apple

Soil salinization,that is,salt stress,can destroy the ionic and osmotic balance of cells,inhibit plant growth and reduce crop yield,and is one of the main abiotic stresses.Apple is one of the main fruit tree species in the world,but its salt tolerance is medium among deciduous fruit trees.Breeding salt-tolerant apples is one of the key measures to improve apple salt tolerance.Previous researches mostly focused on the combination of exogenous hormones and different rootstocks or scions,but the selection of new apple cultivars was rarely reported.The author’s research group took the lead in constructing a hybrid population of Xinjiang red meat apples and cultivated apple cultivars in 2006,and selected a new variety ‘Meihong’ apple.In this study,‘Meihong’ apple and its parent ’Gala’ apple are used as materials to explore their salt tolerance.The results are as follows:1.Analysis of physiological characteristics of ’Meihong’ and ’Gala’ apple seedlings under salt stress: It is concluded that ’Meihong’ and ’Gala’ apple seedlings are treated with 300 mmol / L NaCl for 24 days,(1)The content of chlorophyll a,chlorophyll b and net photosynthetic rate in the leave show a downward trend with the increase of salt stress time,which is negatively correlated with the salt stress time.The decline of ‘Meihong’ apple is smaller than that of ’Gala’ apple;(2)The relative electrical conductivity of the leave show an increasing trend with the increase of salt stress time,which is positively correlated with the salt stress time.The increase of ‘Meihong’ apples is smaller than that of the ’Gala’ apple;(3)The content of H2O2 in the leaves is proportional to the time at the beginning stage with the increase of salt stress time,and then remains at a high level for a period of time.The content of H2O2 in ’Meihong’ apple has always been less than that in ’Gala’ apple H2O2 content;(4)The MDA content,SOD activity,POD activity and CAT activity in the leaves showed a trend of first increase and then decrease with the increase of salt stress time.The increase of MDA content in ’Meihong’ apple was less than that of ’Gala’ The increase in MDA in Apple,the SOD activity of ’Meihong’ apple is higher than that of ’Gala’ apple,which could maintain a higher level for a longer period of time.The POD and CAT activities of ’Meihong’ apple are significantly increased in the early stage of salt stress,and the whole salt stress is followed by The process is maintained at a relatively high level,which is also higher than the ’Gala’ apple.2.Analysis of the expression levels of two salt-tolerant genes under salt stress for two apple seedlings of ’Meihong’ and ’Gala’: It is concluded that ’Meihong’ and ’Gala’ apple seedlings are treated with 300 mmol / L NaCl for 24 days The expression levels of the salttolerant genes Md NHX1 and Md SOS1 in the leaves of two apple trees,’Meihong’ and ’Gala’ both show an upward trend and then decreas with the increase of salt stress time.After salt treatment,the expression level of salt-tolerant genes is significantly higher than that of ’Gala’ apple seedlings.3.Different apple varieties have different salt tolerances.Analysis of various physiological growth and salt tolerance gene expression indicators shows that the salt tolerance of the ’Meihong’ apple is higher than that of its parent ’Gala’ apple Salinity.