| Dwarf rootstocks close planting has become the main mode of apple cultivation in the world.It has become the inexorable trend of the development of apple industry in China.Due to the topographic diversity and climate variability,it is greatly significant to breed the rootstocks which are both dwarfing and cold resistant.In this thesis,the electrolyte leakage rate was measured and half lethal temperature was calculated in the shoot of 25 kinds of apple dwarf rootstocks.The correlation of the lethal temperature with soluble sugar and starch content,SOD,POD and CAT activity,and MDA content were analyzed.Moreover,the effects of different middle rootstocks on the tree growth,yield and quality of fruit were carried out with 16 kinds of scion-rootstock combinations(Malus hupehensis + middle rootstock+ ‘Fuji’).The results are as following:(1)The half lethal temperature of the branches were different in 25 types of rootstocks,but the similar in same series of rootstocks.SH series had the strongest cold resistance,MD001,B9,P22,CG24 and G16 took second place,M and MM did not have a little cold resistance.(2)Under low temperature stress,the soluble sugar content,starch content,SOD activity,POD activity,CAT activity and MDA content of different types of rootstock shoots were related to the cold resistance.The correlation analysis showed that the soluble sugar and MDA content were correlated to the half lethal temperature.(3)In different scion-rootstock combinations,the electrolyte leakage rate and half lethal temperature of shoots were different obviously.SH28 had the lowest half lethal temperature,-40.15 ℃;M7 had the highest half lethal temperature,-32.59 ℃.The result was similar to dwarf rootstock cold resistance;it indicated that the rootstock could affect the cold resistance of grafted varieties.(4)The tree height,trunk circumference,coverage rate and total branches of different scion-rootstock combinations were roughly proportional.MM106/ Fuji and YL1/Fuji were the highest,which were 4.4 m and 4.5 m respectively.SH6/ Fuji was the lowest,which was 3.2 m.The rate of coverage of MM106/Fuji and SH3/Fuji were the biggest,which were 85.0% and 84.7% respectively,the rate of coverage P22/Fuji was the lowest,34.4%.MM106/Fuji and M7/Fuji had the largest total branches,which were 47.30×104·hm-2 and 50.41×104·hm-2 respectively.B9/Fuji and P22/Fuji had the smallest total branches,which were 18.67×104·hm-2 and 19.81×104·hm-2 respectively.YL1/Fuji and SH3/Fuji had the largest trunk circumference,which were 118.00 mm and 111.75 mm respectively.M26/Fuji and P22/Fuji had the smallest trunk circumference,which were 71.15 mm and 69.50 mm respectively.(5)SHa/Fuji had the highest proportion of short branches and lowest proportion of long branches,the ratio was about 73% and 13% respectively.The P22/Fuji has highest proportion of long branches and lowest proportion of middle branches,the ratio was 30% and 10% respectively.On the whole,the combination of SH3/Fuji and SH6/Fuji were relatively reasonable,the proportion of short branches was about 65%,and the proportion of long was about 10%,the tree potential was moderation.(6)The individual yields of SH40/Fuji and SH6/Fuji were the highest,which were 17.35 kg and 16.3 kg respectively,SHa/Fuji,YL1/Fuji and SHc/Fuji were the lowest,which were 6.33 kg,6.22 kg and 5.71 kg respectively.SH18/Fuji and SH6/Fuji had the highest large fruit rates,the ratio of single fruit to 200 g was more than 60% in total production.SHa/Fuji and SHc/Fuji had the lowest ratio of single fruit to 200 g,only about 10%.Took into account of single plant yield and large fruit rate,SH6/Fuji,SH18/Fuji and SH40 were better than others.(7)In terms of fruit quality at the same level,the soluble solids content of SH6/Fuji,SH9/Fuji,SH12/Fuji and SH18/Fuji were relatively high,which were 15.68%,16.15%,15.70% and 16.43% respectively,SHa/Fuji,SHc/Fuji,and M26/Fuji were the lowest,which were 14.18%,14.20% and 13.93% respectively,.The solid acid ratio of SHa/Fuji,SHc/Fuji and SH6/Fuji were the highest,which were 68.74%,61.95% and 67.09% respectively,SH3/Fuji,SH38/ Fuji and M26/Fuji were the lowest,which were 46.38%,44.99% and 42.72% respectively.The fruit hardness of scion-rootstock combinations were similar. |
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