Effects of different dwarfing interstocks on tree growth characteristics, leaf physiology and fruit quality of‘Nagano Fuji No.2’appl

Abstract:【Objective】High density planting with dwarfing rootstock is a new cultivation pattern for ap- ple in China. Screening of rootstock-scion combination is important for high density planting. Dwarfing effect, adaptabilty, productivity and fruit quality are the main indexes for the evaluation of rootstock-sci- on combination. This article aimed to study the effect of different dwarfing interstocks on the growth structure composition and antioxidant enzyme activity and fruit quality of‘Nagano Fuji No.2’apple as scion cultivar in order to provide reference for screening scion-rootstock combination suitable for plant- ing in Longdong area of Gansu province.【Methods】‘Nagano Fuji No.2’were grafted onto SH40, M26, SH38, B9, M9, M9-T337, Y-1, GM256 as interstocks with plantlets generated from tissue culture of Malus robusta Rehd. as rootstock in containers (36 cm ×28 cm × 32 cm) in 2012. The grafted plants were transplanted in the field in 2016. The evaluation was carried out in 2018. The effect of dwarfing in- terstocks on the fruit quality were evaluated based on membership values of function ingredients calcu- lated by the method of membership function and all the collected data were analyzed using SPSS 19.0. Growth habits of the trees were quantified by tree height, canopy diameter, circumference and total shoot number and proportions of different types of shoots were measured in 2015. The method of mem- bership function was used to evaluate the suitability and dwarfing effect of the stock/interstock/scion combinations. The tree growth characteristics, morphological appearance, leaf physiological activity, an- tioxidant enzyme and fruit quality were used to evaluate the dwarfing effect of different combinations【Results】The dwarfing degree of the saplings eight rootstock /interstock/scion combinations from strong to weak was M9-T337> M9 > M26 > Y-1 > GM256 > SH40 > SH38 > B9. The effect of 8 dwarf- ing interstocks on the number of main branches and the cross-sectional area of the dry diameter of‘Na- gano Fuji No.2’was Y-1 > M9 > GM256 > B9 > M9-T337 > SH38 > SH40 >M26 from large to small. The variation coefficients of plant height, crown width, number of main branches and cross-sectional ar- ea of dry diameter were 13.34%, 10.78%, 27.40% and 30.20% respectively. The long-branch ratio of M9 and T337 as interstock were 6.57% and 7.30% while the long-branch ratio of other combinations was between 10.80% and 17.57%. The variation coefficients of branch growth, total number of branch- es, proportion of long branches, proportion of medium branches and proportion of short branches were respectively 23.11%, 18.56%, 31.24%, 25.71% and 12.27%. The activity of SOD, POD, PPO and IOD of each combination was M9-T337 >M9 >M26 >Y-1>GM256 >SH40 >SH38 >B9 from large to small. The variation coefficient of SOD, POD, PPO and IOD enzyme activities were 55.22%, 50.98%, 26.30% and 35.83%, respectively. The comprehensive evaluation index of each combination was M9-T337 > M9 >M26 >SH38 >SH40 >Y-1 >GM256 >B9.The tree height and crown width of M9-T337, M26 and M9 interstocks were significantly lower than those of other interstocks, while the number of main branches and the cross-sectional area of trunk diameter were significantly higher than those of other in- terstocks. M9-T337, M26 and M9 had significantly lower shoot growth, total shoot amount and propor- tion of long shoot than other combinations. The activities of SOD, POD, PPO and IOD of each combina- tion from high to low were M9-T337 > M9 > M26 > Y-1 > GM256 > SH40 > SH38 > B9. The single fruit weight, fruit hardness and soluble solid content of the fruits of‘Nagano Fuji No.2’apple grafted on M9-T337, M26 and M9 as interstock were significantly higher than those on other interstocks, while titratable acid was significantly lower than on other interstocks. The content of oxalic acid, tartaric acid and malic acid of the fruits of‘Nagano Fuji No.2’apple grafted on M9-T337, M9 and M26 as inter- stock were significantly higher than those on other interstocks【. Conclsuion】The rank of different inter- stock in dwarfing effect, anatomical structure, antioxidant enzyme activity and fruit quality is M9- T337 > M9 > M26 > SH38 > SH40 > Y-1 > GM256 > B9. M9-T337, M9 and M26 might be the best in- terstock combination in Long dong area of Gasu province which could be possibly considered as the first choice for cultivation. Long term evaluation is needed for more prescise conclution.