Effects of different tree training systems and canopy structures on yield and fruit quality of‘Zaosu'pear

Abstract:【Objective】‘Zaosu' pear (Pyrus bretschneider Rehd.) is a major variety in Gansu province, andthe main tree training systems are delayed- open central leader system, major-branch open centre sys-tem, and spindle training system. So far no integrative management practices have been applied with thesetraining systems, which lead to a dense canopy, lower mechanization, and even to serious pest and diseas-es occurrence. New tree training systems are necessary for high density growing system in pear. Dwarfing,simplification, compact planting, standardization, and mechanization in pear tree management are ex-tremely urgent to replace the present training system. Quince is the major dwarfing rootstock abroad, andserved as the support to early bearing, high quantity, and lower labor cost. The graft compatibility ofquince and China pear varieties was tested since 1970 s, and the results showed that incompatibility, nofreezing resistance, and no saline tolerance. To explore the labor-saving cultivation pattern under currentconditions became the bottleneck problem and difficulty. Researchers in Agricultural University of Hebeistarted to explore pear labor-saving and high-efficient cultivation mode and technique in 2000, which isapplied successfully on‘Xueqing'and‘Hongxiangsu'pear. The new technique was introduced to our re-search base in Jingtai and Zhangye county, Gangsu province in 2010. The objective of this study was to ex-plore the desired tree structures of different training system for‘Zaosu'pear, and to investigate effects oftree canopy structures on yield and fruit quality of ‘Zaosu' pear.【Methods】Correlations between the num-ber and arrangement of the scaffold branches, canopy structure, and fruit quality of‘Zaosu'pear with 3training systems(cylinder, slender spindle and spindle system) were investigated using CI-110 canopy an-alyzer for hemispherical image analysis.【Results】The number of scaffold branches were 30 to 36 per treeat early fruiting stage for the cylinder system, accordingly 99 900 to 104 000 per 666.7 m². The LAI ofpear trees with cylinder system were significantly lower than those of slender spindle and spindle systems.However the yield, fruit weight, soluble solid, soluble sugar and sugar/acid ratio were significantly higherthan those of other two systems. The significant correlations were found between the canopy structure pa-rameters and fruit quality. LAI(in range from 4.94 to 7.28)was significantly and negatively correlatedwith fruit weight(r=-0.883**)and soluble solid content(r=-0.693*), while positively correlated with Vcconten(tr=0.878**). MLA(in range from 13.77 to 21.39) was significantly positively correlated with fruitweight and soluble sugar(r=-0.939**and 0.825**),positively with soluble solid conten(tr=0.716*),while sig-nificantly and negatively correlated with VC(r=-0.999**). TC was positively correlated with FW(r=0.862**),soluble solid content(r=0.907**),and soluble sugar(r=0.946**). The negative correlation was foundbetween TC and Vc content(r=-0.883**).【Conclusion】The potential of producing‘Zaosu'pear with thecylinder system at early fruiting stage has proved to be effective for achieving high yield, high qualityfruits and economic returns.