A new early-ripening bayberry cultivar ‘Zaojia'

Abstract: ‘Zaojia',a new early-maturing bud mutation line of‘Biqizhong'bayberry cultivar,was selected from a bayberry orchard located in Lanxi,Zhejiang. The age of maternal tree is 27 years. Seven-year botanical evaluation between maternal tree and its progeny since 2003 proved that this cultivar is stably,uniquely and differently. Trees of‘Zaojia'exhibits a dwarf phenotype,which has a bigger fruit size,a better fruit color and a higher yield than its maternal tree.‘Zaojia'was finally examinated and approval by the Zhejiang Forest Variety Approval Committee in 2013. The leaves of‘Zaojia'is waxy and oblanceolate with rounded leaf tip,entire margin and wedged leaf base. The average length,width and thickness is 9.61 cm,2.74 cm and 0.023 cm,respectively. All the flowers in‘Zaojia'are female,red and V-shape with breen bracts and cylinder-shaped floral tube,which has 0.88 cm length and 0.22 cm coarsenes. There are about thirty-five flowers in each inflorescence,and the fruit set percentage reaches 15.6%. The fruit is heavy fragrant and spherical in shape with purple black skin and chartreuse pedicel. The flesh is tight with sweet and acid taste. The average fruit weight reaches 12.5 g. The fruit shape index is 0.96.Moreover,the fruit edible rate reaches 95.7%. The content of soluble solids,total sugar,total acidity,citric acid and vitamin C in the fruit juice is 11.4%,10.3%,1.17%,1.08%,and 21.7 mg·kg-1,respectively. There is a small elliptical stone in fruit. In sammary,the fruit quality is excellent. The period of budbreak,peak flowering and late flowering are in late February,early April and middle April,respectively. The scion sprouts three times in one year in Jinhua,Zhejiang. Spring-sprouting is from mid April to mid May,finally forming 11.1 cm-length shoot and 0.48 cm-length internode. Summer-sprouting is in late June resulting in 5.9 cm-length shoot. The fruit core-hardening stage is in middle May and colour-changed period is in late May.Then fruit begins to mature in the beginning of June and then reaches full ripeningt in early June. The fruit developmental periods is about 48 days. The average crown height of 10 years old tree is 2.3 m,which is bigger than‘Biqizhong'and‘Dongkui'for 17.3% and 9.1%,respectively. In comparison,the plant type of‘Zaojia'is dwarf. In addition,it usually bears fruits in the fourth year after grafting. Thus,the first fruit bearing time of‘Zaojia'is earlier than the controls. In most cases,the short and middle-long branches are mainly used for fructifying. The trees of‘Zaojia'show high resistance to various abiotic stresses and pathogens. Neither maternal plant nor its progeny displays damaging disease,such as bacterial gall and brown spot. The fruit exhibits good storage ability,and is feasible for long-distance transportation. Moreover,the fruit could keep excellent quality after storage for 15 days storage at room temperature. The most suitable cultivation area for‘Zaojia'is low altitude region in bayberry-producing areas in Zhejiang,especially in the acid,gravel,red and loess soil with high air humidity and water content.‘Zaojia'cultivar typically bears fruits in the fourth year after grafting,and gradually moves to full fruiting period in the next four years. The average yield of this cultivar is around 10 500 kg per hectare. The growth vigor of this cultivar is moderate. However,it shows some typical characteristics,such as early-bearing,early-ripening,deep dark color,stable commercial character,and good taste quality. The spring planting is usually from late February to late March. For conventional cultivation,the optimum distance should be 5 m ×6 m,with a planting density of 330 trees per hectare. For dwarf and dense planting,it should be 4 m ×4 m,with a planting density of 630 trees per hectare. The planting pit is 0.8 m×0.8 m×0.6 m. A plant technology with modified open center shape is developed and used for reshaping in bayberry production. In the first and second year after planting,the branch pruning is forbidden in order to improve the crown growth. In the following two years,it is needed to restrict the apical dominance of vertical branch by various branch bending including branch drawing,branch pressing and branch hanging,in order to keep ventilating and light transmission to promote flower bud differentiation. In the next years,3-5 oblique secondary scaffold branches are kept as main shaft and horizontal as well as pendulous branches as fruitbearing branch. While the branches which are weak,over-crowded,crossed,superposed and sick are needed to be pruned. In addition,the bearing branch should be truncated for renewal after fruiting,and the watershoot is also needed to be topped. The growth of young tree should be promoted by expanding the depth of the planting pit year by year by increasing some fertilizers,especially the fast released one. Additional fertilization rates of urea or compound fertilizer is 0.05-0.1 kg per tree for one time,and it should be repeated 4-5 times from March to July at the first three years after planting. When it begins to bear friuts in the fourth or fifth years after planting,the fertilizer including 0.1 kg urea and 0.5-1 kg potassium sulfate should be applied in April,July and November,respectively. In order to improve the production and quality,a specific fertilizer(N: P: K is1:0.3:4) can be applied on bearing tree. Three main fertilization methods including broadcasting method,row method and soilcoverage method are used in bayberry production. The application of trace elements is also important,especially boron,zinc and manganese. In November,the major used fertilizers are organic fertilizers which contain folly-fermented livestock manure(10 kg) and folly-fermented cake fertilizer(3 kg) used for each plant. In May,a potassium fertilizer composed of plant ash and potassium sulfate,as the major used fertilizer,is used for each plant. Combined with shearing big branches in inner bore of plant in summer,shoot thinning,flower thinning and fruit thinning are used during the flowering period in the next spring.When the tree with much more flowers,it is needed to cut the straight flowering branches outside directly. When the tree with moderate flowers,it is needed to cut the straight bearing branches. When the tree with less flower buds,it is needed to spray the mixture fertilizer including boron,phosphate and potassium before or after flowering,which can increase flowers and fruits.