Effect Of Root Restriction On Flower Bud Formation And Fruit Quality Of Peach Tree With Central Leader Form

Zhejiang province is a humid region where peach trees grow vigorously because of abundant water supply.Large crown,heavy workload and poor flower bud formation lead to low yield.Root restriction can inhibit vegetative growth and promote reproductive growth,thus suitable for high-density orchard.Peach trees in central leader form have advantages of simple structure,easy pruning,high yield and uniform fruit quality.In this study,‘Yuanmeng’[Prunus persica（L.）Batsch.]peach trees were treated by root restriction and trained to central leader form.Tree growth,flower bud amount and fruit quality were compared.The correlation between flower bud formation process and accumulation of carbon,nitrogen and hormone was discussed.Accordingly,technique of training root-restricted peach trees into central leader form and preliminary mechanism of promoting flower bud formation were clarified.Furthermore,theoretical basis of root restriction technique on central leader peach trees could be established.The results are as follows:1.When inducing secondary shoots,comparing with shoot twisting,shoot pinching can efficiently suppress shoot growth and improve fruiting branch structure,which increases long branches by 45%while decreases spindling shoots by 50%.It appears that flower bud formation benefits most by shoot pinching when shoot length is 20～25 cm.In this experimental group,although peach tree crown is reduced by 41%in root restriction,there is no evident difference of total shoot increment and flowering rate between two treatments.2.Differentiation of flower buds on lower part of primary long branch starts around July 16^th in root restriction,two weeks earlier than control.Along with flower bud differentiation proceeding,leaf total nitrogen declines while C/N rises.Flower bud differentiation develops more rapidly and flowering rate is significantly higher in root restriction treatment than control.Besides,high level of ZR at the ending of initial stage of flower bud primordium differentiation and increase of ABA at the beginning of calyx differentiation stage are propitious to morphological differentiation.ABA content is observably higher in buds than in leaves.3.Applying root restriction to central leader‘Yuanmeng’peach tree makes early yield promising.Flower bud rate of long and short branches of two-year-old peach trees were respectively 0.17 and 0.36 higher in root restriction than control.Fruit yield reaches 407 kg/667m² in root restriction while there is no yield in control.Although fruit size is smaller in root restriction treatment,fruit characteristics such as total soluble solids,titratable acids and fruit color are consistent from top to bottom.In conclusion,root restriction can control tree vigor of central leader form peach trees,promote flower bud formation,and obtain early yield.Also,peaches from each fruiting position is uniform in fruit quality.Thus,root restriction technique is worth popularizing in high-density peach orchard.