Studies On Critical Technique And Their Physiological Mechanisms Of Sweet Cherry (Prunus Avium L.) In Warm Region

Sweet cherry?Prunus avium L.?is one of the most improtant fruit crop which mainly grows in temperate cliamte zones.In China,the cultivations of sweet cherries have expanded quickly from the traditional temperate regions surrounding Bohai Bay to higher latitude areas in the southwest due to the increasing demands of consumers and the high profits for growers.Meanwhile,the possibility of cultivating sweet cherries in the middle and lower Yangtze River regions with a warm winter and few chilling hours has been evaluated in recent years.One of the major challenges of cultivating sweet cherries successfully in these regions is satisfying the chilling requirements,which are generally from 600 to 1400 h according to the 7.2°C model.Symptoms such as delayed sprout,deformed flowers or poor fruit set caused by unsatisfied chill demand will finally lead to reduction in potential yield.Fortunately,with application of hydrogen cyanamide?HC?and rain-shelter-cultivation method,the cultivation areas are increasing rapidly in these economically developed regions.However,because of the inappropritate choice of variteies,configuration of pollinated trees and management of cultivation,the yield,qulity and economic value of sweet cherry were always decreased during the popularization of sweet cherry in these regions.What's more,although the application of HC before field budburst leads to early and uniform bud break,improving flowering and fruiting,the biological mechanism that underlies its dormancy-breaking effect hasn't been fully described.Therefore,in the present study,sweet cherries cultivated in Shanghai were used as materials to study the effect of different combination of varieties and rootstocks,the comprehensive performance of high-density cultivation,and the influence of hydrogen cyanamide on dormancy release and flowering.The main results are as follows:1.Critical cultivation technique of Sweet cherries in warm region8 sweet cherry varieties?‘Brooks',‘Summit',‘Tieton',‘Van',‘Hongdeng',‘Lapins',‘Zaodaguo'and‘Hongmi'?grafted on 2 rootstook varieties?‘Daqingye'?‘DQY'?and/or‘Gisela 5'?‘G5'??were used as materials in this experiment to study the characteristics of their growing and fruiting.The results indicate that dwarfing root stock‘G5'can not noly weaken the vegetative growth,such as tree height,trunk diameter,crown width,branch diameter,branch length,shoot diameter and shoot length,but also promote the flowering characters.When comparising with‘DQY',the densities of buds and flower as well as the proportions of perfect flower and bouquet spur of‘G5'are 1.74,1.07,1.05,1.03 times bigger,respectively.Moreover,‘Brooks',‘Lapins'and‘Hongmi'have the biggest proportions of fruit setting,perfect flower and bouquet spur among all varieties.Combining the application of dwarfing rootstook,the effect of upright fruiting offshoots systems?UFO system,including pruning,planting angle and seedling?to balance the vegetative and productive growth was assessed The results showed that shelter facilities and root restriction planting method should been chosen for the UFO system of sweet cherry cultivation.In addition,small planting angle??30°?,cutting back and virus-free stock benefited more vegetative growth of sweet cherries trees than reproductive growth.2.Effect of application of hydrogen cyanamide on the endodormancy release and flowering of sweet cherry treesThe trial was conducted to verify the effect of foliar application of HC on dormancy release and flowering of Prunus avium L.var.Summit trees,as well as on changes of water content,carbohydrate conten,total nitrogen and protein nitrogen content,the endogenous levels of abscisic acid?ABA?,gibberellic acids?GAs?,indol-3-acetic acid?IAA?and cytokinins?CTKs?in shoots with spurs.Results showed that HC efficiently hastened bud break,shortened flowering duration and improved fruit-set.Moreover,hydrogen cyanamide led to a quick hydrolyzation hydrolysis of strach.The increase of glucose and fructose and the decrease of sorbitol indicating the resume of metabolism.Furthermore,bioactive GAs plays different roles in the process of dormancy release and flowering,GA₃ was recognized the highest isomer of bioactive GA and closely related with dormancy release improved by HC application as well as GA₄.GA₇ displayed a rapidly increase when buds went into sprout stage until full bloom and associated with promoted sprout and flowering by HC application.GA₁ showed irregular changes during the process of dormancy release and flowering.A higher GAs/ABA ratio was coincided with the dormancy release and flowering when HC applied to sweet cherry cv.‘Summit'.In addition,HC also given rise to the increase of IAA and CTKs,which is considered to have a role in promoting dormancy release.Therefore,if economically feasible,HC could be an option for the production of sweet cherries with higher chilling requirement in low winter chill regions.