| Apple(Malus × domestica Borkh)is one of the most cultivated fruit crops in China.Its area and yield rank first in the world.Vigorously developing apple industry is of great significance for increasing farmers’ income and adjusting the structure of agricultural industry.However,in the production and cultivation of apple,the phenomenon that the orchard is overlapped,the degree of mechanization is low,and the labor cost has increased has become an urgent problem in the current production of apple,and the dwarf planting can effectively solve these problems.This method is convenient for intensive production,and the high degree of mechanization is very consistent with the modern cultivation mode of apple.Columnar apple,as a special dwarfing mutation type,is characterized by short internodes,straight main branches and trunks,many short branches without larger lateral branches,small crown and compact structure under natural growth.It is very suitable for high density cultivation and is considered as an ideal plant type for intensive and mechanized production of apple.Some molecular markers linked to Co gene have been screened by some predecessors,but the unique growth characteristics of columnar apple have not been elucidated at the molecular level.Therefore,it is necessary to systematically study the molecular mechanism of columnar traits formation in apple.In this study,the columnar apple varieties ’Runtai 1’,and ’Trajan’,standard apple‘Fubrax’Huashuo’,and‘Fuji’and the hybrid progenies of columnar type and standard type as experimental material were used to identify and analyzed,the candidate genes were identified and analyzed by real-time fluorescence quantitative PCR,and the contents of endogenous hormones were compared and analyzed.The main results were as follows:1.Screening and expression analysis of Co gene in columnar apple.Four apple cultivars,i.e.’Runtai 1’,’Trajan’ and ’ Fubrax ’,’ Huashuo ’,were used as test materials,samples of apical buds,lateral buds,stem tips,stem tips of lateral buds,flowers,fruits,leaves and roots were collected respectively.According to the newly published genome and location interval of apple,the related genes were selected and amplified by PCR on shoot apex and lateral bud shoot apex of columnar apple and standard apple,and the gene expression was analyzed by real-time fluorescence quantitative PCR.The results showed that the genes MD10G1184100,MD10G1185400,MD10G1185600 and MD10G1190500 had significant differences in stem apex and lateral bud apex between columnar and standard apples,and then the gene expression patterns of the four genes in different parts and at different stages were analyzed.The expression of MD10G1184100 in the root of columnar apple was significantly higher than that in other parts.Both genes MD10G1185400 and MD10G1185600 were significantly expressed in the stem apex of columnar lateral bud,while the gene MD10G1190500 was significantly expressed in the apical bud of columnar apple.In different plant stages,the expression of MD10G11185600 was the highest at stem tip growth stage of columnar apple,the others were the highest in columnar apple at germination stage.2.The markers linked to columnar traits were selected to screen and identify columnar traits of columnar apple,standard apple and hybrid progenies of columnar apple and standard apple.The results showed that the 29f1-JWIlr marker and the column-specific primer upstream of normal and downstream of columnar only showed specific target fragments in columnar plants after PCR amplification.The results were simple and intuitive,and could quickly and effectively identify whether it was columnar or not.The results of this study can be used to assist selection of columnar apples with relevant molecular markers.3.The crown diameter,stem diameter,branch number and internode length of columnar apple ’Runtai I’ and standard apple ’Fuji’ were measured and analyzed.The results showed that the crown diameter,stem diameter and internode length of columnar apple were significantly different from those of standard apple.The crown diameter of standard apple was significantly higher than that of high-columnar apple,which was about 1.99 times that of standard apple,the stem diameter of columnar apple was significantly higher than that of standard apple,about 1.18 times that of standard apple,and the internode length of standard apple was about 1.27 times that of columnar apple.At the same time,the number of branch groups of columnar apple was 78.8%,while that of standard apple was 64.7%,1.21 times that of standard apple.The proportion of long,medium and super-long branches in standard apple was higher than that in columnar apple,which was 1.37,1.65 and 1.80 times higher than that in columnar apple except for short branches.4.The contents of endogenous hormones in the leaves of columnar apple and standard apple at different developmental stages were compared and analyzed.The results showed that the contents of ZR,ABA and GA3 in standard apple were higher than those in columnar apple,and changed with the growth of leaves.And,the contents of GA3 and ZR in columnar apple were changed continuously.There were significant differences between columnar apple and standard apple at the early growth stage.ABA was significantly different in the early growth stage,the vigorous growth stage and the later growth stage,while IAA content in columnar type and standard type fluctuated greatly with the growth of the plant,and there was a trend of interlacing between them.During the whole growth period,there was only significant difference between the early growth stage and the vigorous growth stage.ABA was significantly different in the early growth stage,the middle growth stage and the growth stage,while IAA content in columnar type and standard type fluctuated greatly with the growth of the plant,and there was a trend of interlacing between them.During the whole growth period,there was significant difference between the early growth stage and the middle growth stage. |
