Study On The Mechanisim Of Calyx End Rot Incidence In Starkcrimson Pear(Pyrus Communis L.)

Starkrimson pear is an excellent early maturing variety introduced in our country.In order to find out the cause of calyx end rot of Starkrimson pear,the sensitive variety Starkrimson pear was used as the material in this study.According to Koch’s rule,the pathogen of calyx end rot was isolated and identified,and the pathogenicity was detected.The content of mineral elements between the normal pears and diseased pears were compared;The control was clear water,we used spray gibberellin(GA3)and paclobutrazol(PP333)treatment alone before flowering to analyze fruit quality,gibberellin content,the incidence of calyx end rot after fruit dealed;In addition,the transcriptome analysis of the treated Starkrimson pear was carried out.The main results are as follows:(1)Two kinds of fungi were isolated from the fruit of calyx end rot,and identified as Alternaria alternata and Nigrospora spp.The pathogenicity of the two fungi was tested,both were non pathogenic bacteria.(2)The investigation results of the calyx end rot of Starkrimson pear treated with different plant growth regulators showed that the incidence of calyx end rot of Starkrimson pear treated with gibberellin was 71%,which was significantly higher than that treated with clear water 36%,and PP333.The incidence of calyx end rot of Starkrimson pear treated with paclobutrazol was 3%,which was significantly lower than that of clear water control.(3)The results showed that the contents of N,S,P,Ca,Fe,B,Zn in the diseased fruits treated with gibberellin acid were not significantly different from those in the normal fruits treated with gibberellin acid and water.The contents of K,Mg,Mn,Mo in the normal fruits treated with gibberellin acid were not significantly different from those treated with water,but,the contents of K,Mg,Mn,Mo in the diseased fruits treated with gibberellin acid were higher than that treated with water;The contents of Cu in the diseased fruits treated with gibberellin acid were lower than that treated with water,but,The contents of Cu in the diseased fruits treated with gibberellin acid were not significantly different from those in the normal fruits treated with gibberellin acid.which indicated that mineral elements were not the inducement of calyx end rot.(4)The contents of endogenous gibberellin were tested.The results showed that the contents of endogenous gibberellin was significantly higher in gibberellin treatment than in water control and paclobutrazol treatment.Further analysis of gibberellin components showed that there was no significant difference in the level of GA4 between treatments on the 5th and 10 th day,and there was significant difference in the level of GA7 between treatments only on the 10 th day,but there was a negative correlation between the level of GA4 and the incidence of calyx end rot of Starkrimson pear.There were significant differences in GA3 levels among the three groups on the 5th,10 th,15th and 20 th day after treatment.The GA3 content of gibberellin treatment was significantly higher than that water and paclobutrazol treatment,which was positively correlated withthe incidence of calyx end rot of Starkrimson pear.It can be seen that GA3 is the main cause of calyx end rot of Starkrimson pear.The results showed that high concentration of GA3 was the key factor for calyx end rot of Starkrimson pear.(5)The results of quality index analysis of Starkrimson pear showed that,the appearance of Starkrimson pear changed greatly with different regulators.Compared with the control with water,the fruits treated with gibberellin increased significantly,the shape of the fruits lengthened,the transverse diameter was shortened,and the calyx end protruded;the fruits treated with paclobutrazol had smaller deformation,shorter vertical diameter and flat top.There are differences in the internal quality of Starkrimson pear.Compared with the control of water,gibberellin Treatment of fruit acidity slightly increased;PP333significantly increased the contents of fruit soluble solids,hardness decreased,acidity increased.(6)The analysis of transcriptome data showed that 113 differential expression genes(DEGs)were expressed in the samples of Gibberellin Treatment and water control on the5 th,10th and 15 th days after treatment,and these genes were compared to 39 KEGG metabolic pathways,among which 14 genes were annotated to plant hormone signal transduction,3 genes were related to gibberellin signal transduction,164 DEGs were on the 5th,10 th and 1st days after treatment These genes were compared to 44 KEGG metabolic pathways,including 3 pathways related to plant endogenous hormones,4 genes related to gibberellin signal transduction,and 9 DEGs were expressed in the samples of Paclobutrazol treatment and water control on the 5th,10 th and 15 th days after treatment These genes were compared to 8 KEGG metabolic pathways.(7)CXE15、GID1B-like、SCL3、SCL3-1,which are involved in gibberellin signal transduction,have a significant negative correlation with endogenous GA3 and total gibberellin content.Exogenous Gibberellin can regulate endogenous gibberellin content by affecting the expression level of genes,which are related to gibberellin signal transduction.