Study On The Occurrence Mechanism Of Hard-end In Suli Pear Fruit

Pyrus bretschneideri cv.Suli is deeply loved by consumers for its crisp and juicy taste.However,the emerging of fruit hard-end disease in recent years has seriously affected its fruit quality and has brought great obstacles to the development of the Suli pear industry.At present,the cause of the onset of hard-end disease in Suli pear fruit is still unclear.In this study,the pears were used as experimental materials to compare the differences in fruit quality,tissue observation,cell wall composition,gene expression and mineral nutrients between the diseased fruits and normal fruits,and the reasons for the formation of hard-end disease in pear fruits were preliminarily revealed.The results of this study are as follows:1.The symptoms of hard-end disease of Suli fruit were studied.The results showed that from the appearance of the fruit,the fruit of the hard-end was not round and the top of the fruit was prominent.For the fruit quality,the fruit of the hard-end was hard,the content of stone cells increased,the water content decreased,and the soluble sugar content of the diseased fruit significantly lower than normal fruit.Therefore,the main symptom of the hard-end Suli pear is the increase in hardness,accompanied by the deterioration of the appearance and intrinsic quality of the fruit.2.Using tissue observation techniques,it was found that there was no significant difference between the fruit of the hard-end disease and the normal fruit in the cell activity,but the tissue structure showed that the stone cells of the hard-end disease were distributed more,and the accumulation of lignin increased,resulting in serious degree of lignification.The cell wall components of the Suli pear fruit were analyzed.The results showed that there was no significant difference between cellulose content and pectin content,but the stone cell and lignin content of hard-end disease fruit was significantly higher than that of normal fruit.The changes of transcription level in Suli pear fruits were compared by transcriptome sequencing.It was also found that the lignin biosynthetic structure gene(Pbr POD)was up-regulated in Suli pear fruits with hard-end disease.Therefore,the occurrence of hard-end disease in Suli pear fruit is closely related to lignin accumulation.3.In this study,the differences of mineral nutrients between the fruits of the hard-end Suli pear and the normal fruits were further compared.The results showed that the contents of Ca and B in the fruit ofthe hard-end pear were significantly lower than that of the normal fruits,while the content of Fe was significantly higher than that of the normal fruits.In order to verify the effect of Ca on hard-end disease,we also sprayed exogenous Ca Cl2.The results showed that the incidence of hard-end disease decreased significantly after Ca Cl2 spraying.In addition,the change of Ca2+ concentration in the fruit of pear fruit was studied by potassium pyroantimonate precipitation method.It was found that the concentration of Ca2+ in normal fruit was significantly higher than that in the fruit of hard-end disease,and the distribution of Ca2+ in the cells of hard-end disease was sparse.Taken together,the lack of Ca in the fruit may mediate or participate in the induction ofhard-end disease in pear fruit.