Study On The Effect Of Exogenous Melatonin And Calcium On Pear Ring Disease Resistance

Pear is a perennial deciduous fruit tree of the Rosaceae Pyrus genus,and is one of the main fruit trees in the world.Pear ring rot,caused by Botryosphaeria dothidea,is one of the most serious diseases of pear trees.1.According to our research,exogenous melatonin application enhanced resistance to B.dothidea in pear fruits.Melatonin treatment of pears significantly reduced the diameter of disease spot and enhanced endogenous melatonin content under B.dothidea inoculation.2.Compared with H₂O treatment,As the most important and stable ROS,O_-²and H₂O₂are involved in a series of processes of plant development,stress response and programmed cell death.Exogenous melatonin reduces O₂^-and H₂O₂levels and increases the activity of active oxygen scavenging enzymes.At the same time,the contents of AsA,GSH,dehydroascorbic acid（DHA）,and oxidized glutathione（GSSG）in the ASA-GSH cycle after melatonin treatment were also detected.Exogenous melatonin The treatment of the element can keep the ASA-GSH cycle high in reducibility.3.Exogenous melatonin treatment increased the expression levels of core autophagy genes PbrATG1,PbATG8c,PbrATG5 and PbrATG10 in pear fruits.The expression levels of core autophagy genes and autophagosomes formation were elevated by melatonin treatment in pear fruit.After inoculation with B.dothidea,the treatment of exogenous melatonin increased the content of soluble sugar and organic acid in pear fruits compared with H₂O treatment.4.we searched the（DEGs）between calcium and H₂O treatment with B.dothidea inoculation in pear by using the RNA-seq.On the basis of the standard of a proportion of calcium/H₂O fold change>2,and the false discovery rate（FDR）<0.05,2812 and 572genes with significant differential expression were identified between the H₂O and calcium treatment under B.dothidea inoculation at 2 days post inoculation（dpi）（D2）and 8 dpi（D8）,respectively,indicating that significantly more genes in D2 responded to calcium treatment.Results of gene annotation showed that DEGs were focused on plant-pathogen interactions,hormone signal transduction and phenylpropanoid biosynthesis in D2.Moreover,transient silencing of PbrCML30（Pear Cal Modulin-Like proteins 30）,which had significantly higher expression in response to calcium than H₂O treatment,conferred compromised resistance to B.dothidea.Exogenous calcium treatment slightly alleviated the symptoms of TRV2-PbrCML30 leaves compared with TRV2 leaves under inoculation,supporting its key role in pear resistance to B.dothidea.