Study On The Relevant Reasons Of Loquat Fruit Shrinkage Disease

In this study,loquat strain “4-5-1” with 80% fruit shrinkage rate and loquat cultivar‘Dawuxing‘ with almost no shrinkage were used as experimental materials.The causes for fruit shrinkage were explored by comparing the differences of physiological and biochemical indexes,organizational structure characteristics and molecular level between“4-5-1” and Dawuxing at different stages of the disease.The main results are as follows:1.The average daily temperature and humidity during the onset of fruit shrinkage disease were 25 ℃ and 60%.The average daily temperature was higher and the air humidity was lower,and the comprehensive photosynthetic capacity and water-holding capacity of “4-5-1” were lower than those of ‘Dawuxing‘.2.Paraffin section observation showed that the pericarp structure was incomplete,the number of cell layers was small,the shape was irregular,the arrangement was irregular,and there were more lignin deposits dyed red.Apoptosis of pericarp was detected by TUNEL.From the beginning of the onset of the disease,“4-5-1” fruit stalk and panicle axis appeared serious morphological changes such as thinning,deformity,rupture and fracture,while the xylem changed later in ‘Dawuxing‘.3.The ratio of sugar to acid of “4-5-1” at the peak stage(IV)and the end stage(V)was significantly higher than that of ‘Dawuxing‘,which was 1.8 and 3.5 times higher than that of ‘Dawuxing‘.The water content of “4-5-1” at the end stage(V)was 79.99%,which was significantly lower than that of Dawuxing.MDA content,POD activity and CAT activity of “4-5-1” were always significanly higher than those of ‘Dawuxing‘.The activities of PG,PME,SOD and APX in pulp and peel were all increased after the disease emergence.4.The content of B in leaves and fruits of “4-5-1” was lower than that of ‘Dawuxing‘,and the contents of K and Ca in fruits of “4-5-1” were significantly higher than those of‘Dawuxing‘ at the early stage of disease.There was no significant difference in Mg and Zn contents.5.The average expression level of HSP70 in ‘Dawuxing‘ pulp was higher;the expression level of Ej DHN1 in the peel and pulp of “4-5-1” was higher than that of‘Dawuxing‘,and the expression levels of Ej DHN1 and Ej AO increased significantly from the onset of fruit shrinkage;Ej DHN5 in pulp showed an upward trend,and decreased after the peak in the onset of fruit shrinkage.