Physiological Differences And Regulation Mechanisim Of Different Pyrus Ussuriensis Maxim Varieties During Softening

The fruits of Pyrus ussuriensis Maxim need the softening process before eating,but the softening fruits are very difficult for storage which seriously affect their edible period and commercial values further restrict the development of the P.ussuriensis Maxim pear industry.The mechanisms involved in the softening process after harvest are deeply needed to study for the further development of pear industry.In this work,the Jingbai,Nanguo,Huagai,Jianba,Anli pear varieties from P.ussuriensis Maxim were treated by ethephon and 1-MCP or storaged at 0?,the physiological and biochemical changes of tested pears were systematically studied,and the activity of softening related enzymes from harvest to softening were discussed.We aimed at understanding the possible mechanisms or possible factors involved in the softening process,and provide more information about the storage and softening process of P.Ussuriensis Maxim.Results showed that the mature and softening process of P.ussuriensis Maxim is a complex physiological and biochemical process,regulated by a variety of factors,and significant differences were exist among different pear cultivars.The main results obtained were list as follows:1.Five P.ussuriensis Maxim varieties showed significant differences in the storage properties when stored at(20±1)?.Anli pear had the longest shelf life(30 d),followed by Jianba pear(18 d),Jingbai and Nanguo pears(16 d),and Huagai pear showed the shortest shelf life(12 d).1-MCP treatment and low temperature(0?)could significantly extend the shelf life of the pears: for 1-MCP treated pears,the storage time could extend to 26 days for Jingbai,Nanguo and Huagai pears,30 days for Jianba pear,and 56 days for Anli pear after 1-MCP treatment;in addition,the storage time could extend to 210 days for fruits stored at 0?.2.Significant physiological and biochemical differences existed among five Pyrus ussuriensis Maxim varieties.Jingbai pear showed the highest respiration rate(P < 0.05),and Jingbai and Nanguo pears presented the higher ethylene production than other three varieties(P < 0.05).All the tested varieties had the peak of ethylene production except for Anli pear.1-MCP and low temperature treatments could significantly restrain the ethylene production,and delayed the appearance of ethylene production peaks.Huagai pear showed the lowest firmness at harvest,and Jianba pear presented the highest firmness,soluble solid content(SSC),VC and titratable acid(TA)contents,Jingbai pears showed the lowest TA contents.3.The polygalacturonase(PG),?-galactosidase(?-Gal),cellulase(CL)and amylase(AM)played significant role in the pear ripening and softening,significant correlations were found between the enzyme activities and the firmness of Pyrus ussuriensis Maxim.So PG,?-Gal,CL and AM were regarded as the key factors for the softening of tested pear fruits.1-MCP and low temperature treatments could restrain the activities of enzymes,and further delayed the ripening and softening process.For Jingbai and Nanguo pears,significant correlations were found between their firmness and PG,?-Gal and AM activities,in Huagai and Jianba pears,significant correlations were found between firmness and PG,?-Gal,CL and AM activities,for Anli pears,the key enzymes showed to be PG,CL and AM.4.The starch,soluble pectin and cellulose contents showed significant correlation with the fruit firmness.The decomposing of sucrose and cellulose and the increase of water-soluble pectin can promote the ripening and softening of tested pears.Although different contents were existed among different varieties,same trends were found in the contents of starch,soluble pectin and cellulose among tested fruits during storage.The content of sucrose,water-soluble pectin and cellulose were regulated by 1-MCP and low temperature treatments and their regulation effects are similar.5.1-MCP and 0? could significantly delay the softening process of pears by inhibiting the activities of PG,?-Gal,CL and AM and reducing the ethylene production,which restrained the degradation of cell wall and starch,and further regulate the mature and softening process of pears.