Study On The Resistance Physiology Against The Pathogens Of Anthracnose And Ring Rot On Pear Fruit

To understand the mechanism of pear fruit resistance against the pathogens of pear anthracnose and ring rot, anti-expansion capacity of against the pathogens of pear anthracnose and ring rot was evaluated on mature pear fruit from different Pyrus species. Physiology and biochemistry indexes were discussed mainly after incubating the pathogens of pear anthracnose and ring rot in different Pyrus species, especially the changes of phenolic compounds. This provides theoretical basis to reveal the mechanism of resistance against pear anthracnose and ring rot. To develop the study on the resistance physiology against the pathogens of pear anthracnose and ring rot on pear fruit, the extraction process was firstly optimized by orthogonal array for total polyphenols from pear fruitlet pulp. The components of phenolic compounds in pear fruit were also systematically analyzed by high performance liquid chromatography (HPLC); this indicates the distribution of phenolic compounds in different Pyrus species.Results indicate:1. The objective of this study was to optimize the extraction process for total polyphenols from pear fruitlet pulp by orthogonal array and their components were determined using high performance liquid chromatography (HPLC). The results indicated extraction ratio of polyphenols was observably affected by temperature and ethanol concentration. The optimal extraction conditions of polyphenols from pear fruitlet pulp were ethanol concentration of60%, extraction temperature of70℃, extraction time of2h, extraction material-liquid ratio of1:30(g/mL). Under these optimal extraction conditions, the extraction rate of polyphenols was up to1.47mg/g. Nine phenolic compositions were identified by HPLC in which arbutin was the main component with the content of74.1%of the total phenols.2. The components of phenolic compounds in fruit from12of Pyrus species were determined using high performance liquid chromatography (HPLC). Among the12of Pyrus species, ten kinds of phenolic compounds were detected in three different Pyrus species, while nine kinds were detected in other three different Pyrus species, and only eight kinds were observed in the remained six different Pyrus species. The same phenolic compound were more variable in different Pyrus species; the maximal content of vanillin and caffeic acid were44and20times than the minimal content, respectively. Chlorogenic acid contributed62.2%to the total polyphenols, while the content of catechin and epicatechin were2.87mg/100g and1.52mg/100g, respectively; these are the main phenolic compound in pear fruit. In contrast, the level of phloridzin and quercetin were minimal, only reach to2.87mg/100g and1.52mg/100g, respectively. Correlation analysis has been made between different phenolic compounds and total polyphenols. The results indicated chlorogenic acid exhibited positive correlation (correlation coefficient0.954**) with the content of total polyphenols, while other phenols displayed some correlation with total polyphenols.3. Using’Hongnahe’(higher resistant species) and ’Seerkefu’(lower resistant species), the change of total polyphenols, H2O2and four protective enzymes was identified in fruits after incubating the pathogens of pear anthracnose and ring rot. Results indicated that the content of total polyphenols was4times in the healthy fruit of’Hongnahe’than that in ’Seerkefu’. However, the increased level of total polyphenols in’Hongnahe’ exhibited less than ’Seerkefu’ after incubating the pathogens of pear anthracnose and ring rot; while the level of total polyphenols in ’Seerkefu’was lower than’Hongnahe’ during pathogens progress. After incubating the pathogens on fruit of the two Pyrus speices, H2O2increased highly in fruitlet pulp of ’Hongnahe’, but the content of H2O2was stable; the activity of SOD rise with higher rate in ’Hongnahe’ than ’Seerkefu’; the activity of CAT displayed more susceptible to pathogens infection in ’Seerkefu’ than ’Hongnahe’, and the activity of CAT decreased obviously later. After incubating the pathogens of pear anthracnose on fruit of the two Pyrus speices, the activity of POD exhibited firstly rise and then decrease in two speicies; but the change time of POD in ’Hongnahe’ represented later than in ’Seerkefu’. After incubating the pathogens of pear anthracnose on fruit, the activity of POD in’Seerkefu’showed dropping trend and then began to gradually rise, while it showed oscillated trend in’Hongnahe’. After incubating the two pathogens, the activity of PPO in the diseased fruit was lower than that in the health fruit; by contrast to ’Hongnahe’, PPO activity dropped more sharply in ’Seerkefu’ with lower resistant species. These results indicated total polyphenols, H2O2and four protective enzymes might play an important role during pathogens progress.4. Using’Hongnahe’(higher resistant species) and ’Seerkefu’(lower resistant species), the change of components and contents of phenols was identified in fruits after incubating the pathogens of pear anthracnose and ring rot. Results suggested that total polyphenols and each phenolic component were higher in healthy fruit of ’Hongnahe’ than that in ’Seerkefu’. The content of caffeic acid, quercetin, vanillin and chlorogenic in fruit of ’Hongnahe’ was5.54,4.71,3.79and3.65times than’Seerkefu’, respectively. The level of many phenolic components in higher resistant species decreased more during the infective process of the pathogens from pear anthracnose and ring rot, but the reductive content increased later. This may relate to pathogens infection. Three (caffeic acid, epicatechin, rutin)and seven phenolic (caffeic acid, epicatechin, rutin, vanillin, chlorogenic and ferulic acid) components in lower resistant species gradually increased in the infective process of the pathogens of pear anthracnose and ring rot, respectively; this indicated these phenols accumulated in the junctional zone between health and disease during pathogens progression, which may play a role against pathogens infection. Quercetin was not detected in healthy fruit from two Pyrus species, but it was observed in the junctional zone between health and disease, also in the disease spots.5. Anti-expansion capacity against the pathogens of anthracnose and ring rot was evaluated on mature fruit of101pear varieties in room by cluster analysis; correlation analysis has been made between the anti-expansion capacity and physiological factors of pear fruits. The anti-expansion capacity of101varieties to two pathogens can be classified into five groups, within which the ratio of moderately anti-expansion capacity was max, reaching to40.6%and35.6%respectively; while poor anti-expansion capacity was minimum, reaching to5.9%and2.0%respectively. Total phenols display significantly positive correlation with anti-expansion capacity against the pathogen of anthracnose (P<0.01) and that of ring rot (P<0.05). Stone cell content exhibits significantly positive correlation with anti-expansion capacity against the pathogens of anthracnose and ring rot (P<0.01).