Preliminary Study On The Germplasms Selection And Resistance Mechanism Of Camellia Oleifera Abel. To Anthracnose

Camellia oleifera is a significant woody oil tree species in southern China.Camellia oleifera Abel.is the first in the country in terms of planting area and yield.The anthracnose of C.oleifera is the most important disease in the planting area,which leads to the continuous reduction of production and oil content.In order to select the germplasms of C.oleifera against anthracnose and explore its resistance mechanism,Resistance level of 110 C.oleifera cultivars to anthracnose were evaluated based on the disease index for selceting resistant cultivars.The photosynthetic characteristics and physiological and biochemical changes of cultivars after inoculation with anthrax were explored for identification of metabolites related to disease resistance.The main results in the paper are as followings:?1?110 cultivars were evaluated for resistance to anthracnose in order to screen and extend elite resistant cultivars of C.oleifera.Based on anthracnose investigation in 2014 and 2016,the disease index was used to evaluate the disease resistance of 110 cultivars.The results showed that among them 10 cultivars were resistant,30 cultivars moderately resistant,65 cultivar moderately susceptible,5 cultivar susceptible.Based on identification techniques for examining their resistance to anthracnose,3 resistant cultivars include'Changlin 9','Changlin21'and'Changlin 150'were selected,which provides references and breeding materials further study of the resistance mechanism on C.oleifera.?2?Based on the collection of 105 germplasms in Jinhua Dongfanghong Forest Farm,an investigation was conducted on the anthracnose condition in four years.The results of disease index analysis showed that after density adjustment,the number of high-resistance cultivars increased by 4,the number of disease-resistant cultivars increased by 58,the medium-resistant and medium-sensitivity cultivars decreased by 60,and the susceptible cultivars decreased by two.The results showed that there were no significant changes in the disease index of 17 C.oleifera cultivars in density adjustment.Among them,5 cultivars such as'Changlin 3'and other cultivars showed disease resistance before and after density adjustment,and 9 of 11 were before and after density adjustment.The performance was medium,and'Changlin 67','Changlin 76'and'Changlin 102'showed symptoms before and after density adjustment.These cultivars maintained stable disease resistance or susceptibility characteristics before and after density adjustment;'Changlin 15','Changlin 17','Changlin 21',etc.There were significant differences in the disease index of 88 cultivars in density adjustment.It is indicated that the density adjustment can improve the condition of most cultivars.At the same time,three susceptible cultivars such as'Changlin 67','Changlin 76'and'Changlin 102'are selected,which provide the basic materials for studying the resistance mechanism.?3?In order to explore the resistance mechanisms of resistance mechanism,Colletotrichum gloeosporioides was inoculated under the pot experiment,and the leaf photosynthesis Characteristics and defense enzyme activity of the'Changlin 150'?resistant cultivar?and'Changlin 102'?sensitive cultivar?were observed.The study found that the photosynthetic rate and stomatal limit of'Changlin 150'increased net photosynthetic rate at 72h after inoculation,and the net photosynthetic rate of'Changlin 102'and'Changlin 150',Both stomatal conductance and stomatal limit values showed a downward trend.The intercellular CO₂of'Changlin 102'showed an increasing trend,while the'Changlin 150'was at its lowest point at 72h,and then showed an upward trend.The MDA content reached the highest point at72h in'Changlin 150',and the highest point at 48h in'Changlin 102',and then showed a downward trend,but the MDA content in'Changlin 102'was significantly higher than that of'Changlin 150'.The three enzymes such as CAT,POD and SOD were positively correlated with disease resistance.The activities of the three enzymes in'Changlin 150'were the highest point at 72 h after inoculation,and significantly higher than'Changlin 102'.The results showed that the photosynthetic characteristics of'Changlin 150'was less affected by anthracnose stress than'Changlin 102',and the defense enzymes activity of resistant cultivar was higher in early infection,and MDA content was negatively correlated with disease resistance.?4?'Changlin 150'?Resistant cultivar?and the'Changlin 102'?susceptible cultivar?were selected as experimental materials.The leaves were collected at 72h after inoculation with C.gloeosporioides.The differential metabolites and metabolic pathways were analyzed by LC-MS analysis and bioinformatics.Based on establishing a multidimensional statistical analysis model,29 differential metabolites in the vaccinated group and 19 differential metabolites in the control group were identified.The main metabolic pathway differences included citric acid metabolism in the control group was found through metabolic pathway enrichment analysis.In the vaccinated group,galactose metabolism and arginine and proline metabolism were identified.These results indicate that before inoculation of pathogenic bacteria,the structural substances was increased in C.oleifera for physical defense.After inoculation of pathogenic bacteria,carbohydrate metabolism and Amino acid metabolism is the main factor,and the release of antibacterial substances,which lays a foundation for further study on the resistance mechanism of C.oleifera and the selection of disease-resistant cultivars.