Based On Metabolomics To Explore The Effect Mechanism Of Mulch On The Yield And Quality Of Camellia Oleifera

Due to the uneven seasonal rainfall,C.oleifera has lacked water supply and low yield in mountainous and hilly areas without irrigation conditions.To alleviate the effect of seasonal drought on yield,three C.oleifera varieties(‘Huashuo',‘Xianglin 210',and ‘Hengdong Datao')were covered with different organic mulching materials,and the best mulching measures and varieties were selected.Based on this,the effects of different mulching methods on fruit metabolism were explored.qRT-PCR was used to verify gene expression changes of key enzymes in C.oleifera oil synthesis compared with the control group.16 S rRNA was used to evaluate the effect of ecological mat mulching on soil microbial community structure of C.oleifera.This study is based on a reliable experimental design,and two years of research data support the results.We provide a possible scheme for seasonal drought in unconditional irrigation area and analyze the mechanism behind the impact of the scheme on tree species,which has an important reference value for water resource management and drought resistance measures of woody oil.The basic results and conclusions are as follows.(1)To assess the effectiveness of mulching on the yield and quality of three cultivars of C.oleifera(‘Hengdongdatao',‘Huashuo' and ‘Xianglin 210')and its influence of preserving soil moisture,a field experiment was conducted in 2016 in Changning,Hunan.Mulching materials of ecological pad(T1),straw(T2),straw and ecological pad(T3),gravel(T4),sawdust(T5)and camellia shell(T6)were tested and compared with un-mulched(CK).The mulch material with the strongest cooling effect in high-temperature weather was T2.T3 was the most effective at maintaining soil moisture.T1 showed soil moisture by 14.93%,14.98%,14.89% for three cultivars,respectively.All treatments increased yield compared to CK.T1 showed the highest yield and was higher than CK by 58%,61% and 124% for Hengdongdatao,Huashuo,and Xianglin 210,respectively.Mulching with T1 resulted in the highest oil content ratio(40.23% and 39.63%)in‘Hengdongdatao' and ‘Huashuo' and mulching with T4 resulted in highest oil content ratio(36.93%)in ‘Xianglin 210'.Treatment of the ‘Xianglin 210'cultivar with T1 was re-tested in 2017.In all months analyzed,related indicators measured were significantly different compared with CK.This research suggests that mulching organic material to C.oleifera hilly area is an effective measure to solve seasonal drought and increase yield when there are no irrigation conditions present.(2)In this study,multi-platform untargeted metabolomics and qRT-PCR were used to measure the effects of organic mulching on seeds kernel metabolism.Metabolomics analysis revealed that tyrosine,tryptophan,and several flavonoids and polyphenol metabolites were significantly lower in the mulched treatment compared to the non-mulched indicating lower stress levels with mulching.The qRT-PCR analysis showed that key gene of fatty acid EAR,SAD,CoHCD play a positive regulatory role in improving the yield of C.oleifera,while CT,FAD7,FAD8,CoATS1,SQS,SQE,FATB,and ?-AS was a negative regulated.Correlation network analysis was used to integrate data from this multi-omics investigation to analyze the relationships between differentially expressed genes,differential metabolites,fruit and soil indicators concerning mulching treatment of C.oleifera.(3)We used GC-Tof-MS to assess the metabolic characteristics of seed kernel developmental stages under seasonal drought conditions and analyzed the metabolic differences between organic mulching and control during fruit ripening.The results showed that the greatest metabolic differences occurred during high oil conversion(August to October),mainly involving 11 relevant metabolic pathways.In addition,the metabolic differences were significantly different after organic mulching compared to control group.(4)This study also investigated the microbial community of soil under mulching using high throughput 16 S rRNA measurements.The results showed that mulching reduced the diversity of soil microorganisms but not significantly.At the phylum level,the dominant bacteria were mainly proteobacteria,acidobacteria,actinobacteria,chloroflexi,firmicutes,bacteroidetes,and planctomycetes.Correlation analysis showed that soil p H,seed kernel metabolism flavonoids,were most correlated with other indicators,while yield was significantly and positively correlated with soil proteobacteria,bacteroidetes,and soil nutrient indicators.Organic mulching improved physicochemical properties of soils,caused differences in the relative abundance of dominant bacterial groups in soil bacteria,and improved the soil microbiological environment to promote plant growth.In conclusion,it is assumed that different mulching can improve the yield and quality of C.oleifera fruit.Through two years of continuous detecting,it was found that different materials mulched the soil surface of C.oleifera effectively improved effect of seasonal drought on C.oleifera.The concept that soils microbial community may influence plant fruit metabonomics was also introduced.In a word,we found that there was a direct positive correlation between soil microflora(proteobacteria,bacteroidetes)and fruit yield.Similarly,the metabolites(flavonoids,fatty acids,lipids)in the kernel also have a strong positive correlation with some dominant bacteria.It is worth noting that other unknown soil factors or interactions are associated with the observed response.Moreover,it is unclear how soil microbial communities induce changes in seeds kernel metabolites,thereby affecting plant fruits.This effect may involve microbial signals(bioactive molecules)interacting with plant signal transduction pathways,which is worthy of further study.