Effect Of Nutrition Regulation On Growth Of Gannan Navel Orange And Prevention Of Huanglongbing

Gannan is the largest navel orange producing area in China.In recent years,due to irrational fertilization and improper agricultural management,the quality of the orchard soil dropped sharply.This poor soil environment leads to the decline in plant resistance to diseases.The outbreak of Huanglongbing(HLB)is most serious,which is one of the destructive diseases of citrus and threatens the development of Gannan navel orange industry.It is of great significance to replace chemical reagents with nutritional regulation,which is helpful for the sustainable development of orchards.In this study,the effects of nutrient regulation of mineral elements on yield,quality and nutrient content of Gannan navel orange and the incidence of Huanglongbing were clarified.Rhizosphere microorganism group and root exudates metabolic group were used to study the mechanism.The main research results are as follows:1.Compared with the control,the yield of navel orange in Gannan could be increased by 13.6 %～40.5 % in the treatment group with medium and trace elements in the second year.There was no significant effect on the appearance quality of Gannan navel orange,but the solid acid ratio of the fruit was increased.The fruit quality of the soil calcium magnesium boron selenium(T3)treatment group was the best.At the same time,the experimental treatment increased the content of trace elements in Gannan navel orange fruit.In the experiment,the treatment of medium and trace elements increased the content of Fe,Zn,Se and other trace elements in the leaves of Gannan navel orange,which was helpful to promote the growth and development of trees and enhance the disease resistance of trees.2.The incidence of Huanglongbing in Gannan navel orange showed that soil application of calcium,magnesium and boron(T2)could alleviate the incidence of Huanglongbing.PCR identification of pathogen Clas in T2 and control groups showed that the concentration of pathogen Clas in T2 treatment group was lower than the detection limit.The omics analysis of microbial communities in the rhizosphere and leaf of T2 and the control group showed that T2 changed the microbial community structure in the rhizosphere and leaf,improved microbial diversity,promoted the enrichment and recruitment of beneficial microorganisms,and promoted membrane transfer function,photosynthate and organic macromolecule metabolism.3.By metabonomics analysis,the differences of root exudates between calcium magnesium boron deficiency group and normal conditions were found.Under the condition of calcium magnesium boron deficiency,the roots of trifoliate orange secreted more plant hormones(flavonoids and flavanone derivatives,gibberellin),which promoted the absorption of nutrients and the growth and development of plants.Under normal nutrient conditions,the roots of Aurantii Fructus secrete more root exudates related to stress resistance(organic acids,amino acids),thereby improving the tolerance of plants.In summary,mineral nutrition regulation such as medium and trace elements can improve the yield and quality of Gannan navel orange fruit,and improve the content of trace elements in fruit.Among them,soil application of Ca,Mg and B could alleviate the incidence of Huanglongbing,change the microbial communities in the leaf and rhizosphere,and improve the disease resistance of navel orange in southern Jiangxi.The improvement of those resistance ability is closely related to the regulation of root exudates components and the changes of rhizosphere and interleaf microbial communities.