Study On Morphology,physiology,Nutrition And Correlation Of Spring And Autumn Shoot Leaves Of Hlb-infected ’Orah’

Huanglongbing(HLB)is a devastating disease of citrus,and ‘Orah’ is the second major citrus variety in Guangxi.In order to explore the effects of Huanglongbing(HLB)infection on leaf morphology,physiology,nutrition and fruit quality of ‘Orah’,and provide reference for comprehensive prevention and control of Citrus Huanglongbing(HLB).In this study,six-year-old citrus plants were used as test materials to study the effects of Huanglongbing(HLB)infected and healthy plants on leaf morphology,relative content of chlorophyll,stress resistance related enzyme activities,soluble protein,soluble sugar,nutrient elements,rhizosphere soil pH value and fruit quality,and analyze the correlation between them.The main results are as follows:1.The leaf area of susceptible plants became smaller and the whole showed yellow mottled symptoms;The yellowing symptoms of autumn shoots of susceptible plants were more obvious than that of spring shoots;The phloem of new and mature leaves of autumn and spring shoots of susceptible plants were blocked by sieve tubes and generally collapsed;A large number of starch grains accumulated in the veins of new and mature leaves in spring and mature leaves in autumn.2.The relative content of chlorophyll in autumn slightly mature leaves,spring shoot new leaves and mature leaves of HLB-infected plants were significantly lower than that of healthy plants,and the content of chlorophyll in autumn shoot was lower than that of healthy plants,but there was no significant difference.3.The contents of N,P and K in the new leaves of autumn shoot of HLB-infected plant decreased significantly,but there was no significant difference in the contents of Ca,Cu,Mn,Mg and Zn;The contents of P and K in mature leaves decreased significantly,the contents of Ca and Cu increased significantly,and there was no significant difference in the contents of N,Mn,Mg and Zn.The contents of N,K,Ca and Mn in the new leaves of spring shoots of HLB-infected plants decreased significantly,the contents of Cu increased significantly,and there was no significant difference in the contents of P,Mg and Zn;The contents of N and K in mature leaves decreased significantly,the content of Cu increased significantly,and there was no significant difference in the contents of P,CA,Mn,Mg and Zn.4.The activities of CAT and PPO in the new leaves of autumn shoot of HLB-infected plant decreased significantly,and the activity of PAL increased significantly;CAT activity decreased significantly and PAL activity increased significantly in autumn shoot mature leaves;The activities of SOD and pod in new leaves of spring shoots decreased significantly;The activities of pod in mature leaves of spring shoots decreased significantly,while the activities of PAL and SOD increased significantly.5.The soluble protein content of HLB-infected plant increased significantly in new leaves of spring shoots,decreased significantly in new leaves of autumn shoots,and decreased significantly in mature leaves of spring shoots and autumn shoots;The soluble sugar content increased significantly in new leaves and mature leaves of autumn shoots,and decreased significantly in mature leaves of spring shoots.6.The fruit of HLB-infected plant is not evenly colored,and the fruit pedicle has yellow halo;The number of fruit per plant,fruit weight and sugar acid ratio were significantly lower than those of healthy plants;Compared with healthy fruit,there was no significant difference in peel thickness,fruit shape index and juice yield,but the Vc and the seed abortion rate increased significantly.7.The pH value of rhizosphere soil of HLB-infected plants in spring and autumn was lower than that of healthy plants,but there was no significant difference.8.The content of CLas in new leaves was higher than that in mature leaves in autumn and spring shoots,showing a change trend of autumn shoots > spring shoots.There was a significant positive correlation between the length of new leaves and the contents of SOD,PPO,N,Mn and K,while the contents of SOD,PPO,MDA,N and Mn in mature leaves were significantly positively correlated with the contents of CLas;The content of soluble protein in new and mature leaves was significantly negatively correlated with the content of CLas.