Study On The Relationship Between The Occurrence Of 'Black-tip Disease' And Carbon Nutrition In Jujube Fruit

In order to explore the relationship between the incidence of black tip disease and the nutrient transport of fruit vascular bundles,in this study,‘Hupingzao' was used as experimental material to study the occurrence of fruit black tip disease at different developmental stages and its relationship with meteorological factors.On the basis of analyzing the difference in vascular bundle cell shape and soluble sugar content between normal development fruit and black-tip disease fruit,we compared the differences in carbon material transport and cell viability between phloem and explore the causes of black-tip disease.We studied the differences of soluble sugar content,phloem carbon material transport and cell viability and their effects on black-tip disease by means of rain-proof cultivation and fruit development regulation measures.The results are as follows:(1)The black-tip disease of ‘Hupingzao' mainly occurred from white-ripening period to mature period.The occurrence of the disease was negatively correlated with the highest and lowest daily temperature,and positively correlated with the change of air relative humidity.The content of sucrose and fructose at the top of the fruit of the disease was 96.72 mg·g-1FWand 30.77 mg·g-1FW,respectively,which were significantly lower than the top of the normal fruit at 118.40 mg·g-1FWand 49.22 mg·g-1FW.The activity of vascular bundles in diseased fruits decreased,and the sucrose and fructose content at the top of fruits were significantly lower than those at the top of normal fruits.(2)With the development of fruit,the soluble sugar content increased gradually.From white-ripening period to half-red period,the content of sucrose,fructose,glucose and soluble total sugar in the shoulder was significantly higher than that in the top of the fruit.As for the transport of substances in vascular bundles of fruits at different developmental stages,with fruit development,the transport capacity of phloem to substances gradually decreased.At the same developmental stage,the transport capacity of substances in vascular bundles at the top of fruits was lower than that at the shoulder of fruits.In terms of cell activity,the activity of pulp cells and phloem cells decreased gradually with fruit development.At the same development stage,the activity of pulp cells and phloem cells in the top part of fruit was lower than that in the shoulder part.(3)The incidence of black-tip disease in jujube gardens with shelters and sprayed PP333 was 14.64%and 15.31%,respectively,which was significantly higher than that of the control orchard,the incidence was aggravated,and the fourth-grade disease appeared.After GA3 treatment,the fruit incidence rate decreased to 5.75%,which was significantly lower than that of the control by 7.90%,only a small number of primary and secondary disease fruits appeared at maturity period.The incidence of large fruit was higher than that of small fruit after different treatments.After GA3 treatment,the fruit coloring period was postponed.At the same time,the vascular bundles had stronger ability to transport substances than other treatments,and the cell activity and phloem cell activity of the vascular bundles were stronger.After PP333 treatment,the fruit entered the coloring period one week earlier.At the same time,the transport capacity of vascular bundles was weaker,and the activity of fruit cells and phloem cells was weaker.Compared with the control,the fruit coloration period did not change much after canopy treatment.At the same time,the ability of fruit vascular bundles to transport substances was slightly weaker than that of the control group,the cell viability and phloem cell activity in this group were between GA3 treatment group and PP333 treatment group.As the fruit develops,the cell activity of the phloem is gradually weakened,the transport capacity of soluble sugar is reduced,and the content of sucrose and fructose at the top of the fruit is significantly reduced.This phenomenon may be an important cause of the black-tip disease of ‘Hupingzao'.