Effects Of Arbuscular Mycorrhizal Fungi And Sugar Alcohol Chelated Calcium On Growth And Fruit Storage Quality Of ’Benihoppe’ Strawberry

Strawberry’Benihoppe’（Fragaria×ananassa Duch.cv.’Benihoppe’）is an excellent variety widely cultivated in China.However,strawberry fruit has high water content,tender and soft tissue,concentrated production season,and is vulnerable to mechanical damage and microbial infection in the process of picking,transportation and sales.This is the reason why strawberries are hard to store after harvest.Therefore,on the premise of reducing the loss of fruit quality,maintaining fruit flavor and nutrition,improving the firmness of strawberry fruit is of great significance.Calcium is an activator of enzymes and coenzymes in the process of fruit ripening and softening.Application of exogenous calcium can effectively maintain fruit firmness,delay softening and senescence.Different kinds of exogenous calcium can delay the decline of apple fruit firmness and inhibit the activities of cell wall modifying enzymes,among which sugar alcohol chelated calcium has the most significant effect on maintaining fruit firmness.However,the utilization efficiency of calcium in plants is not satisfactory.As an important part of plant-microorganism interaction in sustainable horticulture,Arbuscular mycorrhizal fungi（AMF）can effectively infect strawberry roots and promote the absorption of water and mineral nutrients,including Ca²⁺.Although many studies have reported the effects of AMF or exogenous calcium on strawberry plant growth or fruit quality,the effects of AMF on fruit quality,especially on postharvest storage quality,are rare.The research on exogenous calcium treatment of strawberry mainly focused on the effect of postharvest calcium application on fruit storage quality,while the research on the effect of preharvest calcium application on fruit storage quality was few.The main types of calcium fertilizer were CaCl₂,Ca-（NO₃）₂ and other traditional calcium fertilizers.There were few studies on the effects of soil applying exogenous calcium on plant growth,postharvest storage quality and softening of strawberry fruits.In addition,the results of interaction between AMF and exogenous calcium are inconsistent.Therefore,it is necessary to study the effect of different concentrations of sugar alcohol chelated calcium on plant growth and fruit storage quality before the harvesting of mycorrhizal strawberry seedlings,whether there is synergy between AMF and sugar alcohol chelated calcium,and the suitable calcium concentration of the mycorrhizal strawberry seedlings.It is of great significance to improve the utilization rate of exogenous calcium fertilizer,improve the quality and yield of strawberry,maintain the postharvest commodity of strawberry,and extend the shelf life.A pot experiment was performed in No.9 greenhouse of Southwest University.In this experiment,strawberry’Benihoppe’seedlings were used as the test plants.Funneliformis mosseae,which had better symbiotic effect with’Benihoppe’,was used as the test inoculum.Sugar alcohol chelated calcium（156.03g/L）was used as the test calcium fertilizer.This study investigated the possible roles of different concentrations of alcohol chelated calcium,AMF and duplex treatment in improving the growth,mineral nutrition,yield,storage quality and expression of key genes of cell wall modifying enzymes in’Benihoppe’strawberry fruit after harvest.The treatment methods of inoculating AMF and not inoculating AMF were designed.Four concentrations（0,0.10%,0.15%and 0.20%）of sugar alcohol chelated calcium were set up for 8treatments.Each treatment was repeated 3 times and arranged randomly.The main results are as follows:1.In soilless culture,funneliformis mosseae could effectively infect the roots of’Benihoppe’seedlings.The infection rate of mycorrhiza was increased by 0.20%sugar alcohol chelated calcium significantly.2.AMF inoculation alone or AMF with different concentrations of sugar alcohol chelated calcium can promote the root growth and biomass accumulation of aboveground and underground parts of strawberry plants.Compared with AMF inoculation alone,AMF with different concentrations of sugar alcohol chelated calcium has better effects.Under the condition of duplex treatments,the photosynthetic capacity of strawberry plants was enhanced.Moreover,the interaction effect of 0.15%and 0.20%concentration with AMF was better than that of 0.10%concentration.3.AMF inoculation or AMF combined with different concentrations of sugar alcohol chelated calcium significantly increased the mineral nutrition content of the substrate and plant,especially the total calcium and water-soluble calcium content of the fruit.AMF combined with different concentrations of sugar alcohol chelated calcium significantly increased the yield of strawberry fruit,and AMF combined with 0.20%sugar alcohol chelated calcium had the best effect.4.0.20%sugar alcohol chelated calcium or AMF combined with different concentrations of sugar alcohol chelated calcium significantly increased the contents of total phenolic contents and TSS,inhibited the activities of enzymes related to cell wall degradation,and reduced the fruit weight and hardness loss during storage.The effect of AMF combined with 0.20%sugar alcohol chelated calcium was better.5.The expression of FaPG1 and FaβGal4 genes related to pectin degradation and softening process were down-regulated by preharvest calcium treatment alone or AMF inoculation with calcium treatment.The expression of FaPME1,a gene involved in cell wall strengthening,was up-regulated or maintained by AMF inoculation with calcium treatment.The inhibition of FaPG1 and FaβGal4 expression and the up regulation of FaPME1 expression were stronger than those of calcium treatment alone.In addition,AMF combined with 0.20%sugar alcohol chelated calcium had a strong inhibitory effect on the expression of FaPG1 and FaβGal4,while AMF combined with 0.15%sugar alcohol chelated calcium had a strong up regulation effect on the expression of FaPME1.