Yellowing Characteristics And Mechanism Of Different Blueberry Plants In Tianjin Slightly Acidic Soil

Blueberryisdeeplylovedbyfarmersandconsumersforitsuniqueflavor,richnutrition,anthocya ninandotherphysiologicalactiveingredientsandeconomicbenefits.With the increasing market demand of blueberries,the introduction and cultivation of blueberries in various regions also increased while many blueberry plants appear the phenomenon of chlorosis,which seriously affects the growth,yield and quality of blueberries.Tianjin Yinzhou district currently cultivates 4,000 acres of blueberries.Therefore,it is imperative to explore the yellowing characteristics of blueberry in slightly acidic soil and understand its etiolation mechanism in order to solve the existing problems and to be used in production practice.There are 6 blueberry varieties in greenhouse of Jixian in Tianjin were studied in this study while four stages(flowering stage,young fruit development stage,fruit maturity stage,fruit harvest stage)were used to study the yellowing change of different varieties of blueberry plants in slightly acidic soils of Tianjin.Meanwhile the changes of yellowing index,chlorophyll content,FCR activity and available iron content of 6 blueberry varieties in 4 periods were investigated while the relationship between the growth and yield of different varieties and yellowing was compared.In order to explore the effect of plant etiolation on fruit quality,two varieties(Bluecrop and Bluegold)with serious degree of yellowing were selected to compare the quality of fruit inside and outside under different yellowing grades,and three year old blueberry plantlets(Bluecrop,Northland,O’Neill and Legacy)were used as the research objects while pot experiment was designed and compared under different pH conditions.Moreover,the changes of yellowing index and the effects of different substrate pH on root FCR activity,root available iron,rhizosphere activity and root dry weight were investigated and the effects of yellowing on root growth physiology of blueberry under different pH were investigated.The results show that:(1)The yellowing index of the 6 blueberry varieties had the same tendency during the various phenophases,which showed that the young fruit t development period and the fruit had the highest maturity.The yellowing of leaves at full flowering stage had the lowes mainly showed on the young leaves,the yellowing index was 9.43%~21.94%;the regreening phenomenon appeared in the young fruit development period,the yellowing index dropped to 2.76%~12.24%;the yellowing index of the fruit ripening period It rose to 8.71%~25.59%.After fruit harvest,the phenomenon of plant yellowing did not improve,and the degree of yellowing of individual varieties continued to increase.The yellowing index was 4.64%~31.02%during this period.(2)In the leaves,chlorophyll content,FCR activity,and effective iron content decreased with increasing degree of yellowing,that was the more severe the leaf yellowing,the lower the chlorophyll content,the lower the iron reductase activity,and the lower the effective iron content of the leaves..It was indicated that the yellowing of the leaves of blueberries in the field was due to the low chlorophyll content caused by the low effective iron content in the leaves.The low effective iron content was due to the low iron reductase activity of the leaves.(3)The yellowing degree(average yellowing index)of the six varieties followed from Bluegold,Berkeley,Bluecrop,Brigita,Legacy,and Northland.The iron reductase activity was ranked as Northland in descending order.Legacy,Brigitta,Bluecrop,Berkeley,Bluegold.Explain that the Northland was the most resistant to iron deficiency yellowing.(4)The number of new shoots,shoot growth,and leaf area of different blueberry varieties in Tianjin slightly acidic soil were significantly different.The highest value of the average membership function(comprehensive growth characteristics)calculated from the three growth indexes was 0.781 for the Bluegold,followed by Berkeley 0.687,and the lowest was for the Legacy to 0.001.It was show that both Bluegold and Berkeley grew well,and Lagacy grows weakly.The correlation coefficient between the comprehensive growth characteristics and yellowing index of the three varieties was 0.2377.It was show that the growth potential has nothing to do with the degree of plant yellowing.(5)The average yellowing index of 6 blueberry varieties in slightly acid soil in Tianjin had a significantly negative correlation with the yield per plant.The correlation coefficient was-0.8648,indicating that the yield directly affected the yellowing of blueberry plants,and the higher the yield,the more severe the yellowing..(6)Fruit color,hardness,single fruit weight,soluble sugar content,acidity,vitamin C and anthocyanin content of different yellowing grade blueberry varieties in the slightly acid soil in Tianjin were significantly different.A comprehensive analysis of the membership functions showed that the best quality was a first class yellow gold blue fruit.The chromas,hardness,titratable acid,and anthocyanin with good correlation with the yellowing index.The results showed that the yellowing of the plant affected the coloration of the fruit(yellowish green and white color in the yellow plant),decreased hardness,decreased soluble solids,decreased sugar content,increased acidity,and significant content of vitamin C and anthocyanin reduce.When the degree of yellowing is grade 3,the fruit quality changes significantly.(7)With the increase of pH in the substrate(4.5-7.5),the degree of yellowing of the blueberry plants increased significantly.Among them,the average of the yellowing index of the 4 blueberry varieties was O’Neill,followed by Bluecrop,Legacy,and Northland.Explain that Northland is the most resistant to yellowing.(8)In the 4 pH gradients of substrate culture,the yellowing index of blueberry plants increased at the pH value of pH 6.5-pH7.5,and the FCR activity,available iron content,root activity,and root dry weight of the blueberry declined rapidly.It shows that the slightly acidic substrate is the root cause of yellowing of blueberries.The mechanism is slightly alkaline to reduce the activity of the root system,reduce the iron reductase activity in the root,resulting in effective iron absorption in the root system or reduction of ferric iron in the root system to divalent iron—the amount of available iron is reduced,and eventually the root growth is reduced.(Dry weight decreased),the plants were severely yellowed.(9)In short,the key factor affecting the yellowing of blueberry plants is soil acidity and alkalinity.The yellowing of plants in Tianjin blueberry base was due to the decrease of root activity in the slightly acidic soil(pH6.5)and the low effective iron content in the leaves resulting from the low iron reductase activity in the root system.Among the 6 blueberry varieties,Northland is the most resistant to yellowing.Plant growth has nothing to do with yellowing,and the yield increases yellowing.Yellowing will lighten the color of blueberries and reduce nutrients.