| Actinidia arguta is a new type of small berry tree in China,the fruit is nutritious and of high economic value.Actinidia arguta cultivars‘Kuilv’、‘Pinglv’and‘Fenglv’were used as experimental materials from 15 to 90 d after full bloom（90 d after full bloom for harvesting）.Study of fruit growth and development dynamics,intrinsic fruit quality and changes of endogenous hormones in fruits of different Actinidia arguta cultivars,in order to probe fruit growth and development patterns.This researching result could provide great theoretical guidance for the cultivation and management of Actinidia arguta and improving of fruit quality,as well as preferable references for in-depth research on the developmental mechanisms of Actinidia arguta and other fruit trees.The experimental results are as follows:1.All three cultivars of Actinidia arguta have an obscure double S-shaped fruit development growth curve.Fruit weight per fruit,transverse diameter,longitudinal diameter and lateral diameter changed little during the slow growth period（60-90 d after full bloom）and the growth tended to be stable after harvest（90 d after full bloom）.The fruit shape index of‘Kuilv’tended to increase from 15 to 30 d after full bloom,reaching a maximum of 1.51 at 30 d after after full bloom and then gradually decreasing from 30 to 90 d after full bloom.Fruit development was dominated first by longitudinal growth and later by transverse growth.The fruit shape index of‘Pinglv’and‘Fenglv’showed a decreasing trend from 15 to 90 d after full bloom,with a predominance of transverse fruit diameter growth.2.Fruit hardness of the three cultivars reached a maximum at 60 d after full bloom,their fruit hardness indexes were 24.32 kg·cm-3FW,25.14 kg·cm-3FW,and21.76 kg·cm-3FW,respectively.And then gradually decreased as the fruit developed,their fruit hardness indexes were 7.72 kg·cm-3,7.93 kg·cm-3FW and 6.78 kg·cm-3FW at 90 d after full bloom,respectively.The soluble sugar content of the three cultivars of Actinidia arguta showed an overall upward trend in fruit development,with 8.51%FW,8.68%FW and 8.75%FW respectively at 90 d after full bloom.The titratable acid content of the fruit of all tended to rise and then fall,peaking at 2.49%FW,2.14%FW and 2.52%FW respectively at 45 d after full bloom,and then falling to1.45%FW,1.13%FW and 1.45%FW respectively at 90 d after full bloom as the fruit gradually developed and matured.The soluble solids content of the fruits gradually increasing as the fruit developed and matured,with the greatest increase in soluble solids content from 60 to 90 d after full bloom,with the increase at this stage accounting for 45%,33%and 43%of the soluble solids content at maturity,respectively.The vitamin C content of the fruits showed a trend of rising and then falling,gradually rising from 15 to 45 d after full bloom,with the content peaking at148.00 mg/100g FW,121.20 mg/100g FW and 156.73 mg/100g FW at 45 d after full bloom,respectively,and gradually falling from 45 to 90 d after full bloom,with the vitamin C content reaching 83.55 mg/100g FW,78.08 mg/100g FW and 88.77mg/100g FW at 90 d after full bloom,respectively.The soluble protein content of the fruits all showed a decreasing trend followed by an increasing trend,with the content reaching a minimum at 60 d after full bloom,at 0.16 mg·g-1FW,0.15 mg·g-1FW and0.16 mg·g-1FW respectively.3.There were higher contents of IAA,GA and CTK in fruits of the three cultivars at 45-60 days after full bloom.And there were high contents of ABA and ETH in the three cultivars at 45-90 days after full bloom.The contents of ABA and ETH were positively correlated with single fruit weight,transverse diameter,longitudinal diameter and lateral diameter（p<0.05,the same below）,and negatively correlated with fruit hardness.4.Fruit IAA and GA content of the three cultivars of Actinidia arguta are negatively correlated with soluble sugar content.CTK content was positively correlated significantly with titratable acid and vitamin C content.The ABA and ETH content of the three cultivars were positively correlated significantly with soluble sugar content,negatively correlated with IAA and GA content,and positively correlated significantly with soluble solids content.5.Endogenous hormone biosynthesis and signal transduction pathway gene expression levels in cultivar‘Kuilv’fruit from 45 to 90 d after full bloom.There are six genes annotated by IAA in the signaling pathway and the expression levels of genes in the IAA signaling pathway are higher than the expression levels of genes in the synthetic pathway.The expression levels of AUX1 and TIR1 were positively correlated with the changes in IAA content,and both showed an increasing and then decreasing trend from 45 to 90 d after full bloom;The expression of GA2ox was positively correlated with GA content and showed a trend of increasing,then decreasing and then increasing from 45 to 90 d after full bloom. |
