Study On The Biological Characteristics And The Fruit Development Of Kiwifruit Strain ‘Beimu' (Actinidia Chinensis)

Kiwifruit belongs to the genus of Actinidia in Actinidiaceae which comprises 66 species.Sixty two species of which are native to China and 4 species are native to neighbouring countries.Wuling mountainous area is one of the optimum distribution core areas involving in kiwifruit germplasm in China with 17 species in this region,and most of which are ignored in variety research and cultivation.The diversity of color-fleshed fruit is one of the reasons that attract the consumers commercially.The yellow-fleshed kiwifruit has high nutritional and health value due to its richness in carotenoid and flavonoid,and becomes one of the hot spots in kiwifruit variety selection and breeding in the recent two decades.The yellow-fleshed Actinidia chinensis strain ‘Beimu' was preliminarily selected by the Kiwifruit Research Center of Wuling Mountain Area,Jishou University,and planted in the kiwifruit experimental base of Jishou University.This is a fine strain selected from Wuling mountainous area,and has the potential to be developed as a variety in the future.So “Beimu was employed as the test material in this study.The field investigation and laboratory experimentation were used to study the botanical features,phenological period,fruit growth dynamic,fruit nutrition,as well as the flesh color changes of the fruit.The results were as follows:1.The inflorescence pattern of A.chinensis strain ‘Beimu' was mainly single flower,with 6 green sepals.The corolla is medium size.The order of petal base is overlap,and the top of petal is weak corrugation.The color of adaxial side petals is double-color,with the main color of white and the shallow color of green at the petal base.The number of stamen is 155 with light green filaments and yellow anthers.The number of pistil is one,superior ovary,with 32 white,oblique stilus.2.The diameter of annual branches of ‘Beimu' are about 7.41 mm,with tawny and smooth epidermis in the exposed face.The lenticels are white and multi-shaped.The leaf scars are shallow without bud cover.The type of pith is flake.3.The fruit shape is cylindrical,and the exocarp is sandy beige with rare tomenta.Most of the fruit beak ends are shallow concave.Calyx ring is obvious.All of fruit have square shape of shoulder with persistent sepals.The fruit has round cross section,yellow flesh,and irregular larger core.4.The sprouting phase is in the first ten-day of March.The flower buds appearance in the middle of March and then blooms at the middle of April.The fruit maturation period is in the last ten-day of September to the first ten-day of October.The leaves begin to fall off at the middle of December before the dormant period in December.The bleeding period is in the March of the coming year.5.Amplified length polymorphism(AFLP)showed that significant differenceswere among 33 kiwifruit germplasm resources involving in genetic diversities and genetic differences.Large genetic differences existed among A.latifolia,A.valvata and the group of A.chinensis and A.deliciosa,while the later two species had near genetic relationship.Moreover,‘Beimu' had a close relationship with A.chinensis cultivar‘Cuiyu' which was planted in the same orchard.6.The growth period of ‘Beimu' fruit is mainly concentrated on the days of May and June,followed by a slow growth period.The growth curve in length and breadth of the fruit were as a shape of parabolic curve,which showed a growth rhythm of“slow-fast-slow”.7.The starch content in ‘Beimu' fruit increased at the former period and then decreased at the latter period of the development,arrived at a maximum value of68.36mg/g at the early ten-day of September,and dropped to 40.82 mg/g at maturity.The soluble sugar content increased gradually with the growth of fruit and rose to a maximum value of 40.395 mg/g at maturity.The sucrose content increased gradually along with the development of fruit also,and reached the maximum of 10.04 mg/g at the mature period.The change pattern of fructose was similar to that of sucrose with the highest content of 10.59 mg/g at maturation time.The organic acid content was lower at the early stage and higher at the maturity phase with a value of 7.85g/100 g,which lead to a sugar acid ratio of 4.57.The soluble solid content increased all the way and up to6.85% at the late September,which was suggested to be the beginning period of harvest.The content of Vintamin C increased rapidly at the beginning,followed by a long time of slow increase period,and went up to the highest content at 140 d.8.The changing pattern of flesh color of ‘Beimu' experienced a duration of“green-greenyellow-light yellow-yellow-deep yellow”.Young fruit had flesh of green or greenyellow,while ripe fruit had flesh of yellow to deep yellow.Flesh color was mainly controlled by the content ratio of carotenoid to chlorophyll,that was,low ratio led to green flesh,high ratio led to yellow flesh.Meanwhile,flavonoid was also an important factor that contributed to yellow-fleshed fruit.The key color-changed period was at the 120 d after pollination.