A Study On Flower Bud Differentiation In Different Varieties Of Grape And Expression Of Flower Development Related Genes

Bud break and flowering pattern in different cultivars grown in Guangzhou were observed and related factors were examined.On the top of it,two-year-old'Summer black'and'Oriental star'grape varieties were used as the experimental materials for studying flower differentiation progress in winter buds at different node position and for observing the anatomical structures in winter buds.At the same time carbohydrate accumulation in leaves and internodes at different node positions and the expressions of flowering-related genes in different tissues were compared between the two cultivars.The study aim to understand the flower differentiation pattern among different grape varieties grown in south China and to bring an in-depth of understanding of mechanism of flowering regulation so as to provide reference for production of grape with two crops in a year in south China.The main results are the followings:1.Among the four tested cultivars,'Oriental Star'was most likely to produce flower,followed by'Shine Muscat'and'wink',and'Summer Black'had the lowest flowering rate.Nicking promoted bud break.The winter buds in branches between 0.7-1.5 cm in diameter had the highest breaking rate and flowering rate in one year old vines.The winter buds in canes(2^nd order branches)had higher break and flowering rates than those in the cordons(1^st order branches).In addition,the winter buds in vines of“V”type trellising displayed faster bud-break but much lower flowering rate compared to those of high-cordon“T”trellised vines.After post-harvest summer pruning,treatment of hydrogen cynamide and defoliation promoted winter bud break but had not effect on flowering.2.Based on the flowering in new shoot grown from the winter bud after summer pruning at different node positions and the anatomical observation of winter buds at different node positions,'Oriental Star'had a faster flowering process than'Summer Black'.In the former,new shoots grown from upper-position nodes after decapitation showed flowering,while in'Summer Black'flower appeared in shoots grown from the nodes lower than the 7^th nodes from the top.Therefore,flower initiation occurred earlier in?Oriental Star?than in'Summer Black'.3.Contents of sugars and starch in stem and leaves at different node positions in'Oriental Star'were generally higher than in'Summer Black',providing a better nutrition basis for flowering in the former.4.Four genes related to flowering displayed differential expression levels among different organs.VvSOC1 and VvFLC had higher expression in bud than in stem and leaves,and VvLFY expression was highest in stem.VvFT was expressed in buds,leaves and stem,but highest in the leaves.In'Oriental Star'leaves,VvFT expression in young leaves was high and significantly higher than that in the leaves of'Summer Black',which agrees with the earlier flowering observed in'Oriental Star'.The VvFLC displayed a basically opposite pattern with VvFT,suggesting its negative regulation on VvFT expression.The roles of the other genes in flowering of grape vine awaits further clarification.