| Pakchoi(Brassica campestris L.ssp.Chinensis(L.)Makino var.communis Tsen et Lee)has a long history of cultivation in China.Due to the differences of diet and regional climate between the north and the south,the cultivated species are diverse and rich.All localities need to select suitable varieties in order to achieve annual production and meet market demand.In the annual production process of Pakchoi,with the change of season,the main environmental factors also have great changes,and the early bolting caused by the weather has always been one of the production problems.Exploring the principle of bolting and flowering and cultivating late bolting varieties are the fundamental way to solve the problem of early bolting of Pakchoi.In this study,a late bolting Pakchoi line from Changsha late bolting pakchoi was selected,and the bolting tolerance and the differences in bolting characteristics between different late bolting producing Pakchoi lines and other late bolting cultivars in the field were compared.The relationship between bolting characteristics of Pakchoi planted in artificial climate chamber and field planting was studied.The effects of low temperature vernalization and photoperiod regulation on bolting characters of Pakchoi were further explored.Gene expression characteristics and mechanism of flowering regulated by low temperature vernalization and photoperiod pathway.The results are as follows:(1)Forty pakchoi accessions with different bolting characteristics were treated with 4℃cold vernalization for 20 d and 45 d,respectively,at diurnal temperatures of 25/18℃and 16h light,with a basal light intensity of 196.26μmol/m~2·s climatic chamber for cultivation management,with the open field cultivation natural vernalization group as the control.The results showed that most varieties could bud after 20 days of low temperature vernalization treatment,and after 45 days of low temperature vernalization treatment,the bud time was generally 8.38 days earlier,among which’bai geng bai ye xiao bai cai’,’wan chou tai shanghai wu yue man’,’wu yue man’and three selected inbred lines could not bud,belonging to late bolting materials.When the late bolting varieties were treated at 4℃for 45 days,there were still three late bolting materials from cruciferous vegetable research group of horticulture College of Hunan Agricultural University,which could not bud.It is an excellent late bolting breeding material.The results showed that the coefficient of variation(CV)of budding stage of Pakchoi was 21.96%under the condition of 4℃low temperature treatment for 20 d and 16 h/d illumination,which was significantly correlated with that under the condition of low temperature vernalization(CV=17.13%)(r=0.52,P<0.01).(2)The late bolting characters of different generations of Changsha late bolting lines and different late bolting varieties of Pakchoi were compared by using natural low temperature in the field.Under the condition of open field cultivation,the bolting time of late bolting lines of Changsha late Pakchoi of later generations was later than that of the previous generation,and the bolting time of late bolting lines of Changsha late Pakchoi Cultivated by vegetable Department of horticulture College of Hunan Agricultural University was significantly later than that of other late bolting varieties.The results showed that the indoor late bolting breeding method used in this project was in line with the goal of genetic breeding,and the late bolting line of Changsha late Pakchoi was an excellent late bolting breeding material.(3)The seeds of late bolting line 1102(self bred 4 generations)of Changsha late Pakchoi were treated with low temperature vernalization at 4℃for 20 days,35 days and 50 days respectively.After vernalization,the seedlings were transplanted into 8×17 hole plug.The seedlings of each low temperature group were placed in the light cycle of 16/8 h and 24 h of the whole light intensity of 196.26μmol/m~2·s.IIt was found that no buds developed in the late bolting 1102 strain of Changsha late Pakchoi after 20 d,35 d and 50 d of low-temperature vernalization treatment and moved to 16 h light for 60 d.However,buds could be found after the low temperature treatment over 35 d extended the light period to 24h/d,and under equal light conditions,the longer vernalization time was easier for buds to appear.(4)According to the phenotypic response of late bolting line 1102 of Changsha late Pakchoi to low temperature vernalization and photoperiod treatment,the materials were vernalized 0 d,20 d,35 d,60 d,then under the photoperiod condition of 16 h/d,20 h/d,24h/d.the leaves were taken at 25 d seedling age.The FLC,CO,GI,and FLC regulated by low temperature vernalization and photoperiod pathway were detected by transcriptome sequencing and QPCR The expression characteristics and mechanism analysis of VIN3 and other genes showed that AGL24 and VRN2 were significantly up-regulated in the budding treatment group,and VRN2 was also significantly up-regulated in the treatment group with significantly shortened budding time. |
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