Preliminary Evaluation Of Chilling Requirement Of Sweet Cherry Cultivars And Research Of Dormancy-associated MADS-box Genes

Sweet cherry(Prunus avium L.)belongs to the deciduous fruit tree,that needs some low temperature accumulation in order to survive in winter,while the southern warm winter region such as high temperature,low temperature accumulation,resulting in its abnormal growth and development.There are few studies on the screening of sweet cherry low chilling requirement cultivars.The mechanism of cloning and regulation of dormancy-associated MADS-box genes has not been reported yet.The contents and results of this study are as follows:1.To screen low and moderate chilling requirement cultivars of sweet cherry for warm region of China,shoots of 64 cultivars were collected and cultured in vitro after cold treatment.Rate of bud break was measured after 3 weeks and the chilling requirement ranges were calculated.The same cultivars from different regions were also evaluated.The results showed that the patterns of bud break of sweet cherries cultured in vitro were cultivar-and dormancy stage-dependent,and no significant difference of chilling requirement for a cultivar was observed between different regions.Chilling requirement of most cultivars were fallen into 400~800 hours range and those of twenty-eight cultivars were less than 600 hours.2.Selection of moderate chilling requirement cultivars ’Brooks’ and low chilling requirement ’Royal Lee’,PaDAM3,PaDAM4,PaDAM5 and PaDAM6 genes which were the dormancy-associated MADS-box genes were cloned,and the full-length cDNAs were 720 bp,675bp,729/708 bp and 723 bp,respectively.3.The results of quantitative real-time PCR showed that the expression of four genes were significantly different between the moderate chilling requirement cultivars ’Hongdeng’,?Van‘,?Tieton‘,?Brooks‘ and the chilling requirement cultivars ‘Royal Lee’,‘Royal Mine’ in total dormancy stage.The moderate chilling requirement cultivars possessed higher PaDAM4 gene relative expression level than other DAM genes.The expression of PaDAM5 and PaDAM6 genes in low chilling cultivars were higher than other DAM genes.4.The concentration of 2% cyanamide was applied to 10 trees of ?Van‘ and ?Royal Lee‘,and the other 10 trees were sprayed with clear water as control.The relative amount of gene expression was detected by quantitative real-time PCR.The results showed that cyanamide promoted break the dormancy in the moderate chilling requirement cultivars,while the little impact of low chilling requirement cultivars.