Correlation analysis between flower colors and floral fragrance in 4 Bauhinia variegate varieties

【Objective】 This study aimed to investigate the distribution patterns of flower color and the correlation between floral fragrance volatile compounds and color in Bauhinia variegate,which could provide theoretical basis for color and fragrance regulation and breeding improvement in B.variegata.【Method】Headspace solid-phase microextraction （HS-SPME） coupled with gas chromatography-mass spectrometry （GC-MS） was employed to analyze the floral fragrance volatile compounds of 4 B.variegata varieties:YZJ1 （purple-red）,YZJ2 （pink）,YZJ3 （white with yellow spots）,and YZJ4 （white with red spots）.Color parameters of the flowers,including lightness （L^*）,redness （a^*）,yellowness （b^*）,and chroma （C^*）,were measured using a colorimeter.Partial least squares regression （PLS） was applied to assess the correlation between floral compounds and flower color. 【Result】 Great differences in color parameters were observed among the 4 B.variegata varieties.While the petal colors of YZJ3 and YZJ4 appeared similar,they could be distinguished by the dominant color of the main petal heart,which exhibited distinct variations across varieties.A total of 33 floral compounds were identified,predominantly composed of monoterpenes and sesquiterpenes,accounting for over 95.00% of the total relative content.Phenylpropanoids/benzenoids were present in minimal amounts,with YZJ4 exhibiting a higher relative content of these compounds compared to the other 3 varieties.There was significant positive correlations（|PLS correlation coefficient|≥0.80,the same below） between sesquiterpenoid α-caryophyllene,monoterpenoids terpinolene and γ-terpinene and a^*2 and C^*2 of main color of main petals heart,as well as a^*1 and C^*1 of main color of petals.Monoterpenoids such as 2,6-dimethylocta-7-en-3-one and β-myrcene showed positive correlations with flower color parameters C^*2,a^*1 and C^*1,while monoterpenoid （Z）-β-ocimene was positively correlated with flower color parameters a^*1 and C^*1.Conversely,L^*1 of main color of petals exhibited significant negative correlations with α-caryophyllene,terpinolene,γ-terpinene,2,6-dimethylocta-7-en-3-one,β-myrcene and （Z）-β-ocimene.Similarly,L^*2 of main color of the main petals heart was negatively correlated with α-caryophyllene,terpinolene and γ-terpinene. 【Conclusion】 Some of the terpenoids in the flower volatile compounds of 4 B.variegata varieties are positively correlated with the redness and chroma of the main color of petals and the main color of main petal heart.The redder the petal color is,the more terpenoids are released.Some terpenoids are negatively correlated with the brightness of the main color of petals and the main color of main petal heart.The higher the brightness of the petal color,the less the release of terpenoids.