| Field trials were carried out in Yunnan tobacco science research institute from 2004 to 2005. The genetic variation laws and heterosis performance of main aroma matter in the parents and F1 combinations of flue-cured tobacco were studied, and the correlations between parents and offspring and among different kinds of heterosis were analyzed. The main conclusions were as follows:1. The variation of the content of aroma matter in different flue-cured tobacco genotypes was analyzed. The result showed that there existed some variation for the contents of aroma components among different flue-cured tobacco genotypes. The genotypes studied were all classified into 3 groups based on the content of aroma matter: (1) There were highly significant differences among high, medium and low genotype groups for polyphenol compounds, free amino acid and petroleum ether extracts. (2) Organic acids: comparing with other genotype groups, the contents of total content of organic acids and non-volatile organic acids were medium and senior fatty acids were the highest in group I; in group II, the contents of total content of organic acids and non-volatile organic acids were the highest and senior fatty acids were medium; in group III, all the contents of total content of organic acids, non-volatile organic acids and senior fatty acids were the lowest. (3) Neutral aroma matter: in group I, the contents of other aroma matter were the highest except products of Maillard reaction and products degraded by cembrane with medium contents among 3 groups; in group II, the content of products of Maillard reaction was the highest and the content of products degraded by carotene was medium, and the contents of the others were the lowest; in group II, the content of products degraded by cembrane was the highest, but the contents of products of Maillard reaction and products degraded by carotene were the lowest, and the others were medium.2. Multivariate statistical analysis of main chemical components and aroma matter in different flue-cured tobacco genotypes indicated that the first canonical correlation coefficient (0.728**) of main chemical components was significant at the 1% level with aroma compositions, and nine significant traits were obtained including reducing sugar content, total nitrogen content, nicotine content, chlorine content, the ratio of potassium to chlorine, the ratio of reductive sugar to nicotine, the ratio of total nitrogen to nicotine, free amino acid and neutral aromatic components. On the basis of canonical correlation analysis, the principal component analysis was done, and four principal components were selected and named nicotine factor, chlorine factor, carbon-nitrogen factor and aroma factor. The accumulated contribution of the first four factors to total variation of population accounted for 86.09%. According to the value of the principal components, the genotypes studied were classified into 3 groups. The variation for main chemical components and aroma compositions was big among different genotype clusters, but small among genotypes within the same cluster.3. Descriptive statistics analysis was done for the content of aroma matter in the F1 combinations and parents of flue-cured tobacco. (1) The content of polyphenol compounds for F1 combinations was 2.75%±0.15% and 2.76%±0.24% for parents. The content of free amino acid for hybrid was 0.15%±0.02%, the same as parents. The content of petroleum ether extracts was 5.97%±0.54% for F1 combinations, and 5.87%±0.84% for parents. (2)The total content of organic acid for F1 combinations was 39.40±6.37 mg·g-1 and 37.68±5.11 mg·g-1 for parents. The content of non-volatile organic acids was 27.69±4.92 mg·g-1 for F1 combinations, and 27.36±4.62 mg·g-1 for parents. The content of saturated senior fatty acidsfor F1 combinations was 5.42±1.30 mg·g-1, and 4.85±0.76 mg·g-1 for parents. The content of unsaturated senior fatty acids was 6.29±1.68 mg.g-1 for F1 combinations, and 5.46±0.96 mg.g-1 for parents. (3) The total contents of neutral aroma components for F1 combinations and parents were 1031.17±216.22 and 911.76±176.60μg.g-1. The contents of products of aromatic amino acid metabolism, products of Maillard reaction, products degraded by cembrane, products degraded by carotene and neoplytadiene were 15.77±3.30,42.58±6.48,12.96±2.88, 75.13±13.02 and 884.73±203.59μg·g-1 for F1 combinations, respectively, and14.61±2.82, 41.55±6.90, 13.02±4.09, 71.09±7.92 and 771.50±168.18μg·g-1 for parents, respectively.4. The different significance for the content of aroma matter btween the F1 combinations and parents of flue-cured tobacco was tested. Comparing with the content of patents, the contents of all of aroma matter in 48 F1 combinations of flue-cured tobacco were highly significantly higher than their low-parent value. The contents of polyphenol compounds, free amino acid, petroleum ether extracts, non-volatile organic acids, products of Maillard reaction and products degraded by cembrane were no significant difference comparing with their mid-parent value, but highly significantly lower than their high-parent value; the content of other aroma matter were significantly or highly significantly higher than their mid-parent value and no significant difference with their high-parent value.5. Correlation analysis between parents and offspring of the content of aroma matter in flue-cured tobacco showed that there were significantly or highly significantly positive correlations among polyphenol compounds, free amino acid, senior fatty acids with mid-parent value, low-parent value, but no significant difference with high-parent value or difference between two parents; the correlation coefficients between parents and offspring were little and no significant for petroleum ether extracts, non-volatile organic acid and total content of organic acid. Aroma matters except products degraded by carotene could be significantly or highly significantly affected by parents, and there were close positive relationships with high-parent and mid-parent values, but feeble relationships with low-parent value and difference between two parents. The correlation coefficients between parents and offspring of products degraded by carotene were not significant.6. The heterosis of F1 combination was analyzed and the result indicated that: (1) Both polyphenol compounds and free amino acid showed negative heterosis over mid-parent and high-parent; petroleum ether extracts showed positive heterosis over mid-parent and negative heterosis over high-parent, however, but there still was 13 combinations with positive heterosis over high-parent. (2) The order of heterosis over mid-parent was non-volatile organic acid > saturated senior fatty acid > total content of organic acid > non-saturated senior fatty acid. The order of heterosis over high-parent was the same as heterosis over mid-parent. Non-volatile organic acid and total content of organic acid showed negative heterosis over high-parent, but there still were 15 and 20 combinations with positive heterosis over high-parent, respectively. (3) All kinds of neutral aroma matter showed positive heterosis over mid-parent. The order of heterosis over mid-parent was: neoplytadiene > total content of neutral aroma matter > products of aromatic amino > products degraded by carotene > products degraded by cembrane > products of Maillard reaction. The order of heterosis over high-parent was the same as heterosis over mid-parent. Both neoplytadiene and total content of neutral aroma matter showed positive heterosis over high-parent and other aroma matters showed negative heterosis over high-parent, however, there still were many combinations with positive heterosis over high-parent.7. The heterosis relationship analysis of all kinds of aroma matter in flue-cured tobacco indicated that there were highly significant correlations among different kinds of heterosis for polyphenol compounds and petroleum ether extracts, but no significant correlations with free amino acid. There were highly significant correlations among different kinds of heterosis for organic acids except non-volatile organic acid. Significant or highly significant correlations among heterosis over mid-parent and among heterosis over the better parent were found for most volatile aroma components except products of Maillard reaction and products degraded by cembrane.
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