| Summary: | 碩士 === 國立嘉義大學 === 農學研究所 === 95 === Abstract
This study was aimed at exploring the quantitative genetic characteristics of tomato fruit. A total of 494 inbred lines from the breeding program were used for the data collection and analyses of fruit characteristics including brix, titratable acid, sugar/acid ratio, hue angle, chroma and brightness. After preliminary evaluation, six best lines were selected as parents for half 6x6 diallel cross. A randomized complete block design (RCBD) with three replications was used in the experiments containing six parents and 15 F1 hybrids. Data of the fruit characteristics including brix, fruit weight, titratable acid, sugar/acid ratio, hue angle, chroma and brightness were collected for the statistic analyses following the method developed by Hayman and Griffing. Results showed that large variation was observed in the fruit characteristics data collected from the 494 inbred lines. Except fruit brightness, the frequency distributions curve of the other five characteristics were all unsymmetrical with skewness and kurtosis. The curve of fruit brightness was a typically normal distribution. A negative correlation coefficient (r=-0.74**) were observed between brix and fruit weight. Positive correlation coefficients (r= 0.55** and r=0.63**) were also observed between brix and sugar/acid ratio. These three correlation coefficients were all significant at 1% level. Both of Hayman and Griffing methods were used in the statistic analyses of brix, fruit weight and sugar/acid ratio and the quantitative genetic behavior of the three characteristics was very similar to each other. Results are summarized as follow：1. Additive effect is more than dominant effect, therefore high sugar content of tomato fruit must be put in the first priority in the breeding of inbred lines. 2. The data of the three characteristics in the 15 F1 hybrids were all ranged between the six parents. This result showed the existence of partial dominant and almost no complete dominant or super dominant was observed. 3. Analysis of the variances showed the quantitative genetic behaviors of the characteristics were partial dominant. Frequency of gene distribution is not equilibrium in the parents, more dominant genes and polygene were observed and they were controlled by minor genes. 4. Figure of Wr/Vr showed the existence of partial dominant effect. Some parents have more dominant genes and the others have more recessive genes. 5. The results is also showed that general combing ability(GCA) is much more important than specific combing ability(SCA) in the three characteristics. GCA varied positively with variation of the mean value of Parents GCA. The SCA of F1 is smaller in general. Differences of genetic phenomenon among the three characteristics was presented in the Yr and Wr+Vr standardized deviation graph. Exceptionally, fruit weight, different from the other two characteristics, brix and sugar/acid ratio, has regular plot distribution and correlation coefficient was significant at 1% level. Dominant and recessive genes were correlated to the direction of negative and positive effect. The graph of Yr and Wr+Vr standardized deviation of brix and sugar/acid ratio were very similar to each other. But, plot distributions were irregular. Dominant and recessive genes were not correlated to the direction of negative and positive effect.
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