| Summary: | 碩士 === 國立臺灣大學 === 園藝學研究所 === 93 === The objective of this study was to identify the genetic diversity among the lines and cultivars of Luffa spp., including L. cylindrica and L. acutangula. L. cylindrica and L. acutangula have well-differented morphological characters, differing in floral structure, time of anthesis and the fruit structure etc. In this study, genetic diversity was assessed among the lines and cultivars of Luffa spp., using 20 randomly amplified polymorphic DNA (RAPD) primers. These primers produced 148 stable bands, among which, 123 bands were polymorphic. Based on the RAPD data, the L. cylindrica cluster differentiated from the L. acutangula cluster at the level of 0.02 to 0.11 genetic similarity, indicating high level of genetic diversity between L. cylindrica and L. acutangula. The interspecific hybrid, the line 208, was produced by crossing L. cylindrica with L. acutangula. The interspecific hybrid differentiated from the L. cylindrica cluster and from the L. acutangula line A28 at the level of 0.36 to 0.45 and 0.45 genetic similarity, respectively, indicating that interspecific hybrid was genetically intermediate between both parental plants. The line 247 was produced by backcrossing of interspecific hybrids to L. acutangula line A28. The line 247 differentiated from individual parents at the level of 0.79 and 0.57 genetic similarity, respectively; moreover, the line 247 differentiated from L. cylindrica cluster, except the cultivar Shuang-Yi, at the level of 0.31 to 0.39 genetic similarity, indicating that the line 247 had closer relationship with L. acutangula than with L. cylindrica. This result was consistent with the genetic background of the line 247. The cultivar Shuang-Yi differentiated from the L. cylindrica cluster at the level of 0.60 to 0.73 genetic similarity. According to the ordination of all the 80 lines and cultivars determined by the first two principal component axes on the basis of 123 polymorphic bands, the cultivar Shuang-Yi was located between the L. cylindrica cluster and the line 208. It could be hypothesized that there had been some genetic introgression of L. acutangula germplasm into the cultivar Shuang-Yi. There was high level of genetic similarity among all the L. cylindrica lines and cultivars tested; some of the L. cylindrica lines and cultivars were identical genetically, indicating low level of genetic diversity and narrow genetic base among the L. cylindrica. However, all the L. cylindrica lines and cultivars tested could be divided into two clusters, and all the cultivars from China were in the same cluster, indicating they had closer relationship with each others. This study indicated that RAPD marker can be useful in assessing the genetic diversity and relatedness of the domesticated varieties of Luffa.
In addition to RAPD analysis, the analysis of 19 phenotypic characters was carried out to assess the genetic diversity of L. cylindrica. The phenotypic characters investigated included seed length, seed width, seed length/seed width, seed thickness, weight per one hundred seed, seedcoat color, leaf length, leaf invagination, leaf length/leaf invagination, flower color, fruit skin color, fruit skin texture, fruit weight, fruit length, fruit width, fruit length/fruit width, pedicel length, remnant of stigma length, and remnant of stigma width. However, because of the serious damage caused by melon fly, the fruit characters of many lines and cultivars were lost. For this reason, the analysis of 12 phenotypic characters, not including the fruit characters, was also carried out to assess the genetic diversity. The result of the analysis of 19 phenotypic characters resembled the result of RAPD analysis more than that of 12 phenotypic characters did. According to cluster analysis and principal component analysis, fruit length/fruit width, fruit width, fruit length, pedicel length, and fruit skin color were the major discriminating characters, indicating that fruit characters had more influence on clustering than other characters did. Data based on the analysis of phenotypic characters showed that fruit characters played important roles in assessing the genetic diversity among L. cylindrica.
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