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  • Author or Editor: Seung-Ryong Cheong x
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Common watermelons have an indeterminate growth habit with normal internode length, thus allowing the vine to grow indefinitely under the normal conditions. Watermelon breeders have identified four dwarf genes (dw-1, dw-1 s , dw-2, dw-3) and used these for developing dwarf watermelon cultivars. We discovered a naturally occurring new dwarf and seedless mutant (NDSM) from a landrace cv. Mudungsan that had been cultivated in the Mountain Mudung area nearby Gwangju City in Korea. The progenies of this mutant segregated in a ratio of 3 vine to 1 dwarf indicating a single recessive gene nature. Morphological characteristics of the NDSM were markedly different from those of the four known dwarf genotypes. NDSM plants grow shorter than 1 m in length with fan-shaped leaves and have fewer leaf lobes than normal plants, which could be clearly distinguished at 2 or 3 true leaf stage. Male and female flowers have just one petal and failed to open completely even at the anthesis. Even though there were some fertile pollen grains, the fruits of NDSM had no seed after fertilization. The F2 progenies, obtained from crossing `920533' (normal vine type) and NDSM, segregated in a ratio of 3 vine to 1 dwarf. All F1 plants from crosses between 2 dwarf types, `Sugar Bush' (dw-1dw-1) and `NH 9' (dw-2dw-2), and NDSM were normal, while F2 showed 9 vines, 3 dw-1 or dw-2 types, 3 NDSM types, and 1 double dwarf. The backcross generation segregated in a ratio of 1 vine to 1 dwarf. These results indicate that the genes for the NDSM and 2 dwarf types are non-allelic. We named this new dwarf genotype (NDSM) as dw-4 in addition to four dwarf genes previously identified.

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Genetically modified herbicide-tolerant (GMHT) and non-GM chile pepper plants (Capsicum annuum L. cv. `Subicho') were grown in an isolated GMO field to evaluate horticultural characteristics. Phosphinotricin acetyltransferase (bar gene), which has a function of herbicide-resistance in plant, was introduced into chile pepper plants using the protocol of Agrobacterium-mediated transformation. Thirty nine characteristics were evaluated, consisting of 14 qualitative, 18 quantitative and 7 other characters. The evaluations were achieved by visual assessment for qualitative characteristics and numerical measurement for quantitative ones. The GMHT and non-GM plants did not differ in the 39 characteristics tested. Pollen viability and germination rate were not significant different between the GMHT plants and the non-GM plants. These results indicated that genetic transformation of bar gene into the chile pepper did not affect those horticultural characteristics and pollen viability.

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