To produce high quality watermelon, three tetraploid watermelon breeding lines (‘SA03-1’, ‘SA06-1’ and ‘SB01-1’) were developed by treatment with different chromosome doubling reagents. To identify the optimal tetraploid inductive conditions, the three watermelon breeding lines were selected by counting the number of doubled chloroplasts in guard cells. Tetraploid induction rates differed depending on the genotypes and treatment with doubling reagents. However, the highest induction rate occurred with 1.0% colchicine (82.2%). These putative tetraploid lines were re-confirmed for ploidy using flow cytometric analysis and chromosome counting. The internode length of the tetraploid breeding lines was different when the leaf size was larger in all three tetraploid lines compared to their diploids. The fruit weight of the tetraploid fruits for ‘SA03-1’ and ‘SB01-1’ was lower than for their diploid, and the rind thickness and total sugar content (°Brix) of tetraploid SB01-1 were significantly different from those of its diploid. Tetraploid lines were sterile, yielded a lower number of seeds per fruit for ‘SA03-1’ (21), ‘SA06-1’ (62), and ‘SB01-1’ (34.7), and the seeds were larger and thicker than those of their diploids. These tetraploid breeding results will be useful for breeding new seedless watermelon cultivars.

수박의 대목으로 사용되고 있는 참박의 재분화조건을 확립함으로서 병저항성 형질전환 식물체를 얻어 보고자 본 실험을 실시하였다. 참박의 자엽을 잘라 재분화에 미치는 식물생장조절물질의 효과를 조사하였고 오이 galactinol synthase (CsGolS1) 유전자를 참박에 형질전환하였던 결과는 다음과 같다. 참박 신초의 재분화는 7일째 된 유묘의 자엽부위 중 전반부위에서 기장 높은 효율을 나타내었고, cytokinin으로 BA나 zeatin을 단용처리하는 것보다 옥신으로 IAA를 혼용처리하는 것이 신초 분화에 더 효과적이었다. 복합스트레스 내성 유전자인 오이 CsGolS1유전자를 pBI121 binary vector에 재조합하여 아그로박테리움을 이용, 참박에 형질전환하였던 결과, 형질전환체는 kanamycin이 첨가된 배지에서 생장하였고 PCR 및 Southern blot 분석에 의해 유식물체의 20% 정도가 형질전환체임을 확인할 수 있었다.