The present studies were carried out to compare characteristics of leaf, flower, pollen morphology with SEM (scanning electron microscope), number of somatic chromosome, isozymes, and resistance of Aphis of Hibiscus syriacus ´Diana´ and ´Helene´ with those of the diploid ´Youngkwang´ and the tetraploid ´Red Heart CV´ ´Purple CV₂´ in order to obtain basic data for future breeding of Aphis resistant and cold resistant cultivars. The results are summarized as follows;
1. Shoulder width of leaf in the triploid of H. syriacus ´Diana´ and ´Helene´ were larger than the comparative cultivars, and ´Helene´ had larger leaf length and leaf width than any other cultivars.
2. H. syriacus ´Diana´ with large flower and pure white color was much longer than those of the comparative cultivars for the diameter of flower, petal length, petal width, pistil length and pistil width. ´Helene´, white with a reddish purple blush at the base, was also much longer than those of the comparative cultivars for the diameter of flower, petal length, petal width, pistil length and pistil width. Red eyed spot at the base of petal in ´Helene´ was larger than those of diploid and tetraploid cultivars.
3. Flowering times of ´Diana´ and ´Helene´ were from 4 a.m. June 29, 1992 to 6 p. m. in the following day, and then total flowering time required 38 hours, flowers bloomed for more than a day. A triploid, ´Diana´ huge, waxy, pure white flowers, and fully 12.4 cm cross, bloomed all summer and remained open at night. ´Diana´ bloomed from June 29, 1992 to the frost time and ´Helene´ bloomed from July 6, 1992 to Mid October. However ´Youngkwang´, ´Red Heart CV´ and ´Purple CV₂´ from July 6, 1992 to Oct. 2, 1992 therefore, the period of flowering in the triploid of H. syriacus ´Diana´ and ´Helene´ were much longer than those of the comparative cultivars ´Youngkwang´, ´Red Heart CV´, and ´Purple CV₂´.
4. The number of spines showed 52 in ´Helene´, 45 in ´Diana´ respectively, H. syriacus ´Diana´ and ´Helene´ were much more than the number of spine of the diploid ´Youngkwang´, Apertures at the pollen exine sculpture in ´Diana´ showed them, whereas the other cultivars were without them.
5. The somatic choromosome number of ´Youngkwang´ was 2n=80, and that of tetraploid ´Red Heart CV´ was 4n=160. That of both ´Diana´ and ´Helene´ were 3n=120, indicating that ´Diana´ and ´Helene´ were proved to be triploids.
6. The results of leaf isozyme, glucose phosphate isomerase (GPI), glutamate oxaloacetate transaminase(GOT), analyses through starch - gel electrophoresis, isozyme Isozyme - band patterns in GPI at ´Helene´ showed the same value of Rf in ´Youngkwang´.
7. The numbers of Aphis gossypii in triploid cultivars of H. syriacus ´Diana´ and ´Helene´ were less than the comparative cultivars. Therefore, triploid ´Diana´ and ´Helene´ were regarded resistant to Aphids.
8. The results from intrageneric crosses, percentages of crossing in H. syriacus ´Diana´ (♀) with ´Hansarang´ (♂), with ♀ ´Youngkwang´ (♂) showed 43%, 22% respectively, but ´Diana´ (♀) x ´Red Heart CV´ (♂), ´Diana´ (♀) x ´Purple CV₂´ (♂) and ´Diana´ (♀) x ´Blue Bird´ (♂) failed to crossing, and percentages of crossing in H. syriacus ´Helene´ (♀ with ´Hansarang´ (♂), ´Helene´ (♀ ) with ´Youngkwang (♂)´ ´Helene´ (♀) with ´Red Heart CV´ (♂) showed 70%, 30%, and 25% respectively. ´Helene´ (♀) x ´Purple CV₂´ (♂) failed to crossing.
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