Cucurbit Genetics Cooperative Report 19:4-6 (article 2) 1996
O. Kawaide and S. Matsuura
Tohoku Seed Co., 1625, Himuro, Nishihara, Utsunomiya 321-32, Japan
S. Iida
Chugoku National Agricultural Experimental Station MAFF, 6-12-1, Nishifukatsu, Fukuyama 721, Japan
In Japan, the seeds of some hybrid varieties are produced by hand-pollination using monoecious inbred lines. Since technical errors in pollination can cause contamination of self- and/or sib-crossed seeds of female lines used for hybrid production, the purity of individual seed lots must be assessed. Molecular techniques [e.g., restriction fragment length polymorphism (RFLP) of nuclear DNA] are often used in Japan for purity assessments (2). If it were possible to use a recessive morphological marker to assess the purity of female inbred lines, then purity testing could be done more rapidly and economically.
Materials and Methods. Seeds and pollen of inbred line ‘T-1’ were irradiated with gamma rays. Line T-1 is monoecious and has been used as a female line to produce a monoecious hybrid. Self-pollinated M2 lines were derived from 100 seed irradiated (100Gy) M1 plants. In addition, 272 M2 lines originating from pollen irradiation were evaluated. These lines were derived from a cross between non-irradiated staminate flowers and the irradiated (20Gy) pistillate flower. The method of pollen irradiation was according to Iida and Amano (1). Forty individuals per one M2 line were examined in order to identify mutant characters.
Results and Discussion. Eleven mutants were observed as a result of seed irradiation and two mutants were observed following pollen irradiation. Characteristics of these mutants are detailed in Table 1. Segregation in the M2 generation suggested that all of these characters were governed by one recessive gene at each locus (Table 2).
Table 1. Characteristics of induced mutants.
Mutant |
Characteristics |
Seed irradiation derived |
|
| Albino-1 | White cotyledon. Seedlings die after 6-7 days. |
| Albino-2 | White cotyledon. Seedlings die after 10 to 11 days. |
| Yellow | Yellow cotyledon. Seedlings die before the development of the 2nd true leaf. |
| Pale green | Pale green stem and fruit. Seedling growth is slower than in the original inbred line, but acquires normal seed fertility. |
| Round leaf | Round heart shaped leaves. This character is distinguishable after the 5th true leaf stage. |
| Small leaf | Small leaves. Seedling growth is slightly slower than in the original inbred line and seed fertility is low. |
| Mottled leaf | White mottled leaves associated with normal seedling growth. |
| Flat stem | Flat stems. Expression of flat stem can be observed after the 5th true leaf stage. Seedling growth is slower and poor bud development inhibits flowering. |
| Dwarf-1 | Short internode. Seedling growth is slower than in the original inbred line. The leaves, flowers and fruits are normal. |
| Compact | Reduced size of leaves, flowers, stems, fruits and seeds when compared to the original inbred line. Seed fertility in mutant plants is normal. |
Pollen irradiation derived |
|
| Bush | Short internode with thick and vigorous leaves with bush type plant habit. |
| Dwarf-2 | Short internode with small leaves. Seedling growth is slightly slower than that observed in the original inbred line. |
Table 2. Segregation ratios in M2 generation after gamma-ray seed and pollen irradiations.
No. observed |
Expected ratio |
X2 |
P-value |
|||
Irradiation method |
Characters segregated in M2 |
Normal |
Mutant |
|||
| Seed (100Gy) | Albino-1 | 29 | 11 | 3:1 | 0.133 | <0.05 |
| Albino-2 | 30 | 10 | 3:1 | 0.000 | <0.05 | |
| Yellow | 33 | 7 | 3:1 | 1.200 | <0.05 | |
| Yellow to green | 31 | 9 | 3:1 | 0.133 | <0.05 | |
| Pale green | 34 | 6 | 3:1 | 2.133 | <0.05 | |
| Round leaf | 35 | 5 | 3:1 | 3.333 | <0.05 | |
| Small leaf | 34 | 6 | 3:1 | 2.133 | <0.05 | |
| Mottled leaf | 35 | 5 | 3:1 | 3.333 | <0.05 | |
| Flat stem | 35 | 5 | 3:1 | 3.333 | <0.05 | |
| Dwarf-1 | 32 | 8 | 3:1 | 0.533 | <0.05 | |
| Compact | 33 | 7 | 3:1 | 1.200 | <0.05 | |
| Pollen (20Gy) | Bush | 35 | 5 | 3:1 | 3.333 | <0.05 |
| Dwarf-2 | 32 | 8 | 3:1 | 0.533 | <0.05 | |
Literature Cited
- Iida, S. and E, Amano. 1990. Pollen irradiation to obtain mutants in monoecious cucumber. Gamma Field Symp. Japan. 29:95-111.
- Matsuura, S., A. Saito and Y. Fugita. 1994. An approach for rapid checking of seed purity by RFLP analysis of nuclear DNA in F1 hybrid of cucumber (Cucumis sativus L.). J. Japan. soc. Hort. Sci. 63:379-383.