Cucurbit Genetics Cooperative Report 7:6-7 (article 2) 1984

Facilitation of Self-pollination in Gynoecious Cucumber with Silver Nitrate Treatment of Cuttings

Soo-Nyeon Kwack and Kunimitsu Fujieda

University Farm, Faculty of Agriculture, Kyushu University, Kasuyamachi, Fukuoka, Japan

Obtaining self-pollinated seeds from gynoecious cucumber plants selected from segregating populations presents a serious problem for the plant breeder. In this study, we have investigated the application of gibberellic acid (GA) and silver nitrate (1,2,4) to induce staminate flowers in female lines of cucumber as a means of obtaining the necessary selfed seeds.

In order to determine the optimum method for the propagation of cucumber cuttings, cuttings were taken at the time of harvest from the tips of lateral branches of cucumber cultivar 'Sachimidori'. They were trimmed down to two expanded nodes from the tip, treated with indolebutyric acid, IBA, (0, 0.5, or 1.0%) on the cut face, and placed in baked rice chaff or pumice (less than 5 mm diameter). The cutting bed was covered with plastic film and black cheese cloth for 10 days. After 7 days, the percentage of rooted cuttings and the number of roots per cutting were recorded.

All cuttings in baked rice chaff produced roots regardless of IBA concentrations, but IBA treatment decreased the percentage of rooted cuttings in pumice. In both cases, IBA application increased the number of roots per cutting, but slightly suppressed root growth.

Induction of staminate flowers in gynoecious cuttings by GA₃ or AgNO₃ was investigated. Cuttings from gynoecious cultivars, 'Pandex', 'Noval' and 'Fertila', were rooted as above in baked rice chaff without IBA treatment. GA₃ (1000 ppm) or AgNO₃ (100 or 200 ppm) was applied as a foliar-spray, and after treatment, the cuttings were grown in water culture with OK-F-1 solution for five weeks.

All cultivars treated with GA₃ or AgNO₃ produced functional staminate flowers (Table 1). Plants treated with AgNO₃ formed staminate flowers at lower nodes than those treated with GA₃, and in addition, a larger number of nodes bore staminate flowers on plants treated with AgNO₃. It should be noted that, although it has been reported (4) that GA₃ lengthens internodes, we observed our GA₃ plants to have shorter internodes than controls.

When cuttings are taken from the tips of lateral branches of adult plants, placed in baked rice chaff, and treated with AgNO₃ after rooting, functional staminate flowers can be produced. This method makes possible the production of selfed seeds from gynoecious cucumber plants selected from a segregating population.

Table 1. Effects of GA₃ and AgNO₃ on induction of staminate flowers in gynoecious cucumber cuttings.

Cultivar	Treatment (ppm)	1st staminate nodez	No. staminate nodes/plantz	Internode length (mm)y
'Pandex'	None	-	0	70
	GA3 1000	14.3	4.0	59
	AgNO3 100	11.0	9.0	62
	AgNO3 200	8.7	13.7	71
'Noval'	None	-	0	73
	GA3 1000	15.7	1.7	57
	AgNO3 100	10.7	9.7	74
	AgNO3 200	9.7	11.3	68
'Fertila'	None	-	0	73
	GA3 1000	11.3	2.3	62
	AgNO3 100	8.0	9.7	63
	AgNO3 200	7.7	14.7	67
zBased on the main stem.
yMean length of 10 internodes from first to 11th node.

Literature cited:

1. Peterson, C.E. and L.D. Andher. 1960. Induction of staminate flowers on gynoecious cucumbers with gibberellin A₃. Science 131:1673-1674.
2. Pike, L.M. and C.E. Peterson. 1969. Gibberellin A4/7 for induction of staminate flowers on the gynoecious cucumber (Cucumis sativus L.). Euphytica 18:106-109.
3. Rodriquez, B.P. and V.N. Lambeth. 1972. Synergism and antagonism of GA and growth inhibitors on growth and sex expression in cucumber. J. Amer. Soc. Hort. Sci. 97:90-92.
4. Tolla, C.E. and C.E. Peterson. 1979. Comparison of gibberellin A4/7 and silver nitrate for induction of staminate flowers in gynoecious cucumber line. HortScience 14:542-544.