Cucurbit Genetics Cooperative Report 3:22-23 (article 12) 1980
A.P.M. den Nijs
Institute for Horticultural Plant Breeding, Wageningen, The Netherlands
The amino-ethoxy of rhizobitoxine, amino-ethoxy-vinyl-glycine (AVG), inhibited ethylene production in muskmelon seedlings and improved fruit set following hand-pollination of emasculated muskmelon flowers (1).
Staminate flowering in gynoecious cucumbers can be induced by gibberellins, silver nitrate (AgNO3) and silver thiosulphate (Ag(S3O3)33-), which interfere with ethylene-production. Because of the promising results of AVG-treatment obtained by Tolla (personal communication), I compared its effectiveness for induction of staminate flowers with that of standard treatments of other silver compounds.
In a glasshouse trial six potted plants each of gynoecious hybrid slicing cultivars Farbio and Sandra and of gynoecious inbred pickling line were treated at the first true leaf stage with three concentrations of AVG along with AgNO3 and Ag(S3O3)33-. Seeding was on June 15 and treatment two weeks later. All solutions were prepared with distilled water and sprayed with an atomizer. Plants were transplanted two weeks after treatment and trained vertically without pruning. Temperature was set at 20°C night/23°C day, but it sometimes rose to 30°C on bright days. About two months after owing, each node of every plant was scored for sex expression (Table 1). Only mean numbers of staminate flowering nodes of the main stem are given because this correlates rather well with the total amount of staminate flowers produced (2, 3).
The silver treatments gave a similar number of staminate flowering nodes. The 1,000 ppm AVG treatment gave a slightly lower level of staminate induction than the silver compounds, whereas the other two treatments resulted in relatively fewer staminate flowers. The phytotoxicity of AVG is, however, very severe at the effective concentration. The first three to four leaves became extremely chlorotic and necrotic, and growth was checked for about three weeks. Although the plants eventually recovered, they remained unthrifty. The 100 ppm AVG application did only slight damage while the silver treatments gave no noticeable side effects. The AgNO3-treated plants of Farbio were not scored for reasons other than phytotoxic effects. The extent of staminate flowering on side shoots followed the same pattern as that on the main stem, with most staminate flowers occurring on the pickle line.
I conclude that under our conditions AVG should not be preferred over treatments with the standard silver compounds. The fact that staminate flowers did occur lends support to the notion that blocking ethylene production/action is important in staminate induction. I also should like to mention that, in contrast with an earlier report (2), both silver compounds were about equally effective in this and other experiments (3).
Table 1. Mean number of staminate nodes following treatment of three gynoecious cucumber genotypes with various chemical compounds.z
Genotype |
||||
Compound |
Treatment rate |
F1-Sandra |
F1-Farbio |
Gynoecious pickle inbred |
| AVG | 10 ppm | 5.0 | 3.0 | 4.7 |
| 100 ppm | 5.8 | 5.3 | 6.0 | |
| 1000 ppm | 14.0 | 15.0 | 14.0 | |
| AgNO3 | 500 ppm, 3 mM Ag+ | 17.0 | — | 19.0 |
| Ag(S3O3)33– | 3 mM Ag+ | 17.0 | 17.0 | 19.0 |
z No other statistical analyses performed.
Literature Cited
- Natti, T.A. and J.B. Loy. 1978. Role of wound ethylene in fruit set of hand-pollinated muskmelons. J. Amer. Soc. Hort. Sci. 103:834-836.
- Nijs, A.P.M. den and D.L. Visser. 1979. Silver compounds inducing male flowers in gynoecious cucumbers. Cucurbit Genetics Coop. Rpt. 2:14-15.
- Nijs, A.P.M. den and D.L. Visser. 1980. Induction of male flowering in gynoecious cucumbers (Cucumis sativus L.) by silver ions. Euphytica 29 (accepted).