Cucurbit Genetics Cooperative Report 10:62-63 (article 33) 1987
A. Sauton
INRA, Station d’Amèlioration des Plantes maraîchères, 84140 Montfavet, France
In Cucurbitaceae, failure of interspecific hybridization may be due to an early abortion of the hybrid embryos (3). Young Cucumis embryos when they are extracted at globular or heart shape stages are sometimes able to continue their differentiation in vitro (1). However it is often difficult to isolate embryos at these stages.
The results reported here involved the development of a new in vitro culture technique to obtain embryos from very young fertilized ovules of Cucumis melo.
Plants of melon commercial F1 hybrid (‘Alfa’) were grown in a greenhouse under normal light and culture conditions. Plants were self pollinated. The ovaries were harvested 5 days after pollination.
They were surface sterilized by dipping for 10 min. in a solution of 10% calcium hypochlorite with a few drops of tween 20 emulsifier. Ovaries were then rinsed three times with sterile distilled water and aseptically transferred to moistened sterile filter paper in Petri dishes. Ovules were excised under binocular, placenta tissue was carefully removed.
Twenty naked ovules were placed in a 5 cm Petri dish filled with the following culture medium :
– macronutrients and micronutrients as described for pepper anthers culture (2) but used half strength.
– Na2EDTA 18.65 mg/l and FeSO4 13.9 mg/l
– Fuji and Morel vitamins as detailed for pepper (2)
– sucrose 20 g/l; Agar 10 g/l.
pH of the medium was adjusted to 5.9 before autoclaving at 115°C for 20 min. Culture was made at 25°C with 12 hrs light per day.
Germination of the embryos occured within 3 or 4 weeks. One ovule gives always only one embryo. Embryos grew very fast and developed into complete plants; in about four weeks they reached a developmental stage suitable for transplanting to soil.
This technique presents 2 advantages:
– the artificial culture can start 5 days only after pollination. That may be important in the case of early embryo abortion;
– isolation of young ovules is easier than extraction of embryos at the globular stages.
So its application to interspecific crosses in this genus can be envisaged.
Literature Cited
- Custers, J.B.M. 1981. Heart shape stage embryos of Cucumis species more successful in embryo culture than advanced stage embryos. Cucurbit Genetics Coop. Rpt. 4:48-49.
- Dumas de Vaulx, R., D. Chambonnet, and E. Pochard. 1981. Culture in vitro d’anthères de piment (Capsicum annuum L.): amélioration des taux d’obtention de plantes chez différents génotypes par des traitements à +35°C. Agronomie 1:859-864.
- Niemirowicz-Szczytt, K., and B. Kubicki. 1979. Cross fertilization between cultivated species of genera Cucumis L. and Cucurbita L. Genetica Polonica 20:117-124.
Acknowledgements:
My thanks are due to Research GIE of Clause/Limagrain for financial support. I am also grateful to R. Dumas de Vaulx for his helpful comments.