Mystery Of Sterility Of The Garlic Plant

Restoration of fertility to the now-sterile garlic plant has been accomplished by Israeli researchers, thus opening the way to wide-ranging scientific research that could lead to improved yields and quality.

Garlic is one of the most popular vegetable condiments in the world. Its origins are in Central Asia, where in the past, several fertile or semi-fertile garlic plants were identified. However, the cultivated, commercial plants we know today are totally sterile and are propagated only asexually. The reasons for this as well as the means to restore the plants’ fertility have remained unknown.

Recently, however, a team of researchers headed by Prof. Haim Rabinowitch, rector of the Hebrew University of Jerusalem and a researcher in the university’s Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, and Dr. Rina Kamenetsky of the Volcani Institute has succeeded in solving this ancient puzzle. Seven years of research that included study of the morphology and the developmental physiology of the plant have resulted in a simple solution to the garlic’s infertility.

In its growth process, the garlic plant’s bulbing and flowering occur simultaneously in the spring — both processes regulated by temperature and day length. During generations of cultivation, farmers selected those plants that displayed early ripening and large bulbs. The rapid growth of the bulbs drew most of the nutrient and energy resources of the plant, leaving little for blossoming. This shortage resulted in abortion of the floral bud at a very early stage of development, and hence complete sterility. In those cases in which the plants succeeded in producing a floral stem, the developing flower buds were strangulated by the small bulbs at the top that were developing rapidly under conditions of lengthening days.

Once the Hebrew University and Volcani Institute researchers understood the conditions that were contributing to the plants’ sterility, they experimented with growing garlic plants under controlled conditions in which temperature and daylight were regulated. In this way they succeeded in delaying the bulb growth in favor of flowering, regaining fertility and production of seeds. “In creating this flowering and seed production, we were able to open up the possibilities for genetic diversity of the garlic plant which had remain frozen for thousands of years,” said Prof. Rabinowitch.

The work by the Israeli scientists has been hailed as “landmark research” by experts abroad and opens the possibility for new physiological and genetic research on one of the most important vegetable condiments in the world. The seeds obtained in the experimental work can now be utilized in breeding programs to produce various desired characteristics through the use of classical techniques.

Among the scientific goals are the development of plants that would be resistant to various pests and plant diseases, provide improved yields and quality, be adaptable to various climatic conditions, have adjustable seasonal growth patterns, and show increased storage life.

The researchers are now turning their attention to investigating the molecular basis of the flowering process and to identifying the genes involved in the control of that flowering. The results of the research appeared recently in one of the leading American horticultural journals, the Journal of the American Society for Horticultural Science.