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| Flowering garlic |
Scientists believe that the wild relatives of garlic were widely
dispersed in Central Asia about 10,000 years ago. Semi-nomadic tribes
cultivated this plant as food condiment and medicinal plants. From
Central Asia, garlic was introduced into the Mediterranean basin,
India and China. There is evidence that garlic has been in use in
China and India for more than 5,000 years and in Egypt since before
2,000 BCE. European traders facilitated its further distribution,
and, from the Mediterranean region, garlic was introduced into sub-Saharan
Africa and the Americas by explorers and colonists. Today garlic is
known only as a cultivated plant, and its wild relatives are not to
be found.
During its cultivation history in different regions, garlic was adapted
to various climates and selected for cold resistance, bigger bulbs,
or higher pungency. In order to obtain a larger bulb, flower stalks
were often removed or clones with reduced flowering potential were
selected. Thus, the thousands of years of active selection by man
resulted in the loss of garlic fertility, and today garlic varieties
are completely sterile. They don't produce seeds and are propagated
only vegetatively. In modern garlic varieties, the presence of vegetative
topsets (bulblets), which develop in garlic inflorescence, is one
of the major causes of the inability of this plant to develop normal
flowers and true seeds.
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| Garlic inflorescence with flowers |
The sexual sterility of garlic markedly reduces its potential for
the improvement of its economically important traits, including pest
resistance, yield, and quality. Restoring fertility in this crop would
provide new genetic combinations for breeding purposes or genetic
studies. This consideration has stimulated attempts by many researchers
to restore fertility to garlic.
In the early 1980s, Japanese researcher Prof. Takeomi Etoh made several
expeditions to Soviet Central Asia and collected a number of garlic
bulbs. The collected clones were then grown in Kagoshima, Japan, and,
following topset removal, 17 clones developed fertile flowers with
over 3,000 viable seeds. However, seed germination rates were low,
ranging between 10 and 12%. Later, in the 1990’s in California,
Maria Jenderek obtained a large number of garlic seeds from plants
which originated in Central Asia. Removal of topsets was necessary
only in the early generations, as the strong selection pressure for
blooming and seed production resulted in improved seed set. Fertile
accessions were also identified in the USA garlic collections.
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| Garlic inflorescence with topset |
In 1998, a special project for restoring the fertility of garlic
was initiated in Israel by Dr. Rina Kamenetsky (The Volcani Center)
and Prof. Haim D. Rabinowitch (The Hebrew University of Jerusalem).
This project is a part of a large European Community program called
“Garlic and Health”, which is aimed at the development
of high quality garlic, and to study its influence on human diseases.
In the framework of this project, collection missions to Central Asia
have resulted in the gathering of over 300 garlic genotypes from locally
cultivated or natural populations in Uzbekistan, Tadjikistan, Kirgizistan,
and Kazakhstan. This region is recognized as the primary centre of
origin of garlic and the main and richest source for genetic diversity,
worldwide. The collected clones were evaluated in Israel for their
potential fertility and other useful traits.
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| Garlic seeds |
It was found that following stalk elongation, flower differentiation,
pollination, and fertilization, true garlic seeds might be obtained
in more than 30 clones. In seven of the most fertile accessions, about
400-500 seeds were produced per umbel, without the removal of the
topsets. Germination rates reached about 90%, and the seedlings developed
into young plants with two to five leaves. At the end of the season,
single-clove bulbs with white, purple, gray and brown skins, differing
in bulbing ability and ripening, were obtained. These plants vary
widely in their physiological and horticultural characteristics, and
probably contain most of the worldwide variability of the garlic genepool.
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| Garlic bulbs from seed |
Seed propagation of garlic on a massive scale may become a feasible
option in the future. Sexual reproduction can be exploited in plant
breeding, for improvements to yield, tolerance to biotic and abiotic
stresses and quality. In addition, in established varieties, seeds
(which normally do not transmit viruses) may be used for the production
of virus-free propagation material.
References:
Kamenetsky, R. and H. D. Rabinowitch (2001)
Floral development in bolting garlic. Sexual Plant
Reproduction, 4, 235-241.
Kamenetsky, R. London Shafir, I., Zemah,
H., Barzilay, A. and. Rabinowitch H. D. 2004. Environmental
Control of Garlic Growth and Florogenesis. Journal
of the American Society for Horticultural Science,
129: 144-151
Kamenetsky, R., London Shafir, I.,
Baizerman, M., Khassanov, F., Kik, C. and H.D. Rabinowitch
(2003) Garlic (Allium sativum L.) and its wild relatives
from Central Asia: evaluation for fertility potential
Proceedings of the XXVIth International Horticultural
Congress, Acta Hort. in press
Kamenetsky, R., London Shafir, I.,
Khassanov, F., Kik, C., van Heusden, A.W., Vrielink-van
Ginkel, M., Burger- Meijer, K., Auger, J., Arnault,
I. and Rabinowitch, H.D. Diversity in fertility potential
and organo-sulphur compounds among garlics from Central
Asia. Biodiversity and Conservation. in press
