Elsevier

Scientia Horticulturae

Volume 103, Issue 2, 1 January 2005, Pages 155-166
Scientia Horticulturae

Evaluation of allicin content and botanical traits in Iranian garlic (Allium sativum L.) ecotypes

https://doi.org/10.1016/j.scienta.2004.07.001Get rights and content

Abstract

Twenty-four garlic ecotypes collected from the main cultivation areas of Iran were analyzed to evaluate their genetic diversity. Pre-culture evaluation of phytomedical (allicin content) and botanical traits are discussed in this paper. The studied morphological characters were: bulb mean weight, clove mean weight and clove number per bulb. We found a significant positive correlation between clove and bulb mean weight as well, negative correlation between clove mean weight and clove number. Phytomedical evaluation by HPLC showed that all samples are rich in allicin and their recorded values were higher than pharmaceutical grade. Statistical analysis showed that the allicin content in Ge5, a local selected clone from northeast, was at least two times higher than other ecotypes. There was no significant correlation between the ecological condition and the allicin content. Cluster analysis on morphological and phytomedical characters arranged the ecotypes in six main groups. The ecotype of group A showed the highest botanical and pharmaceutical potential which could be considered in future breeding programs. In general we did not detect significant relationship between genetic diversity and geographical origins, so probably the genetic factors have more influence than ecology.

Introduction

Garlic (Allium sativum L.) is one of the most important bulb vegetables grown and used as spice and flavoring agent for foods (Velisek et al., 1997). The center of origin of garlic has been considered to be central Asia. From the center of origin, garlic has been spread west, south and east (Etoh et al., 2001).

Garlic is also cultivated for its medicinal properties and this aspect is steadily increasing in the world. It has benefits in lowering total plasma cholesterol, reducing blood pressure and decreasing platelet aggregation (Mayeux et al., 1998, Sterling and Eagling, 2001). Garlic products have become popular in recent years and a variety of culinary and pharmaceutical preparations are now available in market (Velisek et al., 1997).

In Iran cultivation and consumption of garlic has a long history and areas under its cultivation is estimated about 10 000 ha. At present six pharmaceutical garlic products exist in the Iranian markets under license of the health ministry.

The constituents of garlic are divided into two main groups: sulfur-containing compounds and non-sulfur-containing compounds. Most of the medicinal effects of garlic are referable to a sulfur compound known as allicin (Schulz, 1998). The intact garlic clove does not contain allicin but rather its precursor, the non-protein amino acid alliin. Alliin is converted to allicin, pyruvate and ammonia by the enzyme allinase, when the bulb is cut or crushed (Rabinkov et al., 1994).

The amount of allicin in fresh garlic is highly variable (Schulz, 1998). It has been known that allicin content, which released from garlic samples from various regions, is very variable (Iberl et al., 1990, Ueda et al., 1991, Schulz, 1998). Furthermore agronomic parameters also cause variations in phytomedical levels (Mayeux et al., 1998). According to British pharmacopoeia (1998), the minimum allicin content to ensure pharmaceutical and economical viability of garlic powder products should be 4.5 mg/g. Hence it is important to standardize garlic, i.e. breeding a garlic clone with suitable content of allicin and agronomical traits which are needed for the large-scale culture and drug production.

Garlic is a sterile species and reproduces only by vegetative propagation. A series of different ecotypes have been established over time in various areas of cultivation. Considerable morphological and biochemical variations between and within ecotypes are displayed (Bradley et al., 1996, Avato et al., 1998). These differences were described with the objective of selection the best quality of active substance (Avato et al., 1998).

Based on the previous information, it is first time that a research program has been considered in order to evaluate genetic diversity of Iranian garlic ecotypes. In our study 24 ecotypes were collected from the main production regions. Since the study of genetic variability in different traits of available ecotypes is a prelude to crop improvement, genetic variation and diversity for different traits including botanical characteristics, allicin content (before and after culture) and molecular studies were conducted.

The present article is the result of botanical and phytomedical pre-culture studies. In the next stage of the research (field experiment), we will evaluate morpho-physiological characters including the presence or absence of floral stem, low temperature requirement for auxiliary bud differentiation, day length threshold for bulb enlargement, number and size of inflorescence bulbils and clove dormancy (Messiaen et al., 1993, Lallemand et al., 1997). These will help to delimit varietal groups in Iranian garlic ecotypes.

Section snippets

Plant material

A total of 24 garlic clones were collected from different areas. This sampling was done according to the information of local agricultural extension offices and producers from all over Iran (Fig. 1). Geographical origins of the 24 garlic ecotypes are listed in Table 1. A sample of 20 bulbs per ecotype was randomly chosen and then evaluated for variability of three botanical characteristics: mean bulb weight, mean clove weight and clove number per bulb.

Allicin determination

An HPLC method using butyl

Botanical evaluation

Quantitative characteristics are listed in Table 2. Clove and bulb mean weight varied from 0.7 to 5.44 and 16 to 62.34 respectively. The range of variation for clove number per bulb varied from 7 in Ge11 to 40 in Ge22. There was a significant positive correlation between clove mean weight and bulb mean weight (P < 0.01 and r = +0.8) as well as negative correlations between clove mean weight and clove number (P < 0.05 and r = −0.4; Table 3). The color of the external bracts in almost all the

Conclusion

The analysis of genetic divergence plays an important role in breeding programs. Garlic is sterile species with variability in desirable morphological and physiological characteristics. The vegetative mode of multiplication of the species restricts breeding methods. A solution is sought in the use of domestic ecotypes, which are fully adapted to local conditions and are important genetic resources and initial breeding material (Gvozdanovic-Vagar et al., 2002). The preliminary analysis of the

Acknowledgments

We gratefully acknowledge the excellent laboratory work of Mr. Erfatpoor. Further we express our thanks to Mr. K. Larijani for his co-operation in HPLC analysis.

References (14)

  • P. Avato et al.

    Agronomic evaluation and essential oil content of garlic (Allium sativum) ecotypes grown in southern Italy

    Adv. Hort. Sci.

    (1998)
  • K.F. Bradley et al.

    Classification of Australian garlic cultivars by DNA fingerprinting

    Aust. J. Exp. Agric.

    (1996)
  • T. Etoh et al.

    RAPD variation of garlic clones in the center of origins and the western area of distribution

    Mem. Fac. Agric. Kagoshima Univ.

    (2001)
  • Gvozdanovic-Vagar, J., Vasic, M., Cervenski, J., 2002. Variability of characteristics of garlic (Allium sativum)...
  • B. Iberl et al.

    Quantitative determination of allicin and alliin from garlic by HPLC

    Planta Med.

    (1990)
  • J. Lallemand et al.

    Delimitation of varietal groups in garlic (Allium sativum L.) by morphological, physiological and biochemical characters

    Acta Hort.

    (1997)
  • Messiaen, C.M., Cohat, J., Pichon, M., Leroux, J.P., Beyries, A., 1993. Les Allium alimentaries reproduits par voie...
There are more references available in the full text version of this article.

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    Citation Excerpt :

    However, the effect of the various steps in sample preparation and drying process on allicin recovery and alliinase activity has not been conclusively established. Firstly, the dicing of garlic cloves at room temperature (RT) in preparation for oven drying (Arnault et al., 2003; Baghalian et al., 2005; de Diego et al., 2007) releases the alliinase enzyme at the cut (damaged) surfaces from which alliin is converted to allicin. Secondly, oven-drying crushed garlic at elevated temperature (55 °C) can lead to volatile losses and degradation of allicin during the drying process.

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