An individual that is barren but everlasting, that not only nourishes but also cures is no less than a wonder- a unique genetic material with extraordinary evolutionary history. What can fit in this description very well is our much loved plant-garlic. A plant of Central Asia, now spread all over the earth, garlic cannot bear its progeny but manages to live forever via its body part; the clove. Sexually completely sterile, this species’ stem is not really a stem and its leaves start under the ground, not in the air. A completely ‘mixed up’ plant, which is not exactly like our standard plant, garlic is an ancient food being eaten by mankind for more than 5000 years. It was offered as ambrosia to Gods in Egypt and has been treating humans of excess cholesterol, blood impurities and pathogens since antiquity.
The phylogeny and the DNA of garlic
Garlic, scientifically known as Allium sativum L. originated more specifically in Kazakhstan and spread to other parts of world through trade and gift. Many taxonomists conjecture its beginning from wild species Allium longicuspis Regel, while others are of the thought that both of these form one species complex. Therefore, in any case, garlic is regarded very close to this wild species. The story of this wonder plant takes a mysterious turn when you look at its genetic material. Genetic material makes living beings what they are. Right from their physical characteristics to physiological traits, it is their DNA that largely determines how they would look and behave. The amount of DNA in any species is quantified in giga base pairs (Gb). The DNA of garlic amounts to staggering 16.7 Gb, which is 39 times that of human DNA at 0.43 Gb. This incredibly large DNA has left scientists in awe and hit a rough patch on their way to understand garlic genome. In the discipline of genomics, such a genome as that of garlic is labeled as ‘Giant’. Its enormity has largely been attributed to repetition of DNA over and over in the course of evolution. Reason for this repetition, however, is unclear.
Why garlic cannot bear flowers and set seeds has been on the minds of plant breeders for a very long time. Seed bearing by garlic is very important for man since a farmer finds it easier and cheaper to keep and sow a seed than to store and plant a clove. Cloves are very large in size and predisposed to rotting and deterioration compared to seeds. This problem elevates a farmer’s cost of production to an undesirable level. Breeders and geneticists tried to bring garlic to flowering by using many lab and field level manipulations and some even got viable seeds but the amount was so little that they couldn’t commercialize them, nor could they develop a method for the farmers to make their own seeds. Scientific opinion is that garlic used to reproduce and set seeds in the wild but with its domestication by humans who practiced knotting or cutting of its flower bearing scape (stem like organ) in an attempt to increase clove size forced it to evolve into a non-flowering species. It was like garlic read the mind of man and fulfilled his wish. The irony is that man now wants garlic to regress to what it used to be.
Garlic not only confounds us with its mystery but also benefits us with its magnanimity. It imparts a characteristic aroma to our foods, which occurs due to ‘allicin’ produced from sulphur containing amino acid ‘alliin’ by its enzymatic breakdown by ‘alliinase’ when we crush or cut garlic cloves. Apart from enhancing our food’s taste, allicin also protects us from cancer by interfering with cellular processes leading to carcinogenesis. Research has also shown it to protect humans from bacterial infections and help alleviate neural injuries. Neuroprotective property of garlic against neurodegenerative diseases like Alzeimer’s, Parkinson’s and Hunington’s has also been documented. Various biochemical and molecular studies have demonstrated how garlic prevents and heals periodontitis, diabetes, obesity and oxidative stress in humans. The side effects and toxicity that have frequently been associated with allopathic system of medicine has given way to research on plant based therapeutic components of which garlic is a great source.
The way forward for garlic
In garlic, genetic and molecular studies are being carried out on enzyme ‘alliinase’, which is key entity responsible for generating allicin; our ‘doctor compound’! In future, we might start breeding garlic for ‘superactive alliinase gene’ and end up creating a variety which we could label as ‘Allicin Factory’. This variety may then have industrial application for manufacturing pills or potions with no risks and dangers.
Another area of interest in garlic research is true seed setting. Despite having failed to reach a breakthrough in their attempts to produce commercial garlic seed, the scientists haven’t got over their passion to make garlic set its own seed as yet. Recently, molecular studies have been done to comprehend the mechanism of sterility/fertility in garlic. Garlic homologues of genes responsible for various processes that lead to fertility in other plant species have been proposed. Specifically, a gene MS2 has been reported as potential marker for fertility in garlic owing to its intense expression in some fertile lines available with the scientists. In future, with combined efforts of garlic breeders, geneticists and biotechnologists, seed producing garlic may become a reality that would relieve our resource poor farmers of burdensome activity of clove storage and maintenance.
Considering its history and functions, it looks like this regular looking plant growing in our backyards that we use to flavor our food so casually is, after all, not as ordinary in its character and abilities. Respecting this gift of nature, we may slightly alter the old adage and say ‘a garlic a day keeps the doctor away’. However, we surely must keep working to understand this species in order to make it go hand in hand with humans who could grow it more conveniently and take as many benefits as it has to offer.
(Author is PhD, ARS, Indian Council of Agricultural Research (ICAR), Scientist, ICAR-Central Institute of Temperate Horticulture, Srinagar)