March 16, 2011

 The Business of "cloning" Plants

One of the hottest topics in horticulture in recent decades has been that of tissue cultured (TC) plants. I have been part of heated arguments for both sides of the equation, wherein both commercial growers and private plant collectors weigh in with heavy arguments. In short, TC provides very large quantities of very consistent, high quality plants to growers at very good prices. With great accuracy, the plants are statistically identical. This is the primary argument both for and against TC plants. Let's look at some of the pro-and-con aspects of tissue culture.

Alocasia lutea
the brilliant color and variegations
due to a stable virus, no longer
propagated by TC  

On the plus side of TC, growers can produce a very predictable crop of plants with nearly identical characteristics on a very predictable schedule. If a grower wants to produce 100,000 Spathiphyllum 'Supreme', a registered and patented plant, he can get the TC plantlets he needs to produce a uniform crop that will grow predictably, with a LOT of background data available to him on how to produce the crop. Many TC plants flower in the same period, and this is especially valuable in flowering plants like Spathiphyllum, Anthurium, and some orchid groups. I left bromeliads out of this group since they can be induced to flower on schedule, with a few months of lead time. Some companies have produced limited quantities of really rare plants such as Amorphophallus titanum, one of the "Holy Grail" species on plant collectors' lists. The plant was hard to find and rather expensive until TC producers made them by the hundreds.

Sometimes the plant that was cultured had extraordinary qualities, and these extraordinary plants can be made available to buyers at very reasonable prices. This has been the case in many rare aroids such as Alocasia reticulata, notorious for dying on no particular cue. A strong variant of it was grown via TC in Homestead at Fennell's Orchid Jungle, and the "new and improved' version is a lot easier to care for. The same easy care goes for hybrids that might have unpredictable qualities if you try to grow them from seed, whereas TC can produce a lot of plants that have all the good qualities you want. The big ideas of TC are consistency of plantlets, and predictability of the resultant crop, with very minor variations. Consequently, the price of the finished plant is a fraction of what  vegetatively produced plant would be. Sometimes, though, growers intentionally grow plants from seed or spores in order to get the natural variations that Mother Nature intended. Tc is not genetic modification as some people think, it is rapid propagation with consistency in mind.

Alocasia reticulata

Alocasia infernalis
photo courtesy of Agri-Starts and
Monrovia Nursery

Phalaenopsis hybrid with unusual coloring
via tissue culture

Paphiopedilum rothschildianum
propagated only by seed or division

Wollemi Pine
until  recently, one of the rarest plants in the world
and widely thought to be extinct, now available at
nurseries worldwide via tissue culture

On the "other" side of TC devotees is the seller of rare plants who makes his living by vegetatively propagating plants in limited quantities to keep the price high, and by ensuring that the number of plants is fairly low. This is classic supply-and-demand economics; keep the interest in a rare plant going by limiting the supply of it. For this type of plant seller, tissue culture is disastrous, akin to the difference between custom built hardwood furniture and mas produced particle board materials at a discount store. For those who have spent hundreds of hours and many thousands of dollars collecting plants, sometimes risking their lives in the process, it is rational to expect a return for your efforts. To nearly fall off some tropical mountain cliff to collect a prized plant, grow it for years while worrying over it through storms and cold weather, sell it at a princely sum to recoup the collecting costs, and then see dozens of it at Kmart two years later is a serious disappointment. This disparity in ideals brings about a quandary. For those who can afford the collector's plants, part of the thrill is the hunt for rarity. For those who enjoy mass-marketed plants, the lower costs bring neat plants into their buying range.

Where can TC go wrong ? The ways it can go wrong are when plants are badly handled in the laboratory, and lots of mutations or inconsistencies show up. While the mutations might yield something really desirable like Alocasia lutea, more often than not the plants come out stunted or warped out of proportion. There have been instances where a plant was 'TC'd' only to lose the parent plants AND the cultures. These plants have been lost forever. There are many tales of horror about labs losing the identity of plants, only to have the plants pop up unexpectedly in another nursery under another name. Patenting a plant can help quell the problem, but problems still arise.Sometimes mutations go badly, sometimes they turn out interesting plants. The positive spin on this is that occasionally a mutant goes in a good direction, e.g. when a plant is more floriferous, shows better flower color due to increased chromosome count, or shows a better plant habit than its "parent".

Perhaps more importantly, where is it best to use TC tactics ? Sometimes a virused plant can be cultured and the virus can be removed from the culture, yielding clean, virus-free plants.  In some cases, rare plants have been saved from extinction with TC tactics such as the Wollemi Pine of Australia. Many top botanical gardens have used TC methods to propagate hyper-rare plants, wherein the plant may not flower often, if at all. Breeding plants the "old fashioned" way by cross pollination is still the method of choice for making new or better varieties of plants. This is the preferred way to see the differences between seedlings, and a breeder will look for variations with good characters.  Unfortunately this is a slow way to make millions of uniform plants. Fueling a large demand for uniform plants requires the rapid propagation techniques of tissue culture. There are places in the modern plant world for both of these tactics, and each has a permanent home in our world. Especially in agriculture, TC changes the way we eat, feed the hungry, and bring about positive change in under-developed countries.

Craig Morell
Pinecrest Gardens     

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