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Recently I spent five years in southern France looking at potential biological control agents for Onopordum thistles that had been introduced into southern Australia and have become serious weed problems in pastures. One of the stringent criteria to be met before any new biological control agent can be introduced is that it must be specific to the target weed i.e. no other plant, crop or native is placed at risk. In the case of thistles, one of the first such plants tested is artichoke (Cynara scolymus), a cultivated thistle.
In the course of conducting these host-specificity tests, I came across another Cynara species being trialed as an alternative crop plant in southern France for landholders forced out of the traditional, but overproducing wine industry. This plant, referred to as Cynara 507, could also have some potential as an alternative crop plant in Australia.
Cynara 507 is a cultivar selected originally from infestations of weedy artichoke thistle, Cynara cardunculus, in Uruguay. This weed had been introduced into South America from southern Europe, and has also been introduced into Australia where it is a problem in parts of South Australia and Victoria. The selection process leading to Cynara 507 was, however, commenced in the 1930s and the crop cultivar is different in many respects to its wild progenitor.
A Spanish company, Cardoleo Cellulosa Inter SA, took over development of the plant in 1981 and has been trialing it in Spain and southern France. They have carried out fairly extensive tests on the properties and yield of the plant and the quality of its products.
Apart from the appeal of turning a weed into a cash crop, what makes Cynara 507 interesting as an alternative crop plant? The plant is a deep-rooted perennial whose productive life in trials has extended to 10-15 years. There are three phases to its annual growth-cycle:
Its main commercial attribute is that it is a multipurpose plant with three products: stock feed, vegetable oil and cellulose for fibre or energy. Once established after 12 months, all three stages can be harvested annually for these products.
Stock feed:The large rosettes with leaves up 80 cm long can be harvested with standard harvesting machinery in autumn for stock feed. Yields in Spain of 40 tonnes of foliage (more than 6 tonnes of dry matter) per hectare have been achieved. The quality of the feed is comparable to that of lucerne, but with a higher protein content (16-20%)and in-vitro digestibility (75%), according to tests carried out by the company. In Europe this would be either used on-farm as silage or pelletised for sale to lot-feed enterprises.
Vegetable oil:The flower heads are large and contain large oil-bearing seeds, which can be harvested in mid summer with the same equipment as is used for sunflowers. Yields of 2.5 tonnes of seed have been obtained in Spain. The yield of oil from these seeds has been measured at 20% and the oil is comparable to sunflower oil, being particularly rich in polyunsaturates such as linoleic acid (63-70%), but having virtually no linolenic acid, thus making it stable to oxidation.
What makes the oil more interesting is that it has a low content of silymarine (0.4%), a natural liver protectant, and thus could be of interest to the dietetic market. The oil has been approved for human consumption in France (the author has tried it and can attest to its good flavour). Seed husks could provide a source of silymarine (0.3%) for use by pharmaceutical companies for the manufacture of drugs to treat liver disorders. Usually wild thistle infestations are the source of this compound, and there are Australian farmers harvesting variegated thistle (which they would normally control with herbicide). This is being done since one of the sources of silymarine used by European drug manufacturers has become unreliable due to the collapse of the Soviet Union. Another by-product of the seeds following extraction of the oil is an edible meal, high in protein (40%) and suitable for feeding animals.
Cellulose:In the normal growth cycle, the flowering stems die back at the completion of flowering. These can either be slashed and left as green manure, or harvested and baled for their cellulose. Fibre yield from this material has been measured at 15 tonnes per hectare with a cellulose content of more than 60%. This could be used to either produce lower quality paper or as a source of energy. The calorific value of Cynara fibre is similar to that of wood.
One of the more interesting ideas being promoted by the developers of Cynara 507 is its use as an environmentally-friendly energy source for isolated communities. It is claimed that a 4500 ha plantation would provide enough energy to power a 10MW thermal power station - oil and stock feed production being a bonus.
A major question is whether the plant is suited to Australian conditions. This is in part answered in the affirmative by the presence of its wild progenitor here as a weed already.
Trials in Spain, Uruguay and Israel suggest that it is a robust plant that can grow in relatively poor soils and areas of low rainfall, once established. Optimum yields have been achieved in areas with Mediterranean-type climates (i.e. low summer rainfall) and annual rainfalls of 550 mm plus.
One advantage in Australia is that it would not have the same pest problems as in its native European range. In southern France there was a severe problem with weevils that fed inside the flower head and subterranean voles that ate the roots and crown, but such herbivores are not found here. Pest problems would most likely be similar to that experienced by the artichoke industry, with aphids and sucking insects being the worst problems. One thing I can guarantee is that, with the stringent host-specificity testing that we carry out before introduction, none of our biological control agents introduced for other thistles would become a pest of the crop.
Quarantine clearance could be one area of difficulty for the plant, in view of the fact that its progenitor, artichoke thistle, is already a weed here. However, recent taxonomic studies have shown that commercially grown artichoke cultivars are also descended from the same progenitor, and this crop plant has never become invasive.
Cynara 507 could thus be considered in the same light as artichoke, though its introduction would probably be looked at closely. Another problem is that, like thistles, Cynara 507 bears large thorns, though this appears to have been recently overcome by the development a thornless cultivar, Cynara 804.
Many alternative crop plants are promoted for their use either as stock feed (tagasaste), oil (jojoba, linola) and fibre (hemp, kenaf). What makes Cynara intriguing is that it is promoted as one crop capable of all three applications, with the advantage of being a long-lived perennial.
Cardoleo Cellulosa SA are the only current source of selected seed, and they are interested in associations with organisations or entrepreneurs interested in further developing the potential of this alternative crop. The productivity of the crop under varying Australian conditions would need to be studied closely, while its potential use as a multi-purpose cash crop in Australia would no doubt depend on the existence of, or development of, markets for its diverse products.
Any claims made by authors in the Australian New Crops Newsletter are presented by the Editors in good faith. Readers would be wise to critically examine the circumstances associated with any claims to determine the applicability of such claims to their specific set of circumstances. This material can be reproduced, with the provision that the source and the author (or editors, if applicable) are acknowledged and the use is for information or educational purposes. Contact with the original author is probably wise since the material may require updating or amendment if used in other publications. Material sourced from the Australian New Crops Newsletter cannot be used out of context or for commercial purposes not related to its original purpose in the newsletter
Contact: Dr Rob Fletcher, School of Land and Food, The University of Queensland Gatton College, 4345; Telephone: 07 5460 1311 or 07 5460 1301; Facsimile: 07 5460 1112; International facsimile: 61 7 5460 1112; Email:email@example.com
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originally created by:GK; latest update 6 June 1999 by: RF