The carob tree is an exceptional tree that creates a real fascination. Its silhouette of noble beauty evokes the sun and heat. Its evergreen green leaves make it one of the most beautiful trees all year round. Without forgetting its fruits, with various virtues and uses.
The carob tree is a Mediterranean species known, acclimatized, and cultivated in our latitudes since the highest antiquity. Its importance has increased considerably in recent years, due to the industrial development of carob, which has become an essential raw material.
The carob tree has assets worthy of interest both ecologically (adaptation to drought, is content with poor and rocky soils, tolerates temperatures of -6 to 50 ° c, organic (nitrogen fixation, resists fire, mutilation, and disease), agronomic (high yield in arid zones compared to olive, almond, common wheat, and barley), genetic (presence of great genetic variability) than socioeconomic ( stable source of income for the local population, participates in the development of the national and regional economy).
It is an agro-silvo-pastoral species with many utilizations. It can be used for the development of marginal land, as a barrier against desertification, for the fight against erosion, as a firebreak and as a windbreak; it is also used as a fodder, ornamental, aromatic and medicinal species.
The carob tree is particularly abundant in certain zones (Marrakech, El ksiba, Khenifra, Beni Mellal, Meknès, Essaouira, Elhaouz, Kasba Tadla), it offers the means, to the farmers of this region, to put in the value of land unusable for all other crops. These regions could become centers of carob production in Morocco. There is no reason to prevent the success of the carob tree in these areas where one can also see some specimens growing without care and giving interesting yields.
The identification and multiplication of trees in natural populations, based mainly on yield performance, is a good alternative for our country where there are a large number of ecotypes in the wild.
With a particularly favorable environment, equal if not superior to its competitors, our country must develop cratonic culture and become the first world producer.
This book is part of the policy for the development of sustainable forest management of the High Commission for Water and Forests and the Fight Against Desertification. The objective is to make available to all forest managers, producers, industrialists and investors, tools for managing carob plantations, and enhancing existing stands.
This guide is primarily intended for foresters who wish to better understand the production potentials of their carob plantations, knowingly choosing the appropriate scenarios in the case of a reforestation project or enhancement of uncultivated and unproductive land. It can also be usefully consulted by anyone wishing to learn about the carob tree and the cratonic culture (student, researcher, farmer, NGO).
Biology and ecology
Description
Ceratonia siliqua L.
The word “carob tree” comes from the Moroccan Arabic el kharroube, tasliroua or tikida in Berber, carob tree in French and carob tree in English, algarrobo in Spanish, carrubo in Italian, alfarrobeira in Portuguese, karubenbaum in German, charaoupi in Greek and charnup in turkish. It is also called the bread of Saint John the Baptist, guier of Egypt or bean of Pythagoras.
Its Latin name Ceratonia comes from the Greek keratia meaning “little horn” (in reference to its locust beans, pods in the shape of mature horns). The name of the species, siliqua, designates in Latin a pod or pod.
The genus Ceratonia belongs to the family of legumes, the order of Rosales, under the family of Caesalpinioideae.
- Reign: Plantae
- Sub-reign: Tracheobionta
- Division: Magnoliophyta
- Class: Magnoliopsida
- Subclass: Rosidae
- Order: Rosales
- Family: Legumes
- Subfamily: Caesalpinioideae • Sub-tribe: Ceratoniinae
- Genus: Ceratonia
The carob tree, an evergreen tree, with a very wide crown, can reach 8 to 17 m in height, 85 cm in diameter, and live up to 200 years. Its bark is brown, rough. Its leaves are persistent and leathery, dark green in color, large from 10 to 20 cm, paripinnate composed of 2 to 6 oval or elliptical leaflets. Their epidermis is protected by a thick layer of polyphenols, and the stomata are grouped in the lower part of the epidermis. The carob tree does not lose its leaves in autumn, but only in July every two years, and the latter is partially renewed in spring (March – April).
Its hard and reddish wood is very appreciated in cabinetmaking. Its growth is very slow during the first years. The taproot is strong and can reach 20 m in length.
Distribution area
Originally from the Middle East, the carob tree is today spread throughout the Mediterranean basin. It is mainly found in Portugal, Spain, Italy, Morocco, Greece, Algeria, Turkey, Lebanon, Tunisia, Cyprus, and Egypt. In recent years the carob tree has also been introduced into Australia, South Africa, the United States, India, and South America (Tous et al., 1996).
In Morocco, it is localized, in association with the olive tree, the mastic tree, the thuja or the argan tree, in the plains and the middle mountains of the Rif, the Middle Atlas, the High Atlas, and the Anti-Atlas, (Zouhair, 1996) in humid, sub-humid, semi-arid and arid coastal bioclimates with warm and temperate variants. Its density per hectare ranges from 5 to 25 feet.
Ecology
The carob tree is a species, very plastic, heliophilous, thermophilic, very resistant to
drought (200 mm of rain) but not cold.
It has no particular requirements with regard to the nature of the soil, it can thrive in the most diverse terrains (Morton, 1987), from the richest alluvial lands to the rockiest arid. It does not fear slightly salty soils. It tolerates poor, sandy, heavy loamy, and rocky soils, from pH 6.2 to 8.6, but fears acidic and humid soils. The carob tree prefers calcareous soils, well-drained and aerated and not too clayey. He dreads spring frosts in certain localities. Its growth is all the slower since it is placed in bad conditions. The tree fixes nitrogen from the air and resists disease and fire.
Flowering and fruiting
The carob tree is trioic (male / female ratio 50-50, including some hermaphrodites), the number of chromosomes is 2n = 24. It is among the rare trees that bloom in autumn (September to November) from its sixth year. The female inflorescence consists of a cylindrical pistil 6 to 12 mm long, on which are spirally arranged 17 to 20 brownish flowers, unisexual.
The ovary is made up of two carpels, 5 to 7 mm long, containing several ova. The male inflorescence consists of a large nectar-bearing disc surrounded by five stamens.
The pods or locust beans, whose development is very long (10 to 11 months), are indehiscent, from 10 to 30 cm in length by 1.5 to 3 cm in width, hanging.
First green in November-December, they turn dark brown in July of the following year when they are ripe. Each carob weighs about fifteen grams, contains the fleshy pulp (80 to 90%), and 10 to 15 seeds (10 to 20%) hard, waterproof, a beautiful dark brown, shiny, and of regular weight. The different constituents of the seed are the seed coat (30 to 33%), the endosperm (42 to 46%), and the embryo (23 to 25%).
In general, in marginal areas, the vegetative period is long, from 6 to 8 years, while in better conditions, the prayer begins at the age of 3 or 4 years. Carob trees begin to fruit in the 5th or 6th year when planting is carried out with grafted plants and in the 7th or 8th year when the plants are not grafted.
Diseases of carob tree
Although the carob tree is a disease-resistant species, it can, however, under certain conditions be attacked by the carob tree sphaerella (Sphaerella cuprea), which stains the black leaflets, sometimes abundantly, the leaflets.
Similarly, the trunk can be attacked by the small white scale (Aspidiotus hederae vallot). The latter is generally more apparent than a real threat to the carob tree because often, a ladybug (Chilocorus bipustulatus L), is responsible for reducing the invasion before it has reached too great a proportion.
In Spain, the most formidable polyphagous insect is Zeuzera pyrina L. In fact, its larva attacks the wood of the trunk and branches and thus causes significant damage. A beetle, Cerambyx velutinus, can also dig holes in the trunk.
The pods can be infested with a small polyphage: the carob borer (Myelois ceratoniae Z.). It lays eggs on newly formed pods or pods, the larvae then penetrate into the pods and ruin them. When stored in humid conditions, they can also be attacked by the carob tree moth (Ectomyelois ceratoniae), and by the larvae of a gnat, Asphondylia gennadii.
The deformation of young pods can be caused by the fungus Oidium ceratoniae C. The latter can also cause damage to the leaves (rust, especially in a humid atmosphere).
Rodents, especially rats, can climb trees and gnaw bark under certain conditions until the branches die.
Properties and uses
Composition of locust beans
The chemical composition of the various constituents depends on the cultivar, the growing area, and the harvest date. In Turkey, a study comparing the main sugar profiles of carob pulp of cultivated and wild varieties, showed that sucrose is the most abundant sugar with smaller amounts of glucose and fructose than cultivated varieties have a higher high concentration of sucrose compared to wild varieties. Whereas the rates of individual sugars compared to total sugars were similar in both cases.
The fleshy pulp is made up of around 50% sugars (mainly sucrose, glucose, fructose, and maltose), 18% cellulose, and hemicellulose, 16 to 20% tannins and 1 to 2% protein. Carob, unlike its cocoa counterpart, contains neither theobromine nor caffeine. It is rich in calcium, phosphorus, potassium, magnesium, and pectin.
The seed is mainly composed of antioxidants and polysaccharides (galactose and mannose in a proportion of 1 to 4). Her embryo is rich in protein (52%) and carbohydrates (27%). Also, analysis of the chemical composition of carob seed flour has shown a high amount of amino acids, such as glutamic acid, aspartic acid, and arginine.
Yields
The tree begins to produce pods from the age of 6 years. Production gradually increases with age and stabilizes at 40-50 years. It is insignificant until the age of 7 years, from 10 to 40 kg/tree up to 20 years, from 50 to 80 kg up to 30 years, from 60 to 120 for up to 40 years and reaches 100 to 200 kg/tree from 50 years. The yield depends on the conditions of the environment, the cultivars, the year, and the cultivation. Under favorable conditions, some isolated individuals can produce up to 1000 kg/year; female feet have a higher yield than hermaphrodites.
In Catalonia, Spain, (precipitation 500 mm / year) the adult trees with the drip system receive approximately 300 l of additional water per tree and per year more than nine irrigations during dry periods, the average yields obtained vary between 6 and 7 t / ha at the age of 11 years.
Although trees produce low yields in old plantations (1,500-3,000 kg/ha), the production potential in modern orchards is very high (5,000-7,000 kg/ha).
Also, the ability of the carob tree to survive in marginal conditions of aridity and drought should not be used as a basis if the objective is commercial production.
Transformation of locust beans
After harvest, the locust beans have a high humidity level (10-20%) and vary according to harvest conditions and fall precipitation. To avoid decomposition, the pods require more drying and are stored under cover in dry and ventilated places to bring the humidity down to around 8%.
To separate the two main components and seeds, the locust beans are mechanically crushed, then get rid of the seeds. This first coarse grinding can be followed by roasting and grinding of the pieces of pulp to obtain a powder that is marketed under the name of flour or carob powder.
The price of pulp depends directly or indirectly on the price of corn or other products that are used for animal feed and for the extraction of bioethanol.
Carob seeds are transported in bulk by truck to gum factories. It is difficult to treat the seeds since the integuments are very hard. The two main methods for removing the integuments are:
- soaking in sulfuric acid,
- roasting (the seeds roast in a rotary oven)
During the peeling process, the endosperm can be separated from the cotyledons due to their difference in friability. In fact, fragile embryos are transformed into a powder (germ meal) and can be separated from the endosperm by a sieving operation. Then the endosperm is ground to the desired size to give the gum.
Uses
The carob tree has been cultivated for a long time for various uses. Its fruits are edible and sweet. Two main products are obtained from locust beans. The flour, obtained by drying, roasting, and molding the pods after having rid them of their seeds, is used especially in food processing as an antioxidant thanks to its composition rich in polyphenols and for the industrial production of bioethanol and citric acid.
The gum extracted from the white and translucent endosperm from the seed is used in the food, pharmaceutical (mainly against diarrhea), film, textiles, and cosmetic industries.
It has very interesting characteristics as a multi additive (for example, for chocolate, ice cream, yogurt, mayonnaise, orange jams, candies, soups, sauces, ketchup, dietetics, etc.). However, this substance, despite its advantages, faces serious competition from chemicals with similar properties. 100 kg of seeds gives, on average, 20 kg of pure and dry gum.
Analysis of the gum, raw and refined, from seven populations from northern and central Tunisia (humidity, ash, protein, matter not soluble in acid and the mannose/galactose ratio) showed that the climatic and geographic origin of the locust bean and the cultivation method has a great influence on the chemical and rheological properties of the gum.
In addition, the carob tree is honey and pastoral plant; its honey is of good quality, and its leaves and the pulp of its fruits are rich in fodder units (respectively 0.29 and 0.6 to 0.9 UF / kg of dry matter). It is also used in the fight against soil erosion, as a windbreak and as an ornamental tree given its spherical crown, and its evergreen, dense and shiny foliage. As such, it is widely planted in California and Australia (Morton, 1987) as a shade and ornamental tree along the streets for its resistance to drought and its tolerance to air pollution. Its wood is very appreciated in cabinetmaking and for the manufacture of charcoal. The bark and roots are used in tanning.
Economic importance and marketing
Economic importance
The carob tree is becoming more and more interesting due not only to its hardiness, its indifference towards the nature of the soil, its highly developed root system, its quality wood, but especially its fruits which make the ‘subject to annual commercial transactions whose value far exceeds that of wood production.
Compared to cereals and other fruit species, the carob tree is economically more profitable in the stock market.
There are around twenty crushers, processing, and production units for gum in the country with a capacity exceeding 80,000 tons. The processing units use the import of certain derivatives despite the high production potential at the national level
carobs to meet the supply shortage, Algeria is Morocco’s main supplier. All these products are then, after processing, exported to Spain.
Whole pods, pulp, seeds, and gum are traded extensively in Europe.
In 2006, the value of imports was MAD 46,074 million. Exports during the same year amounted to 500 765 million dirhams.
The trade balance of the sector is MAD 454,691 million in favor of exports. In addition, Morocco is the second-largest exporter of locust beans in the world.
Marketing in Morocco
The High Commission for Water and Forests and the Fight Against Desertification puts out carob tenders produced in forests every year. The pods are harvested by the users, on behalf of the contractor, in the forestry sector, and by the owner when it comes to the private sector.
The collection is made in the souks and depots by wholesalers who deliver the products to the various industrial processing units.
The sale prices of locust beans vary according to the month (from 3 Dh / Kg in the month of August- September until 18Dh in the month of April- July), and according to the regions (3 to 12 Dh in the Rif, 5 to 18 Dh elsewhere), the general average is around 8 Dh / Kg. The seeds alone are sold between 22 and 45 Dh / kg.
World production
The global area reserved for carob production was around 104,000 ha in 2006. European countries (Spain, Italy, Portugal, Greece, and Cyprus) represent 79.7%. Morocco ranks second after Spain with 11.5%.
In 2006, world production was estimated at 186,279 tons, produced in approximately 103,931 ha, or 1.8 tons/ha. Spain is the leading producer with 70,000 tons while Morocco is in third place with 26,000 tons.
The evolution of carob production varies from country to country, in Spain, for example, production went from 550,000t in 1930 to 70,000t in 2006, or 480,000t less. The main reasons are the rising cost of labor combined with urban development in coastal regions.
Moroccan production has, on the contrary, increased during the last 30 years and it was estimated at 26,000t in 2006. The most productive regions are Marrakech, Fez, Agadir, Taza, Essaouira, Khenifra, El Hoceima, and Beni Mellal.
Cultivation techniques
Harvesting and extracting seeds
Harvesting takes place manually from April to September, depending on weather conditions and the region. The process of extracting seeds involves different stages. The dry pods first pass 2-3 times through the grinder, where they are broken into small pieces.
The product is then sorted to separate the seeds from the pieces of the pulp.
The seeds, once dried in the sun, to reduce their water content by up to 8%, are stored in the cold room at a temperature of 4 ° C.
Germination of seeds
Plants can be obtained from seeds or cuttings. Fresh seeds normally germinate well without prior treatment, but dried, they become very hard and no longer absorb water, which prevents their germination. They must be soaked either in concentrated acids (sulfuric or hydrochloric) for 30 min or in boiling water for 15 minutes. Even if these pretreatments are effective and allow maximum germination to be obtained during the first three weeks, soaking in boiling water remains the simplest pretreatment. Scariation requires much more time.
Sowing should be done in March-April, followed by sparse watering. Germination is obtained within an average of 1 to 2 months.
The plants develop a taproot with a few lateral roots less than 1 cm in length. The long taproot can be broken easily, and it is, therefore, advisable to sow the seeds in a substrate, allowing them to be easily extracted (a light mixture of sand and peat).
Soil preparation
Proper soil preparation is an essential factor for successful planting. The planting holes should be opened well before planting, and the dimensions should be around 60x60x60 cm. In the arid areas, it is recommended to make bowls around the base and V-shaped channels above these to centralize rainwater from which the trees will readily benefit.
Planting and irrigation
Planting usually takes place in February-March on the well-prepared ground. Plants must be at least two years old. Water supplies, at the time of transplantation and during the first two summers (4 to 6 weeks apart), are necessary in order to ensure at least 360 liters/plant/year. Table 6 gives the monthly distribution of this quantity.
It is always advantageous to cover the perimeter of the plant with a straw mulching, stones, or gravel on a radius of 1m or more and about 5 to 10 cm thick. Mulching absorbs rainwater and does not let it evaporate. In fact, in many semi-arid regions and on marginal soils where the carob tree is well adapted and cultivated, the quantity and quality of irrigation water are the main limitations to production.
Density
Traditionally in Mediterranean countries, the densities of trees in carob orchards are low and variable, within the range of 25-45 trees/ha and the average spacing from 20 x 20 m to 15 x 15 m. Intercropping with species such as olive, vine, or almond is frequently encountered. However, when the carob tree is planted in fertile soils, plants are planted at high density and thinnings are then carried out.
In Spain, 8 x 9 meters are used in arid conditions. In Portugal and Australia, there is generally a tendency to adopt spacing of 6 x 8 meters, 6 meters between the trees, and 8 meters between the lines, which gives approximately 200 trees per hectare.
The density also depends on the availability of water and the shape of the tree, which is very variable according to the clones.
Whatever the geometrical shape adopted, we must not lose sight of the need to incorporate into the planting a proportion of at least 10% of male or hermaphrodite feet, which will be distributed so as to ensure the widest pollination of female subjects.
Fertilization
The issue of maturing remains the most controversial. However, we agree on the general effectiveness of organic fertilizers, especially farmyard manure, but its composition does not make it possible to fill all the deficiencies in all circumstances. It is necessary to compensate for its partial insufficiency by adding additional chemical fertilizers, compound or simple, with more or less slow action depending on the nature of the soil and the age of the plantation. It is the owner’s responsibility to carefully monitor and observe the behavior of the trees and fruiting bodies and to reinforce, if necessary, the supply of fertilizing elements, following the guiding principles of their use and their respective actions. In all cases and to avoid trial and error and loss of precious time, the owners should not engage in fertilization tests without knowing exactly the weak point of the constitution of their soils, which only can clearly reveal the Chemical analysis.
The formula used in traditional orchards consists of an NPK of 50, 20, 50, spread over time, part being brought in autumn and the other in spring. Recent studies have shown a positive effect of nitrogen supply on yields (trees rarely form nodules).
On young carob plants raised in nurseries in 2.3-liter containers proposed adding the following concentrations to irrigation water: 100-150 mg / l of nitrogen N, 70 mg / l phosphorus P2O5, 100-150 mg / l potassium K2O. A study on the mineral concentration of flowers and the seasonal fluctuation of macroelements (nitrogen, phosphorus, potassium, calcium, and magnesium) and microelements (iron, manganese, zinc, and copper) of carob leaves has shown that the latter depends not only from the phenological stage but also from the sex of the trees.
The leaves of females are richer in food than those of male trees. Hermaphrodites maintain the development of inflorescences and fruits with seasonal variation and a lower nutrient concentration in the leaves compared to other sexes, which indicates a more efficient use of resources.
The flowers generally had a higher concentration of N, P, and K, and a lower concentration of manganese than the leaves. Females had a lower nutrient concentration compared to male and hermaphrodite flowers.
In general, the mineral composition of the leaves is closely related to the yield, giving the optimum contents of macro elements and microelements of the leaves. These values were obtained under different soil and climatic conditions and different cultivation methods.
For adult trees aged 15-20 years, the maximum nitrogen dose should not exceed 1kg / tree/year. For the first four years, the concentrations of N, P2O5, K2O must have proportions of 2, 1, 1, respectively.
But as soon as the trees return to fruiting, it is advisable to replace these proportions by 2, 1, 2, and this because of the effects of potassium on the development of the fruit and on the resistance to drought.
Table 8 gives the quantities (in grams/tree) of N, P2O5, K2O to be applied depending on the age of the trees.
In addition, it should not be forgotten that the judicious application of fertilizers has a positive effect on the regularity of abundance in production and on consistency in the quality of products. For commercial planting, it is, therefore, advisable to integrate fertilization into the total equation.
Soil maintenance
Preparing the soil for planting promotes the development of herbaceous vegetation, especially in the early years when young plants are still poorly equipped to face this competition. Weeding is, therefore, the first objective of the interviews, it must be carried out before the vegetation begins to seed.
The favorable period varies depending on the area and the climatic conditions of the year. It generally takes place in March-April.
As for hoes, they are carried out in the majority of cases just after the rainy season.
Care should be taken with particular care in the first year of planting since it represents for the young plant the generally most critical period of establishment. The two operations can be combined in a single maintenance pass to be carried out between April and the end of May. Two maintenance campaigns are generally sufficient.
Shallow plowing 15 to 20 cm is effective. Farmers in Spain usually plow three times a year, the first in the fall before the rainy season, the second in the spring, and the third when the pods begin to ripen in early summer.
For weeding, the use of herbicides is necessary under certain conditions; the most commonly used chemicals being 2-4D and glyphosate. These products are toxic, and it is therefore recommended to strictly follow their instructions for use.
Simazine (C7H12ClN5), a synthetic herbicide from the triazine chemical family, was widely used in Spain and France in arboriculture until its ban in 2001.
The size
Cutting is necessary to give the tree the most suitable form for its vegetative balance. It constitutes an effective means of regularizing its fruitfulness and of conforming to its productive capacities.
The carob tree abandoned on its own can reach on good ground, 6 to 8 meters in height, it is necessary to seek to reduce the dimensions of the tree.
A first cutting to give a shape of vase to the tree, and a second cutting to shorten the carried axes or the too long lateral branches, to remove the greedy ones or the confused branches are necessary. The best season for cutting is in the fall after the fruit has been harvested.
In April – May, pinches in green are carried out to regularize the vegetation of the tree in general and to hasten the fruiting of the young plantations, in particular. Cutting only needs to be repeated every three or four years. It essentially depends on the manual or mechanical harvesting method.
Depressing and thinning
The carob tree is a tree that vigorously rejects the stump, giving numerous strands per variety. The competition between the many strands greatly delays their growth and, therefore, fruiting. To activate this fruiting, depressing the carob tree stands out as a compulsory operation, thus allowing subjects to lead to rapid fruiting.
Thinning allows the density to be reduced to adequate proportions depending on the stationary conditions and the objectives set.
Vegetative propagation
Vegetative multiplication is based on the ability of a plant to be able to reconstitute an individual identical to itself, from an organ (stem, root, leaf, etc.), a tissue, or a cell. It has been used for centuries to reproduce many species in horticulture and arboriculture.
Cuttings
The cuttings, in March or April, require a rich substrate, hormonal treatment, misting, and large sachets. Its success depends on the genotype, and the part of the tree used. The cuttings must stay 2 to 3 years in the nursery. This approach is interesting because the mass propagation of only the most efficient individuals makes it possible to achieve both very high gains and great homogeneity of production.
In vitro culture
In vitro culture techniques or “micropropagation” consist of placing a plant fragment in a nutritive medium under more or less aseptic conditions and thus multiplying the mother plant in one year into several million copies and that at infinite. They also make it possible to reconstitute disease-free clones (fungal, bacterial, viral, etc.) from sick mother plants.
One of the limitations of the application of this method, apart from technical problems, is undoubtedly the cost of the plant produced, which is often much higher than that obtained by conventional propagation techniques. Thus, at present, the commercial application is limited to the propagation of very precious species or to those for which the classic propagation techniques are difficult.
Attempts to propagate selected carob trees using in vitro culture have had limited success. An in vitro multiplication protocol from axillary buds has been developed; however, browning, contamination, and histogenesis remain the main constraints.
Grafting
The reproduction of the carob tree takes place by sowing, but to obtain a planting of perfectly determined varieties, it is necessary to graft.
Grafting makes it possible to produce varieties guaranteeing fruitfulness both in quantity and in quality and to shorten the time necessary for entry into oration. It can be carried out either:
- in the nursery on one and a half-year-old plants when the stem reaches 1 cm in diameter at the base;
- on adult footsteps.
The most used techniques are grafting in the terminal slit and grafting in the shield.
In the case of split grafting, the wedge-shaped graft is inserted into a slot made at the top of the rootstock. Graft and rootstock must have approximately the same diameter. The cuts must be made with a grafting knife or a scalpel, the blade of which must be kept clean and well-sharpened in order to have a clean-cut and which is not a source of infection. The cut should be done quickly and uniformly to obtain a clean and smooth surface. The union between the graft and the rootstock must be consolidated by a strong link, but enough elastic not to strangle the stem. Usually, the plastic tape is used. The rootstock must be vigorous and healthy. In order to obtain a good weld, it is advisable to choose plants with diameters of 0.5 to 2 cm.
The escutcheon grafting is done either in September or in April-May, when the sap circulates abundantly in the tree and when the bark can be easily lifted without tearing it. The shoots whose buds are taken for grafting (grafts) must be from the last growing season. Care should be taken to take the graft only on healthy, middle-aged trees bearing the highest quality fruit. Only strong, well-developed buds from the middle of the shoot should be used.
The bud is removed with a piece of bark in the shape of a coat of arms. Two notches are made along the twig and two across, so as to have a piece of bark 4 to 5 cm long and 1 to 1.5 cm wide with a bud in the middle. The bud is removed from the twig by pressing with the thumb and finger on both sides of the bud and detaching it in a lateral direction.
The “seed” of the bud should be kept in its place, which can be seen on the inside of the badge as a small round piece of wood. This is the current starting point for the shoot. The badge is inserted into a cross-shaped slit made in the subject’s bark. The bark is then securely ligated from raffia or any other soft attachment material, leaving only the bud exposed.
About a week after the transplant, if the bud retains its color and roundness, it is because it has “taken”; the ligature should then be slightly relaxed. When the growth starts again clearly, the ligature is completely removed. In the case of a spring graft, the subject is cut approximately 5 cm above the graft, and the resulting stump is used as a support to attach the young shoot to it. In the case of an autumn graft, only the end of the subject is slightly pruned, and the bud may remain dormant until the following spring.
It should be noted that success rates depend not only on the physiological quality of the plant material and the technique used but above all on the experience of the grafter.
Valuation spontaneous stands
In Morocco, the carob trees resulting from the planting of female and male carob plants from nurseries do not represent 1/10 of all the trees in production.
In nature, the number of male feet is three times that of female feet. The males are not fruiting, and only the females are, that is why they must be grafted with buds taken from good subjects.
In general, the majority of the carob trees are massive and grow free-standing with very large crowns. The grafting of this category of trees can only be done after a tadpole cut, eliminating the crown. The subjects are then grafted in March, preferably at 0.80m or 1m from the ground, either in the terminal slit or in the crown or in escutcheons.
As soon as the transplant is resumed, the young scions must be protected and above all removed, as soon as they appear, the shoots that the subject generally emits in large numbers and which are sure to starve the graft. These wild shoots are cut gradually, as the graft grows and it becomes large enough to receive all the sap from the tree.
Pollination of the carob tree
The most important cultural operation is certainly artificial pollination. It is compulsory, when there are no male or hermaphrodite feet in the vicinity, or else for lack of coincidence in the blooming of flowers of both sexes because then natural pollination cannot take place.
This practice resembles the operations carried out in the south for the fertilization of date palms. For the carob tree to fruit, it is essential that its flowers have been fertilized by pollen from the male carob tree or hermaphrodite.
Thus, when the subjects of different sexes are close to each other, fertilization can take place naturally either by wind or with the help of insects, especially bees.
But it often happens that males and females are very distant from each other. We must, therefore, ensure reconciliation. For this purpose, as soon as the female inflorescences have blossomed, a number of twigs carrying male flowers ready to open are picked from the male or hermaphrodite feet. These branches are then suspended in the canopy so that the pollen spreads by simple gravitation through the latter.
All these operations are avoided, when the plantation has a suitable proportion of male feet or grafted hermaphrodites flowering at the time of the blooming of the female flowers, and arranged in relation to the prevailing winds, so as to ensure the best dispersion of the pollen.
Improvement and conservation of genetic resources
Genetic improvement
The main challenges for the genetic improvement of the carob tree are the reduction of the vegetative period, the adaptation, and the increase of the yield. However, other criteria such as vigor, pod size, gum quality, and pulp are also important.
The reproductive system, particularly pollination mechanisms and sex expression in response to environmental conditions, remains unknown.
The use of molecular markers for the sex determination of plants in nurseries would be of great help for early selection. Clonal variability in old orchards can be exploited for the selection of the best clones having accumulated adaptive traits.
The overall objective depends on the intended use of products from the selected varieties.
The most important selection criteria are the fruit yield and especially the percentage of seeds compared to the fruit, the quantity, and quality of the gum, the alternation of fruiting, the resistance to diseases and the power of abscission of ripe fruit to facilitate harvesting.
Among the main varieties used are “Negra” and “Matalafera” in Spain, “Gibiliana” and “Racemosa” in Italy, “Mulata” and “Aida” in Portugal, “Hemere” and “Tylliria” in Greece and Cyprus, “Sisam” in Turkey, ” Sfax “in Tunisia,” Santa Fe “and” Bolser “in California, and” Bath “and” Princess “in Australia.
Furthermore, any culture of an improved variety reduces the genetic richness of the wild population from which it originates. The improver’s action cannot, therefore, be limited to the supply of efficient and suitable plant material. It also includes, just as importantly, a conservation activity.
Genetic improvement is therefore necessarily accompanied by protection and conservation work to avoid the depletion of genetic capital, the degradation of ecotypes, and to manage the improvement population essential for the sustainability of a breeding program. ‘improvement.
Conservation of genetic resources
DESCRIPTION OF GENETIC DIVERSITY
Genetic diversity is described using genetic, biochemical, and molecular markers. The latter provides the knowledge necessary to rapidly construct a genetic typology of populations and allow the selection schemes and programs for the conservation of genetic resources to be based on more objective and more rigorous bases.
Very little work has been carried out and published on the carob tree:
In Tunisia, a study of genetic diversity using isozymes, in 17 populations distributed in four bioclimatic zones, revealed a great genetic diversity and a substantial level of endogamy in these populations.
In Portugal, genetic diversity in 15 7-year-old cultivars planted in an experimental plot was assessed using 12 phenotypic characters from the pod and seed. The values of the morphological qualities acquired by cultivars were linked with those of cultivars from other countries of the Mediterranean basin. Significant differences were found between cultivars for all traits studied, indicating high genetic diversity.
In Morocco, morphometric and molecular approaches (RAPD) have revealed significant genetic variability between 10 accessions of the carob tree.
Analysis of the morphological criteria of the fruits on 104 provenances from different regions of Morocco has revealed a great genetic variability between these populations studied. Eastern origins had the best performance in terms of seed weight.
The percentage of the weight of the seeds compared to the weight of the pods varies between 11.81 My Driss and 27.88 for Ourika.
However, observations made in experimental plantations, under rigorous conditions for comparing genotypes, are essential for objective knowledge of genetic variability.
IN-SITU AND EX-SITU CONSERVATION
Conservation objectives can concern either population with particular characteristics or the maintenance of a sample of populations representative of the natural area of the country, or both.
When natural regeneration is possible and anthropogenic pressures can be controlled, high priority must be given to the in situ conservation of endangered populations. Otherwise, we are moving towards ex-situ conservation. Depending on the state of the stands and the knowledge acquired, a list of priority populations must be established in order to ensure their sustainability.
Ex-situ conservation should be reserved for cases where populations are doomed to disappear rapidly. It can be dynamic (conservatory plantings, clone parks) or, in the most urgent cases, static. Collections of genetic resources conserved ex-situ are commonly called “gene banks,” although the genes themselves are not stored there, genotypes are stored there.
Updating the inventory of natural stands will help identify the stands most at risk due to their small size and / or poor vegetation.
Conservative planting of these stands would constitute additional insurance for safeguarding the genetic heritage. Limited in area, these plantations should preferably be located near the corresponding natural stands. For interesting subjects, clone conservatories should be considered.
It is necessary to underline the need to integrate as much as possible the concerns of the conservation of genetic resources in the management plans of the forests where the carob tree is present.
Perspectives
Since the early 1980s, this crop has seen a considerable revival of interest due to the generally high prices and the increased demand for pods (pulp and seeds).
Although trees produce low yields in old plantations (1,500-3,000 kg/ha), the production potential in modern orchards is very high (5,000-7,000 kg/ha). In addition, under optimal conditions, the carob tree requires a minimum of maintenance compared to most other fruit trees.
In view of international demand and the import of certain carob derivatives, manufacturers have invested in intensive carob plantations in the regions of Beni Mellal, Khémisset, and Agadir.
Civil society, convinced of the role that the carob tree can play both ecologically and above all socio-economically, is also starting to take an interest in this species. In 2005, an NGO initiated a project to plant a million plants in Tiznit over a period of 5 years.
Moroccan production will certainly increase in the coming years to at least satisfy the local industry. Its current production remains competitive compared to other countries on the northern shore of the Mediterranean, thanks to the cost of labor, which represents only a third of the total cost of production. With some encouragement from the public authorities (subsidies, premiums for grafting trees in forests, free distribution of grafted plants, organization of the sector), Morocco is likely to become the world’s leading producer of locust bean.
Finally, one hectare of rock garden carrying only one hundred productive trees in their twenties, giving an average harvest of 20 Kg per locust tree, or 2000 Kg in total, represents, at a price paid today for this commodity, an income of 16,000 to 20,000 DH per year at least.
Let us hope that these figures decide some investors invest in ceratoniculture and owners of marginal land to use this tree of the future.
