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Family: Graminaceae (Gramineae or Poaceae)
Species: Triticum durum
French: blè; English: wheat; Spanish: trigo; German: Weizen.
Origin and diffusion
Wheat or durum wheat evolved rather late (4th century BC), supplanting spelled throughout the Mediterranean and Middle Eastern area in a hot and dry climate, where it still has the greatest diffusion. The introduction of durum wheat to other continents is very recent.
Durum wheat in the world is grown on a much less extensive area than common wheat and is mainly used for the preparation of pasta, after special milling that leads to the production of semolina, instead of flour.
Official FAO statistics only have the entry "wheat" without distinction between tender and hard; however it is estimated that the hard is extended on 9% of the total wheat surface.
In Europe the main producer of hard is Italy which in 2000 allocated 1.6 Mha out of a total of 2.3 Mha wheat, with a production of 4.5 Mt.
Durum wheat had a significant expansion in Italy in the 1970s following the agricultural policy followed by the European Community. Noting that the consumption of pasta increased and that European production was largely in deficit, the EC wanted to encourage the Community production of durum wheat to reduce imports.
This policy has been and is of considerable advantage for Italy, which is the largest producer of durum wheat, and in particular for its southern and island regions where the production of this cereal has traditionally been concentrated. The Community contributions per hectare, much higher than those of the common wheat, stimulated the expansion of the cultivation of durum wheat from the regions where before it was exclusively limited (Sicily, Sardinia, Puglia, Basilicata, Lazio and Lower Tuscany) to other regions of the Central Italy and northern Finanche as a substitute for common wheat.
TO Triticum durum - B Triticum aestivum var. Sword - C Triticum aestivum var. Brasilia (www.ense.it)
A typical soft wheat caryopsis differs from a typical hard wheat caryopsis for its opaque appearance and non-vitrescent fracture, its smaller size, more rounded shape, the embryo embryo, the presence of hairiness at the opposite end to that embryo. However, the recognition of common wheat kernels in durum wheat samples presents considerable difficulties and requires great experience, in particular in the case of some varieties of common wheat (eg. Sword) whose grains have morphological characteristics more similar to those of durum wheat. to others. (from www.ense.it)
Durum wheat (Triticum Durum) belongs to the group of tetraploid wheat. It is likely the result of anthropic selection in hot-arid climates, due to the useful characteristics of the ears and grain (bare caryopsis, vitreous endosperm and rich in proteins) starting from primitive tetraploid wheat.
Durum wheat differs from common wheat in the following morphological characteristics;
- Spike laterally compressed, instead of square, if viewed in section; glumes keeled up to the base and lower giumella always ending with a very long and often pigmented remains;
- Very large karyoxide (45-60 mg), with a subtriangular transversal session, with albumen that typically has a vitreous, amber, corneal, rather than floury structure;
- Last full internode, whereby the stalk under the ear is crush resistant.
The adaptation of durum wheat is less wide than that of common wheat: less of this resists adversities such as cold, excessive humidity, lodging and foot pain; much more than this sees the quality of the grain compromised by improper environmental conditions.
As far as the soil is concerned, durum wheat gives better results in rather clayey ones, with good water capacity, while it shuns those that tend to loose.
Durum wheat is better than soft, adapted to arid and hot environments, where it manages to achieve the best expression of quality.
The genetic improvement of durum wheat proceeded very late and slower than that of common wheat.
Only in the last decades of the twentieth century has there been a lively recovery of interest in the improvement of this species, which has resulted in the creation of several new radically renewed varieties of the Italian varietal panorama.
The problems of genetic improvement of durum wheat have been driven by two needs: that of creating agronomically better varieties for the areas of traditional cultivation of durum wheat (South and Islands), and those of creating new varieties in order to extend its cultivation in Italy north-central.
The main aspects to be addressed in the improvement of durum wheat are the following:
- Resistance to lodging. The susceptibility to this adversity, preventing to exceed modest production thresholds, was the main factor responsible for the low yields of durum wheat, as well as one of the strongest obstacles to the extension of the crop to the north of its typical range, in soils, generally, of greater fertility.
- precociousness. The delay in flowering and ripening has always in the past constituted another very serious limit to the productivity of durum wheat. In fact, the more the crucial phase of granigione takes place in late season, the higher are the drought and / or rusts that hinder it.
- Resistance to cold. This field includes resistance to strong and prolonged winter temperature drops and spring frosts. This problem arises with a prejudicial character for the extension of the crop in central-northern Italy with winters much more rigid than the typical southern durum wheat cultivation areas.
- Resistance to diseases. The same adversities that affect common wheat can attack hard. Indeed this is even more sensitive than that to the agents of foot ache and horned rye.
- Qualitative improvement. The characteristics required for a good commodity level of durum wheat concern both the yield in semolina during the grinding process and the pasta making process. cause of commodity depreciation of the product as the yield in semolina, the color of this and the homogeneous coloring of the pasta are worsened.
Other qualitative characteristics required for durum wheat are:
- Caryoxides of high hectolitre weight; translucent, bright yellow; absence of dark spots on the embryo or other parts of the karyoxide (spot or foxing).
- Well colored semolina (high yellow index) for high content of carotenoids and flavonoids, without residues of casings, good granulation and with sharp edges, with low ash content (not higher than 0.85% ss) high protein content and gluten, good gluten qualities;
- Paste of beautiful yellow color, transparent, homogeneous, with good cooking behavior, as regards elasticity, stickiness, resistance.
Even for durum wheat, the first "elected breeds" were obtained by selection within indigenous peoples.
The closest approach to the durum wheat ideotype was made today with the varieties derived from the hybridization of durum wheat with a Japanese common wheat.
These varieties, due to their earliness and resistance to lodging, have a very high production potential, not less than that of soft wheat.
The 10 most popular varieties of durum wheat, which in 2003 covered 70% of the entire surface, are the following, in descending order: Simeto, Duilio, Ciccio, Arcangelo, Creso, Colosseo, Iride, Rusticano, Grazia and Svevo.
The cultural technique of durum wheat closely follows that of common wheat. The points for which it diversifies will be mentioned below.
Sowing. The sowing of durum wheat must be done slightly ahead of that of the soft wheat; in this way it favors the preparation and anticipates, albeit slightly, flowering and ripening.
Quantity of seed. In the past it was sown much less dense than the tender: 120Kg / ha; today's trend, especially in areas that are not particularly arid, is to use much larger quantities of seed, not much lower than those recommended for the tender: 350-400 caryopsis per square meter, equal to 180-200 kg ha-1 and sometimes more, if the variety, as often occurs, is coarse grained.
turnover. The new varieties are as demanding as the soft ones: therefore they rotate as the first grain; to be avoided, given the sensitivity of the hard to foot pain.
Composting. For potassium and phosphatic fertilization it behaves as with the soft, based on the soil endowment. For nitrogen fertilization, the tendency to force it should be followed, considering however the dangers of lodging and grasping (made particularly dangerous and fearsome by the late ripening). The varieties resistant to lodging can be fertilized even with 150-200 kg ha-1 of nitrogen, but in drought environments the fertilization must be suitably reduced. In addition to increasing areic yields, nitrogen fertilization decreases the percentage of whitening making the grain more protein. Late nitrogen is particularly effective in preventing whitewashing.
Weeding. Durum wheat is a little more sensitive than the soft to the toxicity of herbicides which, therefore, must be used in slightly lower doses. The technique and products are the same as those indicated for common wheat.
Collection and use
The yields obtainable with durum wheat are now of the same order of magnitude as those obtainable under the same conditions with soft wheat, so the economic convenience of growing one or the other species essentially depends on the market value of the grain and the EC contribution; the latter, in the case of durum wheat, is reserved for determining regions and is subject to the cultivation of varieties with good quality characteristics.
In many areas of southern Italy they must be considered good, yields higher than 3.5 t / ha.
Durum wheat produces a grain from which semolina is obtained, a raw material for the preparation of pasta, consisting of more or less large, sharp-edged, non-floury endosperm fragments.
The grinding of durum wheat is therefore done with a different system from that adopted for common wheat, being aimed at obtaining semolina, instead of flour, in addition to the bran and farinetta by-products. The most important qualitative data for the oil industry is the grinding yield, i.e. the kg of semolina obtainable from 100 kg of grain.
This value depends on the weight per hectolitre, on the degree of whitening and mainly on the ash content; in fact, the law establishes a maximum ash content of 0.85% for the semolina and in order not to exceed this limit, the miller is sometimes forced to lower the grinding yield.
The minimum requirements required for the acceptability of durum wheat are practically the same as those indicated for common wheat bread-making with the following additional: weight per hl: 76kg; maximum% of black and white grains, even partially: 50%, of which soft wheat grains: 4%. The tolerance relative to the% of whitening is 20%: this means that deductions are made only when the whitening is higher than this value up to the maximum admissibility limit.
The superior quality hard cheeses are obtained only in the typical regions of Southern Italy, thanks to the edaphic and climatic conditions that ensure all the determining characteristics of an excellent pasta quality.
The absolutely prevalent use of durum wheat is for the preparation of the pasta, defined by law as follows: "products of durum wheat semolina" and "pasta of durum wheat semolina" are the products obtained by drawing, rolling and subsequent drying of dough prepared respectively and exclusively:
a) with durum wheat semolina and water;
b) with durum wheat semolina and water.
The first processing to which the durum wheat grain is subjected is, therefore, a special grinding (crushing of the kernels with scaled rollers) with which semolina and semolina are obtained from the amyliferous endosperm, germ and bran.
It is called semolina the sharp-edged granular product obtained by grinding and consequent reduction of durum wheat, freed from foreign substances and impurities.
It is called granulated the product obtained as above, after the semolina extraction.
The characteristics that the two products must have are as follows:
- semolina: ash, minimum 0.70%, maximum 0.85%; cellulose, minimum 0.20%
maximum 0.45%; nitrogenous substances, minimum 10.50%;
- caster: ash, minimum 0.90%, maximum 1.20%; cellulose, maximum 0.85%; nitrogenous substances, minimum 11.50%.
Adversity and pests
Prolonged stagnation of water causes irregular births, thinning, poor tillering, susceptibility to disease on crops; then there are: greater invasions of weeds, which generally tolerate asphyxia better than cultivated plants, and dispersion of mineral nitrogen by denitrification and leaching.
allurement. Violent rains accompanied by the wind can provoke lodging, that is, the lying down of the culms that bend at the base prostating on the ground. It is clear that lodging can only happen after the crop has started to rise.
The damage that the lodging causes is of a different nature and severity depending on when it occurs: near the collection, when the filling phase is completed, the damage consists only of some difficulty in the collection; after rising, the damage has been limited since the bedrams are straightened as they curl their internodes and resume their erect position; it is when the lodging occurs towards the end of the rising, when the culms no longer have the ability to straighten, that the damage is maximum. In fact, the anomalous structure of the vegetation seriously affects the assimilation of the crop: the folding of the stalks hinders the rise of the raw sap; instead of being stretched out to receive the light, the leaves are found prostrate on the ground in a cluster where light does not enter, the air circulates badly, leaf diseases find favorable conditions for attacking. The result is that the photosynthetic assimilation process is compromised in the crucial stages of flowering and / or grains, always with poor and poor quality grain production.
The lodging occurs for a mechanical reason: the horizontal force of the wind, and its occurrence or not depends, for the same wind force, on the characteristics of the vegetation cover: plant height, robustness, elasticity and health of the culms.
These characteristics of vegetation depend partly on varietal factors, genetically determined, partly on environmental factors. The height of the culms is a predominantly varietal characteristic, but also influenced by the level of fertilization. The sturdiness of the culms depends mainly on the fertilization conditions. The elasticity of the culms mainly depends on the conditions of cultivation: too dense sowing and imbalances or excess nitrogen fertilization predispose the crops to become enticed because due to the strong mutual competition the culms during the raising are of little significance and remain thin and weak, especially the internodes lower, those less illuminated and more mechanically stressed.
The lodging is also the consequence of the attack of a fungus (foot ache produced by Cercosporella) which makes the straw fragile in the basal part of the wheat stalks.
The lodging is the main determining factor for the productivity limit of "straw" cereals (wheat type). The extraordinary increase in the production level of the varieties obtained in the last fifty years is the result of the progress of genetic improvement combined with the progress of the cultivation technique. The geneticists have selected varieties more resistant to lodging that have allowed to change the cultivation technique, intensifying the nitrogen fertilization and consequently the unit productions.
Hailstorm. The hail causes particularly sensitive damage if it falls to the earing and ripening.
There are numerous pathogenic fungi that can attack wheat in its various organs, from the roots to the ear, alone or in association, at different times or simultaneously. There are pests considered secondary in the past that today, with the intensification of cultivation, are increasing their danger.
The most important and common are the following.
Foot ache. By foot ache we mean a pathological picture that occurs on the basal part of the wheat stalk and on the roots and which is caused by various possible pathogens.
The best known are:
- 1 Ophiobolus graminis, very frequent in Italy in the areas of cultivation of common wheat and only exceptionally in those of durum wheat;
- 2 Cercosporella herpotricoides whose attacks make straw fragile and therefore cause carpet entreaties; it is very frequent and feared in the fresh and humid cereal areas of central-northern Europe, while in Italy it is found only in exceptionally rainy years;
- 3 Mushrooms of the gen. Fusarium (F. nivale, F. culmorum, F. graminearum), are the most important and widespread agents of foot pain both in central-northern Italy on common wheat and in southern Italy on durum wheat.
The most evident symptom is the browning of the basal part of the culms accompanied by alterations of the roots. As a consequence of this, the development of the tillers culms stops, and therefore a reduction in the number of ears of corn per m2; if the affected culms form the ear, they dry out early, becoming whitening, and the ear remains empty of grains or with small and skimpy grains.
Foot ache is favored by the following factors:
- Stagnation of water: in fact, it is often observed with different intensity in different points from the same field;
- Too early sowing;
- Bad nutritional status: good nitrogen fertilization is a powerful means of prevention;
- A cereal as a previous crop: the most important negative effect of thanksgiving, i.e. the monosuccession of wheat, is the intensification of foot ache attacks;
- Presence of straw on the surface.
There are no effective treatments or resistant varieties for foot pain. Consequently, this disease can be prevented only with agronomic means that reduce the predisposing causes: burying the straw of the previous cereal; landscaping that ensures adequate drainage of water; abundant nitrogen fertilization; crop rotation other than cereals; delayed sowing in risk lands.
rusts. The characteristic symptom of this family of diseases is made up of different colored pustules, depending on the fungus responsible.
Three rusts mainly attack wheat:
- The yellow rust (Puccinia glumarum or striiformis) which forms small, rounded, yellow pustules aligned between the veins of the leaves and on the ears; being the least thermophilic, attacks can also occur very early in the spring, causing very serious damage in certain years on sensitive varieties;
- The black rust (Puccinia graminis variety tritici): it is the most thermophilic, which belatedly attacks the sheaths and the culms of the wheat forming elongated pustules, brown-blackish and causing the "close" in the very late varieties (while the current early varieties escape them );
- Brown rust (Puccinia recondita or triticina) which causes yellow-reddish pustules scattered on the two sides of the leaves, has intermediate thermal requirements between the previous ones and causes sporadic but serious attacks.
The spread of rust is favored by the vegetative luxuriance and by the hot and humid climatic course; therefore rusts are particularly fearful in valley, humid soils, in misty climates, on late wheat or on those fertilized with excess nitrogen. The preventive remedies are therefore evident. However, the choice of tolerant varieties remains the most effective means of avoiding rust damage; for brown and black rust a type of efficient resistance has proven to be earliness that allows you to escape attacks.
Powdery mildew. Powdery mildew or badly white (Erisiphe graminis variety tritici) affects leaves, stems and ears forming a superficial fluff, first white then grayish dotted with black points. This disease develops especially in very dense and luxuriant crops and when the sky is overcast.
Strong attacks reduce the assimilation capacity of the foliage; the attacks on the penultimate and last leaf (leaf-flag) are especially serious.
septoria. Septoriosis is caused by septoria tritici and Septoria nodorum. The first develops on wheat leaves during mild winters, causing light brown spots in the shape of a lozenge that end up flowing to dry up the leaves.
The second also attacks the culms' nodes, which become soft, then the ears which turn grayish due to the drying out of the glumes.
Septoriosis, in the case of contaminated seed, causes the rotting of seedlings in germination; to avoid this danger, seed tanning is needed.
Caries. The various (Tilletia tritici and Tilletia laevis) are other fungal parasites that transform the grains of wheat into squat, gray-brown ovoid grains, filled with a dark powder with the smell of soaking fish. Excluding grain from infected fields from sowing and tanning the seed are fully effective remedies.
Coal. Much less dangerous than caries is coal (Ustilago tritici), which appears on the ear. The young ears are without spikelets and covered with a dark-brown powder.
Seed tanning with the systemic fungicides available today is the best remedy.
Ergot. (Claviceps purpurea). Although this disease is much more widespread and severe in rye, in rare cases it is also detectable on wheat, especially hard wheat. The parasite develops in the ovary of the flowers which transforms, with aging, into a hard, elongated, black-violet body, which is the mushroom sclerotium. These sclerotia contain several alkaloids (ergatoxin, etc.) which are highly toxic to humans. The legal tolerance limit in cereals is 1 ‰ of sclerotia in the mass.
While seed tanning is an indispensable preventive intervention, the recent tendency to make anticryptogamic treatments to prevent and / or combat the aforementioned leaf diseases is very questionable.
In the countries of Central Europe these treatments have become ordinary, considered necessary to achieve the very high productions achievable there thanks to a climate favorable to cereals but also to leaf cryptogams.
In Italy, where the climatic conditions are less humid and therefore less conducive to fungal attacks, it is generally sufficient to avoid cultivating susceptible varieties but to choose genetically resistant or tolerant ones, so that these treatments can be omitted: which is an economic advantage no less. that ecological.
The animal parasites that attack the wheat plant do not usually cause widespread damage, and generally do not require special interventions during vegetation.
The seed just entrusted to the ground can be prey to mice, voles, sparrows and other birds.
The base of the culms can be mined by the larvae of the elateridae (Agriotes lineatus, A. obscurus, A. pilosus).
The larvae of the wheat fly (Clorops taeniopa, Oscinella frit) can cause sensitive damage by digging tunnels in the stem.
On the ears, at the time of flowering, colonies of aphids can be found (Sitobium avenae, S. granaria). Also on the ears, in certain cereal areas there may be massive attacks by plant bugs (Aelia rostrata) which damage the crop with their stings on the ears and the kernels. Only after careful evaluation of the severity of the attacks and the extent of the expected damage ("intervention thresholds") will it be necessary to decide whether to intervene.
The stored grain is subject to attacks by moths and awl. The larva of the real moth (Sitotroga cerealella) penetrates the grain feeding on its starch content and can produce considerable damage. Instead, the larva of the false moth (Tinea granella) gathers more grains with silky threads and feeds on them. When the attack is intense, a felt of kernels connected to each other forms on the surface of the piles. The female of the awl (Calandra spp.) Lays an egg for caryopsis; the larva feeds on nibbling the inside of the grain.