tiny pest - but a big $20 million problem for farmers in the semi-arid areas of Morocco - that's the Hessian fly which is being brought under control with new resistant wheat varieties.
       At just 3mm long this midge-like pest doesn't look like much to the untrained eye but cereal growers throughout the Mediterranean rim have long been suffering its devastating effect on their crop yields. Average losses of 36% yield of affected bread wheat and 32% in durum wheat in Morocco can be expected but individual farmers might lose their entire crop yield if the infestation by larvae takes place during early plant growth stages.
        The potential scale of these losses is deeply troubling for Morocco which has about four million hectares of spring bread wheat (Triticum aestivum) and durum wheat (Triticum turgidum) under production each year. However, yields are being kept down to an average of about one tonne per hectare because of this and other constraints.

tant lines by the introgression of the H5 resistance gene, previously identified in the bread wheat work, into durum wheat.
          As a result, three new lines are almost ready to be released as varieties. Named Telset 1, 2 and 3 to reflect the cooperation between Tel Hadya in Syria and Settat in Morocco, these new varieties combine the essential good quality of durum wheat with the ability to grow well under drought and heat conditions in Mediterranean dryland. The breeding program continues for both types of wheat and further improved varieties will be released in future years.
          So what does this mean for the Moroccan wheat grower? Wheat yields in the country's dry marginal areas are being increased by 30-50% to give a substantial income boost to poorer farmers. One unofficial estimate suggests that extending the Hessian fly resistant varieties throughout wheat-growing areas in Morocco would allow farmers to recover grain losses worth $336 million.

        This is costing the country dearly because it then has to import replacement stocks of both wheat for breadmaking, and durum wheat which is a staple part of the Moroccan diet. Durum is the ingredient of the country's best known dish, couscous, and it features in other foods favored in North Africa, including pasta, burghul (cracked wheat), and frike (green grains)
        Hessian fly (Mayetiola destructor) is the major pest on the country's wheat and, although the biology of this pest had been studied in Morocco, no effective control method was previously available. Damage is actually caused by the larvae which feed on the lower stem reducing the flow of nutrients to the ear, so the plant lodges or breaks off below the head as it begins to fill. Mild winters in Morocco permit up to three generations of Hessian fly per season.
        Reducing pest carryover from season to season by plowing under infested wheat stubble after harvest doesn't fit in with local farming practices. Wheat stubble provides valuable grazing for the livestock of more than 90% of farmers who have very small farms. For them, chemical control is also expensive and, more seriously, the available insecticides have a negative impact on the environment.
          With this shortfall in home-produced grain, the Moroccan government has no option but to import about three million tonnes of bread wheat each year to meet demand from an expanding population.
          The solution for this long-term pest problem is not coming from the use of expensive and environmentally-questionable insecticides but from a successful collaborative plant breeding program between Morocco's own National Institute of Agronomic Research (INRA), Mexico-based CIMMYT (International Maize and Wheat Improvement Center), ICARDA, and Kansas State University.
         Scientists decided about 15 years ago to combine efforts into developing wheat varieties resistant to the Hessian fly. Initial screening of plants for resistance is carried out in selected known 'hot spots' in the wheat-growing areas of Morocco and in INRA greenhouses.
          Germplasm was exchanged between Morocco and the USA, which has a long-standing serious problem with Hessian fly. Kansas State University, in particular, helped identify resistance genes from the exchanged germplasm.
          Crossing to obtain new varieties is carried out at ICARDA's Tel Hadya headquarters in Syria, and in Morocco, using adapted Moroccan cultivars and the newly identified sources of resistance.
         The resulting crosses are sent back to Morocco as segregating populations or fixed lines for field testing of their ability to withstand Hessian fly attack and, just as importantly, that they have good agronomic performance in other ways.
         So far, the greatest success has been the identification of 15 sources of resistance in  bread wheat and the release of three new varieties--Massira in 1996, Arrihane and Aguilal in 1998--to Moroccan growers. Several other new lines are in the breeding pipeline. They include three varieties developed using the doubled-haploid technique.
         Durum wheat presented the scientific teams with a greater challenge. Only one source of resistance has been identified in durum wheat itself.
          However, the collaboration between INRA (Morocco) and the CIMMYT/ ICARDA durum wheat program for WANA, paid off in the development of resis

          A study has shown there is a 39% internal rate of return on the investment in the development of  resistant varieties -- a particularly high pay off.
          Other benefits of the international cooperation include the multiple sources of environmentally-friendly genetic resistance now put in place against Hessian fly, and the much improved scientific knowledge of how to control this pest. This means that growers facing a similar problem in other Mediterranean countries such as Algeria, Tunisia, Spain and Portugal now stand to benefit from access to the resistant material. The cooperating universities in the USA have also been able to make use of the Moroccan material in their own research.

       A multi-disciplinary team of entomologists, breeders and economists has been carrying out this collaborative research work:

Dr A. Amri, Cereal Breeder, INRA, Morocco; Dr M. Jiblene, Bread Wheat Breeder, INRA; Dr N. Nsarellah, Durum Wheat Breeder, INRA; Dr S, Lhaloui, Cereal Entomologist, INRA; Dr M. Moussaoui, Agricultural Economist, INRA; Dr M. El-Bouhssini, Entomologist, ICARDA; Dr M.M. Nachit, Durum Wheat Breeder, CIMMYT/ICARDA; Dr O. Abdalla, Bread Wheat Breeder, CIMMYT/ ICARDA; Dr G. Ortiz-Ferrara, Bread Wheat Breeder, CIMMYT/ ICARDA; Dr M. Mergoum, Cereal Breeder, CIMMYT; Dr J. Hatchett, Wheat Entomologist, KSU, USA; Dr S. Azzam, Economist, UNL, Lincoln, USA;
Dr O. Benlhabib, Cytogeneticist, INAV Hassan II, Morocco; Dr A. Be  Belaid, ICARDA WANNADIN Economist.

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