Potential for nitrogen fertilization and Hessian fly-resistance to improve Morocco's dryland wheat yields

Hessian fly (Mayetiola destructor, Say) is a perennial scourge of cereal production in the Mediterranean region, particularly in North Africa. In Morocco, it accounts for considerable yield losses of wheat (Triticum spp.), especially in the semi-arid southwestern coastal provinces. Breeding for resistance is the only feasible approach to abate its effects. Nine major Hessian fly-resistance genes have been identified in bread wheat. Two bread wheat varieties have these characteristics; the first variety with complete resistance was ‘Saada’, released to farmers in 1989, whereas a tolerant variety ‘Massira’ was released in 1994. Another widespread limiting factor for all cereals in Morocco is lack of adequate nitrogen (N). With favorable farmer acceptance, Saada became the focus of on-farm N fertilizer trials throughout the low rainfall (250-450 mm year⁻¹) zone, where it consistently out-yielded the susceptible common bread wheat, Nesma, except when no Hessian fly infestation occurred. In most cases, 40 kg N ha⁻¹ was adequate for maximum yield. Substituting resistant cultivars for Hessian fly-susceptible cultivars and increased N use could have an immediate and positive effect on wheat production in Morocco, especially in areas where the insect is endemic. The future impact will be greater when Hessian fly resistance is also transferred to other bread wheat cultivars and to durum (T. durum) wheat, the major staple food in the Mediterranean region.