POTENTIAL FOR NITROGEN-FERTILIZATION AND HESSIAN FLY-RESISTANCE TO IMPROVE MOROCCO DRYLAND WHEAT YIELDS

Hessian fly (Mayetiola destructor, Say) is a perennial scourge of cere al production in the Mediterranean region, particularly in North Afric a. In Morocco, it accounts for considerable yield losses of wheat (Tri ticum spp.), especially in the semi-arid southwestern coastal province s. 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 fa rmers in 1989, whereas a tolerant variety 'Massira' was released in 19 94. Another widespread limiting factor for all cereals in Morocco is l ack of adequate nitrogen (N). With favorable farmer acceptance, Saada became the focus of on-farm N fertilizer trials throughout the low rai nfall (250-450 mm year-l) zone, where it consistently out-yielded the susceptible common bread wheat, Nesma, except when no Hessian fly infe station occurred. In most cases, 40 kg N ha(-1) was adequate for maxim um yield. Substituting resistant cultivars for Hessian fly-susceptible cultivars and increased N use could have an immediate and positive ef fect on wheat production in Morocco, especially in areas where the ins ect is endemic. The future impact will be greater when Hessian fly res istance is also transferred to other bread wheat cultivars and to duru m (T, durum) wheat, the major staple food in the Mediterranean region. (C) 1998 Elsevier Science B.V.