Effects of two endoparasitic nematodes (Pratylenchus coffeae and Meloidogyne konaensis) on ammonium and nitrate uptake by Arabica coffee (Coffea arabica L.)

Coffee plants (Coffea arabica L.) infected by two endoparasitic nematodes (Pratylenchus coffeae and Meloidogyne konaensis) exhibited reduced NO3- and NH4+ uptake rates in shea-term solution culture experiments. Infection by the sedentary nematode (M. konaensis) decreased by half the proportion of fine roots per root system and reduced NO3- and NH4+ uptake rates by 63% and 54%, respectively. The migratory nematodes (P. coffeae) reduced NO3- uptake rate by 56% and NH4+ uptake rate by 24% without affecting the proportion of fine roots per root system. Such lower NH4+ and NO3- uptake rates in the presence of nematodes are consistent with visual symptoms and foliar analyses indicating N deficiency in long-term field experiments with nematode-infected coffee plants. The nematode parasitic behaviors have a strong incidence on the mechanisms involved in the reduction of N uptake. The sedentary endoparasitic nematode (M. konaensis) decreased N uptake by a reduction of fine roots caused by gall formation without apparently affecting the uptake capacity of uninvaded fine root regions. The migratory endoparasitic nematode (P. coffeae) seemed to directly affect the root uptake capacity by damaging root cells during nematode penetration, exploration and feeding. (C) 1998 Elsevier Science B.V.