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

Abstract

Coffee plants ( Coffea arabica L.) infected by two endoparasitic nematodes ( Pratylenchus coffeae and Meloidogyne konaensis) exhibited reduced NO − 3 and NH + 4 uptake rates in short-term solution culture experiments. Infection by the sedentary nematode ( M. konaensis) decreased by half the proportion of fine roots per root system and reduced NO − 3 and NH + 4 uptake rates by 63% and 54%, respectively. The migratory nematodes ( P. coffeae) reduced NO − 3 uptake rate by 56% and NH + 4 uptake rate by 24% without affecting the proportion of fine roots per root system. Such lower NH + 4 and NO − 3 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.