The effect of arbuscular mycorrhizal root colonization on growth and nutrient uptake of two different cowpea (Vigna unguiculata [L.] Walp.) genotypes exposed to drought stress

In the present investigation, the effect of arbuscular mycorrhiza (AM) fungal rootcolonization on nutrient uptake, growth and soil water depletion of cowpea plants exposed to adrought stress period was studied in a greenhouse experiment. Arbuscular mycorrhizal and non-AM plants of an old, local variety from Brazil 'Carioca', and of the breeding improved cultivar'Epace-10' were exposed to 24 days of drought, with or without a subsequent period of water resupply.Control plants remained well watered throughout the growth period. The AM symbiosisgreatly enhanced nutrient uptake of drought stressed plants. However, water uptake, growth andnet photosynthesis were unaffected by AM root colonization during drought stress. Recoveryafter water resupply was much faster when plants were inoculated with AM, probably due to animproved plant nutritional status. The cultivar Epace-10 was much more dependent on the AMsymbiosis for growth and nutrient uptake compared with Carioca in all irrigation treatments. Onlywhen roots were AM colonized, Epace-10 plants were able to recover from drought stress afterwater resupply. Our study suggests that the AM symbiosis constitutes an important strategy bywhich leguminous plants overcome periods of drought. Under conditions of low soil water and Pavailability, the presence of AM fungal propagules in the field soil appears to be a prerequisite forsuccessful cultivation of cowpea, particularly with respect to the breeding improved cultivarEpace-10.