Minimising the effects of drought stress on growth of two peanut cultivars, using arbuscular mycorrhiza (AM) inoculants

Peanut (Arachis hypogaea L.) is a major cash crop in the semi-arid tropics, where it is mainly grown under rainfed conditions. Inadequate soil fertility (especially N and P), drought and diseases are important factors causing low yields. Peanut forms two types of symbiotic associations with micro-organisms, one with Bradyrhizobium involving N2-fixation and with arbuscular mycorrhizal fungi (AM). The positive effect of AM fungi on plant growth and development make AM a potentially very useful biological resource of assuring high plant productivity, with minimum application of chemical fertilizers or pesticides. Effects of two different AM inoculants on root colonization, leaf growth and dry matter accumulation and distribution were studied in two peanut cultivars: Local and Falcon. The cultivars differed in their dry matter partitioning pattern, drought tolerance strategies and degree of colonisation with AM inoculants (Quilambo, 2000). The plants were grown for 13 weeks, in a non-sterile soil Mozambican soil with and without drought stress. The indigenous Soil Mozambique inoculant significantly increased root colonisation, leaf growth and dry matter in both cultivars under drought stress conditions. The commercial Hannover inoculant increased growth only under well-watered conditions. In general, there was a tendency of allocating more dry matter to the pods with inoculation, followed by leaves, while drought stress and non-inoculation, delayed the formation of pods. Drought stress effects could be alleviated by inoculation with Soil Mozambique inoculant. Therefore, peanut productivity, particularly under drought stress, may be improved by an adequate management of the AM symbiosis. Key Words: AM inoculation, arbuscular mycorrhiza, drought stress, growth and peanut Journal of Tropical Microbiology Vol.1(1) 2002: 22-2