Inoculation of Ceratonia siliqua L. with native arbuscular mycorrhizal fungi mixture improves seedling establishment under greenhouse conditions

Abstract

The potential benefits of inoculation with arbuscular mycorrhizal (AM) fungi were investigated on carob tree Ceratonia siliqua, a Mediterranean legume in Morocco. The parameters under study were the effect of an inoculation on growth, mineral nutrition and roots mycorrhizal colonization of the plant under nursery conditions. C. siliqua growth was measured after six months of culture in plastic bags arranged in a randomised complete block under greenhouse conditions. Fungal inoculation consisted of a mixture of native AM fungi propagated on Zea mays roots. Results show that the fungal symbionts were effective to improve the growth of C. siliqua, confirming the requirement of mycorrhizal symbiosis for the successful establishment of C. siliqua in a degraded soil. The approach used with indigenous AM fungi complex isolated under C. siliqua appeared to be effective in promoting growth and nutrition of C. siliqua. After 6 months of culturing in nursery conditions, height, shoot and root biomass, total biomass, phosphorus and nitrogen foliar contents of the plants inoculated with native AM fungi were significantly higher than in the control. Glomus spores were extracted from the soil under C. siliqua and were observed on permanent slides under a microscope connected to a computer with digital image analysis software. Seven spore morphotypes were detected under C. silqua in the Ourika Valley, Morocco. Five Glomus species were classified as Glomus aggregatum, Glomus intraradices and Glomus constrictum, whereas, two other Glomus species were not identified. The analysis of this spore community revealed the presence of two other species belonging to Gigaspora genera. The use of a mixture of native AM fungi as fungal inoculum improves clearly growth, nutrition and roots colonization of C. siliqua seedling.

Key words: Arbuscular mycorrhizal fungi, diversity, growth, soil microbial activity, Ceratonia siliqua.