In vitro mycorrhization of Argania spinosa L. using germinated seeds

Abstract

The beneficial effects of arbuscular mycorrhizal fungi (AMF) on the growth and nutrition of argan plants have been reported in several studies conducted under greenhouse or field conditions. However, none of these studies considered the in vitro mycorrhization of those plants, despite the benefits of this technology on the enhanced survival and fast recovery at transfer to hardening conditions reported in several plants of economic importance (e.g. banana and hevea). In our study, we succeeded for the first time the association of argan plants with an AMF (Rhizophagus irregularis MUCL 41833) under in vitro culture conditions and their successful transfer from in vitro to greenhouse conditions. We tested three argan accessions, Tidzi (TD), Mejji (MJ) and City Hanchan (CH), and grew surface-sterilized seeds in the mycelium donor plant in vitro culture system. Whatever the accession, root colonization, with the presence of arbuscules, vesicles/spores and hyphae, was observed after 8\xa0weeks of growth in the extraradical mycelium network of the fungus, and reached values between circa 30 and 50% of total root colonization after 11\xa0weeks, with significant differences between the accessions. Plants survived transfer from in vitro to greenhouse conditions (peat-sand mixture substrate), and roots remained highly colonized after five months. Whatever the accession, a significant increase was noticed in the growth of AMF-colonized plants. Differences were also observed between accessions, with TD showing the highest relative mycorrhizal dependency and CH the lowest. The relative mycorrhizal dependency was correlated with the % of total colonization, % of arbuscules colonization and % of hyphae colonization within roots. The concentration of chlorophyll a and b was also increased in the leaves of the AMF-colonized plants, whatever the accession. In conclusion, the in vitro association of argan seedlings with R. irregularis MUCL 41833 allowed good root colonization and improved the growth of the plants after transfer to the greenhouse. This technology thus represents a promising approach for the production of biotized argan plants with faster recovery and growth at transfer to the greenhouse and possibly to the field.