Mycorrhizal Status and Inoculation Response of Proteaceae Cultivars on Terceira Island (Azores): Implications for Sustainable Crop Establishment

Arbuscular mycorrhizal fungi (AMF) can support sustainable crop production, but their role in Proteaceae remains poorly understood because many members of this family are considered non-mycorrhizal. This study assessed the mycorrhizal status, AMF taxon occurrence, and seasonal colonisation patterns in four ornamental Proteaceae cultivars on Terceira Island, Azores. The effects of early inoculation with native AMF on the growth and survival of Protea ‘Grandicolor’ cuttings were evaluated under nursery conditions. AMF colonisation was detected only in Protea ‘Grandicolor’ and Leucospermum ‘Succession II’, with total root colonisation ranging from 26–59% and 29–78%, respectively. Arbuscules were observed in both cultivars, providing morphological evidence consistent with a symbiotic interface. Nine AMF morphotypes belonging to Claroideoglomeraceae, Gigasporaceae, and Glomeraceae were detected, and Funneliformis mosseae was the most frequently detected taxon. AMF taxon richness was highest in samples from Protea ‘Grandicolor’ and varied seasonally for this cultivar. Native AMF inoculation increased survival of Protea ‘Grandicolor’ from 50% to 90% and significantly enhanced shoot and whole-plant growth, leaf and root production, and fresh and dry biomass. These findings reveal cultivar-related variation in detected AMF colonisation and support further evaluation of locally adapted AMF inoculum for sustainable nursery production of ornamental Proteaceae in agroecosystems.