The arbuscular mycorrhizal fungi status of selected tree nurseries in the Ethiopian highlands

Abstract

We investigated the arbuscular mycorrhizal fungi (AMF) status of ten nurseries suitable for restoration of dry evergreen Afromontane forests in Ethiopia. We quantified AMF root colonization (RC) and spore abundance (SA) in seedlings of nine native tree species namely Acacia abyssinica Hochst. ex Benth., Cordia africana Lam., Dovyalis abyssinica (A. Rich.) Warb., Hagenia abyssinica J.F. Gmel., Juniperus procera Hochst. ex Endl., Millettia ferruginea (Hochst.) Baker, Olea europaea L. subsp. cuspidata (Wall. ex G. Don) Cif., Podocarpus falcatus (Thunb.) R. Br. ex Mirb. and Prunus africana (Hook. f.) Kalkman. We used the ink and vinegar method to stain AMF in roots. RC levels ranged from 8.00 to 99.67% and were generally higher than the RC levels reported from other similar nurseries in Ethiopia. SA levels ranged from 1 to 25 spores g−1 and were comparable with some reports from the field in Ethiopia but they were lower than levels reported by another similar study. RC was more affected by host species than nursery location, while the reverse was true for SA. The results also showed that nursery management could improve AMF status among seedlings. When all nursery tree species were considered, RC and SA levels were unrelated. No strong correlation existed between the nursery management variables considered and RC or SA. However, considering C. africana, J. procera and P. falcatus separately, RC-age (rs = 0.829, P = 0.042) correlation for O. europaea and RC-pot diameter (rs = 0.820, P = 0.046), RC-pot volume (rs = 0.928, P = 0.008) and SA-age (rs = 0.943, P = 0.005) correlations for C. africana, were significant, strong and positive. Generally, most of the tree species and particularly, early-mid successional tree species had sufficient AMF inoculum. Hence, only the mid-late successional tree species; J. procera, P. falcatus, and P. africana may require AMF inoculation, preferably, during filed planting. Based on our results, age and pot volume were identified to be important variables potentially affecting RC and SA. To better understand the effects of these and other nursery management variables, additional study is required. We demonstrated for the first time that black Hero ink is suitable for staining root AMF and can be used in future AMF research.