Arbuscular Mycorrhizal Association Contributes to Cr Accumulation and Tolerance in Plants Growing on Cr Contaminated Soils

Abstract

Arbuscular mycorrhizal (AM) fungi are well known root symbionts in heavy metal polluted soils. To assess AM fungal association and their contribution to the host plants naturally growing on a highly chromium (Cr) contaminated soil, the present study has been undertaken. The soil of the study site was contaminated with 32,562 ppm Cr coming from tannery industry. The study site was dominated by Cynodon dactylon (L.) Pers., Parthenium hysterophorus L., Croton bonplandianum Baill and Prosopis juliflora (Sw.) DC. High mycorrhizal colonization (31–83%) and low spore population (5–11 spores/g) was recorded. The diversity of AM fungi was very low because of stress caused by Cr. Only seven AM fungal isolates have been recovered. Funneliformis mosseae, Rhizophagus intraradices, Funneliformis geosporus and Glomus sinuosum have been recovered from two hosts, while, Rhizophagus fasciculatus, Glomus aggregatum and Acaulospora scrobiculata from single host only. Cr accumulation in the roots were analyzed through AAS and correlated with various mycorrhization parameters. The results of correlation through PCA showed that, various mycorrhization parameters were under strong influence of Cr accumulation in the roots. Furthermore, all the AM fungi showed certain adaptive features like compact sporocarp, thick spore wall, sloughing outermost wall layer and formation of water stable aggregates. Low species diversity, high mycorrhizal colonization, presence of adaptive features and strong correlation of mycorrhizal parameters with the Cr accumulation in the roots clearly indicated that, these AM fungi have contributed to the Cr accumulation and tolerance to the host plants in Cr sludge deposit.