Impact of macronutrients and monsoon on the AM fungal community structure within lateral root systems of Hevea brasiliensis.

Abstract

Arbuscular mycorrhizal fungi (AMF) are important root symbionts that enhance nutrient acquisition, water uptake, stress tolerance, and soil ecosystem functioning in terrestrial plants. In perennial plantation systems like Hevea brasiliensis, understanding the dynamics of root-associated AMF communities under varying seasonal and nutrient conditions is essential for developing sustainable nutrient management strategies, particularly in emerging rubber growing regions. In the present study, we investigated the, composition, diversity, and seasonal dynamics of AMF communities directly associated with the roots of 12 year old H. brasiliensis plants maintained under long term nutrient withdrawal treatments. AMF specific barcoding regions were selectively amplified and sequenced from root samples collected during pre- and post-monsoon seasons. Species level analysis revealed seasonal differences in AMF community structure, with post-monsoon samples having comparatively higher abundance and species richness. Pre-monsoon communities were largely dominated by members of the Glomeraceae, whereas post-monsoon samples showed greater phylogenetic diversity, including representatives of Diversisporaceae, Acaulosporaceae, and Entrophosporaceae. Nutrient omission treatments showed variation in root AMF community composition with respect to the availability of phosphorus, nitrogen, potassium, calcium, and magnesium. The treatment specific occurrence of Acaulospora scrobiculata, Entrophospora infrequens, Acaulospora fragilissima, and Dominikia bernensis identified them as potential candidates for further ecological investigation under nutrient deficient conditions, whereas the consistent occurrence of Glomus, Rhizophagus intraradices, Dominikia disticha, and Dominikia gansuensis across multiple treatments suggests that they may constitute a core component of the symbiotic fungal community within rubber roots. Overall, the findings suggest that seasonal changes and nutrient stoichiometry may be associated with variation in root-associated AMF community structure in Hevea. The study also identified candidate AMF species for further investigation toward sustainable rubber cultivation under changing tropical conditions.