Arbuscular Mycorrhizal Fungi Inoculation as a Climate Adaptation Strategy for Establishment of <i>Swietenia macrophylla</i> King. Seedlings

<i>Research Highlights:</i> Drought stress significantly decreased the performance of seedlings in the nursery. Seedlings inoculated with <i>Claroideoglomus etunicatum</i> is recommended to produce superior planting stock of mahogany seedlings with better drought resistance in the nursery. <i>Background and Objectives:</i> With numerous intense droughts across tropical regions due to climate change, it is crucial to understand effects of drought stress on tree seedlings to improve crop management practices and avoid failures on large scale planting. <i>Swietenia macrophylla</i>, a commercial timber species in India, is poorly studied in relation to its management including physiological responses to various environmental stresses. Arbuscular mycorrhizal fungi (AMF) is known to improve performance of tree seedlings under drought conditions and produce quality planting stock in nursery. This study aims to understand the responses of mahogany seedlings under different levels of drought stress when inoculated with three types of AMF, namely <i>Funneliformis mosseae,</i> <i>Claroideoglomus etunicatum,</i> and <i>Rhizophagus intraradices</i>. <i>Materials and Methods:</i> The experiment is conducted in pot culture using a factorial completely randomized design. Different irrigation regimes were applied at 100, 80, 60, and 40 percentage of weekly cumulative evapotranspiration. The seedlings were tested for biometric, physiological, and mycorrhizal parameters periodically. <i>Results:</i> Physiological attributes such as rate of photosynthesis, stomatal conductance, transpiration rate, chlorophyll content, and water potential were found to be higher in the daily irrigated (control) seedlings. Performance of the seedlings were poorest in the least irrigated treatment. It was apparent that inoculated seedlings performed better than the non-inoculated ones. <i>Conclusions:</i> Among the three different AMF species used, <i>C. etunicatum</i> was found to be the most beneficial and suitable for the young mahogany seedlings. These seedlings also recorded higher root colonization percentage and total spore count in the rhizosphere soils. Seedlings inoculated with <i>C. etunicatum</i> showed positive influence on rate of photosynthesis, stomatal conductance, transpiration rate, chlorophyll content, relative growth rate (RGR) and water potential of seedlings.