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

Abstract

Research Highlights: Drought stress significantly decreased the performance of seedlings in the nursery. Seedlings inoculated with Claroideoglomus etunicatum is recommended to produce superior planting stock of mahogany seedlings with better drought resistance in the nursery. Background and Objectives: 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. Swietenia macrophylla, 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 Funneliformis mosseae, Claroideoglomus etunicatum, and Rhizophagus intraradices. Materials and Methods: 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. Results: 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. Conclusions: Among the three different AMF species used, C. etunicatum 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 C. etunicatum showed positive influence on rate of photosynthesis, stomatal conductance, transpiration rate, chlorophyll content, relative growth rate (RGR) and water potential of seedlings.

Fungal diversity and colonization in roots seed trees of Swietenia macrophylla King (Magnoliophyta: Meliaceae) in the tropical rainforest of Laguna Om, Quintana Roo, Mexico

“…Meanwhile, colonization between 30% and 69.3% was reported from plantations of introduced populations of mahogany in Southeast Asia (Shi et al, 2006;Mridha & Dhar, 2007;Dhar & Mridha, 2012;Nandi et al, 2014) and 53.2% was noticed on mahogany plants after two years in Costa Rica (Holste & Kobe, 2017). A pot experiment found a percentage of root colonization between 27.4% and 44.9% according to AMF inoculation after 180 days (Rajan et al, 2020). Our findings show different percentages of root colonization in mahogany compared to previous works, where they have studied various environments such as natural and introduced populations (Shi et al, 2006;Mridha & Dhar, 2007;Rajan et al, 2020).…”

“…Certain species in this family have been shown to be easily propagated in trap cultures, which can be used to obtain inoculum for commercial forest plants (Schüßler et al, 2016). The interaction between these species and mahogany seedlings has been demonstrated to improve their relative growth rate and water potential, both of which are key factors in increasing seedling survival in commercial plantations and restoration programs (Rajan et al, 2020). The first step in this process is to isolate the AMF from seed tree stands in conserved and natural populations of mahogany, and then to test the different effects of single AMF species or consortia in controlled environments (Holste & Kobe, 2017).…”

Crecimiento y desarrollo fotosintético de Swietenia mahagoni en sustratos inoculados con micorrizas arbusculares

“…Ramírez et al (2018) señalan que la actividad y el beneficio de la simbiosis son más visibles cuando estos se encuentran en suelos deficientes en fósforo. En esta condición, plantas de Swietenia macrophylla inoculadas con hongos micorrízicos arbusculares (HMA) presentaron mayores tasas de crecimiento, obtenidas en una casa de cultivo en la Universidad Agrícola de Kerala, India (Rajan et al 2020).…”

“…Estudios previos en especies forestales tropicales han demostrado que la actividad fotosintética aumentada de las plantas con HMA podría deberse a factores no estomáticos como un mayor contenido de clorofila y de actividad de rubisco (Uc-Ku et al 2019). Por su parte, Rajan et al (2020) señalaron que los HMA inoculados en S. macrophylla no solo incrementaron la tasa fotosintética, sino que también originaron una mayor transpiración y conductancia estomática, lo que es benéfico para el crecimiento de los cultivos y posterior desarrollo en el campo.…”

“…En este estudio se encontró que a los 120 días, la tasa fotosintética en los tratamientos micorrizados fue significativamente mayor que en los no micorrizados. Un comportamiento similar observó Rajan et al (2020) en plantas de S. macrophylla, cultivadas en el vivero forestal de la Universidad Agrícola de Kerala, India, donde se inoculó la especie con hongos micorrízicos, el cual mejora la supervivencia y crecimiento de las plantaciones, al proveer de buenas condiciones iniciales a las plántulas.…”