Enhancing Teak (Tectona grandis) Seedling Growth by Rhizosphere Microbes: A Sustainable Way to Optimize Agroforestry.

Leardwiriyakool Chaiya,Wasu Pathom-Aree,Neung Teaumroong,Saisamorn Lumyong,Rungroch Sungthong,Paiboolya Gavinlertvatana,Amornrat Chaiyasen

doi:10.3390/microorganisms9091990

Abstract

With its premium wood quality and resistance to pests, teak is a valuable tree species remarkably required for timber trading and agroforestry. The nursery stage of teak plantation needs critical care to warrant its long-term productivity. This study aimed to search for beneficial teak rhizosphere microbes and assess their teak-growth-promoting potentials during nursery stock preparation. Three teak rhizosphere/root-associated microbes, including two teak rhizobacteria (a nitrogen-fixing teak root endophyte-Agrobacterium sp. CGC-5 and a teak rhizosphere actinobacterium-Kitasatospora sp. TCM1-050) and an arbuscular mycorrhizal fungus (Claroideoglomus sp. PBT03), were isolated and used in this study. Both teak rhizobacteria could produce in vitro phytohormones (auxins) and catalase. With the pot-scale assessments, applying these rhizosphere microbes in the form of consortia offered better teak-growth-promoting activities than the individual applications, supported by significantly increased teak seedling biomass. Moreover, teak-growth-promoting roles of the arbuscular mycorrhizal fungus were highly dependent upon the support by other teak rhizobacteria. Based on our findings, establishing the synergistic interactions between beneficial rhizosphere microbes and teak roots was a promising sustainable strategy to enhance teak growth and development at the nursery stage and reduce chemical inputs in agroforestry.

Highlights

Based on morphological and genotypic characteristics of teak rhizobacteria used in this study (Table 1), they belong to the genera Agrobacterium and Kitasatospora
Teak growth and development were highly dependent on the interactions with its beneficial rhizosphere microbes
Our findings suggested that applying these microbes in the form of consortia could optimally promote teak growth and development compared to non-inoculated controls and other individual treatments

Summary

Introduction

Teak (Tectona grandis)—a sizeable deciduous dicot tree that belongs to the family. Verbenaceae—is an indigenous plant in South and Southeast Asia’s tropical and subtropical zones [1]. Over 29,000 million hectares of natural teak forest are in India, Laos, Myanmar, and Thailand [2]. The teak plantation area is around 4346 million hectares and accounts for a total of 38 countries, in Asia (83%), Africa (11%), and tropical America (6%) [2]. Thailand is among the top ten countries, holding the largest planting area of teak. In 2010, the United Nations’ Food and Agriculture Organization reported that Thailand’s natural teak

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