A DBT supported multi-institutional research has found a method to speed up production of agarwood, a fragrant dark resinous wood used in incense and perfume, from Aquilaria trees.
Agarwood is a dark, resinous wood formed in the stem, branch of Aquilaria trees after they are wounded and infected by fungus. It is rare and very costly. Under natural conditions the wounds can be caused by wind, lightening strikes, the gnawing of ants or insects or microorganism invasion.
TERI has identified specific microbes that have capacity to induce production of agarwood through artificial infection methods. By using these organisms via methods developed by TERI, agarwood production could be induced in Aquilaria tree within 3 months of infection as against 30-50 years in natural infection conditions. Further work is in progress to optimize and validate the method during the second phase of the project.
Biosynthesis pathway decoded, which may help in studying defense mechanism of Agarwood of Aquilaria trees during infection. Chemical markers, which can be used for identification of infection in natural and artificially inoculated population, were also found by TERI.
To carry out the study more than 300 trees were selected from different villages of Assam and Arunachal Pradesh. Seeds were collected from these villages. These were sown in the nursery beds and poybags. About 15,000 seedlings were produced and 1300 seedlings were planted by SFRI, Itanagar. A total of 528 fungi and 279 bacteria were isolated from Aquilaria stem and surrounding soil samples collected from different sites of Assam and microbes with the capacity to induce infection were identified from among them.
Chemical markers were found by TERI based on GC-MS data, which can be used for identification of infection in natural and artificially inoculated population. The study helped understanding the mechanism of agarwood formation in wounded trees, which is crucial to establishing an efficient induction method for agarwood.
Further a large number of microsatellites (over 2200) containing sequences using next generation sequencing on Ion Torrent PGM platform were identified and developed. Thus, a large resource of molecular tools has now become available for application in genetic diversity and population mapping studies in Aquilaria.
Microsatellites are parts of genome, which have small repeats of 2-6 nucleotides (such as AGAGAGAGAG). These regions are highly variable among individuals and therefore, useful in study of genetic relatedness. The microsatellites are variable but their flanking regions are conserved. Therefore, diagnostic methods can be developed using the conserved regions flanking the microsatellites.
The study also found a high level of genetic diversity of Aquilaria from Assam to Arunachal Pradesh in contrast to earlier reports of low genetic diversity in Aquilaria in general. This underlined the importance of on farm conservation of Aquilaria in farmers’ plantations and home gardens and their sustainable utilization simultaneously.
A total of42 core accessions of Aquilaria has been identified for further utilization in multiplication and plantation by SFRI, Itanagar. Each individual tree that was selected for analysis of genetic diversity or relatedness is an accession. Core accessions are those, which contain all the genetic diversity of the original germplasm and are the main targets of future conservation.
The research also differentiated infected and normal Aquilaria plants in terms of differential gene expression. A numbers of differentially expressed Transcripts derived fragments (TDFs) were identified.
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