Genetic diversity and the origin of commercial plantation of Indonesian teak on Java']Java Island

Teak (Tectona grandis) has been widely planted in 70 tropical countries because of the utility and value of its wood. This species was introduced to Indonesia more than 100 years ago, and large plantations-covering 1.2 million ha-can be found on Java Island. However, little information currently exists about the genetic diversity and origin of these trees. We collected plant materials from three regions across Java Island (east, central, and west) and sampled trees spanning three age classes in each region, to clarify the genetic diversity and structure of teak plantations on Java Island. We investigated teak plantation and clonal experiment populations using multiplexed ISSR genotyping by sequencing (MIG-seq) and compared the genetic diversity and structure with the provenance test populations derived from natural teak forest in India, Myanmar, Thailand, and Laos. Analyses using 459 single-nucleotide polymorphism (SNP) loci revealed that native provenances had higher genetic diversity than the Indonesian teak plantations. Moreover, old teak plantations demonstrated lower genetic diversity than young plantations. Further analyses showed that most Indonesian teak plantations are genetically related to Laos, Thailand, and Myanmar provenances. We conclude that there is a weak genetic structure on teak plantations among the regions, which indicates that most plantations were established using plant materials from a specific part of the natural teak distribution. Information regarding the genetic diversity and structure of plantation forests should be taken into account when making future plantation programs.