Genetic variation associated with relative resistance in teak (Tectona grandis L. f.) against the leaf skeletonizer, Eutectona machaeralis Walker

Abstract

BackgroundPhotosynthesizing tissue of teak (Tectona grandis L. f.) foliage is damaged by a host-specific insect pest called leaf skeletonizer (Eutectona machaeralis Walker) that severely eclipses annual growth increment and carbon sequestration of natural populations and plantation of teak. Gene-assisted selection of relatively resistant teak clones may efficiently control the damage in the populations and plantations. The present investigation aimed to identify genetic variation associated with relative resistance in teak against the pest. MethodThe investigation was carried out on 106 teak plus tree clones assembled at the National Teak Germplasm Bank from the Indian meta-population of teak. Resistance data were obtained recording the ocular damage caused by the pest to teak accessions for four years. Genotyping of the teak accessions was performed with 21 co-dominant markers and marker-trait association mapping was performed confirming the genetic structure of the germplasm bank and linkage disequilibrium (LD) among the marker loci. ResultsThe sampled teak accessions exhibited a low albeit highly admixed genetic structure (FST=0.07) and low level of LD (16.66%) among loci, making them suitable for high-resolution association analysis. A significant correlation (p[≤]0.01, R2=0.67) was obtained between intra-specific heterozygosity and the relative resistance against the pest. A marker locus CCoAMT-1 representing the enzyme caffeoyl-CoA O-methyltransferase of phenylpropanoid pathway was also found significantly (p[≤]0.05) associated with the relative resistance against the pest explaining 6.6% of the phenotypic variation (R2=0.066) through positive effect (0.57) on the trait. ConclusionsThe present work exhibited a significant correlation of intra-specific heterozygosity with relative resistance in teak against a pest. It is the first report on teak identifying genetic markers associated with relative resistance against the pest. The marker can be applied for the selection of resistant planting stock for breeding and commercial plantation. Further investigation can be performed to understand the expression level polymorphism linked with the resistance applying next-generation sequencing approaches.