Genetic diversity studies in endangered desert teak [Tecomella undulata (Sm) Seem] using arbitrary (RAPD), semi-arbitrary (ISSR) and sequence based (nuclear rDNA) markers

Abstract

Tecomella undulata (Sm) Seem (family bignoniaceae) is a medicinally important agroforestry tree yielding quality timber commercially known as desert teak. This slow growing tree found in hot arid regions of western Rajasthan is used to treat various ailments and disorders. This monotypic genus with three colour morphotypes is also used for phytoremediation of soils, biosorptive removal of inorganic salts, synthesis of silver nanoparticles, rehabilitation of lignite mine backflls and as bio-fertilizer. This multifaceted tree is heading towards extinction due to over exploitation, unscientifc management and negligible plantation efforts. No initiatives have been undertaken to conserve, domesticate or genetically improve this pharmacologically important timber tree. An attempt was made to analyze the genetic variability existing in western Rajasthan, the natural hub of this species, using RAPD, ISSR and rDNA markers for the frst time. The RAPD markers (69.05%) detected polymorphism more efciently compared to ISSR (61.76%) among the 119 samples belonging to 22 populations. Likewise, average number of amplicons, polymorphic amplicons and polymorphism information content (PIC) were more for RAPD (11.25, 7.95 and 0.52, respectively) than for ISSR (10.4, 6.45 and 0.40) markers. The percent variability within and between populations varied among ISSR (64 and 36%, respectively) and RAPD (71 and 29%) markers. A positive correlation coefcient (r) of 0.402 was observed between RAPD and ISSR markers. The UPGMA dendrogram separated the samples into 13 (RAPD) and 11(ISSR) clusters with one out group each. At places, associations based on corolla colour, climatic, and geographical proximity were also recorded at subgroup levels. The single distinct amplicon (~ 650 bp) of 5.8S gene region showed a uniform nucleotide length of 163 bp for the conserved 5.8S rDNA region while length variations were for observed in ITS-1 (223 to 226) and ITS-2 (238 to 242) regions. The phylogram delineated the 23 samples into 5 major clusters. Sufcient genetic variability recorded vide this study was conserved (8.5 kg winged seed from 317 trees) under long-term storage facility to ensure availability for futuristic breeding and improvement programs.