SPAR methods reveal high genetic diversity within populations and moderate gene flow of pointed gourd (Trichosanthes dioica Roxb.) germplasm

Pointed gourd (Trichosanthes dioica Roxb.) is one of the most nutritive cucurbitaceous vegetable crops cultivated in tropical and subtropical regions around the world. Poor characterization of the available germplasm, vegetative means of propagation and dioecy are the main constraints in developing a systematic breeding programme in pointed gourd. In this investigation, genetic variability of pointed gourd accessions belonging to four agro-climatic zones of Bengal region of India was evaluated by employing polymerase chain reaction (PCR) based single primer amplification reaction (SPAR) methods, viz., random amplified polymorphic DNA (RAPD), inter-simple sequence repeats (ISSR) and directed amplification of minisatellite DNA (DAMD). Percentage of polymorphic loci, Nei's gene diversity index (h) and Shannon's Information index (I) indicated a moderate level of genetic heterogeneity in studied germplasm. The mean coefficient of genetic differentiation (Gst) between populations for RAPD, ISSR and DAMD were 0.419, 0.305 and 0.315 respectively, indicating that 58.1%, 69.5% and 68.5% of genetic variability prevailed within the population. Similarly, analysis of molecular variance (AMOVA) revealed that majority of the genetic variation were partitioned among the individuals within a population. Gene flow estimate (Nm) calculated for RAPD, ISSR and DAMD marker were 0.692, 1.139 and 1.086 respectively indicating a moderate gene flow among the populations. The clustering pattern based on the combined marker systems was primarily related to the geographical distribution of the accessions. This study clearly demonstrates the efficiency of single primer based amplification reactions (SPARs) in duplicate identification, core collection and improvement of pointed gourd germplasm.