Analysis of genetic diversity of Cucurbita moschata (D.) germplasm accessions from Mesoamerica revealed by PCR SSCP and chloroplast sequence data

Abstract

The aim of this research was the genetic characterization of 218 accessions of Cucurbita moschata Duchesne, a squash, and its relationship with morphological characteristics of agronomic interest, which are part of the international collection conserved at Tropical Agricultural Research and Higher Education Center (CATIE), Costa Rica. The majority of the accessions came from Mexico and Central America; single genotypes from Curaao, Colombia, Peru and the Russian Federation were also included. The polymerase chain reaction (PCR) and single strand conformation polymorphism analysis (SSCP) were used for the analysis of the regions amplified with ITS1-ITS2 nuclear primers and tRNL-F chloroplast primers. Haplotypes were constructed according to band patterns in SSCP gels. Twenty-five haplotypes were found using the ITS1-ITS2 markers, and 24 haplotypes were found with the tRNL-F markers. Unique haplotypes were found with both markers. Two individuals of each tRNL-F haplotype were sequenced. The results indicated a high level of genetic diversity in CATIE squash collection. Using ITS1-ITS2 primers, it was found that the number of haplotypes was independent of the geographical source of the accession, and haplotypes were distributed randomly throughout the study area. Mexico had the highest values of total heterozygosity (HE), genetic diversity (H) and Shannon index (I) while Panama showed the lowest values. Sequences obtained from tRNL-F intergenic marker showed the highest diversity index values were present in the group of additional sequences and Mexico, and lower values were observed for Nicaragua, Guatemala and Panama. PCoA based on morphological data showed three groups and by ANOSIM (R) all group differences were significant. Results obtained in this study suggest that high diversity is a characteristic of C. moschata from Mesoamerica.

Genetic diversity in Cucurbita pepo landraces revealed by RAPD and SSR markers

“…However, C. pepo distributed in different districts of KwaZulu-Natal with long geographical distance, had a very low possibility of the pollen spread by bees between populations. Therefore the main way of gene exchanges was probably enhanced by seed exchanges between farmers of different districts in KwaZulu-Natal, which agrees with the reports of Barboza et al (2012); Du et al (2011) and Mujaju et al (2010). The Nei's gene diversity index (H = 0.1506 and 0.0675), Shannon's information index (I = 0.2829 and 0.1454) and the genetic diversity index within populations (H S = 0.1499 and 0.0672), as revealed by RAPD and SSR markers, respectively, also indicate molecular genetic diversity for the C. pepo populations studied herein.…”

Genetic diversity in Cucurbita pepo landraces from northern KwaZulu-Natal, South Africa, revealed by random amplified polymorphic DNA (RAPD) markers

“…The same was reported earlier by other researchers in cucurbits (Montes-Hernandez and Eguiarte, 2002;Ferriol et al, 2004a;2004b;Barboza et al, 2012) and other species (Yuan et al, 2007).…”

“…The TS and TNS populations were the highest in genetic identity (I N = 0.9996) and the closest in the genetic distance (D = 0.0004), probably because they originate from the same district, but CPSP and TNS populations were the lowest in genetic identity (I N = 0.9985) and the furthest in genetic distance (D = 0.0015), because they were collected from distant geographical regions, where most of the farmers have maintained the productions of these landraces for many years. The same was reported among Punica granatum cultivars (Yuan et al, 2007), T. dioica accessions (Khan et al, 2009) and C. moschata accessions (Du et al, 2011;Barboza et al, 2012). However CPSP and MNS populations, both from Umkhanyakude district, were also the lowest in genetic identity (I N = 0.9985) and the furthest in genetic distance (D = 0.0015), possibly because CPSP populations do not change fruit colour to orange or yellow at maturity whereas MNS population do change.…”

“…Therefore the main way of gene exchanges can be occasional introduction of seeds as enhanced by seed exchanges between farmers of different districts in KwaZulu-Natal (Montes-Hernandez and Eguiarte, 2002;Ferriol et al, 2004a;2004b;Yuan et al, 2007;Mujaju et al, 2010;Du et al, 2011;Barboza et al, 2012).…”

“…This intercropping practice enhances the geneflow among the cucurbit species due to the random bee pollination (Cuevas-Marrero and Wessel-Beaver, 2008;Mujaju et al, 2010). Gene exchange among plant populations located in distant geographical areas can be influenced by occasional introduction of seeds and seedlings as well as informal seed exchanges among farmers (Yuan et al, 2007;Du et al, 2011;Barboza et al, 2012).…”