Characterization of 17 novel microsatellite loci in the Nile monitor (Varanus niloticus) via 454 pyrosequencing

We used 454 pyrosequencing to characterize 17 novel microsatellite loci from the Nile monitor (Varanus niloticus), using samples from an invasive population in the US state of Florida. These markers were screened for variation in 40 individuals from the City of Cape Coral. Observed heterozygosity ranged from 0.18 to 0.73 (mean ± SE = 0.46 ± 0.06) and the number of alleles per locus ranged from 1 to 4 (mean ± SE = 2.5 ± 0.2). Preliminary genotyping of samples from populations in West Palm Beach and Homestead revealed two loci (Mon6andMon15) that are monomorphic in Cape Coral, but polymorphic in these other two populations. We found no statistical departures from Hardy-Weinberg equilibrium or evidence of null alleles. However, there was statistical evidence for genotypic disequilibrium betweenMon1-Mon14andMon3-Mon8. BLASTn searches of NCBI’s nr/nt database identified four microsatellites containing 454 fragments that exhibit substantial sequence similarity to loci in other reptilian genomes, suggesting these markers should be prioritized by researchers interested in cross-amplification in other varanids. The resources we have developed will enable investigations of the population genetic dynamics of invasive Nile monitors in Florida and may facilitate studies within this species native range.

Characterization of 14 novel microsatellite loci in the Argentine black and white tegu (Salvator merianae) via 454 pyrosequencing

We have developed 14 novel microsatellite loci for the Argentine black and white tegu (Salvator merianae), using samples from invasive populations from the US state of Florida. Pyrosequencing was used to identify 3154 potentially amplifiable microsatellite loci and to subsequently develop 14 informative markers. These 14 markers were screened for variation in 40 individuals from Miami-Dade County, Florida. All loci were polymorphic and contained between 2 and 4 alleles per locus (mean ± SE = 2.71 ± 0.24), with observed heterozygosity ranging from 0.00 to 0.88 (mean ± SE = 0.38 ± 0.07). Four of the loci (Teg4, Teg5, Teg17, Teg19) significantly deviated from Hardy-Weinberg proportions and three of these loci (Teg4, Teg5, Teg19) showed evidence of null alleles. In addition, there was statistical evidence for genotypic disequilibrium between Teg14 and Teg19. BLASTn searches of NCBI’s ‘nr/nt’ database using microsatellite containing 454 fragments as queries were largely uninformative; however, it is likely that some of these markers will be of utility in S. merinae’s native range.

Investigating the Mendelian inheritance, genetic linkage, and genotypic disequilibrium for ten microsatellite loci of Araucaria angustifolia

Araucaria angustifolia is a dioecious and wind pollinated conifer that typically occurs in higher attitudes of Southern Brazil. After a significant reduction of its population during the twentieth century, public policies have enabled natural populations to recover. As new studies focus on the genetics of the species it is important to investigate Mendelian inheritance, genetic linkage, and genotypic disequilibrium for the microsatellite loci developed for the species. Here we analyze ten microsatellite loci developed for A. angustifolia by genotyping 295 adult trees and 13 open pollinated progenies from a forest fragment in Santa Catarina, Brazil. The likelihood G-test shows a perfect 1:1 Mendelian segregation for all ten loci, indicating that these molecular markers are genetic markers. Significant genetic linkage between pairwise loci was detected in only 3% of the tests, suggesting that these loci are not located in the same linkage groups within the chromosomes. However, genotypic disequilibrium was detected in 51% of pairwise loci for adult trees, probably due to the strong spatial genetic structure of the population. Our results indicate that the ten loci analyzed can be used in studies on genetic diversity and structure, mating system, and gene flow of the species.

Population structure of Sclerotinia sclerotiorum in an Australian canola field at flowering and stem-infection stages of the disease cycle

Populations of the ascomycete pathogen Sclerotinia sclerotiorum sampled from a canola field were analysed using microsatellite markers. Fifty isolates were collected from ascospore-infested canola petals and, later in the season, another 55 isolates were obtained from stem lesions; these isolates were used to compare inoculum and disease-causing populations. Fifty-five unique haplotypes were identified, with gene diversity ranging from 0.40 to 0.71. Genotypic diversity was higher in the inoculum population than it had been in the previous year, but analysis of molecular variance (AMOVA) showed that less than 10% of the variation was attributable to differences between the 2 years. Genotypic disequilibrium measures were consistent with the occurrence of both clonal reproduction and out-crossing. There was no significant population subdivision between the ascospore and stem-lesion populations, as measured with fixation indices (RST = 0.015, p = 0.90) and AMOVA, suggesting that there are no genetically defined subgroups of isolates more likely to proceed from petal colonization to cause stem infection. This might be because S. sclerotiorum possesses wide-ranging pathogenicity mechanisms that account for the lack of host specificity observed to date.