Revealing Genetic Diversity, Population Structure and Cultivar-Specific SSR Alleles in Pistachio Using SSR Markers

Pistachio (Pistacia vera L.) is the only cultivated species in Pistacia genus and one of the most important nut crop in terms of production. Pistachio cultivars have significant level of variation in their phenotypic appearance and productivity. Understanding the genetic diversity between pistachio cultivars could facilitate breeding programs. Simple sequence repeat (SSR) markers are powerful tools in genetic diversity and germplasm collection studies. However, published information about the characterization of large scale pistachio cultivar germplasm with adequate number of SSR markers is limited. In this study, sixty-six pistachio cultivars and genotypes originated from six different countries were characterized and fingerprinted by 74 genomic and 18 genic SSR markers. SSR analysis identified 576 alleles for all 66 cultivars and genotypes. The number of alleles per locus ranged from 2 to 20 (CUPOhBa1592) alleles with a mean value of six alleles per locus. The polymorphism information content (PIC) values ranged from 0.07 (CUPVEST2939) to 0.87 (CUPSiOh2460) with a mean PIC value of 0.58. The pistachio cultivars and genotypes were divided into five clusters according to Structure and UPGMA (Unweighted Pair Group Method with Arithmetic Average) analysis. Total of 61 cultivar specific alleles were detected in 34 cultivars, among them three primers (CUPOhBa1592, CUPBaPa1606 and CUPOhBa2127) produced more than four cultivar-specific loci therefore very promising for cultivar identification, fingerprinting and breeding studies in pistachio.

Genic microsatellite marker characterization and development in little millet (Panicum sumatrense) using transcriptome sequencing

Little millet is a climate-resilient and high-nutrient value plant. The lack of molecular markers severely limits the adoption of modern genomic approaches in millet breeding studies. Here the transcriptome of three samples were sequenced. A total of 4443 genic-SSR motifs were identified in 30,220 unigene sequences. SSRs were found at a rate of 12.25 percent, with an average of one SSR locus per 10 kb. Among different repeat motifs, tri-nucleotide repeat (66.67) was the most abundant one, followed by di- (27.39P), and tetra- (3.83P) repeats. CDS contained fewer motifs with the majority of tri-nucleotides, while 3′ and 5′ UTR carry more motifs but have shorter repeats. Functional annotation of unigenes containing microsatellites, revealed that most of them were linked to metabolism, gene expression regulation, and response to environmental stresses. Fifty primers were randomly chosen and validated in five little millet and 20 minor millet genotypes; 48% showed polymorphism, with a high transferability (70%) rate. Identified microsatellites can be a noteworthy resource for future research into QTL-based breeding, genetic resource conservation, MAS selection, and evolutionary genetics.

Assessment of Microsatellite Markers (SSRs) For Genetic Diversity in Asparagus Officinalis L. And Allied Species

The present study was hypothesized to evaluate a set of SSRs for the assessment of genetic variations in Asparagus officinalis L. and their allied species. Nine genic SSR markers were especially developed for Asparagus genome and employed for DNA profiling studies of Asparagus species. These SSRs markers have revealed the allelic polymorphism ranging from 1.0 to 2.0. Allele frequency was found highest for psbD-trnL (1.0), petB (1.0) and AG7 (1.0), while it was lowest for ZHD1 (0.1). Polymorphism Information content (PIC) was highest for TC7 (0.9) while it was lowest (0.0) for psbD-trnL, petB and AG7 respectively. The genetic similarity coefficients were found to range from 0.42 to 1.0. The UPGMA clustering algorithm based on SSRs data have clustered Asparagus species into 4 groups (I, II, III & IV) indicating Asparagus officinalis (L.) cultivars and allied species in the first clade, while Asparagus officinalis (L.) ‘Gersengum’, Asparagus densiflorus (Kunth) Jessop, and Asparagus racemosus willd. were clustered in separate clades respectively. The present study has endorsed the origin status of Asparagus officinalis and their allied species. A. officinalis cultivars and other allied Asparagus species are clustered in separate clades, and it was revealed that they have monophyletic origin. It was established that SSRs markers could be informative markers for the differentiation of Asparagus officinalis cultivars, and their allied Asparagus species. Bangladesh J. Bot. 50(3): 595-602, 2021 (September)

The Development of the Genic SSR Markers for Analysis of Genetic Diversity in Gooseberry Cultivars

Gooseberry is one of the most promising and underrated small fruit crops. There is a need to improve and genotype the existing cultivars, and this work requires the use of new efficient DNA marking techniques. Marker-assisted selection (MAS) is a modern approach for work with genetic resources. However, the genetic determinants of key qualitative traits are poorly studied. Therefore, we developed SSR markers located in flavonoid biosynthesis genes that can affect the resistance of plants to biotic and abiotic stresses to study the genetic diversity of gooseberry cultivars grown in the Russian Federation and varying in genetic and geographical origin. We have genotyped 22 gooseberry cultivars using a set of 19 of our original microsatellite markers and two neutral previously published ones. A total of 53 alleles were found. Nine of the 21 analyzed loci were polymorphic. The most polymorphic loci of flavonoid biosynthesis were found in the DFR gene (RucDFR1-2, RucDFR1-3, RucDFR2-1), their mean PIC (polymorphism information content) being 0.65, comparable to the PIC values of neutral markers. Our set of gene-targeted SSR markers showed that most of all the studied gooseberry cultivars differed in origin, based on which they were divided into three groups: European cultivars, Russian cultivars, and interspecies hybrids. Thus, the polymorphic markers can be used for cultivar identification and certification as well as for the marker-assisted selection of gooseberry plants having different origins and phenotypic traits.

Development of genic SSR marker resources from RNA-seq data in Camellia japonica and their application in the genus Camellia

Camellia is a genus of flowering plants in the family Theaceae, and several species in this genus have economic importance. Although a great deal of molecular makers has been developed for molecular assisted breeding in genus Camellia in the past decade, the number of simple sequence repeats (SSRs) publicly available for plants in this genus is insufficient. In this study, a total of 28,854 potential SSRs were identified with a frequency of 4.63 kb. A total of 172 primer pairs were synthesized and preliminarily screened in 10 C. japonica accessions, and of these primer pairs, 111 were found to be polymorphic. Fifty-one polymorphic SSR markers were randomly selected to perform further analysis of the genetic relationships of 89 accessions across the genus Camellia. Cluster analysis revealed major clusters corresponding to those based on taxonomic classification and geographic origin. Furthermore, all the genotypes of C. japonica separated and consistently grouped well in the genetic structure analysis. The results of the present study provide high-quality SSR resources for molecular genetic breeding studies in camellia plants.