Sweet cucumber (Solanum muricatum) sect. Basarthrum, is a neglected horticultural crop native of the Andean region. It is naturally distributed very close to potatoes (Solanum sect. Petota) and tomatoes (Solanum sect. Lycopersicon), two groups of high economic importance. To date, molecular tools for this crop are still undetermined. We here obtained the first complete chloroplast (cp) genome of sweet cucumber and compared with seven Solanaceae species. Pair-end clean reads were obtained by PE 150 library and the Illumina HiSeq 2500 platform. The complete cp genome of S. muricatum had a 155,681 bp with typical quadripartite structure, containing a large single copy (LSC) region (86,182 bp) and a small single-copy (SSC) region (18,360 bp), separated by two inverted repeat (IR) regions (25,568 bp). The annotation of chloroplast genome predicted 88 protein-coding genes (CDS), 8 ribosomal RNA (rRNA) genes, 37 transfer RNA (tRNA) genes, and one pseudogene. A total of 48 perfect microsatellites were identified, divided in mononucleotide repeats (32), followed by tetranucleotide (6) and dinucleotides (5). SSRs with trinucleotides repeats (3), pentanucleotide (1) and hexanucleotide (1) repeats motifs in these genomes were identified in lower quantity. Most of these repeats were distributed in the noncoding regions. Whole chloroplast genome comparison with the other seven Solanaceae species revealed that the small and large single copy regions showed more divergence than inverted regions. Finally, phylogenetic analysis resolved that S. muricatum is a sister species to members of sections Petota + Lycopersicum + Etuberosum. This study reports for the first time the genome organization, gene content, and structural features of the cp genome of S. muricatum. Also, this study may provide the basis for evaluating genetic diversity within Solanum, and will be useful to examine the evolutionary processes in sweet cucumber landraces.

Screening of pollen traits in diploid wild potatoes (Solanum sect. Petota, Solanaceae) is desirable to develop heat-tolerant potato (S. tuberosum) cultivars. To accomplish this goal requires exploring potato genetic resources that are conserved in genebanks. The goal of this study was to assess pollen viability and 2n pollen production of the diploid potato wild relatives under heat stress condition. We assessed pollen viability and size of nine potato accessions conserved at the Embrapa Potato Gene Bank, including S. chacoense (BRA 00167447-2, BRA 00167017-3, BRA 00167023-1, BRA 00167028-0), S. commersonii (BRA00167007-4, BRA00167420-9, BRA00183760-8), and S. malmeanum (BRA 00183755-8), along with a control accession from the cultivated species S. tuberosum (BRA 00167251-8). The plant accessions were cultivated in different growth chambers, simulating both control temperature (ranging from 14 to 27°C) and supraoptimal temperature conditions (ranging from 24 to 34°C). At heat stress, the accessions BRA 00167251-8 did not bloom, and BRA 00167023-1 did not produce pollen. The remaining accessions did not exhibit a significant reduction in pollen viability as the temperature increased. Pollen viability at the control temperature had the lowest value in BRA-00167420-9 (S. commersonii) with 68.5% and the highest in BRA 00183755-8 (S. malmeanum) with 100%. At the supraoptimal temperature the lowest value was in BRA 00167420-9 (S. commersonii) with 54.5% and the highest in BRA 00183755-8 (S. malmeanum). The average of pollen size was 20 μm in all wild potato genotypes, and the increase of temperature did not lead to 2n pollen production. Estimated Genotypic Coefficient of Variation (GCV) was lower than Phenotypic Coefficient of Variation (PCV) for pollen viability. The observed heritability values ranged from 58.82% in BRA00167007-4 to 91.32% in BRA 00183755-8. Our results highlight the genetic variability available in wild potato germplasm concerning pollen viability under heat stress. Furthermore, these first insights offer valuable guidance for ongoing and future endeavors in diploid potato breeding.

The goal of germplasm enhancement is to introgress traits from wild crop relatives into cultivated material and eventually cultivars. It seeks to restore genetic diversity that has been lost over time or to augment cultivated material with novel alleles that improve parents in breeding programs. This paper discusses potato germplasm enhancement efforts in the past, focusing on effective examples such as disease resistance and processing quality. In addition, it outlines new strategies for enhancement efforts, shifting the focus from evaluating phenotypes to tracking and manipulating specific DNA sequences. In the genomics era, germplasm enhancement will increasingly be focused on identifying and introgressing alleles rather than traits. Alleles will come from a broad pool of genetic resources that includes wild species relatives of potato, landraces, cultivated potato itself, and distantly related species. Genomics tools will greatly increase the efficiency of introgressing multigenic traits, and will make it possible to identify rare alleles and utilize recessive alleles.

Within the family Solanaceae, Withania is a small genus belonging to the Solanoideae subfamily. Here, we report the de novo assembled, complete, plastomed genome sequences of W. coagulans, W. adpressa, and W. riebeckii. The length of these genomes ranged from 154,198 base pairs (bp) to 154,361 bp and contained a pair of inverted repeats (IRa and IRb) of 25,027--25,071 bp that were separated by a large single-copy (LSC) region of 85,675--85,760 bp and a small single-copy (SSC) region of 18,457--18,469 bp. We analyzed the structural organization, gene content and order, guanine-cytosine content, codon usage, RNA-editing sites, microsatellites, oligonucleotide and tandem repeats, and substitutions of Withania plastid genomes, which revealed close resemblance among the species. Both the substitution and insertion and deletion analyses confirmed that the IR region was significantly conserved compared with the LSC and SSC regions. Further comparative analysis among the Withania species highlighted 30 divergent hotspots that could potentially be used for molecular marker development, phylogenetic analysis, and species identification.