Mitochondrial Genome Recombination in Somatic Hybrids of Solanum Commersonii and S. Tuberosum

Interspecific somatic hybridization has been performed in potato breeding experiments to increase plant resistance against biotic and abiotic stress conditions. We analyzed the mitochondrial and plastid genomes and 45S nuclear ribosomal DNA (45S rDNA) for the cultivated potato (S. tuberosum, St), wild potato (S. commersonii, Sc), and their somatic hybrid (StSc). Complex genome components and structure, such as the hybrid form of 45S rDNA in StSc, unique plastome in Sc, and recombinant mitogenome were identified. However, the mitogenome exhibited dynamic multipartite structures in both species as well as in the somatic hybrid. In St, the mitogenome is 756,058 bp and is composed of five subgenomes ranging from 297,014 to 49,171 bp in St. In Sc, it is 552,103 bp long and is composed of two sub-genomes of 338,427 and 213,676 bp length. StSc has 447,645 bp long mitogenome with two subgenomes of length 398,439 and 49,206 bp. The mitogenome structure exhibited dynamic recombination mediated by tandem repeats; however, it contained highly conserved genes in the three species. Among the 35 protein-coding genes of the StSc mitogenome, 21 were identical for all the three species, and 12 and 2 were unique in Sc and St, respectively. The recombinant mitogenome might be derived from homologous recombination between both species during somatic hybrid development.

Drought and Saline Stress Tolerance Induced in Somatic Hybrids of Solanum chacoense and Potato Cultivars by Using Mismatch Repair Deficiency

Global climate change, especially when involving drought and salinity, poses a major challenge to sustainable crop production, causing severe yield losses. The environmental conditions are expected to further aggravate crop production in the future as a result of continuous greenhouse gas emissions, causing further temperature rise and leading to increased evapotranspiration, severe drought, soil salinity, as well as insect and disease threats. These suboptimal growth conditions have negative impact on plant growth, survival, and crop yield. Potato is well known as a crop extremely susceptible to drought, which is primarily attributed to its shallow root system. With potato being the fourth major food crop, increasing potato productivity is thus important for food security and for feeding global population. To maintain a sustainable potato production, it is necessary to develop stress tolerant potato cultivars that cope with the already ongoing climate change. The aim of our study is to analyze the response of potato somatic hybrids to drought and salt stress under in vitro conditions; the somatic hybrids studied are the wild relative Solanum chacoense (+) Solanum tuberosum, with or without mismatch repair deficiency (MMR). Upon this selection of drought and salt tolerant genotypes, somatic hybrids and their parents were phenotyped on a semi-automated platform, and lines tolerant to medium water scarcity (20% compared to 60% soil water capacity) were identified. Although none of the parental species were tolerant to drought, some of the MMR-deficient somatic hybrids showed tolerance to drought and salt as a new trait.

Analysis of Cytosine Methylation in Genomic DNA of Solanum × michoacanum (+) S. tuberosum Somatic Hybrids

Interspecific somatic hybridization is a noteworthy breeding strategy that allows the production of novel genetic variability when crossing barriers exist between two parental species. Although the genetic consequences of somatic hybridization have been well documented, little is known on its impact at the epigenetic level. The objective of our research was to investigate the epigenetic changes, in particular DNA methylation, occurring in a population of potato somatic hybrids. The analysis of 96 Solanum × michoacanum (+) S. tuberosum somatic hybrids from five fusion combinations and their parents was carried out by methylation-sensitive amplified polymorphism (MSAP) and high-performance liquid chromatography (HPLC) methods. Six MSAP primer combinations generated 622 unique bands, of which 295 were fully methylated. HPLC analysis showed from 15.5% to 16.9% total cytosine methylation within the parental forms. Overall, the MSAP and HPLC methods indicated an increase in DNA methylation in the somatic hybrids in comparison to their parents. Among the latter, a lower degree of DNA methylation in the wild S. × michoacanum species than S. tuberosum was found. Our findings indicated that somatic hybridization changed the level of cytosine methylation in the studied potato somatic hybrids.

Interspecific Potato Somatic Hybrids Between Solanum Malmeanum and S. Tuberosum Provide Valuable Resources for Freezing-Tolerance Breeding

Freezing stress affects the geographic distribution, growth, and development of potato, resulting in loss of its yield. Solanum malmeanum , a diploid wild species with strong freezing tolerance, was fused with a freezing sensitive dihaploid S. tuberosum by somatic hybridization. In our study, 980 calli were obtained, and 248 differentiate shoots from the calli. Parental-specific SSR markers were used to analyze the chromosome composition of the randomly selected 80 regenerated plants, resulting in 51 somatic hybrids. Among them, 44 somatic hybrids were tested with ploidy analysis in the years 2016 and 2020. During subculture, the genomic ploidy levels changed due to the composition of the unstable chromosome in 56.82% of the somatic hybrids. Compared with the cultivated parent, somatic hybrids showed better freezing tolerance. After freezing-tolerant somatic hybrids were selected to backcross with cultivars, we obtained some valuable breeding resources with enhanced freezing tolerance while similar tuberization capacity close to cultivars. The correlation analysis shows that freezing tolerance has no relation with tuberization capacity, which indicates that they are controlled by independent genetic loci. In all, we successfully conducted the protoplast fusion between S. malmeanum and S. tuberosum for the first time, which provided valuable resources for freezing-tolerant breeding.

Study on Artificial Seeds of Plants

The establishment and development of artificial seed technology is to quickly reproduce excellent varieties or hybrids, which can be applied to hybrid generation seeds produced by the three-two line method. For some varieties that are difficult to propagate with seeds or plant species with unstable genetic traits and poor fertility, artificial seed technology can also be used for mass reproduction. In particular, some new plants created through genetic engineering, such as somatic hybrids or transgenic plants, can be propagated or maintained by artificial seed technology. In addition, artificial seed technology can be used for the maintenance and rapid propagation of virus-free seedlings. Compared with ordinary test tube seedlings, artificial seeds have low cost, convenient transportation, and to a certain extent reduce vitrified seedlings. In particular, the production of artificial seeds does not occupy a large amount of soil. It can be produced all year round. Therefore, the research on artificial seeds has developed rapidly in the world.

KANDUNGAN FENOL DAN LIGNIN TANAMAN NILAM HIBRIDA (Pogostemon sp.) HASIL FUSI PROTOPLAS

<p><strong>Evaluation of phenols and lignin in the root of hybrid patchouli (Pogostemon cablin Benth.) front protoplast fusion</strong></p><p>One of the problems faced in patchouli production is nematode infection (Pratylenchus brachyurus). Improvement of the plant resistance to nematode in patchouli is dificult 10 be conducted through conventional method as the plant never llowcrs. One of the methods of improving (he plain resistance is by using protoplast fusion of Aceh patchouli (Pogostemon cablin, cv Sidikalang ) and Java patchouli (/' heyneanus. cv (iirilaya). It has been found thai Ihe plain resistance lo nematode is closely related to phenols and lignin content of the root Therefore. Ihe level of resistance of different clones of somatic hybrids lo nematode was approached by evaluating ihe content of phenols and lignin of the roots The study was conducted al the laboratory of the Research Institute for food Crop Biotechnology, Bogor in November 2000. Phenol content was determined with high performance liquid Chromatography (IIPI.C). while lignin content was determined with Klasou method. Result showed that Java patchouli (Girilaya) contained phenols and lignin respectively 76.53 and 21 900 pp. higher than those of Aceh patchouli (Sidikalang and Tapak Tuan) respectively 38 2-81 45 and 8 000-7 200 ppm. Phenol and lignin content in the somatic hybrids were dilferenl in Ihe respective pairs. In the fusion of Girilaya x Sidikalang. all clones contained phenol lower than those of Iheir parents, some clones (29%) contained lignin higher than Sidikalang but lower than (iirilaya. and the rest (71%) contained lignin lower than the two parents. Meanwhile, from Ihe fusion of Girilaya, Tapak Tuan. I clone (4%) contained phenols higher than those of (he two parents (97 ppm). 39% contained phenols higher than Tapak Tuan but lower than Girilaya (38.75-60.12 ppm) and the rests (60%) contained phenol lower than the two parents. Furthermore, the lignin content, of 78% somatic hybrids was lower than Girilaya but higher than Tapak Tuan, but the rest (22%) was lower than the two parents. Based on the distribution of phenols and lignin content. Ihe somatic hybrids can be categorized in three group The irst groups (5 clones) contained high phenols (higher than the average). Ihe second group (9 clones) contained high lignin. and Ihe third (I clone) contained high phenol and lignin.</p>