Regenerative plantlets with improved agronomic characteristics caused by anther culture of tetraploid potato (Solanum tuberosum L.).

Objective: As the primary means of plant-induced haploid, anther culture is of great significance in quickly obtaining pure lines and significantly shortening the potato breeding cycle. Nevertheless, the methods of anther culture of tetraploid potato were still not well established. Methods: In this study, 16 potato cultivars (lines) were used for anther culture in vitro. The corresponding relation between the different development stages of microspores and the external morphology of buds was investigated. A highly-efficient anther culture system of tetraploid potatoes was established. Results: It was shown in the results that the combined use of 0.5 mg/L 1-Naphthylacetic acid (NAA), 1.0 mg/L 2,4-Dichlorophenoxyacetic acid (2,4-D), and 1.0 mg/L Kinetin (KT) was the ideal choice of hormone pairing for anther callus. Ten of the 16 potato cultivars examined could be induced callus with their respective anthers, and the induction rate ranged from 4.44% to 22.67% using this hormone combination. According to the outcome from the orthogonal design experiments of four kinds of appendages, we found that the medium with sucrose (40 g/L), AgNO3 (30 mg/L), activated carbon (3 g/L), potato extract (200 g/L) had a promotive induction effect on the anther callus. In contrast, adding 1 mg/L Zeatin (ZT) effectively facilitated callus differentiation. Conclusion: Finally, 201 anther culture plantlets were differentiated from 10 potato cultivars. Among these, Qingshu 168 and Ningshu 15 had higher efficiency than anther culture. After identification by flow cytometry and fluorescence in situ hybridization, 10 haploid plantlets (5%), 177 tetraploids (88%), and 14 octoploids (7%) were obtained. Some premium anther-cultured plantlets were further selected by morphological and agronomic comparison. Our findings provide important guidance for potato ploidy breeding.

Transcriptome Profiling of the Potato (Solanum tuberosum L.) Plant under Drought Stress and Water-Stimulus Conditions.

Drought stress can seriously affect tuberization, yield and quality of potato plant. However, the precise molecular mechanisms governing potato stolon's response to drought stress and water supply are not very well understood. In this work, a potato (Solanum tuberosum L.) variant, Ningshu 4, was subjected to severe drought stress treatment (DT) and re-watering treatment (RWT) at tuber bulking stage. Strand-specific cDNA libraries of stolon materials were constructed for paired-end transcriptome sequencing analyses and differentially expressed gene (DEG) examination. In comparison to untreated-control (CT) plants, 3189 and 1797 DEGs were identified in DT and RWT plants and 4154 solely expressed DEGs were screened out from these two comparison groups. Interestingly, 263 genes showed opposite expression patterns in DT and RWT plants. Among them, genes homologous to Protein Phosphatase 2C (PP2C), Aspartic protease in guard cell 1 (ASPG1), auxin-responsive protein, Arabidopsis pseudo response regualtor 2 (APRR2), GA stimulated transcripts in Arabidopsis 6 (GASA6), Calmodulin-like protein 19 (CML19), abscisic acid 8'-hydroxylases and calcium-transporting ATPase, et al. were related with drought-stress and water stimulus response. Sixteen DEGs involved in starch synthesis, accumulation and tuber formation exhibited significantly different expression upon re-watering. In addition, 1630, 1527 and 1596 transcription factor encoding genes were detected in CT, DT and RWT. DEGs of ERF, bHLH, MYB, NAC, WRKY, C2H2, bZIP and HD-ZIP families accounted for 50% in three comparison groups, respectively. Furthermore, characteristics of 565 gene ontology (GO) and 108 Kyoto Encyclopedia of Genes and Genomes pathways (KEGG) were analyzed with the 4154 DEGs. All these results suggest that the drought- and water-stimulus response could be implemented by the regulated expression of metabolic pathway DEGs, and these genes were involved in the endogenous hormone biosynthesis and signal transduction pathways. Our data provide more direct information for future study on the interaction between key genes involved in various metabolic pathways under drought stress in potato.