Glycoalkaloids of Solanum Series Megistacrolobum and related potato cultigens

Glycoalkaloids were used as evidence of the affinities of nine taxa of Solanum Series Megistacrolobum and related potato cultigens from western Bolivia. S. boliviense, S. sanctae-rosae and S. toralapanum contain the commertetraose sugar moiety and appear to represent a relatively wild group within the Series. S. megistacrolobum, S. sogarandinum and S. raphanifolium show anomolous glycoalkaloid profiles that probably reflect hybridization associated with human disturbance. Primitive forms of the S. χ ajanhuiri cultigen are indistinguishable chemicaliy from conspecific weeds that were previously classified as S. megistacrolobum. Variation in total glycoalkaloid content within Series Megistacrolobum likely reflects direct selection by humans for reduced glycoalkaloid levels during the domestication process.     

Molecular changes associated with tuberisation in Solanum tuberosum. Differential expression of α-tubulin isotypes

Changes in gene expression that occur in the stolon tips of potato ( Solanum tuberosum L.) cv. Record during tuberisation were investigated. Protein extracts from stolon tips at various stages in the tuberisation process were analysed by two-dimensional gel electrophoresis. A number of quantitative and qualitative changes in polypeptide composition accompanied the very early stages of tuberisation. In vitro translation of RNA extracted from stolon tips also revealed quantitative and qualitative changes associated with tuberisation. Immunoblotting of protein extracts with monoclonal antibodies raised against α- and β-tubulin showed quantitative changes in the relative level of β-tubulin, but not α-tubulin, as the stolon tips tuberised. Changes in the pattern of α-tubulin isotype expression were shown to occur at early stages in the tuberisation process.     

In vitro organogenesis and plant regeneration from leaves of Solanum candidum Lindl,S. quitoense Lam. (naranjilla) and S. sessiliflorum Dunal

Adventitious shoots and roots were regenerated from leaf segments of 3 Solanum species: S. candidum Lindl., S. quitoense Lam. and S. sessiliflorum Dunal. Leaf explants differentiated shoots on modified MS medium supplemented with 23–163 M kinetin and 0–5.7 µM indoleacetic acid (IAA). Excised shoots were induced to form roots by transfer to media with benzyladenine (BA) and naphthaleneacetic acid (NAA) at 0.09 and 0.11 µM respectively for S. quitoense and 0.01 µM NAA for S. candidum and S. sessiliflorum. Adventitious roots were produced directly from leaf explants with 0–140 µM kinetin and 0–5.7 µM IAA in combination. Rooted plants were successfully established in the greenhouse.     

The regulation of respiration and growth of potato tuber callus by endogenous ethylene. Suppression of ethylene action by 2,5-norbornadiene

The growth (fresh and dry weight increase) of potato tuber ( Solanum tuberosum L. cv. Bintje) callus discs was stimulated by incubation in air with 500 ppm 2,5-norbornadiene (NBD, a competitive inhibitor of ethylene action) and inhibited by incubation in air with 4 000 ppm NBD. Ethylene formation by the callus was stimulated by NBD. The development of the alternative pathway, measured in isolated mitochondria was inhibited by NBD in a concentration-dependent way. The alternative pathway capacity, measured in vivo, was inhibited by 4 000 ppm NBD, but not by 500 ppm. Uninhibited in vivo respiration, which consists of cytochrome path activity and alternative path activity, was stimulated by the treatment with 500 ppm NBD. The main contribution to this stimulation was made by the cytochrome pathway. In 4 000 ppm NBD-treated callus, uninhibited respiration seemed to be unaffected as a consequence of an inhibited cytochrome path activity, which was compensated by a stimulated alternative path activity. Both in 500 and 4 OIK) ppm NBD-treated callus the alternative path activity in vivo was stimulated.
The regulatory role for endogenous ethylene in potato tuber callus is discussed in relation to: 1) The induction of respiratory pathways, 2) the supply of reduction equivalents in vivo and 3) growth.     

Alteration of growth ofSolanum opacum andPlantago drummondii and inhibition of regrowth of hyphae of vesicular-arbuscular mycorrhizal fungi from dried root pieces by manganese

Addition of MnSO₄ or MnCl₂ to a fine sandy soil from South Australia had a negative effect on shoot growth and root elongation ofSolanum opacum in the absence of significant presence of vesicular-arbuscular mycorrhiza (VAM). VAM ameliorated the reduction of plant growth by Mn, even though mycorrhizal development was decreased. Mn inhibited infection of roots by a fine endophyte less than that by some coarse endophytes. High concentrations of available Mn inhibited growth of hyphae of VAM fungi from dried root pieces, a significant source of infection by mycorrhizal fungi in the soil used.     

Herbicide tolerant regenerates of potato

Summary Culture-derived plants and cell cultures of potato (Solanum tuberosum L.) respond to the application of the herbicides SYS 67 ME (MCPA) and OMNIDEL (Na-2,2-dichloropropionate) in a comparable fashion. By gradually increasing the herbicide concentration, cell lines were developed which tolerated 50 mg/l of ME or 300 mg/l of OMNIDEL. Any further increase in concentration resulted in the death of all cell cultures. From cell cultures that had been able to grow on media supplemented with 30 mg/l of ME, regenerate plants were obtained that were also tolerant to this concentration. This new trait was retained even after repeated vegetative propagation of the plants.     

Isolation of an amylose-free starch mutant of the potato (Solanum tuberosum L.)

Summary An amylose-free potato mutant was isolated after screening 12,000 minitubers. These minitubers had been induced on stem segments of adventitious shoots, which had been regenerated on leaf explants of a monoploid potato clone after Röntgen-irradiation. The mutant character is also expressed in subterranean tubers and in microspores. Starch granules from the mutant showed a strongly reduced activity of the granule bound starch synthase and loss of the major 60 kd protein from the starch granules.     

Differential expression within a family of novel wound-induced genes in potato

Summary Wounding in higher plants leads to an increased synthesis of specific messenger RNAs. A cDNA clone complementary to a wound-induced message from potato tubers was used to isolate a lambda clone from a genomic library of Salanum tuberosum var. Maris Piper. DNA sequence analysis has shown that this single genomic clone contains two novel wound-induced genes, called win1 and win2, organised in close tandem array. The coding sequences of these two genes are highly homologous and are interrupted by a single intron. However, the sequences of the introns and flanking regions have diverged widely. Win1 and win2 encode cysteine-rich proteins of 200 and 211 amino-acids, respectively, which show striking homologies to several chitin-binding proteins. Southern analysis of genomic DNA has shown that win1 and win2 are members of a small multi-gene family which is estimated to have a minimum of five members per haploid genome of Maris Piper and appears to be conserved within the Solanaceae. We have shown by Northern analysis and S1 mapping that the two genes exhibit differential organ-specific expression after the wounding of a potato plant.     

Selection of somatic hybrids between diploid clones of potato (Solanum tuberosum L.) transformed by direct gene transfer

Summary Five diploid potato clones have been transformed by electroporation of protoplasts with different selectable markers. The resulting diploid regenerated plants have been used in somatic hybridization. It has been shown that hybrid cell selection on the basis of antibiotic or herbicide resistances brought by the two parents of fusion is an efficient method for the recovery of tetraploid somatic hybrids.     

Effect of maltose on the response of potato anthers in culture

Anthers of the Solanum tuberosum genotype H3703 were cultured on medium containing equimolar concentrations of sucrose or maltose. It was found that significantly more pollen embryos became plants after culture on maltose and hence the yield of plants per 100 anthers cultured increased significantly. Mechanisms by which carbohydrate source may influence response to anther culture are discussed.