Growth and development temperature influences level of tolerance to high light stress

The influence of growth and development temperature on the relative tolerance of photosynthetic tissue to high light stress at chilling temperatures was investigated. Two tuber-bearing potato species, Solanum tuberosum L. cv Red Pontiac and Solanum commersonii were grown for 4 weeks, at either 12 or 24°C with 12 hours of about 375 micromoles per second per square meter of photosynthetically active radiation. Paired leaf discs were cut from directly across the midvein of leaflets of comparable developmental stage and light environment from each species at each growth temperature treatment. One disc of each pair was exposed to 1°C and about 1000 micromoles per second per square meter photosynthetically active radiation for 4 hours, and the other disc was held at 1°C in total darkness for the same duration. Photosynthetic tissue of S. tuberosum, developed at 12°C, was much more tolerant to high light and low temperature stress than tissue developed under 24°C conditions. Following the high light treatment, 24°C-grown S. tuberosum tissue demonstrated light-limited and light-saturated rates that were approximately 50% of their paired dark controls. In contrast, the 12°C-grown tissue from S. tuberosum that was subjected to the light stress showed only a 18 and 6% reduction in light-limited and light-saturated rates of photosynthetic oxygen evolution, respectively. Tissue from 24°C-grown S. commersonii was much less sensitive to the light stress than was tissue from S. tuberosum grown under the same conditions. The results presented here demonstrate that: (a) acclimation of S. tuberosum to lower temperature growth conditions with a constant light environment, results in the increased capacity of photosynthetic tissue to tolerate high light stress at chilling temperature and (b) following growth and development at relatively high temperatures S. commersonii, a frost- and heat-tolerant wild species, has a much greater tolerance to the high light stress at chilling temperature than does S. tuberosum cv Red Pontiac, a frost-sensitive cultivated species.     

Freezing injury in potato leaves

Time-temperature profiles of freezing leaves from frost-resistant (Solanum acaule Bitt.) and frost-susceptible (Solanum tuberosum L. subsp. tuberosum Hawkes) types of potatoes did not reveal any major differences. The pattern of change in resistance of leaves to low voltage, low frequency current during freezing was different in the frost-resistant and susceptible leaves. In tissue sections from both types of leaves, cells freeze extracellularly at cooling velocities lower than 5 C per minute. Cells from leaves of resistant plants showed a higher osmotic pressure but not a higher water permeability than those from susceptible plants. The extent of injury caused by even very slow freezing was greater than that caused by equivalent isopiestic desiccation, particularly in susceptible leaves. The higher osmotic pressure in cells of leaves from resistant plants can account for the greater desiccation resistance but not for the frost resistance observed.     

Assimilation of carotenoids with food by the beetle, Leptinotarsa decemlineata

The author investigated by means of columnar and thin-layer chromatography the carotenoids in the leaves of Solanum tuberosum L. and in larvae and adults of Leptinotarsa decemlineata.     

Joint Influence of Pratylenchus penetrans (Nematoda) and Leptinotarsa decemlineata (Insecta) on Solanum tuberosum Productivity and Pest Population Dynamics

The joint action of a plant parasitic nematode, Pratylenchus penetrans (root-lesion nematode), and an insect defoliator, Leptinotarsa decemlineata (Colorado potato beetle), on growth, development, and yield of Solanum tuberosum cv. Superior was studied in the field. Three population densities of P. penetrans were superimposed on each of three population levels of L. decemlineata. The major impact of P. penetrans on final yield was through a reduction in the number of tubers formed during tuber initiation. Defoliation by L. decemlineata increased with time as larvae advanced through successive instars and densities increased. This resulted in a significant reduction in tuber weight and numbers. Total yield of S. tuberosum was decreased by 66% with increasing population densities of L. decemlineata and 27 % with increasing densities of P. penetrans. L. decemlineata feeding did not affect soil population densities of P. penetrans. Root population densities of P. penetrans, however, were significantly (P = 0.05) higher in plants maintained beetle free than in plants grown in the presence of the beetles.     

Effects of 3,5-Dihalogenated-4-hydroxybenzonitriles on the Activity of Mitochondria From White Potato Tubers

Effects of the herbicide 3,5-diiodo-4-hydroxybenzonitrile (ioxynil), and its dibromo and dichloro analogs, upon the respiration of mitochondria isolated from white potato tubers (Solanum tuberosum L.) were investigated. Mitochondrial-mediated oxygen uptake was monitored polarographically with a platinum oxygen electrode.     

Studies on plant recovery from mesophyll protoplasts ofSolatium tuberosum L. andSolanum phureja Juj. et Buk

Plants were regenerated from mesophyll protoplasts of axenically growing plants of four dihaploid clones and five tetraploid cultivars ofSolanum tuberosum L. andSolanum phureja Juz. etBuk.     

Non-reversion of Impatiens in the absence of meristem commitment

Purple-flowered plants of Impatiens balsamina maintained floral development on transfer from inductive short days (SD) to long days (LD), a treatment in which red-flowered plants of Impatiens are known to revert to leaf production. An investigation into the non-reverting nature of purple-flowered plants was carried out to establish whether these plants achieved meristem commitment or whether their non-reverting state was controlled by the leaves. When the leaves that had unfolded during the inductive SD treatment were removed at the time of transfer to LD, the purple-flowered plant did revert. This result suggests that, as in red-flowered Impatiens, meristem commitment is absent, but that purple-flowered plants maintain flowering in LD conditions because of a more permanent supply of signal from their leaves than occurs in red-flowered plants. A working hypothesis is proposed to explain how a signal from the leaves can retain a controlling role during flower development.Key words: Floral commitment, Impatiens, floral reversion, floricaula.      

Temperature-induced fluorescence changes : a screening method for frost tolerance of potato (solanum sp.)

Field-grown tuber-bearing potatoes were screened for frost tolerance in a late stage of development. Three different clones of Solanum tuberosum L. and two interspecific crosses between clones of S. tuberosum and the wild potato species S. demissum Lindl. were studied. Two different methods were used. (a) Temperature-induced fluorescence changes of intact leaves were measured in freeze-thaw cycles between 20°C and −10°C. The variable fluorescence pattern was characterized in relation to frost tolerance. (b) Controlled freezings of plants in a climate chamber with successively increased low temperature stress, of 1 to 2 hours duration during the dark period. Freezing damages were classified visually.     

Potato tuber callus: validation as a biochemical tool

Callus was initiated from explants of tubers of the Norchip cultivar of Solanum tuberosum L. and grown on medium with a single carbon source and without addition of coconut milk, protein hydrolysate, or amino acid. Callus samples were harvested at intervals and compared to mature tubers for which there was good biochemical knowledge.     

Unexpected synchronous differentiation in Mediterranean and Canarian Cistus (Cistaceae)

Diversification rates of insular oceanic lineages have been historically considered to be higher than those of mainland counterparts. In order to test this hypothesis in a group of Canarian endemics (Cistus), we estimated phylogeny and conducted both network analyses of haplotypes and molecular clock estimates using plastid DNA sequences of the trnS?trnG and the trnK?matK. Net differentiation rates in the Canarian purple-flowered lineage parallel those of the mainland (Mediterranean) purple-flowered sister group, as revealed by a similar number of species (five vs. three), haplotypes (seven vs. eight) and haplotype clades (four vs. four). Splitting dates in the Canarian (0.33±0.14/0.28±0.16 Ma) and Mediterranean (0.66±0.18/0.38±0.19 Ma) lineages reveal concordance in tempo of diversification. All these results are interpreted as evidence of two synchronous evolutionary histories given that Cistus ancestors had to cope with factors promoting differentiation in two hotspots of plant diversity: the Macaronesian and Mediterranean floristic regions. Analysis of Canarian populations suggests that a geographical rather than ecological differentiation was primarily responsible for early stages of a non-adaptive radiation of the Canarian lineage. Differentiation patterns of mainland populations appear to be more complex.     

Application of somatic hybrids between dihaploids of potato Solanum tuberosum L. and wild diploid species from Mexico in breeding: Generation and backcrossing of dihaploids of somatic hybrids

The efficiency of an original approach to involvement of the valuable genetic pool of wild diploid potato species from Mexico is estimated. The essence of this method is in generation of dihaploids (2n = 2x = 24) of tetraploid somatic hybrids (2n = 4x = 48) followed by backcrossing with dihaploids of Solanum tuberosum. A haploid producer, S. phureja IvP35, was used to generate ten dihaploids of S. tuberosum + S. pinnatisectum, all of which crossed with fertile S. tuberosum dihaploids and developed plump viable seeds. This gives the possibility of an efficient introgression of the genes valuable for breeding from wild species to the bred plants at a diploid level, which has several advantages compared with the corresponding procedure at a tetraploid level. A part of the dihaploids produced was compatible (the pollen tubes reached the ovary) with diploid and tetraploid forms of S. pinnatisectum; however, no viable seeds were developed. The attempt to generate the dihaploids of S. tuberosum + S. bulbocastanum somatic hydrides using the haploid producer S. phureja IvP35 was unsuccessful.     

Identification of granule-bound starch synthase in potato tubers

Starch granules isolated from potato (Solanum tuberosum L.) tubers were extracted with sodium dodecyl sulfate and the extract was analyzed. A major protein with a molecular weight of 60,000 daltons was detected. This protein was purified by preparative sodium dodecyl sulfate-gel electrophoresis and specific antibodies were prepared. The anti-60-kilodalton antibodies obtained (a) cross-reacted with the waxy proteins of both maize (Zea mays L.) and grain amaranth (Amaranthus hypochondriacus L.), and (b) inhibited starch synthase activity in partially digested starch granules of the grain amaranth. This evidence strongly suggests that the major 60-kilodalton protein present in potato starch granules represents the granule-bound starch synthase.     

The evolution of cultivated potatoes

In the first stages of potato evolution in the northern Andes, diploid cultivated species of theSolanum stenotomum complex were selected, in all probability, from wild progenitors in theS. brevicaule complex. TetraploidSolanum tuberosum ssp.andigena arose by fusion of unreduced gametes of a parent in theS. stenotomum complex with those of an unidentified wild species having actinomorphic calyces. Unreduced male gametes of several diploid species fertilized eggs of ssp. andigena leading to extensive introgression.Solanum tuberosum ssp.tuberosum probably originated from a cross between ssp.andigena as staminate parent and an unidentified wild species which contributed cytoplasmic sterility factors encoded in mitochondria and/or plastids having a distinctive type of DNA. Derivatives of this hybridization, which may have occurred in northwestern Argentina, evolved to ssp. tuberosum in southern Chile and southern Argentina. In the 1570’s ssp.andigena was imported to Europe and spread from there to become a major crop with worldwide distribution. In the 1840's it was essentially eliminated by late blight,Phytophthora infestans.Solanum tuberosum ssp.tuberosum was introduced from Chile into North America and Europe in the late 1800's, and in turn achieved a worldwide distribution, filling the vacated agricultural niche of ssp.andigena. The differences between ssp.andigena and ssp.tuberosum in South America are sufficient that the two could reasonably be considered to be separate species. Since the 1960’s the two taxa have been hybridized often in breeding programs. Neotuberosum, a northern-adapted strain of ssp. andigena, has been selected to mimic ssp.tuberosum. Substitution back-cross products have been produced that have the chromosomal genes of ssp.tuberosum combined with cytoplasmic factors of Andean species. These breeding activities are blurring the distinctions between the two subspecies throughout much of the world, though they remain distinct in their native areas in South America.     

Phytochrome B Affects the Levels of a Graft-Transmissible Signal Involved in Tuberization

Grafting experiments between phytochrome B antisense and wild-type potato (Solanum tuberosum L. subsp. andigena [line 7540]) plants provide evidence that phytochrome B is involved in the production of a graft-transmissible inhibitor of tuberization, the level of which is reduced in the antisense plants, allowing them to tuberize in noninducing photoperiods.     

One-Leaf Cuttings as a Model to Study Second Growth in the Potato (Solanum tuberosum) Plant

Second growth is an important physiological disorder of thepotato (Solanum tuberosum L.) plant. A model system to studysecond growth was developed using one-leaf cuttings. Photoperiod,temperature, decapitation and leaf removal treatments were carriedout on the plants from which the cuttings were taken and onthe cuttings themselves. Tuberized, one-leaf cuttings takenfrom moderately-induced plants and exposed to 35 °C afterleaf removal showed 95% second growth within 10 d after treatmentinitiation. Conditions that promoted second growth also reducedstarch and dry-matter content, even in tubers that did not developsecond growth. Cuttings, second growth, potato, Solanum tuberosum L, cv, Bintje, Solanum tuberosum L. cv., Désirée, Solanum tuberosum L. cv., Russet Burbank, tuberization, starch content, dry-matter, heat, photoperiod, decapitation, leaf removal     

Behavioral Response of Nothanguina phyllobia to Selected Plant Species

The silver-leaf nightshade nenmtode, Nothanguina phyllobia, is a promising biological control agent for its only reported host, Solanum elaeagnifolium Cav. When infective larvae of N. phyllobia and stem tissue of 39 econmnically important plant species were suspended in 0.5% water agar, nematodes aggregated about S. elaeagnifolium, Solanum carolinense L., Solanum melongena L., Solanum tuberosum L., and Prunus caroliniana (Mill.) Ait. Nematodes responded to Solanum spp. via positive chemotaxis and/or klinokinesis, but aggregated near tissue of P. caroliniana as a result of orthokinetic effects. Nematodes aggregated away from tissue of Hibiscus esculentus L., Triticum aestivum L., Santolina sp., Rosa sp., and Kochia scoparia (L.) Schrad. in the absence of orthokinetic effects. Experiments that excluded light and maintained relative humidity at 100% showed N. phyllobia to ascend the stems of 35 plant species to a height of > 9 cm within 12 h. Differences in stem ascension were not attributable to stem surface characteristics.     

Characterisation of a gene that is expressed in leaves at higher levels upon tuberisation in potato and upon flowering in tobacco

A partial cDNA clone has been isolated which represents a gene that is induced in potato (Solanum tuberosum L.) leaves upon tuber initiation. The gene is also present in tobacco (Nicotiana tobacum L.) where it is induced upon flowering, and in tomato (Lycopericon esculentum, L.) where it is induced when the plant starts to form fruit. This provides further evidence for the similarity of the floral-induction and tuber-induction pathways, and raises the possibility that this gene may be involved in a common step in both of these pathways. Alternatively, it could be involved in a secondary process that is induced during tuberisation, flowering and fruit development.