Protein analysis during the ontogeny of normal and male sterile stamenless-2 mutant stamens of tomato (Lycopersicon esculentum Mill.)

The levels and synthesis of proteins during the ontogeny of normal and male sterile stamenless-2 (sl-2/sl-2) mutant stamens of tomato (Lycopersicon esculentum) were examined. The mutant stamens contained low levels of soluble protein which were related to reduction in protein synthesis. The mutant stamens, however, possessed many polypeptides similar to the normal and synthesized a 53-kd polypeptide at stages when there are abnormalities in tapetum development. The mutant stamens also possessed a 23-kd and some low molecular weight polypeptides that were considered as degradative proteins. Normal stamens exhibited the synthesis of many polypeptides not found in the mutant, from microspore mother cell to the preanthesis stages. In addition, at the time of pollen maturation there was a greater synthesis of several polypeptides, particularly those of 42 and 37 kd. Although the causative mechanisms of male sterility in the sl-2/sl-2 mutant are not known, the synthesis, and the lack, of specific polypeptides reported here appears to be associated with pollen degeneration.This work was supported by an operating grant from the Natural Sciences and Engineering Research Council of Canada to V.K.S.     

Comparison of the response to aluminum toxicity in gametophyte and sporophyte of four tomato (Lycopersicon esculentum Mill.) cultivars

Summary We tested pollen from four tomato cultivars differing in sensitivity to aluminum in the sporophyte to determine if Al sensitivity was also expressed in pollen. Pollen sensitivity to Al was measured by the ability to germinate and grow in a control solution after a short period in a high concentration of Al. The response was ranked and compared to the Al sensitivity ranking of the four cultivars based on top growth in Al toxic soil. In addition, seedlings from the most and least sensitive cultivars, based on pollen germination, were compared for Al sensitivity in nutrient solutions. Treatment with Al significantly reduced pollen germination in the two more sensitive cultivars, but not in the two more resistant cultivars. However, the ranking was not the same as that based on the shoot growth of the sporophyte. Root growth as a criterion of sporophytic Al sensitivity produced results similar to pollen germination. The study suggests that although the correspondence is better for some phenotypic responses of the sporophyte than others, Al tolerance appears to be another character expressed in both pollen and sporophyte.     

Ultrastructural changes in the cell wall,nucleus and cytoplasm of pollen mother cells during meiotic prophase I inLycopersicon esculentum (Mill.)

Summary Throughout the premeiotic to late prophase I stages of meiosis in the anthers of tomato (Lycopersicon esculentum) extensive changes occurred in the ultrastructure of pollen mother cells (PMCs). During early prophase, the wall of each PMC developed a layered appearance and was broadened both by the widening of the middle lamella as well as by intensive deposition of microfibrils in the wall. By late prophase, however, the microfibrils adjacent to the plasmalemma dissipated. At the same time, callose was deposited between the wall and the plasmalemma. The nucleus of the PMCs also underwent changes. During early prophase, the nucleolus consisted of a linear series of three segments, with a separation of the granular and fibrillar portions. By late prophase, the nucleoli were less distinct as the nucleus was highly vacuolate. Mitochondria were initially simple with lightly stained matrix and few cristae but, during the course of prophase, they acquired a more densely-stained matrix with dilated cristae. Plastids remained relatively undifferentiated and, at late prophase, many were convoluted in appearance and constricted at intervals indicating their division. Cytoplasmic connections between adjacent PMCs were broad enough to permit the passage of organelles and were retained through to metaphase I. These cytological and wall changes appear to be a prerequisite for the subsequent development of microspores.Abbreviations PMC pollen mother cell - NOR nucleolus organizing region     

Role of ABA in stamen and pistil development in the normal and solanifolia mutant of tomato (Lycopersicon esculentum)

Summary The role of abscisic acid (ABA) in stamen and pistil development of the normal and solanifolia (sf/sf) mutant of tomato (Lycopersicon esculentum Mill.) was analyzed. The solanifolia mutant produces flowers with separate floral organs, unlike the fused organs of normal flowers, and has greater number of carpels and locules per ovary than the normal. Applications of 10^–5 M ABA to normal floral buds produced flowers with separate stamens, but higher concentrations (10^–4 M ABA) resulted in the complete suppression of stamen growth or stamens that were devoid of anthers. ABA at both 10^–4 and 10^–5 M also induced an increase in the number of carpels and locules in normal flowers, but not in mutant ones. Analysis of endogenous ABA by a radioimmunoassay revealed that the pistils of mutant flowers contained a significantly higher level of ABA than those of normal flowers, but there was no difference in the ABA content of the stamens. The non-fusion of the stamens and the high number of carpels and locules in solanifolia mutant flowers may be explained by the high level of ABA in the floral apex during the initiation and development of carpels.     

The histogenesis of somaclones from tomato (Lycopersicon esculentum Mill.) cotyledons

Summary A histological study ofin vitro cultured cotyledonary expiants of tomato (Lycopersicon esculentum) was performed in order to determine the site (differentiated tissue or developing callus) and the mode of plant regeneration.Results have shown that callus develops at the excision sites of cotyledonary expiants and that shoots are formed exclusively within the unorganized callus: excision areas are the only morphogenetic sites and the proximal excision is the preferred site for plant regeneration.Shoots differentiate by organogenesis within the superficial region of the callus. Few neocambial cells cooperate in the neoformation. Origin from a single cell is highly unlikely since rarely observed single activated cells never developed into shoots.Regenerated plants may be chimeras if invitro culture induces genetic diversity in the initial cells.Abbreviations IAA Indole-3-acetic acid - c callus - d vegetative dome - s shoot - ad adaxial - ab abaxial - t tracheid - p parenchyma - S sieve tube     

A genetic analysis of a tomato (Lycopersicon esculentum) genotype with a high frequency of twin spots

Among pale-green tomato plants heterozygous for the xanthophyllic2 (xa-2) mutation that were transformed with a T-DNA harbouring the NPTII and GUS gene, a plant with a high frequency of green/white twin spots was found. The genetic analysis of this plant indicated that the occurrence of these twin spots was caused by a genetic defect located at the distal end of chromosome 10S, where xa-2 also is located. The genetic analysis of green plants regenerated from leaf expiants of this twin-spot plant revealed that the green sectors derive from non-disjunction of the xa-2 ⁺ allele. In an analysis of mitotic chromosome behaviour bridges were observed in approximately 5% of the anaphases, providing arguments that a breakage-fusion-bridge cycle caused by a tissue culture-induced genomic instability is the most likely cause of this aberrant behaviour of chromosome 10.     

NMR characterization of endogenously O-acetylated oligosaccharides isolated from tomato (Lycopersicon esculentum) xyloglucan

Eight oligosaccharide subunits, generated by endoglucanase treatment of the plant polysaccharide xyloglucan isolated from the culture filtrate of suspension-cultured tomato (Lycopersicon esculentum) cells, were structurally characterized by NMR spectroscopy. These oligosaccharides, which contain up to three endogenous O-acetyl substituents, consist of a cellotetraose core with alpha-D-Xylp residues at O-6 of the two beta-D-Glcp residues at the non-reducing end of the core. Some of the alpha-D-Xylp residues themselves bear either an alpha-L-Arap or a beta-D-Galp residue at O-2. O-Acetyl substituents are located at O-6 of the unbranched (internal) beta-D-Glcp residue, O-6 of the terminal beta-D-Galp residue, and/or at O-5 of the terminal alpha-L-Arap residue. Structural assignments were facilitated by long-range scalar coupling interactions observed in the high-resolution gCOSY spectra of the oligosaccharides. The presence of five-bond scalar coupling constants in the gCOSY spectra provides a direct method of assigning O-acetylation sites, which may prove generally useful in the analysis of O-acylated glycans. Spectral assignment of these endogenously O-acetylated oligosaccharides makes it possible to deduce correlations between their structural features and the chemical shifts of diagnostic resonances in their NMR spectra.     

Importance of myo-inositol,calcium, and ammonium for the viability and division of tomato (Lycopersicon esculentum) protoplasts

Plants from four cultivars of Lycopersicon esculentum were grown under different conditions, in controlled environment chambers. Low light intensity, long photoperiod (16 h), 25° C/17°C temperature alternance (day/night) were found to be the most convenient conditions for obtaining viable protoplasts. The use of myo-inositol as an osmoticum in the digestion medium and the adjustment of the pH to 6.5, instead of the usual 5.8, for this medium increased the yield of viable protoplasts and enhanced their stability. Under these conditions neither pretreatment (dark and cold treatments), nor preplasmolysis of leaf tissues, were required before protoplast isolation. The concentrations of ammonium nitrate, calcium chloride, myo-inositol, and sucrose were found to be critical for the success of protoplast culture. A medium containing 5 mM ammonium nitrate, 40 mM calcium chloride, 10 mg l^-1 adenine sulfate, 0.5% myo-inositol and 6% sucrose gave sustained protoplast divisions. Under these conditions, plating efficiency ranged from 5% for the cultivar Lukulus to 15% for the cultivar Golden Sunrise.Abbreviations BA benzylaminopurine - CaCl₂ calcium chloride, 2,4,-D-2,4-dichlorophenoxyacetic acid - EDTA ethylene diamine tetraacetic acid - KCl potassium chloride - MES-2-N morpholino ethane sulfonic acid - MgCl₂ magnesium chloride - NH₄NO₃ ammonium nitrate - NAA naphthalene acetic acid, p-protoplasts     

Effect of salinity on tomato (Lycopersicon esculentum Mill.) during seed germination stage

A study was conducted using ten genetically diverse genotypes along with their 45F₁ (generated by diallel mating) under normal and salt stress conditions. Although, tomato (Lycopersicon esculentum Mill.) is moderately sensitive to salinity but more attention to salinity is yet to be required in the production of tomato. In present study, germination rate, speed of germination, dry weight ratio and Na⁺/K⁺ ratio in root and shoot, were the parameters assayed on three salinity levels; control, 1.0 % NaCl and 3.0 % NaCl with Hoagland’s solution. Increasing salt stress negatively affected growth and development of tomato. When salt concentration increased, germination of tomato seed was reduced and the time needed to complete germination lengthened, root/shoot dry weight ratio was higher and Na⁺ content increased but K⁺ content decreased. Among the varieties, Sel-7 followed by Arka Vikas and crosses involving them as a parent were found to be the more tolerant genotypes in the present study on the basis of studied parameters.     

Increase in the rate of recombinants in tomato (Lycopersicon esculentum L.) after in vitro regeneration

Summary Modification to the cross-over (C. O.) rate of tomato (Lycopersicon esculentum) was attempted by using in vitro plant regeneration. F1 hybrids with the same genetical homozygous background were compared at two loci: bs-ms32 on chromosome I, and aa-d on chromosome II. For each, the genetic distance separating the two markers was about 20 to 30 map units. One cotyledon of each F2 hybrid seedling was used as in vitro tissue culture material, while the rest of the plantlet was grown as a control. Recombination rates of the selfed progenies from each regenerated and matched control couple were compared. For the first set of markers 59,000 seeds were analysed (5 controls' and 7 regenerated progenies), and for the second, 11,000 (5 controls' and 8 regenerated progenies). There were significant increases in the genetic distance between markers in about half the regenerated individuals. For the first set the increases ranged from 6.07 to 6.91 units out of a control distance of the 19.84 to 25.65, corresponding to lengthenings of 30.59 to 35.29%. For the second set they ranged from 4.92 to 6.04 out of a control distance of 25.05 to 26.57, representing increases of 19.64 to 22.75%. Such a phenomenon can be important either from a fundamental or practical viewpoint, regarding selection efficiency in plants, and potential for gene reassortment.The experiment reported in this paper has been submitted by M. Biglary in partial fulfillment of the requirements for Docteur-Ingénieur degree. (Nov. 1982, Laboratoire d'Amélioration des Plantes, Université Paris-Sud, F-91405 Orsay)     

Functional male sterility in tomato (Lycopersicon esculentum Mill.) and its application in hybrid seed production

Advantages and disadvantages in using functional male sterility (positional sterile — ps, positional sterile 2 — ps 2, and excerted stigma — ex) in tomato hybrid seed production and attempts to elaborate systems for their more efficacious use in breeding were discussed in this review. It was concluded that the application of one of these types of sterility, (ps 2) in practice, although in a limited number of countries, showed the functional male sterility in tomato was a potential not to be underestimated in developing approaches that aimed at reducting the time and cost associated with hybrid seed production.     

Endophytic fungi in leaves of Lycopersicon esculentum Mill

Endophytic fungi were isolated from healthy tomato leaves from field-grown plants. Several surface-sterilization techniques were assayed for removing and killing epiphytes on tomato leaves. Surface-sterilization with an undiluted commercial solution of sodium hypochlorite was employed. To determine the spectrum of endophytes, samples were collected in February 1998 and 1999 from tomato plants (cultivar Tommy) cultivated in the experimental fields of Facultad de Ciencias Agrarias y Forestales, Universidad Nacional de La Plata, Buenos Aires, Argentina. In general, different spectra of species were isolated in 1998 and 1999.Alternaria alternata was the fungus most frequently isolated from tomato leaves in 1999, but it was the second most common species in 1998. In contrast, Colletotrichum gloeosporioides was the fungus most frequently isolated in 1998, but it was not found in 1999. Species of other genera, such as Cladosporium and Penicillium, were isolated in both years.     

Physiological response and yield of paclobutrazol treated tomato plants (Lycopersicon esculentum Mill.)

Experiments were conducted to study the physiologicaleffect of the plant growth retardant paclobutrazol(PBZ) and its impact on the yield of tomato plants(cv. Precador). Seedlings were treated at the time of prickingout with soil and foliar applications of PBZ atconcentrations of 1.0 and 25.0 mg l^-1respectively. The results established that:-- The reduced height and the increased thickness ofthe young plant stem, as well as the accelerated rootformation are a significant advantage of the PBZtreatment, contributing to the improvement of seedlingquality at planting.-- Soil treatment (1 mg l^-1) and foliar treatment(25 mg l^-1) with PBZ improves the photosyntheticactivity and water balance of tomato cv. Precador.-- PBZ accelerates fruit formation and increases earlyfruit yield.-- The concentrations of the retardant used and themode of its application ensure the production offruits without any residual retardant and harmless tohuman health from a phytosanitary point of view.     

The distribution and utilization of calcium by two tomato (Lycopersicon esculentum Mill.) lines differing in calcium efficiency when grown under low-Ca stress

Two lines of tomato (Lycopersicon esculentum Mill.) representing extremes in utilization effciency of absorbed Ca were studied to detect internal differences in Ca transport and distribution and factors responsible for strain differences in susceptibility to low Ca-stress. Differences in efficiency of Ca use were expressed as CaER (mg of dry weight produced for each mg of Ca absorbed by the plant).Ca-efficiency in line 113(E) appeared to be associated with a slow continuous movement of absorbed Ca, allowing for continued growth of the shoot apex and upper lamina under Ca-deficiency conditions. In the inefficient line 67(I), in contrast, Ca was rapidly deposited in the lower leaves with little upward movement in the plant after absorption.Fractionation of tissue Ca into various chemical forms suggested that Ca inefficiency also was associated with higher concentrations of insoluble Ca in the shoot tissue. The efficient line, although sustaining growth at lower levels of Ca, was capable of maintaining a higher ratio of soluble to insoluble Ca in all shoot tissues.Calcium was concentrated in the lower plant tissues of the inefficient strain, limiting its availability for continued shoot growth.Autoradiographs of lines fed⁴⁵Ca during the final 8 days of a 24-day experiment suggested that upward movement was sustained in line 113(E), in spite of vastly reduced transpiration rates and a root system characterized by leakage of K ions from the roots back into the solution.     

The position and growth of lateral roots on cultured root axes of tomato,Lycopersicon esculentum (Solanaceae)

Root axes of tomato (Lycopersicon esculentum) were cultured in vitro in three different concentrations of sucrose in order to vary their growth rate. Lateral root growth and the initiation of lateral root primordia were studied on each group of axes. Various aspects of primordium initiation, positioning, and emergence were quantified with a view to discovering variable and constant features of these processes. Variable parameters were the rate and frequency of root primordium emergence. Constant parameters, at least under the prevailing conditions, were the spacing between successive laterals and primordia, and the position of the primordia in relation to the vascular system. A model of primordium initiation is presented which combines controls determined by the divisional history of the potential primordium cell and by the vascular pattern.Dedicated with great respect to Prof. DrElisabeth Tschermak-Woess on the occasion of her 70th birthday in recognition of her distinguished contributions to cytology.     

Allotriploid somatic hybrids of diploid tomato (Lycopersicon esculentum Mill.) and monoploid potato (Solanum tuberosum L.)

Allotriploid somatic hybrids were obtained from fusions between protoplasts of diploid tomato and monohaploid potato. The selection of fusion products was carried out in two different ways: (1) The fusion of nitrate reductase-deficient tomato with potato gave rise only to hybrid calli if selection was performed on media lacking ammonium. Parental microcalli were rarely obtained and did not regenerate. (2) The fusion of cytoplasmic albino tomato with potato gave rise to albino and green hybrid calli and plants. Allotriploids were identified from the two somatic hybrid populations by counting chloroplast numbers in leaf guard cells and by flow cytometry of leaf tissue. Although some pollen fertility of allotriploids and pollen-tube growth of tomato, potato andLycopersicon pennellii into the allotriploid style were observed, no progeny could be obtained. The relevance of allotriploid somatic hybrids in facilitating limited gene transfer from potato to tomato is discussed.     

Regeneration of intergeneric somatic hybrid plants between Lycopersicon esculentum and Solanum muricatum

Summary Mesophyll protoplasts of tomato (Lycopersicon esculentum) and pepino (Solanum muricatum) were fused by using an electrofusion method and cultured in modified MS medium supplemented with naphthaleneacetic acid and kinetin, in which only pepino and somatic hybrid protoplasts could divide. Somatic hybrid plants showing intermediate characteristics in morphology were regenerated from the calli exhibiting vigorous growth in contrast with those of pepino. The hybrid nature of these plants was confirmed by cytological observation and biochemical analyses of phosphoglucomutase isozymes and the fraction-1-protein. The regenerated somatic hybrids grew to flowering stage and set fruits.     

Genes from Lycopersicon chmielewskii affecting tomato quality during fruit ripening

Three chromosomal segments from the wild tomato, L. chmielewskii, introgressed into the L. esculentum genome have been previously mapped to the middle and terminal regions of chromosome 7 (7M, 7T respectively), and to the terminal region of chromosome 10 (10T). The present study was designed to investigate the physiological mechanisms controlled by the 7M and 7T segments on tomato soluble solids (SS) and pH, and their genetic regulation during fruit development. The effects of 7M and 7T were studied in 64 BC₂F₅ backcross inbred lines (BILs) developed from a cross between LA 1501 (an L. esculentum line containing the 7M and 7T fragments from L. chmielewskii), and VF145B-7879 (a processing cultivar). BILs were classified into four homozygous genotypes with respect to the introgressed segments based on RFLP analysis, and evaluated for fruit chemical characteristics at different harvest stages. Gene(s) in the 7M fragment reduce fruit water uptake during ripening increasing pH, sugars, and SS concentration. Gene(s) in the 7T fragment were found to be associated with higher mature green fruit starch concentration and red ripe fruit weight. Comparisons between tomatoes ripened on or off the vine suggest that the physiological mechanisms influenced by the L. chmielewskii alleles are dependent on the translocation of photosynthates and water during fruit ripening.     

Temperature-induced modifications in the surface features of stamens of a tomato mutant: An SEM study

Summary Stamenless-2 (sl₂/sl₂) is a temperature-sensitive mutant of tomato (Lycopersicon esculentum) which exhibits altered stamen development under different temperatures (Sawhney 1983). By using scanning electron microscopy, this study was conducted to investigate the differentiation of surface features of mutant and normal stamens grown under different temperatures, with the view to further determine the role of temperature in gene expression in stamen development. Mutant stamens grown under intermediate temperatures (23 °C day/18 °C night) differed from the normal in hair production, the shape of epidermal cells and in the pattern of cuticular thickenings. Under low temperatures (18 °C day/15 °C night), all surface features of mutant stamens closely resembled the normal, whereas under high temperatures (28 °C day/23 °C night), the patterns and types of hairs, epidermal cells, stomata, and cuticular thickenings on mutant stamens were similar to that of a gynoecium. The staminal features of normal stamens were not affected by different temperatures. This study shows that the expression of the sl₂/sl₂ allele is influenced by temperature conditions to the extent that the pattern of cellular differentiation characteristic of either the stamens or the carpels can be induced in mutant stamens.