Identification of the double genome donor in spontaneous triploid tomato plants by RFLP analysis

Independent spontaneous triploid tomato plants (Lycopersicon esculentum Mill.) were collected among diploid hybrids growing in commercial greenhouses. Ploidy levels were verified by counting chromosomes, and the donor of the double genome dose was determined by restriction fragment length polymorphism (RFLP) analysis. The TG101 probe, which is tightly linked to the Tm-2 ^a locus, revealed different restriction patterns between TMV-resistant and TMV-susceptible parent lines. The parent donor which provided two genomes to the triploid was identified by comparing the relative intensity of alleles in the triploid with that in the diploid. The results indicate that both parents can serve as a double genome donor.     

Yield, transpiration and growth of tomatoes under combined excess boron and salinity stress

Boron is essential to growth at low concentrations and limits growth and yield when in excess. Little is known regarding plant response to excess boron (B) and salinity occurring simultaneously. The influences of B and salinity on tomatoes (Lycopersicon esculentum Mill. Cv `5656') were investigated in lysimeters. Salinity levels were 1, 3, 6 and 9 dSm^–1 and B levels were 0.028, 0.185, 0.37, 0.74, 1.11, 1.48 mol m^–3. Excess boron was found to decrease yield and transpiration of tomatoes. This effect was inhibited when plants were exposed to simultaneous B and salinity stresses. Both irrigation water salinity and boron concentration influenced water use of the plants in the same manner as they influenced yield. While yield was found to decrease with increased boron concentration in leaf tissue, increased salinity led to decreased boron accumulation. Yield response was found to correlate better to B concentration in irrigation water and soil solution than to plant tissue B content. A dominant-stress-factor model was assumed and validated. The model applies the principle that when a plant is submitted to conditions of stress caused by B in conjunction with salinity, the more severe stress determines yield. The results of this study have significance in modeling and management of high salinity high boron conditions. Under saline conditions, differences in crop yield and in water use may not be experienced over a significant range of boron concentrations.     

The effect of increasing NaCl levels on the potassium utilization efficiency of tomatoes grown under low-K stress

Tomato strains were grown under low-K stress (71 μM K) over a wide range of external Na levels (from 0.014 to 27.8 mM Na) to measure strain response in Na substitution capacity in relation to Na concentration. Relative differences among strains for Na substitution capacity were similar at all Na levels except for the minus Na control treatment. Successive doubling of external Na concentration over the range of Na levels tested resulted in a positive linear response in plant dry weight, under low-K stress, with a similar slope for all five strains. The five strains also were grown at a toxic Na level (87 mM Na) under low K and adequate K conditions. Plant dry weight was not reduced at the toxic Na level relative to the minus Na control when the strains were grown under low-K stress; however, plant dry weight was reduced an average of fifty-five percent at the toxic Na level relative to the control when the strains were grown under adequate K conditions. There was no relationship between Na substitution capacity of strains grown under low-K stress and tolerance to toxic Na levels under adequate K conditions.     

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 in vitro metabolism of [8-14C]benzyladenine by excised organs of tomato plants

The metabolic fate of [8-¹⁴C]benzyladenine applied to the excised organs of tomato (Lycopersicon esculentum Mill. cv. Heinz 1370) was investigated after 2 and 6 h of feeding. Although the roots were the most effective at uptake of the cytokinin the leaves metabolised it the most efficiently. The predominant metabolite in all of the tissues was an unknown compound which did not have a retention time corresponding with any of the standards used. The roots contained the most extensive range of metabolites which included the unknown metabolite and compounds co-eluting with adenine, and the riboside, nucleotide and 9-glucoside of benzyladenine. The 9-glucoside was detected only in the root material. The stem yielded the highest levels of radioactivity at the retention times of benzyladenosine-5-monophosphate and benzyladenosine. The radioactivity associated with these two cytokinins was transient in the leaf extract. This organ ultimately yielded radioactivity only at the retention times of the unknown metabolite and adenine. Since only the roots and leaves contained relatively large peaks of radioactivity at the elution volume of adenine it seems that degradative metabolism was more predominant in these organs than in the stem.Abbreviations Ade adenine - Ado adenosine - BA benzyladenine - BAR benzyladenosine - BA3G 3-glucosylbenzyladenine - BA9G 9-glucosylbenzyladenine - BARMP benzyladenosine monophosphate - HPLC high performance liquid chromatography - MS mass spectrometry     

低钾胁迫对番茄叶片活性氧及抗氧化酶系的影响

以2种不同低钾耐性大果番茄(钾敏感型番茄081018和耐低钾型番茄081034)为材料,比较低钾处理下2种番茄叶片中活性氧产生及抗氧化酶系活性和相关基因表达差异,明确植物叶片对低钾胁迫的响应机制.结果显示:(1)钾敏感型番茄在低钾胁迫时,叶片中各种保护酶(SOD及其同工酶、POD、CAT、APX)活性随处理时间延长呈下降趋势,同时活性氧(O2-、H2O2)和MDA含量急剧增加;耐低钾型番茄在低钾胁迫条件下,其各类保护酶活性均比对照水平有所升高,而且O2-、H2O2和MDA的含量增加也较少.(2)钾敏感型番茄在低钾胁迫时叶片内Cu/Zn-SOD、CAT和APX基因的相对表达量均有下降趋势,而同期耐低钾型番茄在低钾胁迫时Cu/Zn-SOD、CAT和APX的表达却明显增加,这与其对应的酶活性变化趋势同步.研究表明,低钾胁迫使耐低钾型番茄具有较高保护酶基因表达量,产生较高的保护酶活性,可降低活性氧的破坏作用,防止膜渗透性增加,使之对低钾的适应性较强,而钾敏感番茄品系则相反.     

Photocontrol of anthocyanin biosynthesis in tomato

Juvenile anthocyanin biosynthesis has been studied in dark-grown seedlings of tomato (Lycopersicon esculentum Mill.) wild types (WTs) and photomorphogenic mutants. During a subsequent 24-hr period of monochromatic irradiation at different fluence rates of red light (R) the fluence-rate response relationships for induction of anthocyanin in all the WTs are similar, yet complex, showing a response at low fluence rates (LFRR) followed by a fluence rate-dependent high irradiance response (HIR). In the hypocotyl this response is restricted to the sub-epidermal layer of cells. The high-pigment-1 (hp-1) mutant exhibits a strong amplification of both response components. Theatroviolacea (atv) mutant shows strongest amplification of the HIR component. In contrast, a transgenic line overexpressing an oat phytochrome A gene (PHYA3 ⁺) shows a most dramatic amplification of the LFRR component. The far-red light (FR)-insensitive (fri) mutant, deficient in phytochrome A (phyA), lacks the LFRR component whilst retaining a normal HIR. The temporarily R-insensitive (tri) mutant, deficient in phytochrome B1 (phyB1) retains the LFRR, but lacks the HIR. Thehp-1,fri andhp-1,tri double mutant, exhibit amplified, yet qualitatively similar responses to the monogenicfri andtri mutants. Thefri,tri double mutant lacks both response components in R, but a residual response to blue light (B) remains. Similarly, theaurea (au) mutant deficient in phytochrome chromophore biosynthesis and presumably all phytochromes, lacks both response components in the R and FR regions of the spectrum. Experiments at other wavelengths demonstrate that while there is only a small response in the FR spectral region (729 nm) in tomato, there is an appreciable HIR response in the near FR at 704 nm, which is retained in thetri mutant. This suggests that the labile phyA pool participates in the HIR at this wavelength. The intense pigmentation (Ip) mutant appears to be specifically deficient in the B1 induced anthocyanin biosynthesis. Adult plants, grown under fluorescent light/dark cycles, show a reduction of anthocyanin content of young developing leaves upon application of supplemtary or end-of-day FR. The involvement of different phytochrome species in anthocyanin biosynthesis based on micro-injection studies into theau mutant and studies using type specific phytochrome mutants is discussed.     

Molecular analysis of single copy and repetitive genes on chromosome 2 in intergeneric tomato somatic hybrid plants

Restriction fragment polymorphisms were used to identify and quantify the nuclear contributions from each parent to somatic hybrid plants between tomato (Lycopersicon esculentum Mill.) cv. Sub-Arctic Maxi and Solanum lycopersicoides Dun. Three single-copy clones, 2–13, 2–17, and 3–288, and a clone for the 45s ribosomal RNA, pHA2, all mapped to chromosome 2 of tomato, were used in analysis of 47 somatic hybrids. The amount of hybridizing probe for each parental band was quantified by densitometry of the autoradiograph film. Analyses with the three single-copy clones indicated that there were more than two S. lycopersicoides copies in most somatic hybrid plants. For at least one somatic hybrid there was a loss of one tomato copy. No evidence was found for more than two copies donated from tomato or loss of a copy from S. lycopersicoides. Most of the observed variation in copy number of the single-copy clones was consistent with chromosomal changes occurring in the suspension cells from which S. lycopersicoides parental protoplasts were derived.The number of copies of rDNA derived from each parent varied independently of the number of copies of single-copy clones from each parent. Changes in the copy number of rDNA occurred in both tomato and S. lycopersicoides genomes.     

Localization of proton-ATPase genes expressed in arbuscular mycorrhizal tomato plants

In arbuscular mycorrhizal symbioses, solutes such as phosphate are transferred to the plant in return for photoassimilates. The uptake mechanism is probably facilitated by a proton gradient generated by proton H⁺-ATPases. We investigated expression of Lycopersicon esculentum Mill. H⁺-ATPases in mycorrhizal and non-mycorrhizal plants to determine if any are specifically regulated in response to colonization. Tissue expression and cellular localization of H⁺-ATPases were determined by RNA gel blot analysis and in situ hybridization of mycorrhizal and non-mycorrhizal roots. LHA1, LHA2, and LHA4 had high levels of expression in roots and were expressed predominantly in epidermal cells. LHA1 and LHA4 were also expressed in cortical cells containing arbuscules. The presence of arbuscules in root sections was correlated with lower levels of expression of these two isoforms in the epidermis. These results suggest that LHA1 and LHA4 expression is decreased in epidermal cells located in regions of the root that contain arbuscules. This provides evidence of differential regulation between molecular mechanisms involved in proton-coupled nutrient transfer either from the soil or fungus to the plant.     

Effect of the carmine spider mite (Acarida: Tetranychidae) infestation and mechanical injury on the level of ABA in tomato plants

The aim of this study was to determine the changes in the abscisic acid (ABA) content in tomato leaves infested by the carmine spider mite (CSM) (Tetranychus cinnabarinus Boidsuval) and in leaves that were mechanically injured. It was also investigated whether signalling from stressed to non-stressed organs occurred. Tomato plants (Lycopersicon esculentum Mill.) cvs. Romatos and Slonka (with various susceptibility to CSM) were stressed at the stage of first cluster flowering by either CSM feeding (72 hours) or by mechanical puncturing simulated feeding injury by CSM (18 hours). It was found that under control condition the level of ABA differed significantly between cultivars, being always higher in plants of the susceptible cv. Romatos. In response to CSM feeding, the content of ABA in infested organs of the more tolerant plant (cv. Slonka) increased by 95 % but in the susceptible one by 11 % only. ABA content in the organs non-stressed by CSM feeding either increased (Slonka cv.) or decreased (Romatos cv.). In response to mechanical wounding, ABA content in directly injured organs increased but to a lower degree (49 %) and only in Slonka cv.. The same was true for ABA content in non-injured organs of damaged plants of this cultivar. Observed changes in ABA level in non-stressed organs are probably the results of signalling from stressed organs. Plant response measured by changes in ABA level to the stress generated by CSM feeding, was much stronger than merely by mechanical injury.     

Ac transposition in transgenic tomato plants

Summary As an initial step towards developing a transposon mutagenesis system in tomato, the maize transposable element Ac was transformed into tomato plants via Agrobacterium tumefaciens. Southern analysis of leaf tissue indicated that in nine out of eleven transgenic plants, Ac excised from the T-DNA and reintegrated into new chromosomal locations. The comparison of Ac banding pattern in different leaves of the same primary transformant provided evidnece for transposition during later stages of transgenic plant development. There was no evidence of Ds mobilization in tomato transformants.     

Translocation and effectiveness of foliar-fertilized boron in broccoli plants of varying boron status

The translocation and effectiveness of foliar-fertiilized boron (B) was investigated in broccoli plants supplied via the root system with luxury, sufficient or deficient levels of B. ¹⁰B-enriched boric acid was applied three times to lower leaves, beginning one week prior to inflorescence emergence, and the shoot and floret yields, as well as the ¹⁰B and ¹¹B contents or concentrations of xylem sap, phloem exudate and various plant parts, were determined three weeks after inflorescence emergence. The amount of ¹⁰B translocated in phloem from fed leaves to the remainder of the shoot did not exceed 0.5%, of that supplied, but it was inversely related to plant-B status. The partitioning of translocated ¹⁰B to florets (16–30%) and the degree of enhancement in floret yield (28–75%) was also inversely related to plant-B status. It is concluded that foliar-B fertilization may be more effective for preventing B deficiency than soil-derived B in leaves.Abbreviations ¹⁰B/¹¹B mass isotopes of boron - DM dry matter - FF foliar fertilization - RF root fertilization     

Comparison of physical and chemical characters of tomato fruits grown from plants received from seeds or obtained in vitro

Results of experiments concerning comparison of tomato fruit properties which were collected from plants obtained in three manners are described. Control plants were received from seeds. Remaining plants were derived in vitro from leaf and shoot fragments on MS medium supplemented with IAA 0.2 mg·l⁻¹ and BA 2 mg·l⁻¹ (Górecka and Krzyżanowska 1991, Górecka et al. 1994) or with Fari’s et al. (1992) method of obtaining plants by decapitation of sterile seedlings and culture on MS medium without hormones. Evaluation of physical and chemical fruit characters was performed. In the spring experiment the biggest diameter (72 mm), weight (154 g) and volumne (151 ml) were characterized to fruits from plants obtained in vitro on MS medium with IAA and BA. Also fruits from plants received by Fari’s methods were significantly superior in these characters over fruits from the control plants. The fruits from the plants obtained in vitro on MS medium with IAA and BA had highest sugar content (2.95 % f.wt.) and fruits from in vitro plants after Fari’s method contained highest vit.C-13.4 mg·100 g⁻¹ f.wt (significant differences in comparison to control fruits). In other characters fruits from in vitro did not differ as compared to control ones. In the autumn experiments significant differences among fruit groups and characters evaluated were not stated. Generally, yield quality was poorer in the all autumn treatments.     

Does boron play only a structural role in the growing tissues of higher plants?

In species in which boron (B) mobility is limited, B deficiency only occurs in growing plant organs. As a consequence of the highly localized patterns of plant growth and the general immobility of B it has been extremely difficult to determine the primary function of B in plants. In species in which B is phloem mobile, the removal of B from the growth medium results in the depletion of B present in mature leaves. Thus, it is possible to develop mature leaves with increasingly severe levels of B depletion, thereby overcoming the complications of experiments based on growing tissues. Utilizing this approach we demonstrate here that B depletion of mature plum (Prunus salicina) leaves did not result in any discernible change in leaf appearance, membrane integrity or photosynthetic capacity even though B concentrations were reduced to 6-8 µg/g dwt, which is less than 30% of the reported tissue B requirement. Boron depletion, however, results in a severe disruption of plant growth and metabolism in young growing tissues. This experimental evidence and theoretical considerations suggest that the primary and possibly sole function of B, is as a structural component of growing tissues.     

The effect of temperature on salt uptake by tomato plants with diurnal and noctural waterlogging of salinized rootzones

Summary Tomato plants were grown at three constant temperatures (10, 20 and 28°C) with drained or waterlogged rootzones and were irrigated with saline solution (0.09M NaCl).Each increase in temperature resulted in an increase in leaf Na-ion and Cl-ion concentrations in plants grown with drained rootzones. However, with plants grown with waterlogged rootzones, maximum leaf concentrations of Na-ions and Cl-ions occurred at 20°C.At 10°C there were no differences between Na-ion and Cl-ion concentrations for drained or waterlogged treatments. At 20 and 28°C, waterlogging of the rootzone resulted in significantly higher concentrations of Na-ions and Cl-ions in leaf and stem tissues than occurred with drained rootzones.There were no differences in Na-ions and Cl-ions and Cl-ions in plant tops if plants were waterlogged with saline solution during the day or night.Transpiration increased significantly with each increase in temperature but showed no other treatment dependent responses.     

Photosynthetic acclimation in tomato plants grown in high CO2

The effects of prolonged CO₂ enrichment of tomato plants on photosynthetic performance and Calvin cycle enzymes, including the amount and activity of ribulose-1,5-bisphosphate carboxylase (RuBPco), were determined. Also the light-saturated rate of photosynthesis (P_max) of the 5th leaf throughout leaf development was predicted based on the amount and kinetics of RuBPco. With short-term CO₂ enrichment, i.e. only during the photosynthesis measurements, P_max of the young leaves did not increase while the leaves reaching full expansion more than doubled their net rate of CO₂ fixation. However, with longer-term CO₂ enrichment, i.e. growing the crop in high CO₂, the plants did not maintain this photosynthetic gain. Compared with leaves of plants grown in normal ambient CO₂ the high CO₂-grown leaves, when almost fully expanded, contained only about half as much RuBPco protein and P_max in 300 and 1000 vpm CO₂ was similarly reduced.The loss of RuBPco protein may be a factor associated with the accelerated fall in P_max since P_max was close to that predicted from the amount and kinetics of RuBPco assuming RuBP saturation. Acclimation to high CO₂ is fundamentally different from acclimation to high light. In contrast to acclimation to high light, acclimation to high CO₂ does not usually involve an increase in photosynthetic machinery so the synthesis and maintenance costs (as indicated by the dark respiration rate) are generally lower.     

The role of adenine in the synthesis of cytokinins in tomato plants and in cell-free root extracts

The incorporation of labelled adenine into cytokinin-like compounds was investigated in intact tomato plants, decapitated tomato roots and cell-free root extracts. In all three cases evidence was found for the incorporation of adenine into endogenous cytokinins. In intact plants and decapitated root systems no evidence was found for the incorporation into cytokinin nucleotides. Cytokinin bases and nucleosides were however, labelled. In the cell-free root extract there was some evidence for the incorporation of labelled adenine into cytokinin nucleotides. This suggests that the biosynthetic process may be strictly compartmentalized. The present results provide no evidence for the relative importance of cytokinin nucleotides in the biosynthetic process. What is clear is that the rate of adenine incorporation into cytokinins is extremely low and that only a small proportion of the cytokinins which became labelled were exported to the shoot via the root exudate.The financial support of the CSIR/Israel Collaborative Programme is gratefully acknowledged.     

Altered Tomato (<Emphasis Type="Italic">Lycopersicon esculentum</Emphasis> Mill.) Fruit Cuticle Biomechanics of a Pleiotropic Non Ripening Mutant

Tomato (Lycopersicon esculentum Mill.) fruit ripening involves multiple metabolic changes resulting in softening and pigmentation. We investigated the mechanics and morphology of the enzymatically isolated cuticular membrane (CM) of cv. Ailsa Craig wild-type (wt) and nonripening mutant (nor) at three developmental stages. Cuticle thickness and degree of cutinization increased significantly from immature to fully ripe fruits for both wt and nor without differences between them. Mechanical characterization was carried out on dry and fully hydrated samples in uni-axial tension to determine their modulus of elasticity, stress, and strain at failure. Corresponding stress-strain diagrams were biphasic and showed yield for virtually all dry CM samples, while that of hydrated CM displayed considerable differences between wt and nor fruits. Concerning the mechanical properties, the CM of wt fruits was characterized by increasing stiffness and strength during fruit growth and maturation in both dry and hydrated states, whereas the CM of nor fruits was significantly less stiff and weaker at full maturity. Hydration generally caused lower moduli of elasticity and strength, while breaking strain was significantly affected only for the CM of ripe nor fruits. This plasticizing effect of water increased towards full maturity for both wt and nor, and may be related to fiber content in the CM matrix and hydration state of the cuticle. Comparative analysis of two additional wild-type tomato cultivars supported the ripening-related stiffening of the CM of Ailsa Craig wt and the altered mechanical properties of the nor mutant, as well as the plasticizing effect of water.     

Impaired growth in transgenic plants over-expressing an expansin isoform

Expansins are cell wall proteins characterised by their ability to stimulate wall loosening during cell expansion. The expression of some expansin isoforms is clearly correlated with growth and the external application of expansins can stimulate cell expansion in vivo in several systems. We report here the expression of a heterologous expansin coding sequence in transgenic tomato plants (Lycopersicon esculentum Mill.) under the control of a constitutive promoter. In some transgenic lines with high levels of expansin activity extractable from cell walls, we observed alterations of growth: mature plants were stunted, with shorter leaves and internodes, and dark-grown seedlings had shorter and wider hypocotyls than their wild-type counterparts. Examination of hypocotyl sections revealed similar differences at the cellular level: cortical and epidermal cells were shorter and wider than those from wild-type seedlings. The observed stimulation of radial expansion did not compensate for the decreased elongation, and overall growth was reduced in the transgenics. As this observation can seem paradoxical given the known effect of expansins on isolated cell walls, we examined the mechanical behaviour of transgenic tissue. We measured a decrease in hypocotyl elongation in response to acidic pH in the transformants. This result may account for the alterations in cell expansion, and could itself be explained by a reduced susceptibility of transgenic cell walls to expansin action.