Vegetative Growth Of Tomato Research Articles

The SINA1-BSD1 Module Regulates Vegetative Growth Involving Gibberellin Biosynthesis in Tomato.

In plants, vegetative growth is controlled by synergistic and/or antagonistic effects of many regulatory factors. Here, the authors demonstrate that the ubiquitin ligase seven in absentia1 (SINA1) mammalian BTF2-like transcription factors, Drosophila synapse-associated proteins, and yeast DOS2-like proteins (BSD1) function as a regulatory module to control vegetative growth in tomato via regulation of the production of plant growth hormone gibberellin (GA). SINA1 negatively regulates the protein level of BSD1 through ubiquitin-proteasome-mediated degradation, and the transgenic tomato over-expressing SINA1 (SINA1-OX) resembles the dwarfism phenotype of the BSD1-knockout (BSD1-KO) tomato plant. BSD1 directly activates expression of the BSD1-regulated gene 1 (BRG1) via binding to a novel core BBS (standing for BSD1 binding site) binding motif in the BRG1 promoter. Knockout of BRG1 (BRG1-KO) in tomato also results in a dwarfism phenotype, suggesting BRG1 plays a positive role in vegetative growth as BSD1 does. Significantly, GA contents are attenuated in transgenic SINA1-OX, BSD1-KO, and BRG1-KO plants exhibiting dwarfism phenotype and exogenous application of bioactive GA3 restores their vegetative growth. Moreover, BRG1 is required for the expression of multiple GA biosynthesis genes and BSD1 activates three GA biosynthesis genes promoting GA production. Thus, this study suggests that the SINA1-BSD1 module controls vegetative growth via direct and indirect regulation of GA biosynthesis in tomato.

The effectiveness of young coconut waste biochar application and goat manures to entisol soil on tomatoes (Solanum lycopersicum L.) vegetative growth

This study aims to determine the effectiveness of applying young coconut biochar waste and goat manures to entisol soil on the vegetative growth of tomatoes. The research was conducted at the Biochar Research Center, Agriculture Faculty, Syiah Kuala University, which took place on August to December 2021. This study used a factorial randomized block design consisting of 2 factors. The first factor is treatment of Young Coconut Waste Biochar (B1: control, B2: 18.52 g polybag-1, B3: 37.04 g polybag-1) and the second factor is treatment dose of goat Manure (W), (W1: control, W2: 18.52 g polybag-1, W3: 37.04 g polybag-1 and W4: 55.55 polybag-1). Variables observed in this study were plant height (2, 4, 6, 8 weeks after planting), number of aged branches (2, 4, 6, 8 weeks after planting), net assimilation rate, plant growth rate and relative growth rate. The results showed that the application of young coconut biochar wastes and goat manures had no significant effect on the vegetative growth of tomatoes such as plant height at 4, 6, 8 weeks after planting, number of branches at 4, 6, 8 weeks after planting and net assimilation rate. There was an interaction on plant height at 2 weeks after planting but the application of biochar from young coconut waste and goat manure was not able to increase plant height, while in plant growth rate and relative growth rate the best dose was found in the application of 55.55 g polybag-1 goat manure.

Elevated Atmospheric Ethylene and High Temperature Independently Inhibit Fruit Set But Not Vegetative Growth in Tomato

Ethylene is an essential plant hormone at low concentrations. Concentrations in the field rarely exceed 5 nmol⋅mol−1 (0.005 ppm), but it can accumulate as a gas in closed, indoor environments. These elevated levels can reduce growth and yield. Temperature alters ethylene synthesis and has the potential to influence ethylene sensitivity of crop plants in sealed greenhouses and indoor environments. We studied ethylene sensitivity of tomatoes (Solanum lycopersicum L. cv. MicroTina) using a unique, 12-chamber system. Ethylene levels of 0, 20, and 40 nmol⋅mol−1 (parts per billion) were maintained throughout the life cycle, at an air temperature of 22 or 28 °C. Yield of red fruit was three times higher at 22 than at 28 °C. There was a steady decrease in yield with increasing ethylene concentration, but vegetative growth was reduced less than 10% in any treatment. The highest ethylene concentration reduced yield to 11% of the control at 22 °C and to 4% of the control at 28 °C; the intermediate ethylene level reduced yield to 51% of the control at 22 °C and 37% at 28 °C. Regardless of temperature, filtering of ethylene in indoor environments to below 20 nmol⋅mol−1 is necessary to achieve normal fruit set and yield in tomato.

Evaluating the nitrification inhibition potential of selected botanicals and their non-target effects

Nitrification inhibitors (NI) are aimed at improving N-fertilizer use efficiency in cropping systems. This study aimed to assess the nitrification inhibition potential and non-target effects of dry leaf powders (botanicals) of 10 plant species (neem (Azadirachta indica), lantana (Lantana camara), karanda (Pongamia pinnata), Brachiaria (Brachiaria humidicola), cinnamon (Cinnamomum verum), clove (Syzygium aromaticum), wild-sunflower (Tithonia diversifolia), mee (Madhuca longifolia), nutmeg (Myristica fragrans), and pepper (Piper nigram)). The effect of botanicals on the growth of three ammonia oxidizing bacteria isolates (M4, M5, and M7) and NO3− formation in soil were tested in laboratory experiments. In a pot-experiment, botanicals were applied with urea to assess their effect on vegetative-growth of tomato and capsicum. The non-target effects of botanicals on soil bacteria and fungi, and seed germination were assessed separately. Dicyandiamide (DCD) was used as the positive control in all experiments. Only the growth of M7 was significantly suppressed by all botanicals except neem, Brachiaria, and pepper. The highest shoot-biomass of tomato was obtained when urea was applied with pepper. Nitrate leaching from pots was significantly reduced (P < 0.05) when urea was added with botanicals except for clove and wild-sunflower at basal-dressing. The abundance of culturable fungi and bacteria were not affected significantly by botanicals while seed germination was reduced significantly and consistently by clove only. From the 10 botanicals tested leaf powders of nutmeg, lantana, cinnamon, mee, and pepper were identified as materials with better potential to suppress nitrification with minimum non-target effects.

Downregulation of SlGRAS15 manipulates plant architecture in tomato (Solanum lycopersicum)

GRAS family transcription factors (TF) are involved in multiple biological processes in plants. In recent years among the 54 identified GRAS proteins, only few have been studied functionally in tomato (Solanum lycopersicum). In the present study, a novel and previously uncharacterized member of tomato GRAS transcription factors family SlGRAS15 was isolated and functionally characterized. It was observed that SlGRAS15 preferably expressed in roots, followed by young leaves, stem, and comparatively low transcripts levels were noticed in all other tissues. To explore the SlGRAS15 function in detail, an RNA interference (RNAi) vector targeting SlGRAS15 was constructed and transformed into tomato plants. The transgenic plants carrying SlGRAS15-RNAi displayed pleiotropic phenotypes associated with multiple agronomical traits including reduced plant height and small leaf size with pointed margins, increased node number, lateral shoots, and petiolules length. In addition, transcriptional analysis revealed that silencing SlGRAS15 altered vegetative growth by downregulating gibberellin (GA) biosynthesis genes and stimulating the GA deactivating genes, thus lowering the endogenous GA content in tomato transgenic lines. Moreover, the GA signaling downstream gene (SlGAST1) was downregulated but the negative regulator of GA signaling (SlDELLA) was upregulated by SlGRAS15 silencing. The root and hypocotyl length in SlGRAS15-RNAi lines showed reduced growth under normal conditions (Mock) as compared with the wild type (WT) control plants. Taken together, these findings enhanced our understanding that suppression of SlGRAS15 lead to a series of developmental processes by modulating gibberellin signaling and demonstrate an association between the SlGRAS15 and GA signaling pathway during vegetative growth in tomato.

Effect of Blended NPS Fertilizer Rates on Growth Performance of Tomato (Solanum lycopersicum L) at Wolaita Sodo University, Ethiopia

Filed experiment was conducted as Wolaita sodo University, college of agriculture and department of horticulture filed site to evaluate the response of vegetative growth of tomato to different rate of NPS application. The size of total plot is 7.5m X 5.5m (41.25m 2 ) and the size of each plot was 1.50m X 1.50m (2.25m 2 ). Three rate of blended NPS fertilizer at 80kg /ha, 160kg/ha and 240kg/ha with control (check). The experiment was lay out with 12 plots having 3 blokes and each block have four plots. The data on plant height per plant, the primary branches per plant, and the number of leaves per plants were collected from three plants of the middle rows of each plot and subjected to statistical analysis using ANOVA with computing the treatment by least significance difference at 5 %. As the result the number of leaf number shows significant (P 0.05) different. This shows the tomato crop requires high amount NPS supply enough to maintain the branch, plant height, and the leaf number of tomato vegetative growth. Application of 240kg/ha of blended NPS fertilizer did showed significant factors for all growth parameters. Hence, as this research revealed that application of 240kg/ha was the optimum level for effective vegetative performance of tomato. However, to come up concrete recommendation the study should be repeated across the season and up to yield . Keywords : Tomato, blended NPS fertilizer, Plant height, Leaf number, branch number DOI : 10.7176/JNSR/9-24-01 Publication date: December 31 st 2019

Growth, Physio-Biochemical Aspects, Productivity and Fungicide Residue in Tomato Plants Affected by Tolclofos-Methyl (Rizolex) Fungicide and some Remediating Agents

Vegetative growth of Tomato was negatively influenced by Tolclofos-methyl addition, and its phytotoxic effect was more pronounced on plant height and leaf area than other growth parameters. Application of Tolclofos-methyl fungicide at high rate caused marked decline in leaf chloroplast pigments, and carotenoids were more influenced. Total water content and leaf water deficit increased but the relative water content decreased as a result of Tolclofos-methyl application. Transpiration rate tended to increase at the lower dose of Tolclofos-methyl but decrease at its higher rate. Membrane integrity was increased with increasing the fungicide rate. Mineral elements (N, P, K, Ca, Mg, Fe, Zn, Mn), plant growth promoter substances (IAA, GA3, Cytokinins), and total free amino acids were reduced, whereas ABA, proline content, total phenol and the activity of phenoloxidase and peroxidase were increased in the fungicide exposed plants. Using Tolclofos-methyl fungicide at the high rate significantly reduced the number of flowers and fruit, vitamin C content of the fruits, yield, and water use efficiency of tomato plants. Total soluble solids and acidity in tomato fruits were increased, whereas lycopene content was decreased. Tolclofos-methyl fungicide residue in tomato fruits was dramatically enhanced above the maximum level of residue of Tolclofos-methyl fungicide (100 µg kg-1 in tomato fruits) and reached 176.8 and 423.2 µg kg-1 fresh weight at the rates of 2 and 4 g m-2 soil, respectively. Application of Bacillus, Trichoderma, GA3 and BP caused marked enhancements in the growth, yield, plant water relations, biochemical constituents, photosynthetic pigments and chemical properties of tomato fruits under both of the normal and fungicide pollution conditions. In addition, using these agents reduced the fungicide residue in fruits by about 42, 73, 35 and 5 % at the fungicide rate of 2 g m-2 soil and by about 80, 38, 68 and 47% at the rate of 4 g m-2 soil, respectively. It could be concluded that Trichoderma followed by Bacillus at the recommended dose of fungicide or Bacillus followed by GA3 at the exceeded dose of fungicide are useful tools to alleviate the phytotoxic effects and reduce the residue level of Tolclofos-methyl in tomato fruits below its maximum level.

Mechanism of toxicity and transformation of silver nanoparticles: Inclusive assessment in earthworm-microbe-soil-plant system

Long term and inclusive toxicity studies encompassing soil, plants, and organisms are rare in literature for AgNPs. This study examines AgNP behavior in soil-plant system through 72weeks long soil experiment, earthworm response, and plant metabolic analysis. AgNP exposed earthworms did not show reproductive failure; yet high oxidative stress and reduced protein synthesis led to significant weight loss. Such stress was highest with AgNP50 exposure. Correspondingly, the 50ppm exposure of AgNP was capable to reduce nutrient availability and microbial growth in soil. Contrary to previous reports, we demonstrated that dissolution rate of AgNP increased with time in soil. Dynamic Light Scattering and UV-VIS assessments exhibited concentration and time dependent agglomeration of AgNP in soil and aqueous media. Moreover, lab based experiments in aqueous medium revealed that significant reduction in silver availability was due to formation of Ag2S or Ag3PO4; which also greatly affected the P and S availability. Although the vegetative growth of tomato was normal, AgNP (10mgkg−1) treatment markedly upset the fruit yield. The 10mgkg−1 AgNP exposure significantly enhanced oxidative stress and Ag uptake in plants; consequently, retarded N-assimilating enzyme (glutamate synthase, glutamine synthetase, and nitrate reductase) activity by suppressing their genes in plants. Eventually, photosynthesis and CO2 assimilating efficiency were severely disrupted. These assays were vital to appreciate the true toxicity and are not well attended in most of the studies with AgNPs.

Drought Stress Reduces Stem Elongation and Alters Gibberellin-related Gene Expression during Vegetative Growth of Tomato

Drought stress reduces stem elongation and cell expansion. Since gibberellins (GAs) play an important role in controlling cell elongation, the objective of this study was to determine if the reduction in growth under drought stress is associated with altered GA metabolism or signaling. We exposed ‘Moneymaker’ tomato (Solanum lycopersicum) to drought stress to observe the effects on growth. Irrigation was automated using a data logger, which maintained volumetric water contents (VWC) of 0.35 and 0.15 m3·m−3 for well-watered and drought-stressed conditions, respectively. To further investigate the effect of GAs on elongation, paclobutrazol (PAC), a GA biosynthesis inhibitor, was applied to reduce endogenous GA production. Drought stress and PAC treatment reduced plant height. Internode length, cell size, and shoot dry weight displayed an interaction between the VWC and PAC treatments. The transcript levels of SlGA20ox1, -2, -3, and -4, SlGA3ox2, and SlGA2ox2, -4, and -5, corresponding to enzymes in GA metabolism, and LeEXP1, and -2, encoding expansin enzymes related to cell wall loosening necessary for cell expansion, were analyzed. Downregulation of transcript accumulation due to drought stress was observed for SlGA20ox4, SlGA2ox5, and LeEXP1, but not for any of the other genes. PAC increased expression of SlGA20ox-3, and SlGA3ox2, potentially through feedback regulation. These findings suggest that drought stress effects on elongation are at least partly mediated by altered GA metabolism.

Green Synthesis of Silver Nanoparticles Using Leaf Extract of Rosmarinus officinalis and Its Effect on Tomato and Wheat Plants

Biological green synthesis of silver nanoparticles (AgNPs) from silver salts is a growing advanced approach to avoid the requirement of costly instruments and involvement of hazardous chemicals as well. However, increasing use of AgNPs raises potential toxicity level in the environment. In this investigation, leaf extract of rosemary (Rosmarinus officinalis) used as a reducing and stabilizing agent for biosynthesis of AgNPs. The biosynthesized AgNPs were authorized by UV-vis spectrophotometer and X-ray diffraction (XRD) analysis. The shape and size of the biosynthesized AgNPs were studied using high resolution transmission electron microscope (TEM). The toxicity of the biosynthesized silver nanoparticles on wheat and tomato plants was studied by soaking wheat grains and tomato seeds in 100 mg/L AgNPs and follow its effect on seedling growth of wheat (at 10 days) and on vegetative growth of tomato and wheat plants (at 35 days). Some physiological parameters as germination percentage of wheat seedling, length of seedling, dry weight, pigment fractions (chl.a, chl.b and caroteinoids), soluble proteins, lipid peroxidation (MDA) and antioxidant enzymes (catalase and peroxidase) of two plants were measured. AgNPs has a non-significant inhibitory effect on germination percentage of wheat, dry weight and pigment fractions. The biosynthesized AgNPs has a noticeable stress effect on tomato plant as reduced chlorophyll a and dry weight. Generally, AgNPs stimulate MDA accumulation in tomato and wheat plants. There was a noticeable different effect of AgNPs on soluble proteins and antioxidant enzymes as catalase and peroxidase among tomato and wheat plants.

Use of Urban Sewage Sludge as Soil Amendment and its Influence on the Development of Tomato Plants

Accumulation of waste represents a huge problem for the urban development. One possibility of useful application of such waste is its application in agriculture. Tomato is one of the most important horticulture plants in Spain and especially in the region of Valencia. The effect of urban sewage sludge on the vegetative growth of tomatoes was checked on four types of soils from the Valencian region in Eastern Spain. Young plants were grown during four months in two experimental conditions, a control only with local irrigation water, and a treatment in which sewage sludge was added to each pot at the beginning of the experiment and watered with the same water type. Composition of soils, irrigation water and sewage sludge were analyzed and vegetative parameters, such as total length, length of stems and branches, and biomass of roots, stems, branches and leaves were measured. Plants achieved better vegetative development in the presence of sewage sludge in the four types of soils. The positive effect of the sludge is due to its high content in organic matter which clearly improves the qualities of Mediterranean soils, which are generally very poor.

The Last Reaction Producing Brassinolide Is Catalyzed by Cytochrome P-450s, CYP85A3 in Tomato and CYP85A2 in Arabidopsis

Brassinosteroids are steroidal hormones essential for the growth and development of plants. Brassinolide, the most biologically active brassinosteroid, has a seven-membered lactone ring that is formed by a Baeyer-Villiger oxidation of its immediate precursor castasterone. Despite its potential key role in controlling plant development, brassinolide synthase has not been identified. Previous work has shown that the formation of castasterone from 6-deoxocastasterone is catalyzed by members of the CYP85A family of cytochrome P-450 monooxygenases. A null mutation in the tomato Dwarf (CYP85A1) gene, extreme dwarf (d(x)), causes severe dwarfism due to brassinosteroid deficiency, but the d(x) mutant still produces fruits. Here, we show that d(x) fruits contain brassinolide at a higher level than wild-type fruits and that a new CYP85A gene, CYP85A3, is preferentially expressed in tomato fruits. Tomato CYP85A3 catalyzed the Baeyer-Villiger oxidation to produce brassinolide from castasterone in yeast, in addition to the conversion of 6-deoxocastasterone to castasterone. We also show that Arabidopsis CYP85A2, which was initially characterized as castasterone synthase, also has brassinolide synthase activity. Exogenous application of castasterone and brassinolide to the Arabidopsis cyp85a1/cyp85a2 double mutant suggests that castasterone can function as an active brassinosteroid but that its conversion into brassinolide is necessary for normal vegetative development in Arabidopsis. We postulate that castasterone is the major active brassinosteroid during vegetative growth in tomato, whereas brassinolide may play an organ-specific role in fruit development in this species.

Ethylene Production throughout Growth and Development of Plants

Ethylene production by 10 or 20 m2 stands of wheat, soybean, lettuce, potato, and tomato was monitored throughout growth and development in an atmospherically closed plant chamber. Chamber ethylene levels varied among species and rose during periods of canopy expansion and rapid growth for all species. Following this, ethylene levels either declined during seed fill and maturation for wheat and soybean, or remained relatively constant for potato and tomato (during flowering and early fruit development). Lettuce plants were harvested during rapid growth and peak ethylene production. Chamber ethylene levels increased rapidly during tomato ripening, reaching concentrations about 10 times that measured during vegetative growth. The highest ethylene production rates during vegetative growth ranged from 1.6 to 2.5 nmol m-2 d-1 during rapid growth of lettuce and wheat stands, or about 0.3 to 0.5 nmol g-1 fresh weight per hour. Estimates of stand ethylene production during tomato ripening showed that rates reached 43 nmol m-2 d-1 in one study and 93 nmol m-2 d-1 in a second study with higher lighting, or about 50x that of the rate during vegetative growth of tomato. In a related test with potato, the photoperiod was extended from 12 to 24 hours (continuous light) at 58 days after planting (to increase tuber yield), but this change in the environment caused a sharp increase in ethylene production from the basal rate of 0.4 to 6.2 nmol m-2 d-1. Following this, the photoperiod was changed back to 12 h at 61 days and ethylene levels decreased. The results suggest three separate categories of ethylene production were observed with whole stands of plants: 1) production during rapid vegetative growth, 2) production during climacteric fruit ripening, and 3) production from environmental stress.

Early Vegetative Growth of Tomato Plants in Media Containing Nitrogen Source as Nitrate, Ammonium, or Various Nitrate–Ammonium Mixtures with Bicarbonate Addition

The effect of various concentrations applied in media with , , or various mixtures of both on the accumulation of biomass and early vegetative growth of tomato (Lycopersicon esculentum Mill.) plants was tested in experiments carried out in hydroponics. The optimum concentration was 5 mM and was similar in all the combinations of the N source applied at 3 mM concentration. The average biomass of -grown plants without reached only 50% of the value for the plants if was used as the N source. With respect to the growth without , the biomass increased by about 160% or 130% with or used as the N source, respectively. The biomass of -grown plants in media with reached only about 42% of the value obtained by plants cultivated in media with and . Similar relations were observed in the size of leaf blades. A simultaneous addition of to the medium containing ameliorated the toxic effects of this compound. The optimum ratio of for the growth of plants was ≤ 1. The use of such proportions of nitrogen (N) forms in the medium stimulated the accumulation of biomass to about 115% of the mass attained by -grown plants. The addition of to the medium containing the N source in the two forms at an optimum ratio stimulated an increase in the biomass of plants by about 180% with respect to plants without . Certain growth parameters calculated, i.e., shoot to root ratio, specific leaf area, and relative growth rate confirm the ameliorating effect of if added to media containing and the stimulating effect of on the biomass production of different organs of the plants.

Mycorrhizal infection and high soil phosphorus improve vegetative growth and the female and male functions in tomato

Summary • To further characterize the effects of mycorrhizal infection and soil phosphorus (P) availability on plant fitness, this study examined their effects on the female and male functions, as well as vegetative growth of tomato ( Lycopersicon esculentum ). • Two cultivars of tomato were grown in a glasshouse under three treatment combinations: nonmycorrhizal, low P (NMPO); nonmycorrhizal, high P (NMP3); and mycorrhizal, low P (MPO). • Mycorrhizal infection and high soil P conditions improved several vegetative (leaf area, days until first flower and leaf P concentration) and reproductive traits (total flower production, fruit mass, seed number and pollen production per plant, and mean pollen production per flower). In general, mycorrhizal and P responses were greater for reproductive traits than vegetative traits. In one cultivar, these responses were greater for the male function than the female function. • Thus, mycorrhizal infection and high soil P conditions enhanced fitness through both the female and male functions. Similar trends were usually observed in the NMP3 and MPO treatments, suggesting that mycorrhizal effects were largely the result of improved P acquisition.

Identification and validation of QTLs for salt tolerance during vegetative growth in tomato by selective genotyping

The purpose of this study was to identify quantitative trait loci (QTLs) for salt tolerance (ST) during vegetative growth (VG) in tomato by distributional extreme analysis and compare them with the QTLs previously identified for this trait. A BC1 population (N = 792) of a cross between a moderately salt-sensitive Lycopersicon esculentum Mill. breeding line (NC84173, maternal and recurrent parent) and a salt-tolerant L. pimpinellifolium (Jusl.) Mill. accession (LA722) was evaluated for ST in solution cultures containing 700 mM NaCl + 70 mM CaCl2 (electrical conductivity, EC = 64 dS/m and phiw approximately -35.2 bars). Thirty-seven BC1 plants (4.7% of the total) that exhibited the highest ST were selected (referred to as the selected population), grown to maturity in greenhouse pots and self-pollinated to produce BC1S1 progeny seeds. The 37 selected BC1S1 progeny families were evaluated for ST and their average performance was compared with that of the parental BC1 population before selection. A realized heritability of 0.50 was obtained for ST in this population. The 37 selected BC1 plants were subjected to restriction fragment length polymorphism (RFLP) analysis using 115 markers, and marker allele frequencies were determined. Allele frequencies for the same markers were also determined in an unselected BC1 population (N = 119) of the same cross. A trait-based marker analysis (TBA), which measures differences in marker allele frequencies between selected and unselected populations, was used to identify marker-linked QTLs. Five genomic regions were detected on chromosomes 1, 3, 5, 6, and 11 bearing significant QTLs for ST. Except for the QTL on chromosome 3, all QTLs had positive alleles contributed from the salt tolerant parent LA722. Of the five QTLs, three (those on chromosomes 1, 3, and 5) were previously identified for this trait in another study, and thus were validated here. Only one of the major QTLs that was identified in our previous study was not detected here. This high level of conformity between the results of the two studies indicates the genuine nature of the identified QTLs and their potential usefulness for ST breeding using marker-assisted selection (MAS). A few BC1S1 families were identified with most or all of the QTLs and with a ST comparable to that of LA722. These families should be useful for the development of salt tolerant tomato lines via MAS.

Analysis of the effect of EC and potential transpiration on vegetative growth of tomato

This paper analyses the response of vegetative growth of greenhouse tomato to both root-zone salinity and shoot-environment (potential transpiration), with the purpose of explaining the observed lack of effect on dry matter yield. A reference salinity (EC) of 2 dS m −1 was compared in three experiments with, respectively, 6.5, 8 and 9.5 dS m −1. Another experiment investigated specific effects of sodium chloride, by comparing two high-EC treatments (both 9 dS m −1), one with a high concentration of nutrients and one with addition of sodium chloride to a normal nutrient solution. The shoot-environment was either a “normal” climate regime or the same regime but with depressed potential transpiration, mainly by adaptation of the humidity set point. There was no detectable effect of the potential transpiration treatment, neither of the sodium chloride. Salinity effects on vegetative growth only showed up at EC exceeding 6.5 dS m −1. The most evident EC effect was a reduction of leaf expansion; individual leaf area was reduced by 8% per dS m −1 exceeding 6.5. This was partly compensated by a slight increase (2% per unit EC) in the number of leaves, which explains why cumulative plant leaf area decreased by about 7% per unit EC in excess of 6.5 dS m −1. Therefore, leaf area index (LAI) at the highest EC was reduced by some 20% compared to the LAI at an EC of 2 dS m −1. It is estimated that this would cause a reduction of less than 8% in light interception, and thus in dry matter produced. Indeed, differences observed in dry weight between the EC treatments were never significant.

Relationship Between Cold Tolerance during Seed Germination and Vegetative Growth in Tomato: Analysis of Response and Correlated Response to Selection

The genetic relationship between cold tolerance (CT) during seed germination and vegetative growth in tomato (Lycopersicon esculentum Mill.) was determined. An F2 population of a cross between accession PI120256 (cold tolerant during both seed germination and vegetative growth) and UCT5 (cold sensitive during both stages) was evaluated for germination under cold stress and the most cold tolerant progeny (the first 5% germinated) were selected. Selected progeny were grown to maturity and self-fertilized to produce F3 families (referred to as the selected F3 population). The selected F3 population was evaluated for CT separately during seed germination and vegetative growth and its performance was compared with that of a nonselected F3 population of the same cross. Results indicated that selection for CT during seed germination significantly improved CT of the progeny during germination; a realized heritability of 0.75 was obtained for CT during seed germination. However, selection for CT during germination did not affect plant CT during vegetative growth; there was no significant difference between the selected and nonselected F3 populations in either absolute CT [defined as shoot fresh weight (FW) under cold stress] or relative CT (defined as shoot FW under cold as a percentage of control). Results indicated that, in PI120256, CT during seed germination was genetically independent of CT during vegetative growth. Thus, to develop tomato cultivars with improved CT during different developmental stages, selection protocols that include all critical stages are necessary.

Genetic analysis of cold tolerance during vegetative growth in tomato, Lycopersicon esculentum Mill

The genetic basis of cold tolerance (CT) during vegetative growth in tomato was investigated by evaluating plants of a cold-tolerant primitive cultivar (PI120256) and a cold-sensitive breeding line (UCT5) and their reciprocal F1, F2, F3, BC1P1 and BC1P2 progeny under two temperature regimes of 15/10 °C (cold stress) and 25/15 °C (control). Plants were evaluated for shoot dry weight (DW) under cold stress and by a tolerance index (TI) measured as the ratio of DW under cold stress (DWs) to DW under control (DWc) conditions. Shoot DW was reduced in all genotypes in response to cold stress. However, PI120256 exhibited the highest CT (TI = 90.5%) and UCT5 the lowest (TI = 38.9%). The TIs of the filial and backcross progeny were intermediate to the parents. Across generations, there was a positive correlation (r = 0.76, p 0.05) between DWc and the TI and, in contrast, the presence of a significant correlation (r =0.92, p <0.01) between DWs and the TI suggest that plant vigor was not a determining factor in the expression of CT in PI120256 and its progeny. Generation means analyses of DWs and TI indicated that the variation among generations was genetically controlled, with additive effects accounting for most of the variation. There were no significant dominance effects, and epistatic effects were minor and involved only additive × additive interactions. The results suggest that the inherent CT of PI120256 should be useful for improving CT of commercial cultivars of tomato.

Identification and validation of QTLs for salt tolerance during vegetative growth in tomato by selective genotyping

Identification and validation of QTLs for salt tolerance during vegetative growth in tomato by selective genotyping