Effects of High-Level Acylsugar-Producing Tomato Lines on the Development of Tomato Psyllids (Hemiptera: Triozidae).

Acylsugars have been shown to provide activity against numerous insect pests of tomatoes. Comparison of acylsugar levels in four tomato plant lines, FA7/AS, FA2/AS, CU071026, and 'Yellow Pear', found that the acylsugar contents in the elevated acylsugar lines were significantly higher than the commercial Yellow Pear (control) tomato plant line. Adult choice tests indicated that the tomato psyllid, Bactericera cockerelli, preferred to settle on the Yellow Pear and FA2/AS lines over the line with the highest content of acylsugars, FA7/AS, and the parental line, CU071026. The no-choice test demonstrated that adults laid fewer eggs on the high acylsugar tomato lines than on the control tomato line, Yellow Pear. For all high acylsugar lines, the relative growth index of the psyllid was significantly lower compared with the commercial line, indicating a reduced potential for population growth. Although some tomato psyllids completed their life cycle on the high acylsugar tomato plant lines, the percent survival of psyllids to the adult stage when developing on the high acylsugar lines was significantly less (range = 43.7-57.1%) than on the commercial tomato line (83.8%). All mortality occurred during the early stages of development (egg stage to third instar), which has implications for acquisition and transmission of Candidatus Liberibacter solanacearum, the causal agent of tomato vein greening disease. Therefore, with reduced attractiveness for tomato psyllids and significantly reduced survival, the high-acylsugar tomato plant lines have the potential to be part of an integrated pest management program for this pest

Evaluating soil nitrate dynamics in an intercropping dripped ecosystem using HYDRUS-2D.

The competition mechanisms between crop species for water and nutrients, especially nitrate (NO3-N), in intercropping ecosystems are still poorly understood. Therefore, an experiment involving high (300 kg ha-1 for corn and 250 kg ha-1 for tomato), medium (210 kg ha-1 for corn and 175 kg ha-1 for tomato), and low (150 kg ha-1 for corn and 125 kg ha-1 for tomato) N-fertilizer applications (HF, MF, LF, respectively) was conducted in the corn and tomato intercropping ecosystem during 2014 (a calibration period for modeling) and 2015 (a validation period for modeling). The modified HYDRUS-2D code was used to analyze soil NO3-N concentrations (SNC) in the middle between corn rows (Pc), between corn and tomato rows (Pb), and between tomato rows (Pt), NO3-N exchange in the horizontal direction between different regions, NO3-N leaching from the corn, the bare, and the tomato region, and N uptake by crops. Simulated SNCs were in good agreement with measurements, with RMSE, NSE, and MRE of 0.01-0.06 mg cm-3, 0.75-0.98, and 8.7-19.1%, respectively, during the validation period (2015). Average SNCs in the 0-40 cm soil layer were different between Pc, Pt, and Pb. Intensive NO3-N exchange in the horizontal direction occurred during the second stage (Day After Sowing [DAS] 37-113 in 2014; DAS 29-120 in 2015). NO3-N exchange between the corn and bare regions was lower than between the tomato and bare regions due to smaller concentration gradients. However, in the vertical direction, NO3-N leaching from the corn region in both years was 4.1 and 8.8 times larger, respectively, than from the tomato region under HF since NO3-N mainly moved from the tomato region to the corn region. Our results reveal the competition between corn and tomato for N and provide a rationale for formulating and optimizing different fertilizer regimes for different crops in the intercropping ecosystem

Performance, Competitiveness and Determinants of Tomato Export from India

The performance and competitiveness of export of tomato and its products from India have been analyzed to find (i) production and export performance of tomatoes in India, (ii) impact of trade liberalization on export of tomato and its products, (iii) major destinations of Indian tomato and tomato products, and (iv) determinants of tomato export. The export performance ratio (EPR) has been estimated to examine the export competitiveness of India in tomato and tomato products. Annual compound growth rate and coefficient of variation for two periods, before (1985-1994) and after (1995- 2004) the commencement of WTO have been estimated to study the impact of trade liberalization on the export performance of India in tomato and its products. Export demand function has been estimated using OLS technique and the factors affecting the export of tomato and its products from India have been identified. The study has revealed that the existence of high instability in export of tomato and its products require the attention of policymakers to retain hold on the international market.Crop Production/Industries, International Relations/Trade,

Tomato protoplast DNA transformation: physical linkage and recombination of exogenous DNA sequences

Tomato protoplasts have been transformed with plasmid DNA's, containing a chimeric kanamycin resistance gene and putative tomato origins of replication. A calcium phosphate-DNA mediated transformation procedure was employed in combination with either polyethylene glycol or polyvinyl alcohol. There were no indications that the tomato DNA inserts conferred autonomous replication on the plasmids. Instead, Southern blot hybridization analysis of seven kanamycin resistant calli revealed the presence of at least one kanamycin resistance locus per transformant integrated in the tomato nuclear DNA. Generally one to three truncated plasmid copies were found integrated into the tomato nuclear DNA, often physically linked to each other. For one transformant we have been able to use the bacterial ampicillin resistance marker of the vector plasmid pUC9 to 'rescue' a recombinant plasmid from the tomato genome. Analysis of the foreign sequences included in the rescued plasmid showed that integration had occurred in a non-repetitive DNA region. Calf-thymus DNA, used as a carrier in transformation procedure, was found to be covalently linked to plasmid DNA sequences in the genomic DNA of one transformant. A model is presented describing the fate of exogenously added DNA during the transformation of a plant cell. The results are discussed in reference to the possibility of isolating DNA sequences responsible for autonomous replication in tomato.

Begomovirus quasispecies adapt to hosts by exploring different sequence space without changing their consensus sequences

Geminiviruses possess single-stranded circular DNA genomes that depend on cellular polymerases for replication in the host nucleus. In plant hosts, geminivirus populations behave as ensembles of mutant and recombinant genomes. This favours the emergence of new geminivirus strains able to produce new diseases or overcome the genetic resistance of cultivars. In warm and temperate areas several whitefly-transmitted geminiviruses of the genus Begomovirus cause the tomato yellow leaf curl disease (TYLCD) with important economic consequences. TYLCD is frequently controlled in commercial tomato production using the Ty-1 resistance gene. Over a 45 day period we studied the evolution of infectious clones from three TYLCD-associated begomoviruses: Tomato yellow leaf curl Sardinia virus, Tomato yellow leaf curl virus and the recombinant Tomato yellow leaf curl Axarquia virus. The evolution of their viral progeny was examined in susceptible tomato (ty1/ty1), resistant tomato (Ty1/ty1), common bean, and the wild reservoir Solanum nigrum. We found that in addition to affecting viral accumulation kinetics, the host influenced the sequence space explored by these begomoviruses. In tomato, viral dynamics was not influenced by the presence of the Ty-1 gene. Interestingly, positive adaptation of the coat protein gene was only observed in the common bean and S. nigrum, which correlates with these plants having viral quasispecies with the highest degree of complexity and heterogeneity. Our results underline the importance of analysing the mutant spectra of begomovirus infections, especially in wild reservoirs, which have the potential to give rise to large numbers of emergent variants in spite of the invariance of their consensus sequences.Junta de Andalucía proyecto: P10-CVI-6561. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Tomato: a crop species amenable to improvement by cellular and molecular methods

Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures. In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.

Greenhouse Tomatoes Change the Dynamics of the North American Fresh Tomato Industry

The rapid growth of the North American greenhouse tomato industry has changed the longstanding dynamics of the fresh tomato industry. During the 1990s, Canada emerged as the largest North American producer of greenhouse tomatoes, a prominence it never attained in the fresh field tomato industry. The United States and Mexico have also become important greenhouse tomato producers, consistent with their long dominance in North American fresh field tomato production. Greenhouse tomatoes have changed the look of U.S. retail tomato sales, where they now account for 37 percent of the quantity sold of fresh tomatoes. While the primary U.S. fresh field tomato product, the mature green tomato, long dominated retail sales, its share has decreased significantly due to the growth of greenhouse tomatoes. The U.S. mature green tomato industry is now more dependent on the continuing growth of the foodservice market, which generally prefers its product.Greenhouse tomatoes, field tomatoes, mature green tomatoes, United States, Canada, Mexico, market integration, product differentiation, seasonality in production, Crop Production/Industries,

Modeling of the break process to improve tomato paste production quality : a thesis presented in partial fulfilment for the degree of Master of Engineering in Bioprocess at Massey University

The pectic enzyme, Pectinmethylesterase (PE) and Polygalacturonase I and II (PGI and PGII), in the tomato fruit released after crushing during tomato processing reduce the viscosity of tomato paste by breaking down the insoluble pectin in the cell wall. To achieve higher viscosity tomato paste, the cold break (60-95°C) processes can be used to inactivate the pectic enzyme and to achieve higher viscosity tomato paste. The study of tomato solids and PG enzyme activity showed that the levels of insoluble solids, total solids, pectin, and °Brix in Ferry Morse tomatoes were independent of fruit ripeness. The amount of PG enzymes was high in orange and dark red tomatoes and the activity of PG enzymes increased as a function of ripeness, from green to dark red. In the dark red tomato, the inactivation of PG enzyme activity was required to retain the level of pectin. Cold break temperatures below 60°C can not inactivate the PG enzyme activity. The PG enzymes started to be denatured when the hot break temperature was above 65°C and be completely destroyed when the break temperature was above 80°C. A mathematical model of the break process was formulated and Matlab programme was used to predict the effect of break temperatures on the pectin and PG enzyme concentration of the tomato pulp in the break tank for any inputs of feed rate (the flow rate to the break tank), feed ripeness, and residence time. The model was used to demonstrate the understanding and the optimisation of break process performance. Longer residence time of dark red tomato pulp in the break tank can decrease pectin fraction residual and increase enzyme inactivation in the tank temperature range 40 to 60°C. The pectin fraction remaining increased when the tank temperature was above 60°C because of the inactivation of PG enzymes. At 80°C there was no effect of residence time, the pectin fraction residual increased and reached 90% and enzyme fraction residual decreased to 10%. The effect of mixed tomato ripeness between the ripe fruit (orange and dark red) with the unripe fruit (green, breaker, and turning), the level of PG enzymes in the break tank decreased and affected on the higher pectin fraction remaining. Lower break temperature can be therefore used in this process to inactivate the low amount of PG enzyme and to achieve the same extent of pectin hydrolysis. The interruption of the feed coming into the break tank during tomato processing can increase the pectin fraction remaining and the enzyme fraction remaining in a new steady state when the feed was turned on

Potato R1 resistance gene confers resistance against Phytophthora infestans in transgenic tomato plants

Tomato is challenged by several pathogens which cause loss of production. One such pathogen is the oomycete Phytophthora infestans which is able to attack all the aerial parts of the plant. Although a wide range of resistance sources are available, genetic control of this disease is not yet successful. Pyramiding R-genes through genetic transformation could be a straightforward way to produce tomato and potato lines carrying durable resistance to P. infestans. In this work the R1 potato gene was transferred into tomato lines. The tomato transgenic lines were analyzed by using q-RT-PCR and progeny segregation to determine the gene copy number. To test the hypothesis that R1 represents a specifically regulated R-gene, transgenic tomato plants were inoculated with P. infestans isolate 88133 and IPO. All the plants containing the R1 gene were resistant to the late blight isolate IPO-0 and susceptible to isolate 88133. These results provide evidence for specific activation of the R1 gene during pathogen challenge. Furthermore, evidence for enhancement of PR-1 gene expression during P. infestans resistance response was obtained