A reduced-till (RT) experiment determined the effect of rye seeding density and method of kill on rye biomass persistence, weed suppression, and tomato yield. ‘Wheeler’ rye was seeded at 56, 110, and 170 kg ha−1 in the fall of 1988 and 1989 in Champaign, IL; Lexington, KY; and Lafayette, IN. One wk before transplanting tomatoes, rye was desiccated either by applying glyphosate at 1.1 kg ha−1 and mowing (RT-glyphosate) or by mowing alone (RT-mowed). Both methods left rye residues on the soil surface as a mulch. Seeding density did not affect rye biomass, weed control, or tomato yield. Rye biomass differed depending on location and year, ranging from 320 to 1150 gm−2. Rye was completely killed by glyphosate, but regrew following mowing. RT-glyphosate suppressed weeds for 4 to 8 wk, which was similar to the suppression from conventional tillage (fall plowing with spring disking and harrowing) with trifluralin and metribuzin (CT-herbicide). Weed communities varied, but redroot pigweed and giant foxtail were present at all three locations. All treatments required supplemental weed management for commercially acceptable control. Except for IL in 1990, processing tomato yields (kg ha−1) in RT-glyphosate with hand-weeding were equal or better than yields in the CT treatments.

Laboratory experiments were carried out under aseptic conditions to study the effect of nitrogen applied as ammonium nitrate at 0, 20,40,60,80 and 100 ppm (wt per vol) in either distilled H2O or modified Hoagland's solution on germination and radicle length of branched broomrape in association with growing seedlings of different crops. As nitrogen rate increased, seed germination and radicle length of branched broomrape decreased linearly in flax, lentil, pepper, tomato, and wheat in modified Hoagland's solution. Similar responses to nitrogen application were found with distilled water. The parasite's seed germination was considerably lower in the media with wheat than with other crops, and lower still in the absence of crop seedings.

A time course of Egyptian broomrape development on tomato roots grown in pots in the greenhouse revealed an increase in the number of parasitic attachments from 2.6 at 4 weeks after planting (WAP) to 139 when rated 2 wk later. Rimsulfuron sprayed on tomato foliage as single and split applications (12.5 g ai/ha) 3, 4, 5, 6, and 7 WAP did not decrease Egyptian broomrape damage to tomato plants, as expressed by reduced tomato plant height and fresh weight, and the total number of parasitic attachments on the roots was not significantly different compared to the nontreated control. A single foliar application of rimsulfuron (25 g ai/ha) to tomato at 10 days after planting (DAP) and split applications at 10 and 20 and 10, 20, and 30 DAP significantly reduced the number of Egyptian broomrape inflorescences to 2.2, 0.2, and 0, respectively, 9 WAP compared with 19.6 inflorescences in the nontreated control. Application of the herbicide under the same conditions to tomato plants in pots covered with activated charcoal did not significantly influence the number of Egyptian broomrape inflorescences. Chlorsulfuron and triasulfuron applied directly to the soil at rates ≥ 3: 3.75 g ai/ha completely controlled Egyptian broomrape. Primisulfuron and chlorimuron, each at 22.5 g ai/ha, reduced the number of inflorescences to 0.6 and 0.4, respectively. Chlorimuron did not significantly reduce the total number of parasitic attachments on the roots, but primisulfuron at the same concentration significantly increased the total number of parasitic attachments on the root system to 50 as compared to 23 in the nontreated control. Tribenuron had no effect on the parasitism process, as reflected in the number of inflorescences and parasitic attachments on the roots.

We previously reported that napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] was highly toxic to achlorophyllous callus of tomato (Lycopersicon esculentum Mill. ‘San Marzano’), whereas foliar application to seedlings was almost without effect. Experiments were performed to ascertain the effects of napropamide on green and achlorophyllous calli of tomato and broadleaf dock (Rumex obtusifolius L.). The growth of achlorophyllous tissues was more severely inhibited. Foliar applications were not as inhibitory in both species. Napropamide was applied to tomato seedlings via roots and cut shoots and root growth was more inhibited than shoot growth. Thus napropamide is toxic to achlorophyllous tissue and is either less toxic to, or detoxified by green tissue.

Reductions in yields of processing tomatoes (Lycopersicon esculentum Mill. ‘H2653’ and ‘Earlirouge′) caused by interference from eastern black nightshade (Solanum ptycanthum Dun. # SOLPT) and hairy nighthsade (S. sarrachoides Sendt. # SOLSA) were estimated for transplanted and seeded tomatoes at two locations in southern Ontario. Tomato yield losses were significantly greater in seeded than in transplanted tomatoes. Stomatal conductance and transpiration rates of seeded tomatoes decreased more rapidly with increased nightshade density than did those of transplanted tomatoes. Percent yield losses also differed between sites. Seeded tomatoes grown at high density in twin rows (33 300 and 45 000 plants/ha) had higher yields and lower percent yield losses than did tomatoes grown at low density in single rows (12 500 to 22 500 plants/ha). Nightshade dry weight and seed production decreased per plant but increased per unit area with increasing nightshade density. Nightshade dry weights and seed production did not vary with site or method of tomato establishment. A hyperbolic model provided an excellent fit to data on both tomato yield losses and nightshade seed production as a function of nightshade density.

Sublethal amounts of 2,4-D [(2,4-dichlorophenoxy) acetic acid] were applied to several vegetable crops in order to determine effect on yield and quality in a simulated drift experiment. Tomato (Lycopersicon esculentum Mill.) and root crops were most sensitive to 2,4-D; as little as 2.1 g/ha of acid distorted tomato fruit shape and elongated radish (Raphanus sativus L.) roots. All root crops were rendered unmarketable by 10.4 g/ha and gross yields were reduced by exposure to 104 g/ha. Yield of peppers (Capsicum frutescens L. var. grossum) was increased by exposure to 2.1 g/ha and severely depressed by 104 g/ha. Cucumber (Cucumis sativus L.) fruit shape was distorted at 11 g/ha and yield was reduced slightly. Lettuce (Lactuca sativa L.), onion (Allium cepa L.), and cabbage (Brassica oleracea L. var. capitata) were least sensitive to 2,4-D. Exposure to 20.8 g/ha did not reduce yields of lettuce or cabbage. Onion yields were reduced by application of 104 g/ha. Bush bean (Phaseolus vulgaris L.) yield was decreased by exposure to 22 g/ha, but potato (Solarium tuberosum L.) yield increased at 16 g/ha. Herbicide residues in the crop foliage were proportional to the degree of exposure. Residue analysis combined with foliar symptoms may be useful in predicting crop damage following 2,4-D drift.

Studies were conducted to determine the mechanism of acifluorfen tolerance within the Lycopersicon genus. Absorption of 14C-acifluorfen was not correlated with tolerance. There was a negative correlation (r = −0.57) between absorption 24 h after treatment and wax density. No other surface characteristic correlated with absorption. Less than 3% of absorbed 14C was translocated and there was no metabolism of acifluorfen. All genotypes were susceptible to paraquat, and acifluorfen-tolerant genotypes had lower levels of ascorbate than susceptible genotypes, implying that free radical protectant systems were not involved in tolerance. Genotypes varied in amounts of chlorophyll a, chlorophyll b, and total chlorophyll but the differences did not correlate to acifluorfen tolerance.

Under greenhouse conditions, vaporization of oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] formulations (2 EC, 25 WP, 1G) was studied on cabbage (Brassica oleracea L. var. capitata L. F. alba DC. ‘Market Prize’), tomato (Lycopersicon esculentum Mill. ‘Campbell 37’), cucumber (Cucumis sativus L. ‘Straight 8’), and lettuce (Lactuca sativa L. ‘Salad Bowl’). The emulsifiable concentrate and granular formulations caused vapor injury to plants exposed under glass bell jars. Vapor injury to all species increased when exposure times were increased from 8 to 72 h. Lettuce was the most susceptible test species. Exposure temperatures of 18 and 29 C did not alter the amount of vapor injury apparent on tomato foliage. Oxyfluorfen vapor injury did not reduce dry weight of any test species.

Field studies were conducted to determine the effect of season of the year, sunlight exposure time, and mulch color on paraquat photodegradation rate on polyethylene mulch. Experiments were established in winter, spring, and summer, with white and black polyethylene mulch, and paraquat-applied films were exposed to sunlight for 1, 4, 8, 24, 30, 48, 72, or 96 h after herbicide application. There was significant effect of the season by mulch color by time of exposure interaction on paraquat concentration recovered from mulch eluants. Winter paraquat photodegradation was lower than during the other seasons. At 48 h of sunlight exposure, predicted photodegradation on white mulch was 67, 83, and 88%, during winter, spring, and summer, respectively, whereas these values were 66, 82, and 84% on black mulch. The difference in paraquat photodegradation in winter with respect to the other seasons may be attributed to reduced ultraviolet radiation in winter, when solar radiation has to penetrate a larger atmosphere mass. In practical terms, transplanting on paraquat-applied mulch requires a minimum of 96 h during the spring and summer seasons, when concentrations were 5% or less, whereas a longer waiting period might be necessary in the winter.

An invasive pest, Tuta absoluta (Meyrick) has been observed infesting tomato Solanum lycopersicum L. (Solanales: Solanaceae) in Central Uganda. The affected farmer made the report, and upon visiting the farm, we observed tiny larvae, green to cream in colour with a black head feeding on tomato leaves, fruit, as well as tender stems. Also, we saw several tiny moths resting on screen house linings. Delta traps baited with TUA-Optima® (Russell IPM) were set in and around the affected farm. Dozens of moths were attracted and trapped on the sticky surface of the traps. The team tentatively identified the insect as T. absoluta. Scientists at the International Centre of Insect Physiology and Ecology (icipe) in Nairobi, Kenya identified the insect using morphological features and molecular techniques.

Introduction. Rhizopus stolonifer is thecausal agent of Rhizopus rot disease in various fruit and vegetables.Materials and methods. The effect of chitosan was evaluated invitro on mycelial growth, sporulation, morphological characteristics andgermination of spores of three isolates of R. stolonifer (from peach,papaya and tomato). The effect of chitosan on controlling Rhizopus decayin peach, papaya and tomato fruit in situ in comparison with thesynthetic fungicide dichloran was also studied. Results and discussion. Ourresults showed that the mycelial growth and sporulation of the three isolates weremarkedly inhibited at all tested chitosan concentrations. The highest antifungal indexesand sporulation reduction were observed with chitosan at 2 mg·mL–1. In ourstudy, the morphological characteristics of the spores of R. stolonifershowed different behavior depending on the evaluated isolates. In general, the highesteffect on germination was observed at the chitosan concentration of 2 mg·mL–1.Our results demonstrated that chitosan was effective in reducing the percentage ofinfection and the severity index on peach, papaya and tomato fruit compared with those ofnon-treated control. The chitosan was not more effective than dichloran in reducing thepercentage of infection. The results of the study suggest that chitosan(2 mg·mL–1) is a good alternative for the control ofRhizopus decay on peach, papaya and tomato fruit; it could beconsidered as a potential agent in natural alternatives to control postharvestdiseases.

In addition to constitutive plant resistance against pests or pathogens, plants can activate protective mechanisms upon contact with an invader or a chemical elicitor. Studies on induced plant resistance to herbivores, especially piercing-sucking insects, are less abundant than those devoted to pathogens. Several experiments under controlled conditions have been conducted to demonstrate that infestations by Macrosiphum euphorbiae induce plant resistance to Bemisia tabaci in susceptible tomato plants. After three days of exposure to 20 apterous adult aphids, the plants acquired a transiently induced resistance to B. tabaci when aphid removal occurred one or 18 hours prior to B. tabaci infestation; the effect disappeared when four days passed between aphid and whitefly infestations. The resistance observed was both locally and systemically induced. Other assays were performed to evaluate the effect of preinfestation with ten adults of B. tabaci during 48 h on the tomato responses to two different clones (Sp and Nt) of M. euphorbiae. The numbers of nymph and adult aphids were counted after the same time interval as the pre-reproductive period and 20 (Sp clone) or 22 (Nt clone) days after adult aphid removal. The tomato responses induced by whitefly feeding depend on the aphid clone. For the Sp clone, the number of aphid nymphs ten days after adult removal was significantly higher on whitefly preinfested plants than on uninfested plants. However, no significant differences were observed when the aphid clone Nt was tested. The duration of plant response to a previous infestation by B. tabaci is apparently limited.

A recent hypothesis states that the accumulation of amino-carbonyl reaction products of reducing sugars with proteins (Maillard products) is related to the loss of seed vigour and viability during ageing. Since Maillard products are biochemical end products, their accumulation should provide an index of seed deterioration. A simple fluorescence assay has been used to estimate the quantity of Maillard products in aqueous seed extracts. We tested whether an accumulation of fluorescent compounds correlates with the loss of seed viability during ageing. Fluorescence of extracts from lettuce (Lactuca sativa) embryonic axes increased after controlled deterioration, but was not correlated with ageing period. Fluorescence of extracts from whole broccoli (Brassica oleracea var. italica) seeds was either unchanged or declined during controlled deterioration. Extracts from naturally aged whole seeds of carrot (Daucus carota), tomato (Lycopersicon esculentum), and cauliflower (B. oleracea var. botrytis) had higher fluorescence than controls, but there was no consistent increase in fluorescence in proportion to the loss of viability. Extracts of naturally aged onion (Allium cepa) seeds exhibited less fluorescence than extracts from seeds with higher viability. We conclude that the fluorescence assay does not have general utility as an index of seed deterioration.

Using flow cytometry, we determined relative DNA amounts expressed as C-values, of large numbers of nuclei isolated from embryo root tips in three seed lots of pepper (Capsicum annuum) and tomato (Lycopersicon esculentum). The nuclei in embryos of fully matured dry pepper and tomato seeds predominantly revealed 2C signals, which indicates that the cells of maturing seeds have arrested at G1 phase of the cell cycle. Priming of pepper and tomato seeds in −1.1, −1.3 or −1.5 MPa polyethylene glycol (PEG) for 14 days reduced the mean time to germination. In all seed lots an induction of 4C signals was found after priming, indicating that during priming the cells of the embryonic root tip had replicated their DNA and arrested at the G2 phase of the cell cycle. For both tomato and pepper, the frequency of 4C signals was highest at the lowest PEG concentration (osmotic potential of −1.1 MPa). A significant inverse correlation was found between the frequency of root tip cells expressing 4C DNA signals and the mean time to germination for each individual pepper and tomato seed lot. However, the effect of a specific osmotic treatment differed between seed lots of the same cultivar, with regard to both the decrease in the mean time to germination and to the percentage of 4C cells, suggesting specific differences among seed lots in the response to priming. The present results indicate that flow cytometry can be used to follow the progress in nuclear replication activities during priming. The advancement in DNA synthesis can thus be used to measure the efficiency of a priming treatment with regard to enhancement of seed lot germination rate.

On the premise that seed ageing may be largely a result of free-radical lipid autoxidation, a study was made of the relationship between lipid stability and longevity in seeds of soybean (Glycine max), lentil (Lens culinaris), mungbean (Vigna radiata), chickpea (Cicer arietinum), broadbean (Vicia faba), pea (Pisum sativum), lettuce (Lactuca sativa), and tomato (Lycopersicon esculentum). Seed lipids were examined for α-, γ- and δ-tocopherols, and levels of unsaturated and saturated fatty acids. Using this information, analysis was attempted using linear, multiplicative or exponential models to correlate aspects of lipid stability with seed longevity values from the published literature. No statistically significant correlations could be found between longevity and total lipid unsaturation, tocopherol levels or two protection formulae obtained from the oil chemistry literature. When values for tomato were excluded, a good correlation (r = 0.89, P = 0.007) was obtained using a multiplicative regression model for levels of linolenic acid per unit of total tocopherols in relation to longevity. Possible factors contributing to a lessening of the relationship between lipid stability and seed longevity are discussed.

Although jasmonates (JAs) are involved in germination and seedling development, the regulatory mechanism of JAs, and their relation with endogenous level modifications in these processes, is not well understood. We report here the detection of 12-oxo-phytodienoic acid (OPDA), jasmonic acid (JA), 11-hydroxyjasmonate (11-OH-JA), 12-hydroxyjasmonate (12-OH-JA) and methyljasmonate (JAME) in unimbibed seeds and seedlings of tomato Lycopersicon esculentum Mill cv. Moneymaker (wild type) and tss1, tss2, tos1 mutants. The main compounds in wild-type and tss1, tss2, tos1 seeds were the hydroxylate-JAs; 12-OH-JA was the major component in dry seeds of the wild type and in tss2 and tos1. The amounts of these derivatives were higher in seeds than in seedlings. Changes in JAs during wild-type and tss1 imbibition were analysed in seeds and the imbibition water. In wild-type imbibed seeds, 11-OH-JA content was higher than in tss1. 12-OH-JA showed a different tendency with respect to 11-OH-JA, with high levels in the wild type at early imbibition. In tss1, levels of 12-OH-JA rose from 24 to 48 h of imbibition. At 72 h of imbibition, when radicles had emerged, the amounts of both hydroxylates in wild-type and tss1 seeds were minimal. An important release of the hydroxylate forms was observed in the imbibition water. 11-OH-JA decreased in the imbibition water of wild-type seeds at 48 h. On the contrary, a high and sustained liberation of this compound was observed in tss1 after 24 h. 12-OH-JA increased in wild-type as well in tss1 until 24 h. Thereafter, a substantial reduction in the content of this compound was registered. NaCl-treated wild-type seedlings increased their 12-OH-JA, but tss1 seedlings increased their JA in response to salt treatment. In tss2 seedlings, NaCl caused a slight decrease in 11-OH-JA and JAME, whereas tos1 seedlings showed a dramatic OPDA and 12-OH-JA decrease in response to salt treatment. Under salt stress the mutant seedlings showed different patterns of JAs according to their differential hypersensitivity to abiotic stress. The JA-hydroxylate forms found, and the differential accumulation of JAs during germination, imbibition and seedling development, as well as their response to NaCl stress, provide new evidence about the control of many developmental processes by JA.

Cell cycle activities are initiated following imbibition of non-dormant seeds. However, it is not known whether cell cycle related events other than DNA replication also remain suppressed in imbibed dormant seeds. The objective of this study was to demonstrate that the transitions between the non-dormant and dormant (both primary and secondary) states are reflected in cell cycle events, such as DNA replication and the changing patterns of the microtubular cytoskeleton involved in the processes of growth and development. The present studies were conducted on seeds from tomato (Lycopersicon esculentum cv. Moneymaker) that possessed primary dormancy or were manipulated to attain secondary dormancy. In addition, a non-dormant abscisic acid (ABA)-deficient mutant, sitw, was used. DNA replication, as measured by flow cytometry, and β-tubulin accumulation, analysed by immunoblotting, were compared with immunocytological studies of active DNA synthesis and microtubular cytoskeleton formation. It is shown that the depth of dormancy, which distinguishes primary and secondary dormancy, may depend on the progression of the cell cycle prior to the induction of dormancy.

The distribution of ATP in tomato seeds was visualized by monitoring the luminescence of frozen sections on top of a gel containing all the components of the luciferase reaction, but excluding ATP. ATP was imaged in germinating tomato seeds at intervals of 3, 6, 17, 24 and 48 h and in seeds with primary or secondary dormancy. ATP was present mainly in the embryo and concentrated in the radicle tip towards the completion of germination. In contrast to germinating seeds, ATP was distributed more evenly in dormant seeds. For germination, the ratio of ATP concentration in the radicle tip versus cotyledons was decisive, rather than the absolute concentration.

Cherry tomato (Lycopersicon esculentum Mill.) seeds harvested from fruits at four stages of development [2, 4, 6 and 8 weeks after flowering (WAF)] were washed (1% HCl) and germinated after 72 h of desiccation at 20°C, and 76%, 49% or 12% RH. Seed α-amylase activity was determined at each stage of development and correlated with seed germination. Desiccation at 76% and 49% RH had no significant effect on the germination of seeds at 4, 6 and 8 WAF, whereas it improved germination of seeds at 2 WAF. Low RH (12%) significantly reduced seed germination at all stages of development. There was a positive correlation (r = 0.68, P ≤ 0.05) between germination and α-amylase activity during seed development. Scanning electron microscopy also revealed a correlation between starch grain occurrence in the endosperm and α-amylase activity. Placenta water potential decreased with fruit and seed maturation, and correlated negatively with improved seed germination and α-amylase activity. Promotion of seed germination by desiccation in developing cherry tomato seeds was lost 4 weeks prior to mass maturity (80 ± 3% seed water content and –2.3 ± 0.1 MPa placenta water potential). It is proposed that the water potential differential between the placenta and the seeds influences α-amylase activity and germination behaviour during development.

Introduction. Extraction of juice from fruit is one of the most important ways of producing fruit drinks, but the extraction rate is hindered by natural factors. This has given rise to exploration of better methods such as ohmic heating to enhance juice yield. Materials and methods. Orange (Citrus sinensis), pawpaw (Carica papaya) and tomato (Lycopercium esculentum) were ohmic-heated at 9 V dc and 110 V ac, using different electrode combinations of copper / copper (Cu / Cu) and copper / aluminum (Cu / Al) at time intervals of (5, 10 and 15) min. Juice was pressed out through a muslin cloth, and yield, pH, color and vitamin C content were determined. Structural changes in the electrode were notified, while voltage drops across the system were studied. Results and discussion. There were significant differences in juice yield according to the electrode type, the fruit type and the ohmic heating treatment time. The use of Cu / Cu electrodes at 110 V ac gave the highest juice yield; tomato yielded the highest juice content per fruit, while pawpaw yielded the least. Cu / cu-treated samples gave the worst quality in terms of color and acceptability, with indication of a high electrolysis, which dissolved the electrodes. The pH decreased with the ohmic heating treatment times. The vitamin C content significantly varied with ohmic heating time, electrode type and fruit type, and decreased in pawpaw from (63.3 to 3.91) mg·100 g–1 for Cu / Al electrodes to zero for Cu / Cu electrodes with (10 and 15) min heating. Orange retained more vitamin C irrespective of the treatment. Conclusion. The results showed that enhancement of juice extraction by ohmic heating is feasible. For commercialization of the process, the correct electrodes devoid of electrolysis must be used.