Field-grown Tomato Research Articles

Content of carotenoids at different ripening stages in processing tomato in relation to soil water availability

The influence of 2 water regimes (a fully irrigated treatment receiving 100% of evapotranspiration for the whole growing season and an unirrigated control watered up to plant establishment only) on lycopene and β-carotene accumulation during fruit ripening in a field-grown processing tomato was studied. Since a strong effect of irrigation treatments on fruit water content was expected, carotenoid content on both a fresh and dry matter basis was studied. Regardless of ripening stage and adopted parameter unit (fresh or dry matter), higher amounts of lycopene were measured in the well watered treatment. Positive and no effects of water stress were reported on β-carotene content when expressed, respectively, on a fresh and dry weight basis. Both experimental factors influenced the β-carotene/lycopene ratio mostly in the first 2 ripening stages and there is evidence to suggest that, under soil water deficit conditions, the carotenoid biosynthetic pathway is more ‘β-carotene accumulation’ oriented, especially at the beginning of the fruit ripening process. Appropriateness of adopting both a fresh and dry basis calculation, in order to better evaluate the role of water stress on carotenoid content, is emphasised. The possibility of reducing the irrigation water supply without drastically decreasing the studied fruit quality characteristics is suggested.

Dissipation of Endosulfan in Field-Grown Tomato (Lycopersicon esculentum) and Cropped Soil at Akumadan, Ghana

The dissipation and persistence of endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin 3-oxide) applied to field-grown tomato (Lycopersicon esculentum) were studied at a vegetable-growing location in Ghana. Plant tissue samples and cropped soil collected at 2 h-14 days and 8 h-112 days, respectively, after application, were analyzed by gas chromatography-electron capture detection (63Ni) to determine the content and dissipation rate of endosulfan isomers (alpha- and beta-endosulfan) and the major metabolite, endosulfan sulfate. After two foliar applications of commercial endosulfan at 500 g of active ingredient/hectare, the first-order reaction kinetic was confirmed to describe the dissipation of endosulfan residues in tomato foliage and cropped soil. However, functions that best fit the experimental data were the biphasic process for foliage and the monophasic process for cropped soil. Calculated DT 50 and DT 90 values for endosulfan residues in cropped soil were not significantly (p<0.05) different for each of the two isomers.

Effect of irrigation methods, management and salinity of irrigation water on tomato yield, soil moisture and salinity distribution

The increasing demand for irrigation water to secure food for growing populations with limited water supply suggests re-thinking the use of non-conventional water resources. The latter includes saline drainage water, brackish groundwater and treated waste water. The effects of using saline drainage water (electrical conductivity of 4.2–4.8 dS m−1) to irrigate field-grown tomato (Lycopersicon esculentum Mill cv Floradade) using drip and furrow irrigation systems were evaluated, together with the distribution of soil moisture and salt. The saline water was either diluted to different salinity levels using fresh water (blended) or used cyclically with fresh water. The results of two seasons of study (2001 and 2002) showed that increasing salinity resulted in decreased leaf area index, plant dry weight, fruit total yield and individual fruit weight. In all cases, the growth parameters and yield as well as the water use efficiency were greater for drip irrigated tomato plants than furrow-irrigated plants. However, furrow irrigation produced higher individual fruit weight. The electrical conductivity of the soil solution (extracted 48 h after irrigation) showed greater fluctuations when cyclic water management was used compared to those plots irrigated with blended water. In both drip and furrow irrigation, measurements of soil moisture one day after irrigation, showed that soil moisture was higher at the top 20 cm layer and at the location of the irrigation water source; soil moisture was at a minimum in the root zone (20–40 cm layer), but showed a gradual increase at 40–60 and 60–90 cm and was stable at 90–120 cm depth. Soil water content decreased gradually as the distance from the irrigation water source increased. In addition, a few days after irrigation, the soil moisture content decreased, but the deficit was most pronounced in the surface layer. Soil salinity at the irrigation source was lower at a depth of 15 cm (surface layer) than that at 30 and 60 cm, and was minimal in deeper layers (i.e. 90 cm). Salinity increased as the distance from the irrigation source increased particularly in the surface layer. The results indicated that the salinity followed the water front. We concluded that the careful and efficient management of irrigation with saline water can leave the groundwater salinity levels unaffected and recommended the use of drip irrigation as the fruit yield per unit of water used was on average one-third higher than when using furrow irrigation.

Defense gene expression patterns of three SAR-induced tomato cultivars in the field

Plant activation is an appealing disease management tool, avoiding some of the challenges of traditional chemical control by not directly impacting the pathogen. This study examined effects of acibenzolar -S-methyl (ASM), a plant activator that induces systemic acquired resistance, on defense response activation in three field-grown tomato cultivars in New York. Salicylic acid, ethylene and jasmonic acid-mediated responses were monitored by following expression of a marker gene for each signaling pathway using quantitative real-time PCR over the course of two ASM applications. ASM induced salicylic acid and ethylene, but not jasmonic acid-regulated gene expression in all cultivars tested. All three cultivars demonstrated a significantly stronger gene expression response relative to the untreated control following the second ASM application. Implications of these findings on management practices are discussed.

Foliar application of lipo-chitooligosaccharides (Nod factors) to tomato (Lycopersicon esculentum) enhances flowering and fruit production

Lipochitooligosaccharides (LCO) or Nod factors, which are rhizobia-produced signal molecules, induce deformation of legume root hairs. In addition to triggering legume plant nodulation, Nod factors influence cell division and promote somatic embryo generation in non-legume plants. This suggested to us the potential of using LCO to stimulate the development of tomato flowers and fruit. This study indicated that the foliar application o f LCO to tomato plants during the appropriate stages increased flower numbers and early fruiting in greenhouse trials. Flower stimulation by LCO occurred 1-2 wk after application and fruit numbers increased 2-4 wk after application. The accelerated flowering and fruiting resulted in an increase in tomato fruit yield. The most effective concentration of LCO was 50 ng per plant applied twice in the greenhouse, initially during the early flowering stage and again in the late flowering stage. A field trial in 2002 indicated that the optimal LCO application concentration was 10 ng per plant applied at the early flowering stage, which increased fruit yield and number by up to 29.8 and 29.4%, respectively. When plants received a second LCO application at the early fruiting stage, the fruit yield increased, but most were unmarketable green fruits. Analyses of yield data showed that the yield increase in field-grown tomatoes was due to an increase in the fruit number per plant, but not to individual fruit weight or fruit size. The average weight per fruit due to the treatment was not different from the control. A second field trial, carried out in 2003, showed that a foliar application of LCO at 50 ng per plant produced the best tomato yield. Our studies indicate that an LCO foliar application to tomatoes in the range of 10-50 ng per plant can increase early flowering and fruiting, which results in improved fruit yield. Key words: early flowering, foliar application, fruiting, growth promotion, lipo-chitooligosccharides, tomato yield

Culturable Leaf-Associated Bacteria on Tomato Plants and Their Potential as Biological Control Agents

Culturable leaf-associated bacteria inhabiting a plant have been considered as promising biological control agent (BCA) candidates because they can survive on the plant. We investigated the relationship between bacterial groups of culturable leaf-associated bacteria on greenhouse- and field-grown tomato leaves and their antifungal activities against tomato diseases in vitro and in vivo. In addition, the isolated bacteria were analyzed for N-acyl-homoserine lactone (AHL) and indole-3-acetic acid (IAA) production, which have been reported to associate with bacterial colonization, and resistance to a tomato alkaloid (alpha-tomatine). Leaf washings and subsequent leaf macerates were used to estimate the population size of epiphytic and more internal bacteria. Bacterial population sizes on leaves at the same position increased as the leaves aged under both greenhouse and field conditions. Field-grown tomatoes had significantly larger population sizes than greenhouse-grown tomatoes. Analysis of 16S rRNA gene (rDNA) sequencing using 887 culturable leaf-associated bacteria revealed a predominance of the Bacillus and Pseudomonas culturable leaf-associated bacterial groups on greenhouse- and field-grown tomatoes, respectively. Curtobacterium and Sphingomonas were frequently recovered from both locations. From the 2138 bacterial strains tested, we selected several strains having in vitro antifungal activity against three fungal pathogens of tomato: Botrytis cinerea, Fulvia fulva, and Alternaria solani. Among bacterial strains with strong in vitro antifungal activities, Bacillus and Pantoea tended to show strong antifungal activities, whereas Curtobacterium and Sphingomonas were not effective. The results indicated the differences in antifungal activity among predominant bacterial groups. Analysis of alpha-tomatine resistance revealed that most bacterial strains in the dominant groups exhibited moderate or high resistance to alpha-tomatine in growth medium. Furthermore, some Sphingomonas and Pantoea strains showed AHL and IAA production activities. Strain 125NP12 (Pantoea ananatis) showed particular alpha-tomatine resistance, and AHL and IAA production had the highest protective value (91.7) against gray mold. Thus, the differences of these physiological properties among dominant bacteria may be associated with the disease suppression ability of BCAs on tomato plants.

Vermicompost as a substitute for peat in potting media: Effects on germination, biomass allocation, yields and fruit quality of three tomato varieties

Commercial potting media often contain substantial amounts of peat that was mined from endangered bog and fen ecosystems. The main objectives of this study were to assess (1) whether the amendment of 0, 20, 40, 60, 80 and 100% (v/v) of vermicompost (VC) to a fertilized commercial peat potting substrate has effects on the emergence, growth and biomass allocation of tomato seedlings (Lycopersicon esculentum Mill.) under greenhouse conditions, (2) whether possible impacts on seedlings can affect tomato yields and fruit quality even when transplanted into equally fertilized field soil, and (3) whether effects are consistent among different tomato varieties. Amended VC was produced in a windrow system of food and cotton waste mainly by earthworms Eisenia fetida Sav. Vermicompost amendments significantly influenced, specifically for each tomato variety, emergence and elongation of seedlings. Biomass allocation (root:shoot ratio) was affected by VC amendments for two varieties in seedling stage and one field-grown tomato variety. Marketable and total yields of field tomatoes were not affected by VC amendments used for seedling husbandry. However, morphological (circumference, dry matter content, peel firmness) and chemical fruit parameters (contents of C, N, P, K, Ca, Mg, l-ascorbic acid, glucose, fructose) were significantly affected by VC amendments in seedling substrates; these effects again were specific for each tomato variety. Overall, vermicompost could be an environmentally friendly substitute for peat in potting media with similar or beneficial effects on seedling performance and fruit quality. However, at least for tomatoes, variety-specific responses should be considered when giving recommendations on the optimum proportion of vermicompost amendment to horticultural potting substrate.

Significant transpirational water loss occurs throughout the night in field-grown tomato.

Incomplete stomatal closure at night can result in substantial water loss at times when photosynthetic carbon gain is not occurring in C3 and C4 plant species. To investigate the magnitude of nighttime water loss for a crop species in the field, measurements of nighttime water loss by tomato (Lycopersicon esculentum Mill. cv. Heinz 8892) were made by three methods: a field-scale lysimeter and two leaf-level instruments, an automated viscous flow porometer and a portable photosynthesis system. The portable photosynthesis system indicated nighttime transpiration of 10% of maximal daytime transpiration and the viscous flow porometer demonstrated partially open stomata. Integrated crop water loss during the dark, non-photosynthetic hours measured on the lysimeter was 3-10.8% of total daily water loss. In the glasshouse, a survey of closely related wild and cultivated tomato species showed that under ambient conditions nighttime transpiration varied within and among species and was 8-33% of maximal daytime transpiration. Implications of such a substantial fraction of total daily crop water use occurring during the night are significant in agronomic, environmental, and economic terms. Further, variation within and among species in nighttime water loss has implications for breeding to improve crop water use efficiency.

Model-based evaluation of low-cost drip-irrigation systems and management strategies using saline water

A drip-irrigation module was developed and included in an ecosystem model and tested on two independent datasets, spring and autumn, on field-grown tomato. Simulated soil evaporation correlated well with measurements for spring (2.62 mm d−1 compared to 2.60 mm d−1). Changes in soil water content were less well portrayed by the model (spring r2 = 0.27; autumn r2 = 0.45). More independent data is needed for further model testing in combination with developments of the spatial representation of below-ground variables. In a fresh-water drip-irrigated system, about 30% of the incoming water was transpired, 40% was lost as non-productive evaporative flows, and the remainder left the system as surface runoff or drainage. Simulations showed that saline water irrigation (6 dS m−1) caused reduced transpiration, which led to higher drainage and soil evaporation, compared with fresh water. Covering the soil with plastic mulch resulted in an increase in yield and transpiration. Finally, two different drip-irrigation discharge rates (0.2 and 2.5 l h−1) were compared; however the simulations indicated that the discharge rate did not have any impact on the partitioning of the incoming water to the system. The model proved to be a useful tool for evaluating the importance of specific management options.

Withholding of drip irrigation between transplanting and flowering increases the yield of field-grown tomato under plastic mulch

Experiments were conducted in summer of 2003 and 2004 to study the effect of withholding irrigation on tomato growth and yield in a drip irrigated, plasticulture system. Irrigation treatments were initiated at tomato planting (S0), after transplant establishment (S1), at first flower (S2), at first fruit (S3), or at fruit ripening (S4). An additional treatment received only enough water to apply fertigation (FT). Withholding drip irrigation for a short period (S2–S3) increased tomato marketable yield by 8–15%, fruit number by 12–14% while reducing amount of irrigation water by 20% compared to the S0 treatment. Withholding drip irrigation also increased irrigation water use efficiency (IWUE). Similar trends were observed in 2003 and 2004 despite large differences in rainfall, heat units, and tomato yield between years. This suggests that if soil moisture is adequate at transplanting, subsequent withholding of irrigation for 1–2 weeks after tomato transplanting may increase yield while reducing the amount of irrigation water.

Viruses infecting field-grown tomatoes in Samsun province, Turkey

To detect viruses infecting tomatoes and determine their incidences, surveys were conducted in 31 fields in Samsun province from May to August in 2002 and 2003. Tomato mosaic virus (ToMV), Tomato spotted wilt virus (TSWV), Potato virus X (PVX) and Cucumber mosaic virus (CMV) were detected in tomatoes after analysing 186 samples by enzyme-linked immunosorbent assay. ToMV, TSWV, PVX and CMV were detected 52.1, 12.9, 10.7 and 6.9% of the samples tested, respectively. Thirty samples (16.1%) were found to be mixed infected with these viruses. The most widespread and predominant virus (ToMV) also occurred in mixed infections with TSWV (6.4%), PVX (4.9%) and CMV (3.2%) in our study.

Wild bee species increase tomato production and respond differently to surrounding land use in Northern California

Pollination provided by bees enhances the production of many crops. However, the contribution of wild bees remains unmeasured for many crops, and the effects of anthropogenic change on many bee species are unstudied. We experimentally investigated how pollination by wild bees affects tomato production in northern California. We found that wild bees substantially increase the production of field-grown tomato, a crop generally considered self-pollinating. Surveys of the bee community on 14 organic fields that varied in proximity to natural habitat showed that the primary bee visitors, Anthophora urbana Cresson and Bombus vosnesenskii Radoszkowski, were affected differently by land management practices. B. vosnesenskii was found primarily on farms proximate to natural habitats, but neither proximity to natural habitat nor tomato floral abundance, temperature, or year explained variation in the visitation rates of A. urbana. Natural habitat appears to increase B. vosnesenskii populations and should be preserved near farms. Additional research is needed to determine how to maintain A. urbana. Species-specific differences in dependency on natural habitats underscore the importance of considering the natural histories of individual bee species when projecting population trends of pollinators and designing management plans for pollination services. Thus, to maintain an entire bee community, multiple approaches, including maintaining natural habitat, should be implemented.

(176) Yield Data from 2005 and Instrumental and Sensory Evaluation of Tomato Fruits from Plants Grown in High Tunnels at Beltsville, Md., or Obtained from Commercial Sources

A study of tomato (Lycopersicon esculentum Mill.) production and quality in high tunnels was conducted. Seedlings of `Oregon Spring' and `Red Sun' were transplanted weekly to two high tunnels at Beltsville, Md., from 23 Mar. to 13 Apr. 2005. Data were recorded on the date of anthesis, leaf expansion, and marketable yields of tomato fruits for each cultivar and transplant group under UV-transmitting (+UV) and UV-blocking (–UV) covering materials. Instrumental and sensory quality characteristics of fruit obtained from `Oregon Spring' and `Red Sun' in the two high tunnels were compared with field- and hydroponic greenhouse-grown fruit obtained from a wholesale warehouse. `Oregon Spring' plants flowered in 16-17 days from transplanting vs. 25 days for `Red Sun'. `Red Sun' produced 3× as much leaf area as did `Oregon Spring'. The fresh weight of `Red Sun' tomatoes in the +UV and –UV high tunnel was 60% and 22% greater, respectively, than that of `Oregon Spring'. Intact fruit or extracts were used for measurements of firmness, titratable acidity (TA), soluble solids content (SSC), and aromatic volatile concentration. The SSC of high tunnel-grown tomatoes was higher than that of commercially grown fruit. Field-grown tomatoes had the highest firmness and hydroponically-grown tomatoes had the highest concentration of volatiles. `Red Sun' fruit from plants grown under –UV had a higher SSC than corresponding fruit grown under +UV. High tunnel-grown tomatoes had higher sensory scores for sweetness, flavor, and for acceptability of texture, taste and overall eating quality than commercially grown fruit. These results are the first to show that high tunnel-grown tomatoes generally have better consumer acceptance than those grown commercially.

Occurrence of Three Strains of Cucumber mosaic virus Affecting Tomato in Kuwait

Three strains of Cucumber mosaic virus (CMV) have been found to cause a lethal disease, referred to as fern leaf syndromes and mild mosaic symptoms in tomato (Lycopersicon esculentum Mill.) crops grown in Kuwait. CMV strains were detected and identified based on host range, symptomatology, serology, electron microscopy, and ribonucleic acid (RNA) electrophoresis in polyacrylamide gels. A high degree of viral genomic heterogeneity was detected among CMV strains isolated in Kuwait, with no apparent correlation to symptomatology in tomato host plants. Two different virus satellites of 'CMV associated RNA 5', designated CARNA 5, were detected in two virus strains that caused both lethal disease and mild symptoms, designated CMV-D1 and CMV-S1 respectively. CARNA5 was not detected in the third CMV strain that caused fern leaf syndromes designated CMV-F. All the three isolated strains were serologically indistinguishable from each other and may belong to one serotype according to Ouchterlony gel diffusion tests. These strains transmitted via aphids (Myzus persicae Sulz) in a non-persistent manner. Physical properties of the virus strains were very similar where thermal inactivation test showed that virus withstood heating for 10 min at <TEX>$70^{/circ}$</TEX>, dilution end point was <TEX>$10^{-4}$</TEX>, and the longevity in vitro at room temperature was less than 5 days for all virus strains. CMV-D1 and CMV-F were the most devastating diseases spreading in both greenhouse and field-grown tomato where aborted flower buds failed on fruit setting due to the viral infection. This is the first report to isolate three different strains of CMV in Kuwait.

Foliar Spraying of Vermicornpost Extracts: Effects on Fruit Quality and Indications of Late-Blight Suppression of Field-Grown Tomatoes

ABSTRACT The effect of foliar sprays with aqueous vermicompost extracts on growth, yields, morphological and chemical fruit quality and natural infection with late blight disease (Phytophthora infestons (Mont.) de Bary)) on three tomato varieties (Lycopersicon esculentnm Mill., cv. Diplom Fl, cv. Malina, cv. Rheinlands Ruhm) was investigated in a field experiment. Extracts were prepared of vermicompost produced from fruit, vegetable and cotton waste by redworms (Eisenia fetida Sav., Lumbricidae); tap water served as control treatment. Foliar application (spraying) of vermicompost extracts did not affect plant growth, biomass or nutrient allocation, or yields and number of fruits of the three tomato varieties; however, for several dates it significantly reduced the number of flowers produced. Foliar vermicompost spraying cither increased or decreased peel firmness dependent on tomato variety and increased fruit circumference consistently as well as contents of nitrogen but decreased L-ascorbic acid compared with water sprayed fruits. All other measured parameters of fruit quality (dry matter, C, N, P, K, Ca, Mg, glucose and fructose content) were similar for vermicompost and water sprayed plants. Natural infection of leaves, stems and fruits by P. infestans was generally very low under the experimental conditions; however, across varieties, only half as many vermicompost sprayed plants showed clear signs of P. infestans infection as water sprayed plants; the severity of the infection was unaffected by the two spraying treatments. In conclusion, these results suggest that the use of vermicompost might be considered more in organic farming not only as a substitute for peat in potting media but also as foliar sprays for fertilization and biological disease prevention.

Responses of field grown tomato plants to arbuscular mycorrhizal fungal colonization under varying intensities of drought stress

The effects of root colonization by the arbuscular mycorrhizal (AM) fungus Glomus intraradices Schenck and Smith on growth, flower and fruit production, and fruit quality were studied in field-grown tomato plants exposed to varying intensities of drought stress. Inoculated (M+) and non-inoculated (M−) tomato seedlings were exposed to varying intensities of drought stress by adjusting irrigation intervals. Mycorrhizal plants had significantly higher uptake of N and P in both roots and shoots regardless of intensities of drought stress. AM inoculation also significantly increased shoot dry matter and the number of flowers and fruits. The fruit yields of M+ plants under severe, moderate, mild drought-stressed conditions were higher than M− plants by 24.7%, 23.1%, 16.2% and 12.3%, respectively. Furthermore, M+ plants produced tomato fruits that contain significantly higher quantities of ascorbic acid and total soluble solids (TSS) than M− plants. Mycorrhizal effects increased with increasing intensity of drought. The overall results suggest that mycorrhizal colonization affects host plant nutritional status, water stratus and growth under field conditions and thereby alters reproductive behaviour, fruit production and quality of fruits under both well-watered and drought-stressed conditions.

Disposition of Selected Flavonoids in Fruit Tissues of Various Tomato (Lycopersicon esculentumMill.) Genotypes

Flavonoids have been studied extensively because they offer great potential health benefits. In this study, enzymatic hydrolysis of glycosylated quercetin, kaempferol, and naringin was used to obtain their sugar-free aglycones. The investigation also employed a validated HPLC method to obtain the chiral disposition of the aglycone naringenin enantiomers. These analyses were conducted on exocarp, mesocarp, and seed cavity tissues of field-grown tomato (Lycopersicon esculentum Mill.) mutants (anthocyanin absent, atroviolacea, and high pigment-1) and their nearly isogenic parent (cv. Ailsa Craig) at immature green, "breaker", and red ripe maturity stages. Concentrations of all flavonoids using enzymatic hydrolysis were significantly higher than previously reported concentrations using acid hydrolysis. Presumably, this occurred due to a more specific and rapid hydrolysis of the glycoside moiety by the beta-glucosidase enzyme. The glycoside S-naringin was the predominant enantiomer in all fruit tissues, although the aglycones free R- and S-naringenin were detected in both exocarp and mesocarp. Whereas there was significantly more quercetin than kaempferol in exocarp tissue, they were present in about equal concentrations in the mesocarp. Quercetin concentrations were higher in the exocarp and mesocarp of immature green and breaker fruit of the high pigment-1 mutant than in the other genotypes, supporting the observed photoprotection and potential health benefits of the high pigment-1 tomato genotype.

Early Planting and Fertility Affect Root Production in Fresh Market Tomatoes

ABSTRACT There is limited information on what is the optimal root system size in tomato (Lycopersicon esculentum Mill.) to produce high yield. Environmental and cultural factors can have significant impact on root development. The effect of early versus late spring establishment and different nutrient rates were evaluated for field-grown tomato on how they affected root systems and yield. Minirhizotron observation tubes were used to quantify root production and senescence in field-grown plants of tomato, cv. Mountain Spring. A low fertility regime of pre-plant fertilizer only was compared to a high fertility regime that combined pre-plant fertilizer with additional potassium and nitrogen fertigation during fruiting. Five harvests were conducted and yield of US No. 1 fruit was highest for early established plants treated with high fertility (34,140 kg.ha−1), followed by late established plants receiving the low fertility treatment (32,252 kg.ha−1), and late established plants receiving the high fertility t...

First Report of Gray Mold in Tomato Caused by Botrytis cinerea in Baja California, Mexico.

San Quintin Valley, a 60-mile-long coastal plain (30°30'N, 116°W) in the Baja California Peninsula, is one of the major fresh tomato (Lycopersicon esculentum Mill.) production areas in Mexico with more than 8,000 ha. During the last 10 years, the valley's tomato production has declined because of gray mold and stem canker diseases. Flower rot, reddish brown margins on the leaves and stems, and fruit with a gray mold were observed on field-grown tomato plants (Roma type cv. Tequila) in the autumn of 2003. Severity ranging from 55 to 60% was observed at harvest. Infected tissues were sampled and disinfested by immersion in 1% NaOCl for 1 min, rinsed in sterile water, and placed on malt extract agar at 22°C. Fungal conidia were then transferred to 2% potato dextrose agar (PDA). The resulting fungal colonies were definitively identified as Botrytis cinerea Pers.:Fr. The colonies of B. cinerea were first hyaline and white and became dark gray after 96 h. Mycelia were septate with dark branched conidiophores. Conidia were unicellular, ellipsoid, and ranged from 5 to 8 × 8 to 14 μm. Profuse black sclerotia developed in 7-day-old cultures. Infection site analyses in diseased flowers at different stages during the bloom were done with scanning electron microscopy. Fungal hyphae were located predominantly on the receptacle areas, whereas conidia were located in the ovaries as described previously (3). The identity of B. cinerea was confirmed by a restriction digest with ApoI of the 413-kb polymerase chain reaction amplification product obtained with BA2f/BA1r primers (1) and random amplified polymorphic DNA banding patterns (2). Pathogenicity tests were done by spray inoculation of 1-ml aqueous conidial suspension (106 CFU/ml) on 20 healthy plants during the blossom stage. An equal number of plants sprayed with sterile water was used as the control. Plants were incubated at 20 ± 2°C for 5 days. The fungus was reisolated from diseased flowers and peduncles after surface disinfestation (2.5% NaOCl) and plating on PDA. No symptoms were observed in the noninoculated controls. To our knowledge, this is the first report of B. cinerea causing gray mold disease on tomato in Baja California.

Developing crop coefficients for field-grown tomato ( Lycopersicon esculentum Mill.) under drip irrigation with black plastic mulch

A 2 years field study was conducted to develop crop coefficients for field-grown tomato ( Lycopersicon esculentum Mill.), a major irrigated crop in the Jordan Valley, under drip irrigation system with black plastic mulch. The area of the study field was 1.5 ha surrounded by many similar tomato fields. Actual crop evapotranspiration (ET C) was measured using eddy covariance technique which distinguishes this study from other previous studies conducted in the Jordan Valley that relied on the old indirect approach for ET C estimation based on the soil water balance. Grass reference evapotranspiration (ET O) was determined by using the FAO Penman–Monteith method utilizing the agrometeorological parameters measured at the study site. The crop coefficient ( K C) was determined as the ratio of ET C to ET O. The tomato crop coefficients were determined following the FAO crop coefficient model. The average crop coefficient during the midseason growth stage ( K C mid ) was 0.82 which is far below the adjusted FAO crop coefficient of 1.19 by about 31%. Also, the late season crop coefficient ( K C end ) was much lower than the adjusted FAO crop coefficient of 0.76 by about 40%. Moreover, the weighted average crop coefficient over the entire growing season ( K C GS ) was 0.69, which is about 36% lower than the FAO corresponding value. In fact, the low K C values obtained reflect the effect of practicing both localized drip irrigation and plastic mulch covering. This study showed that there is a big difference between the reported FAO crop coefficients and the one measured in the filed using a precise approach. These exact updated values of crop coefficients will enhance future estimation of crop water requirements and hence irrigation management of tomato crop which is the major irrigated crop in the Jordan Valley.