Carrot Leaf Research Articles

A Laboratory Leaf Assay of Carrot Susceptibility to Botrytis cinerea

Laboratory experiments were conducted to develop an assay for evaluation of carrot (Daucus carota L.) leaf reaction to Botrytis cinerea Pers. ex Pers. The detached carrot leaflets were inoculated with the colonized agar plugs attached to the cut surface of the midrib or by spraying conidial suspension. The estimation of the infected leaflet area expressed as the area under the disease progress curve enabled the discrimination between carrot genotypes differing in their susceptibility to the pathogen. Evaluation based on the measurement of the length of the midrib lesion did not allow such differentiation. The inoculation of leaf surface with suspension of conidia was less reliable and the development of the disease symptoms was not reproducible. The established assay using colonized plugs enables a fast assessment of carrot leaf susceptibility to grey mould and can be particularly useful for a non-destructive, preliminary evaluation of precious and limited source materials.

Field evaluation of carrot cultivars for susceptibility to fungal leaf blight diseases in New York

Carrot cultivars grown in New York were evaluated for susceptibility to the fungal leaf blight pathogens Alternaria dauci (1999) and Cercospora carotae (2000–03) in an experimental field under continuous carrot cultivation since 1996. Replicated plots were established in a randomized complete block design. Plants were rated for disease incidence and severity at regular intervals. Cultivar susceptibility was ranked based on the area under the disease progress curve. An IPM program for carrot leaf blights conducted in growers’ fields provided the opportunity to determine the impact susceptibility had on the date the 25% disease incidence threshold was reached to prompt the first fungicide application. Of the cultivars evaluated, Bolero, Carson, Calgary, Ithaca, and Fullback were less susceptible to A. dauci whereas, Bolero, Carson, and Bergen were less susceptible to C. carotae. Fontana was most susceptible to both fungal leaf blight pathogens. In grower fields less susceptible cultivars reached the 25% threshold later than their more susceptible counterparts. Carrot cultivar susceptibility was incorporated into an IPM program for these diseases.

First Report of a Leaf Spot Caused by Cercospora bizzozeriana on Lepidium draba subsp. draba in Tunisia.

Lepidium draba (L.) subsp. draba (synonym = Cardaria draba (L.) Desv.), commonly known as white-top or hoary-cress (1), family Brassicaceae, is a common weed and emerging problem in wheat in Tunisia. It is also a problematic invasive weed in the northwestern United States and a target of biological control efforts. During the summer of 2002, dying L. draba plants were found around Tunis, Tunisia. Plants had grayish white leaf spots on most of the leaves. In some cases, the leaf spots dropped out of the leaves producing "shot-holes". In most cases, the leaf spots coalesced, and the leaves wilted and died. Diseased leaves were collected, air-dried, and sent to the quarantine facility of the Foreign Disease-Weed Science Research Unit (FDWSRU), USDA/ARS, Fort Detrick, MD. The air-dried leaves were observed microscopically, and numerous conidiophores and conidia were observed on both sides of the leaves within and around the lesions. The fungus isolated (DB03-009) conformed to the description of Cercospora bizzozeriana Saccardo & Berlese (2). Conidiophores were unbranched, pale olive-brown, 1 to 5 geniculate, and uniform in color and width. Conidia were hyaline, straight to slightly curved, multiseptate, and 57 to 171 × 3.8 to 6.7 µm (average 103 to 4.6 µm). Stems and leaves of 12 rosettes (10 to 15 cm in diameter) of 6-week-old L. draba plants were spray inoculated with an aqueous suspension of conidia (1 × 105/ml) harvested from 6- to 8-day-old cultures grown on carrot leaf decoction agar. Six of the plants and two noninoculated plants were placed in a dew chamber at 22°C in darkness and continuous dew. The other half of the plants and two noninoculated plants were placed on a greenhouse bench at approximately 25°C and covered with clear polyethylene bags. After 72 h, plants from the dew chamber were moved to a greenhouse bench, and the bagged plants were uncovered. All plants were watered twice daily. After 9 days, symptoms were observed on the plants that had been bagged but not on the plants from the dew chamber. Symptoms were identical to those observed in the field in Tunisia and included "shot holes". No symptoms were observed on noninoculated plants. C. bizzozeriana was reisolated from the leaves of all symptomatic plants. Completion of Koch's postulates was repeated with an additional five plants. This isolate of C. bizzozeriana is a destructive pathogen on L. draba subsp. draba, and severe disease can be produced by inoculation of foliage with an aqueous suspension of conidia. This isolate is a good candidate for mycoherbicide development in Tunisia where the weed and pathogen are indigenous. However, some commercially grown Brassica species were found susceptible to this isolate, which will preclude its use as a classical biological control agent in the United States. To our knowledge, this is the first report of C. bizzozeriana on L. draba subsp. draba in Tunisia. A voucher specimen has been deposited at the U.S. National Fungus Collections (BPI 843753). Live cultures are being maintained at FDWSRU and the Institut National Agronomique de Tunisie, Tunis, Tunisia.

Development of PCR-Based Assays for Detecting Xanthomonas campestris pv. carotae, the Carrot Bacterial Leaf Blight Pathogen, from Different Substrates.

Detection of the carrot bacterial leaf blight pathogen, Xanthomonas campestris pv. carotae, was achieved using polymerase chain reaction (PCR) along with primer pairs developed from sequences of cloned random amplified polymorphic DNA (RAPD) fragments. Primer pairs 3S and 9B directed the amplification of ∼350-bp and ∼900-bp (or ∼2 kb) DNA fragments, respectively, from genomic DNA of all known X. campestris pv. carotae strains tested, but not from that of 13 other X. campestris pathovars or other bacterial species, including yellow non-xanthomonad bacteria isolated from carrot tissues and seeds. In tests conducted with an extensive collection of X. campestris pv. carotae-like strains isolated from different substrates from California, Idaho, Oregon, Washington, and Canada, the 3S primer pair directed the amplification of the ∼350-bp target fragment from all strains. These results indicated that the 3S primer pair is highly specific for X. campestris pv. carotae detection. Using the 3S primer pair, PCR assays were developed for detection of X. campestris pv. carotae from colonies on agar media, carrot leaf and stem tissues, and seeds. These tests could be performed in a single day. The PCR-based seed assay detected X. campestris pv. carotae from lots with contamination rates ranging from 2 × 102 to 2.3 × 108 CFU per gram of seed. This assay gave results similar to a seed-wash dilution plating assay and proved more sensitive than an enzyme-linked immunosorbent assay (ELISA)-based assay.

Annual Meeting, Ottawa, Ontario, 2004

Annual Meeting, Ottawa, Ontario, 2004

Effect of Nitrogen Rate and Residual Soil Nitrogen on Yield and Quality of Carrots

Residual nitrogen (N) in agricultural soils is an environmental concern. Nitrogen requirements for carrots were examined over a two-year period in Ontario, Canada. Carrots, cvs. `Idaho' and `Fontana' were seeded into organic and mineral soil in 2002 and 2003 in the same plots. In 2002, N was applied at 0%, 50%, 100%, 150%, and 200% of current Ontario recommendations. Each experimental unit was split in half in 2003 with one half getting the same N rate as in 2002, and the second half getting no applied N. At harvest, total and marketable yield, weight per root, and quality were assessed. Yield and quality were unaffected by N rate in both mineral soil in 2002 and organic soil in both years. On mineral soil in 2003 there was a linear increase in total and marketable yield and weight per root with increasing N rate, with total yield ranging between 36 and 55 t/ha. However, in the treatments given no N in 2003, yield also increased from 36 to 47 t/ha between the 2002 no N and high N treatments. Consequently, a large portion of the increase in yield in 2003 on mineral soil was due to residual N from the previous season. Carrots are capable of taking up very high amounts of N from the soil over a growing season, but may only require additional N for maximum total yield if soil N content is low due to low mineralization rates or depletion by a previous crop. However, low N rates can reduce the ability to harvest the crop due to increased carrot leaf blight severity even when yield is unaffected.

Avaliação química da folha de cenoura visando ao seu aproveitamento na alimentação humana

Visando a diminuir o desperdício de alimentos, com a utilização de partes vegetativas de hortaliças tradicionais, realizou-se o presente trabalho, por meio do qual objetivou-se caracterizar quimicamente a folha de cenoura. As folhas de cenoura foram submetidas à secagem em estufa a 60 °C por 72 horas. Em seguida, o material seco foi triturado e homogeneizado para posterior análise. Foram determinados a composição centesimal, vitamina C total e b-caroteno, fibras dietéticas (FDN e FDA), pH, acidez total titulável, teores de minerais (Na, P, K, Ca, Mg, Mn, Zn e Fe) e nitrato. Os resultados foram baseados em matéria-seca, e concluiu-se que as folhas de cenoura apresentaram teores significativos de vitamina C total e b-caroteno, podendo ser considerada como fonte de fibras dietéticas e minerais, destacando-se o Ca e o Fe. Quanto ao teor de nitrato encontrado, este apresenta-se com teor aceitável.

Survival and Persistence of Alternaria dauci in Carrot Cropping Systems.

Alternaria dauci was recovered in California from carrot crop residue and from volunteer carrot plants in fallow carrot fields. The fungus was not recovered from common weeds surrounding fallow fields. To evaluate further the survival of A. dauci on carrot crop residue, infected carrot leaf tissue was placed in fields or in soil in greenhouse pots, and recovered over time. In California, A. dauci was recovered from infected leaf tissue in both fallow and irrigated fields for as long as 1 year. In Florida, A. dauci was recovered from infected leaf tissue in fallow fields for up to 30 weeks. In greenhouse experiments, A. dauci was recovered from infected leaf tissue for as long as 1 year in dry soil, but only up to 30 weeks in soil that was watered weekly. To determine the infectivity of A. dauci borne on carrot crop residue, infected carrot crops were incorporated into organic and mineral field soils, and soil samples were collected over time. Carrot seed were planted in collected soil, and seedling infection by A. dauci was recorded. Seedling infection was detected up to 13 and 14 weeks after crop incorporation in organic and mineral soil, respectively. Seedling infection was detected for up to 5 weeks in soil that remained dry compared with 3 weeks in flooded soil.

A selective medium for the detection ofAlternaria dauci andAlternaria radicina

A selective medium to detectAlternaria dauci andA. radicina on seed, plant debris and other substrates was developed. Growth and sporulation by most undesired organisms was reduced, but adequate mycelial growth and sporulation byA. dauci andA. radicina was maintained so they could be identified by their unusual mycelial growth or characteristic spores. The medium is based upon carrot leaf extract, which promotes profuse sporulation by both pathogens. Glucose, sodium polypectate and mineral salts further enhanced spore and mycelial production. Streptomycin sulfate and metalaxyl (or mefenoxam), combined with either benomyl or thiophanate-methyl, reduced growth and sporulation of unwanted organisms. There were strong interactions among the fungicides, bactericide, and most other medium components. There were also significant effects on the type of mycelial growth produced by some medium components. If the unique, dark mycelia produced by both pathogens is the desired detection method, the medium components must be optimized for eitherA. dauci orA. radicina because the two fungi responded differently in this regard. All medium configurations allowed both fungi to be identified by their characteristic spores. The sensitivity of theAlternaria dauci-radicina selective medium (ADRSM) to detectA. radicina on carrot seeds was similar to other methods presently in use, but ADRSM was more sensitive than the other methods for detectingA. dauci on infested carrot seeds.

First Report of Gray Leaf Spot Caused by Cercospora zeae-maydis on Corn in Ontario, Canada.

During an annual corn disease survey in mid-September 2001, sporadic symptoms typical of gray leaf spot (causal agent Cercospora zeae-maydis Tehon & E.Y. Daniels) (4), consisting of long, narrow, rectangular, 0.3 to 0.5 × 2 to 5 cm, tan or gray-to-tan spots, were found in nine fields in southern Ontario. Leaf samples with symptoms were placed in petri dishes containing moistened filter paper to maintain high humidity and stored at room temperature for 48 h. Clustered conidiophores arose from stomata on both leaf surfaces. Slightly curved, hyaline conidia, 4 to 8 × 25 to 88 µm long with 3 to 5 septa appeared on the tops of conidiophores, similar to those described by Kingsland (3). When single-spore isolates were cultured on carrot leaf decoction agar (2) at room temperature, aerial mycelia were rare, but slightly larger conidia were produced in 3 weeks. When single-spore isolates were cultured on V8 agar (1) at room temperature, aerial mycelia were abundant, and conidiophores and conidia were produced on the tops of mycelia in 1 to 2 weeks, but conidia were slightly smaller. Greenhouse-grown plants of two commercial corn hybrids (Pioneer 32Y52 and Zimmerman NX7208) were inoculated at the 8- to 10-leaf stage by injecting a suspension of 5 × 103 conidia per ml (washed from a V8 agar culture with sterile water) into the whorl and by spraying the suspension on the leaves. High moisture was maintained in the greenhouse by a misting system. After 14 to 21 days, typical symptoms of gray leaf spot and typical conidiophores and conidia were observed. Gray leaf was reisolated from inoculated plants, fulfilling Koch's postulates. We have suspected that gray leaf spot has been present in Ontario for a few years based on unconfirmed reports from the seed corn industry, but to our knowledge, this is the first confirmed report of this pathogen in Canada. Voucher specimens of field material, dried cultures, and greenhouse-inoculated leaves have been deposited in the National Mycological Herbarium (DAOM 229597 to 229600) in Ottawa, ON, Canada; and the isolate has been deposited with the Canadian Collection of Fungal Cultures (CCFC).

Validação de dois sistemas de previsão para a queima das folhas da cenoura

Através de quatro experimentos realizados em campo, no período de setembro/98 a dezembro/99, avaliou-se a aplicabilidade de dois sistemas de previsão no controle da queima das folhas da cenoura (Daucus carotae). Seis esquemas de aplicação de fungicida (protetor ou sistêmico), baseados no acúmulo de valores diários de severidade (VDS) para Alternaria dauci ou equivalentes de infecção (EI) para Cercospora carotae, foram comparados a dois calendários fixos de tratamento e uma testemunha sem fungicida. Enquanto o número de VDS registrados por um coletor eletrônico (Colpam) variou de 25 a 94 por ciclo da cultura, nenhum EI foi detectado ao longo dos quatro experimentos. Com a adoção do sistema de VDS, o número de aplicações do fungicida protetor clorotalonil diminuiu de 7,5 (fixo, sete dias) para 3,5 (VDS 3-5), 2,7 (VDS 6-8) e dois (VDS 9-11) por cultivo. Nas mesmas condições, o fungicida sistêmico metconazole foi aplicado 3,7 (fixo, 14 dias), 2,5 (VDS 3-5), 1,7 (VDS 6-8) e 1,5 (VDS 9-11) vezes. A relação entre a área abaixo da curva de progresso de doença (AACPD) e o peso de raiz foi significativa em dois experimentos (P = 0,005 e 0,016). Quanto ao rendimento de raízes, o limiar de 3-5 VDS igualou-se ao esquema de calendário fixo em 3/4 das situações. Portanto, nas condições locais, o controle da queima das folhas pelo sistema de VDSs está condicionado ao limite de 3-5 VDS e à utilização de fungicidas sistêmicos com eficácia igual ou superior à do metconazole.

Freqüência de Alternaria dauci E Cercospora carotae como agentes da queima das folhas da cenoura em Passo Fundo, RS

A queima das folhas da cenoura (Daucus carota) pode ser causada pelos fungos Alternaria dauci e Cercospora carotae. Com vistas à adoção de um sistema de previsão para a doença, avaliou-se a freqüência de cada patógeno em quatro cultivos de cenoura estabelecidos em Passo Fundo, RS, no período de agosto/98 a dezembro/99. As variáveis analisadas foram a incidência dos fungos em sementes e plântulas, sua freqüência a partir de lesões em folhas e pecíolos e o número de propágulos capturados no ar com coletores de esporos. As incidências dos fungos em sementes de nove cultivares variaram de zero a 5,75% para A. dauci e de zero a 1,25% para C. carotae. Apenas A. dauci foi detectado em plântulas cultivadas em casa-de-vegetação, em percentuais de 3,7 (cultivar Forto) e 17,1% (cultivar Gigante Flakker). O fungo A. dauci esteve presente o ano todo nos cultivos no campo, sendo isolado a partir de 81% das lesões foliares e de 81,9% das em pecíolos. Por outro lado, C. carotae ocorreu de junho a dezembro, com freqüências de 40,4% em folhas e 33,4% em pecíolos. O número de conídios de A. dauci capturados no ar atingiu 207/semana/cm² no início da colheita. Alternaria dauci mostrou-se o principal agente causal da queima das folhas nas condições locais, devendo ser priorizado na adoção de estratégias de controle para a doença.

Effect of Carrot Leaf Supplementation on Egg Yolk βCarotene Content and Egg Quality (Part 2)

Effect of Carrot Leaf Supplementation on Egg Yolk βCarotene Content and Egg Quality (Part 2)

Effect of Carrot Leaf Supplementation on Egg Yolk .BETA.-Carotene Content and Egg Quality.

Our previous study (part 1) showed that carrot leaf (CL), a farm wasteproduct, fed to laying hens elevated -carotene content and Roche color fan score of egg yolk. The present study was designed to see whether fat inclusion in diets potentiates the CLinduced effects, as described for a chemical product of -carotene. To make diets containing CL isocaloric and to retain -carotene content of CL during its drying, nutrient composition of CL and a useful method to make it dry were determined beforehand. Four diets, a basal diet for laying hens (BDLH, control), BDLH with 5% or 10% added CL, and BDLH with 10% added CL plus soybean oil, were each fed to hens in different blocks for 8 weeks. Supplemental CL had no effect on egg production with a slight reduction in food intake. -carotene content of egg yolk was significantly elevated in blocks fed diets containing CL (P<0.05), and with 10% added CL it was nearly 6 times as high as the control. Neither the CL-induced effect nor the ratio of -carotene retained in egg yolk to the total -carotene intake was increased by supplementation of soybean oil. Roche color fan score of egg yolk was invariably higher in blocks fed diets containing CL than in the control. However, there was no significant difference in the score between 5% and 10% of CL inclusion in diets, suggesting that 5% of CL in diets was high enough to increase the score. Egg weight, haugh unit, eggshape index and strength and thickness of eggshell remained almost unaltered after feeding CL to hens.These results suggest that CL may be used as a farm product of improving egg quality by which the market value of eggs is elevated, and that the effect of CL is not potentiated by the

Production and characterisation of monoclonal antibodies to phytoene synthase of lycopersicon esculentum

Monoclonal antibodies have been prepared against the tomato ( Lycopersicon esculentum Mill.) fruit ripening-enhanced phytoene synthase (PSY1). The antigen was prepared as a fn2 fn2 d-thiogalactopyranoside; mab = monoclonal antibody; PMSF = phenylmethylsulphonyl fluoride; PVDF = polyvinylidene difluoride; TBST = Tris-buffered saline\\Tween; TBS = Tris-buffered saline. -galactosidase fusion protein by cloning a 1.13 kb fragment of Psy1 cDNA into pUR291, followed by transformation of E. coli. The fusion protein, induced by IPTG, was purified by preparative SDS-PAGE and used to elicit an immune response. The cell lines were screened for cross-reactivity against β-galactosidase- phytoene synthase fusion protein in E. coli extracts using western blotting and ELISA detection procedures. Positive clones were further screened for their ability to cross-react with the mature phytoene synthase protein on western blots as well as their ability to inhibit enzyme activity. Eleven monoclonal lines were obtained. Nine of these, all of the IgM isotype, exhibited strong responses to phytoene synthase of ripe tomato fruit on western blots, but did not inhibit enzyme activity effectively. The other two lines (IgG\\1a 2 isotypes) inhibited phytoene synthase activity in ripe tomato stroma, but produced a poor response to the protein on western blots. The monoclonals identified a ripe fruit phytoene synthase of 38 kDa, exclusively located in the chromoplast. In contrast, antibodies were unable to detect microbial phytoene synthases, nor phytoene synthase of maize leaf, tomato chloroplast or mango fruit extracts, either on western blots or from inhibition of phytoene synthase activity. However, they did cross-react with a 44 kDa protein from carrot leaf stroma and with three different proteins (44, 41, and 37 kDa) in carrot root. Cross-reactivity was also found with a 37 kDa protein from pumpkin fruit stroma.

Quantification of contact oviposition stimulants for black swallowtail butterfly,Papilio polyxenes, on the leaf surfaces of wild carrot,Daucus carota

Ovipositing black swallowtail butterflies,Papilio polyxenes, make their final host-selection decisions on the basis of compounds present on the leaf surface. Little information is available, however, on the chemistry of leaf surfaces. The purpose of this study was to develop a technique to extract and quantify the concentrations of compounds from the leaf surfaces ofDaucus carota, one of the main host species forP. polyxenes, with particular reference to compounds already identified as contact oviposition stimulants, namelytrans-chlorogenic acid (CA) and luteolin-7-O-(6″-O-malonyl)-β-D-glucopyranoside (L7MG), as well as its degradation product luteolin-7-glucoside (L7G). Plant surfaces were extracted by dipping leaves sequentially in pairs of solvents: (1) CHCl3-MeOH, (2) near-boiling H2O, (3) CHCl3-near-boiling H2O, and (4) CH2Cl2-CH2Cl2. The resulting extracts were fractionated and analyzed using high-performance liquid chromatography. The leaf-surface concentrations of each compound were calculated using regressions relating leaf surface area to leaf weight that were obtained from measurements of field-collected carrot plants. All four methods removed the three compounds from carrot leaf surfaces, but the solvent systems differed in effectiveness. The chloroform-near-boiling water solvent system performed better than the other solvent combinations, but not significantly so. This system also extracted the highest number of polar, UV-absorbing compounds. Methylene chloride was significantly less efficient than the other methods. An additional test confirmed that the chloroform-near-boiling water method removed compounds from the surface alone and probably not from the apoplast or symplast. Surface concentrations of CA (up to 600 ng/cm(2) leaf surface) were substantially greater than those of the two flavonoid compounds. No clear seasonal trend in concentrations was evident from the limited number of sampling dates.

EFFECT OF MOLYBDENUM APPLICATIONS ON PLANT MOLYBDENUM CONCENTRATION AND CROP YIELDS ON SPHAGNUM PEAT SOILS

Studies were conducted on peat soils to determine the effect of Mo application on crop yields and plant tissue Mo concentrations. In a greenhouse experiment Mo applications resulted in highest crop yield increases for cauliflower with lesser increases for onions and red clover. Plant tissue Mo levels of less than 0.06, 0.04, and 0.03 mg kg−1 in onions, cauliflower, and red clover, respectively were in the deficiency range. Sufficiency levels for Mo were 0.1 mg kg−1 for onions, 0.07 mg kg−1 for cauliflower, and 0.27 mg kg−1 for red clover. No response to Mo was found on carrots even at plant tissue Mo concentrations as low as 0.04 and 0.15 mg kg−1 under greenhouse and field experiments, respectively. In the field study liming and Mo both increased carrot leaf Mo concentrations but only liming increased carrot yields. Key words: Molybdenum concentration, vegetables, red clover, sphagnum peat, liming

Evaluation of field resistance of Daucus carota cultivars to Cercospora carotae (carrot leaf spot)

A world collection of 142 cultivars of carrot was tested for resistance to Cercospora carotae in the field. C. carotae infection was observed in all the cultivars. Field resistance was observed in only about 30% of the cultivars, the remainder being highly susceptible.

Effects of Carrot Developmental Stages on Feeding and Oviposition of Carrot Weevil, Listronotus oregonensis (Le Conte) (Coleoptera: Curculionidae)

Adult feeding and oviposition punctures and subsequent larval feeding of the carrot weevil (CW), Listronotus oregonensis (Le Conte), did not decrease carrot stand significantly. CW started to oviposit by 147 ± 9 degree-days (DD) (base 7°C) and 90% of the eggs were deposited by 456 ± 47 DD. However, females started to oviposit in carrot seedlings only when the carrots reached the four-true-leaf stage and 98% of the eggs were found on carrot leaf, petiole and crown. A significant inverse relation was found between the date of sowing and the number of eggs and subsequent damage at harvest. Carrots sown after 400–450 DD would escape most CW damage.

Defense chemicals in leaf surface wax synergistically stimulate oviposition by a phytophagous insect

Propenylbenzenes, coumarins, and a polyacetylene, identified in the surface wax of carrot leaves, stimulate oviposition in the carrot fly. These compounds are known to be powerful inhibitors of the growth of bacteria, fungi, plants, and nonadapted herbivores. Their co-occurence appears to be unique to the Umbelliferae, the host plant family of the carrot fly. An artificial mixture of these compounds proved to be synergistic and as stimulatory as the crude carrot leaf extract.