Glasshouse Cucumber Research Articles

First report of infections with isolates of the Asian genotype of Cucumber green mottle mosaic virus in cucumber crops in Belgium.

In July 2019, four rows of cucumber plants (Cucumis sativus) in a commercial glasshouse in the north of Belgium showed severe mosaic, blistering and distortion of the leaves, with symptoms resembling those caused by Cucumber green mottle mosaic virus (CGMMV). CGMMV is a Tobamovirus that mainly affects cucurbit crops worldwide (Dombrovsky et al., 2017). Phylogenetic analyses in previous studies have shown two major clades, one including isolates that were initially identified in Europe and Russia (European genotype) and the second one with isolates initially identified in Asia and Israel (Asian genotype) (Dombrovsky et al., 2017; Pitman et al., 2022; Mackie et al., 2023). A symptomatic leaf sample was collected and total RNA was isolated from 100 mg of leaf tissue (Spectrum™ Plant Total RNA kit, Sigma-Aldrich). CGMMV was detected using a one-step TaqMan RT-qPCR (Hongyun et al., 2008). High-throughput sequencing (HTS) confirmed the presence of CGMMV. The sample was prepared using the Novel enrichment technique of viromes protocol (NETOVIR protocol, Conceição-Neto et al., 2015). The leaf material was homogenized, enriched for virus-like particles and the RNA was extracted (QIAamp Viral RNA mini kit, QIAGEN). The extract was randomly amplified (Whole Transcriptome Amplification kit, Sigma Aldrich), used for library preparation (Nextera XT DNA library preparation kit, Illumina) and sequenced on a NovaSeq platform. HTS data analysis was performed using Geneious Prime software (Biomatters, Auckland, New Zealand, version 2023.2). After quality filtering and trimming, 26.7M reads were obtained (132 nt mean length). In total, 20.6M reads were mapped to two genomes KP772568 and GQ411361 (considered as reference for the Asian and European genotypes respectively) with Geneious. This revealed 100% coverage of the full sequences (6422 nt) with 99.4% and 90% nucleotide identities to the reference genomes of Asian and European genotypes, respectively. Phylogenetic analyses confirmed that isolate 2019-26A-BE, with GenBank ID OR724740, relates to the Asian genotype. The HTS data were additionally processed using the ViPER pipeline (De Coninck, 2021). The raw reads were quality filtered and trimmed, (Trimmomatic) and then used to perform de novo assembly (metaSPAdes). The produced contigs were classified using DIAMOND and visualized with KronaTools. The results showed that no other virus was detected in the sample. Finally, cucumber seedlings were inoculated using the original symptomatic sample and were grown in a research glasshouse. After 3 weeks, severe CGMMV symptoms, similar to the original symptoms observed in the commercial glasshouse, were observed in the inoculated plants. Infection with CGMMV was verified via RT-qPCR, and the isolate present in the inoculated plants was confirmed to belong to the Asian genotype via RT-PCR-RFLP (Crespo et al., 2017). Later samplings of symptomatic leaves confirmed the presence of isolates belonging to the Asian genotype of CGMMV at four other commercial glasshouse locations, specializing in cucumber crop, in Belgium in 2020, 2021 and 2023 by RT-PCR-RFLP. While the Asian genotype was previously found elsewhere in Europe (Pitman et al., 2022), to our knowledge, this is the first report of infections with isolates of this genotype in glasshouse cucumber crops in Belgium. Further investigation is required to determine the spread and impact of infections with isolates of the Asian genotype in cucumber crops in Belgium.

Dynamic economic thresholds for the management of vegetable leafminer on glasshouse cucumber estimated by simulated defoliation

AbstractDefoliation by the vegetable leafminer, Liriomyza sativae Blanchard (Diptera: Agromyzidae), was simulated by removing known amounts of leaf area with a hole punch in a glasshouse experiment that evaluated 21 combinations of defoliation intensity, timing and duration on cucumber yields. Defoliation was quantified in cm2‐days (leaf area removed x no. days), and linear regression was used to correlate yield losses to simulated damage. The probability of erroneous decisions associated with different intensities of sequential sampling was explored. Spatial heterogeneity in leafminer infestation and the cumulative impact of defoliation over time were both considered, and the economic costs associated with wrong decisions were also assessed. Significant yield loss was observed beyond 10,000 cm2‐days of defoliation, whereas lower defoliation levels were tolerated by plants. The economic injury level (EIL) rose at an increasing rate as the onset of defoliation moved later in the season. An algorithm was used to estimate monthly EILs that farmers can use to guide leafminer management decisions in cucumber and minimize their economic risk.

STUDY OF ELEMENTS OF INTEGRATED FERTILIZER SYSTEMS IN GLASSHOUSE CUCUMBER

The current study goal is to determine the influence of some organic fertilizers over the growth and the productive qualities of the glasshouse cucmbers grown as a substrate culture. The experimental work was conducted in non-heated glasshouse Venlo type in Maritza VCRI Plovdiv with Defense cucumber variety (EZ). Adding Humustim to the nutrition regime of the glasshouse cucumbers increases the first quality production (99550 kg/ha).The quantity of the yield from second quality was not influenced by the use of the studied fertilizing bioproducts. The treatment with Humustim did not significantly increase the total yield in comparison with the conventional fertilization but there was considerable higher influence over the productivity among the rest of the fertilizing bioproducts. As a result of adding the organic fertilizers to the nutrition regime the percentage distribution of the production from first quality was not increased.

Spectrophotometric Assessment of the Differences Between Total Nitrate/Nitrite Contents in Peel and Flesh of Cucumbers

A spectrophotometric method based on the reduction of nitrates to nitrites was applied to the determination of the difference between total nitrate and nitrite contents in the extracts from the cucumber peel and flesh. The content of these ions was determined in glasshouse cucumbers and those grown in the open fields, both marketed in Poland. Nitrate and nitrite extraction was performed using the Griess diazotization reaction and carried out according to the ISO recommendation (ISO 6635, 1984). It was observed that the mean nitrate content in the peel was significantly higher (p < 0.0001) than the mean nitrate content in the flesh. It was also proved that cucumber peel accumulated nearly threefold higher amount of nitrates than the flesh. The nitrite concentrations in all tested samples were below the limit of quantification. Despite statistically significant differences in the nitrate contents between the peel and the flesh, no excessive levels were found. A comparison of the current results to those reported for Poland and other countries is also presented.

Insecticides on the basis of analogs of insect juvenile hormones

Analogs of juvenile hormones (JHAs)—azadirachtin (NeemAzal, EC (10 g/L), fenoxycarb (Phasis, WP (250 g/kg), and pyriproxyfen (Admiral, EC (100 g/L) and Inoxyfen, EC (100 g/L)—have been tested. The effectiveness of insectoacaricide NeemAzal in regulating the population numbers of sucking insects was assessed using glasshouse cucumber in Leningrad oblast. Three applications of this product in 0.5% concentration effectively protected this culture against red spider mite (Tetranychus urticae Koch.) and onion thrips (Thrips tabaci Lind) and, less significantly, against melon aphid (Aphis gossypii Glov). Insecticide Phasis protected vineyards against European vine moth (Lobesia botrana Den&Schiff). Juvenoid Admiral effectively decreased the number of imagoes and larvae of greenhouse whitefly (Trialeurodes vaporariorum Wsfw.) in glasshouse cucumber and tomato in different regions of Russia, while Inoxyfen protected apples against codling moth (Cydia pomonella). The tested products belong to the group of biorational pesticides that can be used in ecologically sound systems of plant protection.

The use of olfactory and visual cues in host choice by the capsid bugs Lygus rugulipennis Poppius and Liocoris tripustulatus fabricius.

Lygus rugulipennis Poppius and Liocoris tripustulatus Fabricius (Heteroptera: Miridae) are pests of glasshouse cucumber and sweet pepper crops respectively. L. rugulipennis has a wide range of foodplants, but L. tripustulatus is specialised with very few food plants. We report behavioural assessments to investigate whether either species exhibits a preference for salad over wild hosts, and whether the role of olfaction and vision in response to cues from host plants can be distinguished. Olfactory responses to leaves were tested in choice chambers. L. rugulipennis was presented nettle (wild host) and a salad leaf of cucumber or sweet pepper, where the salad leaves had higher nitrogen content. L. tripustulatus was tested with nettle and sweet pepper of two different nitrogen contents. Female L. rugulipennis spent more time on the cucumber salad host, and chose it first most often, but males showed no preference. Neither sex discriminated between sweet pepper or nettle leaves, but males made more first contacts with sweet pepper. Neither sex of L. tripustulatus discriminated between sweet pepper and nettle leaves when the sweet pepper had higher nitrogen. When the plant species contained equivalent nitrogen both sexes spent more time on nettle. There was no difference in first choice made by either sex. When visual stimuli were available, and leaves had equivalent nitrogen, L. rugulipennis showed no preference and L. tripustulatus preferred nettle leaves. We conclude that the generalist L. rugulipennis has the ability to use remote olfactory cues for host choice whereas the specialist L. tripustulatus relies mainly on contact chemosensory and gustatory cues.

Modelling photo‐modulated internode elongation in growing glasshouse cucumber canopies

• Growing glasshouse plant canopies are exposed to natural fluctuations in light quantity, and the dynamically changing canopy architecture induces local variations in light quality. This modelling study aimed to analyse the importance of both light signals for an accurate prediction of individual internode lengths. • We conceptualized two model approaches for estimating final internode lengths (FILs). The first one is only photosynthetically active radiation (PAR)-sensitive and ignores canopy architecture, whereas the second approach uses a functional-structural growth model for considering variations in both PAR and red : far-red (R : FR) ratio (L-Cucumber). Internode lengths measured in three experiments were used for model parameterization and evaluation. • The overall trends for the simulated FILs using the exclusively PAR-sensitive model approach were already in line with the measured FILs, but they underestimated FILs at higher ranks. L-Cucumber provided considerably better FIL predictions under various light conditions and canopy architectures. • Both light signals are needed for an accurate estimation of the FILs, and only L-Cucumber is able to consider R : FR signals from the growing canopy. Yet this study highlights the significance of the PAR signal for predicting FILs as neighbour effects increase, which indicates a potential role of photosynthate signalling in internode elongation.

Seasonal dynamics of economic injury levels for Tetranychus urticae Koch (Acari, Tetranychidae) on Cucumis sativus L.

Abstract: Economic injury level (EIL) for Tetranychus urticae Koch on glasshouse cucumbers was established in two ways: EILs based on the number of T. urticae introduced to cucumber early in the growing season and EILs based on mite density and feeding durations (i.e. cumulative mite‐days) in each of four growing seasons. The relationship between yield loss and T. urticae infestation level varied among four growing seasons. One mite introduced to cucumber early in the growing season could reduce the cucumber yield by 5.03, 3.20, 1.12 and 2.86 g per plant in spring, summer, autumn and winter, respectively. One mite‐day (i.e. one mite feeding in a day) reduced cucumber yield by 0.0123, 0.0074, 0.0035 and 0.0073 g per plant in spring, summer, autumn and winter, respectively. When the seasonal dynamics of market values of cucumber was considered, EILs were the lowest in spring and the highest in autumn. When four seasonal data were combined, EILs can be calculated as EIL = C/(0.00276 × K) for the number of T. urticae introduced early in the growing season and EIL = C/(6.8342 × 10−6 × K) for cumulative mite‐days, where K is efficacy of control measure and C the management cost. This study demonstrated the seasonal dynamics of EILs for T. urticae on glasshouse cucumbers, suggesting that decision making for T. urticae management on cucumber needs to be seasonally different under the glasshouse condition.

Occurrence of yellowing viruses (Beet pseudo‐yellows virus, Cucurbit yellow stunting disorder virus and Cucurbit aphid‐borne yellows virus) affecting cucurbits in Greece

A survey of the incidence of yellowing viruses in Greek glasshouse (and occasional field) cucumber and melon crops was carried out during 2000–03. In most cases disease incidence ranged from 50 to 80%. Simplex RT‐PCR was used for the detection of Beet pseudo‐yellows virus (BPYV) and Cucurbit yellow stunting disorder virus (CYSDV), and DAS‐ELISA for the detection of Cucurbit aphid‐borne yellows virus (CABYV). The results showed that BPYV was the predominant virus in cucumber and melon crops, whereas CYSDV, reported for first time in Greece, was isolated only in three regions of southern Greece: Rhodes, Crete and Arkadia. CABYV was detected only in three cucumber glasshouses in Pella (Macedonia). A simplified triplex RT‐PCR method using a simple sample‐preparation protocol was developed to allow rapid, sensitive and simultaneous detection of the three viruses. Sequence comparisons of the PCR products of BPYV and CYSDV revealed 98·7 and 100% amino acid identity, respectively, with previously reported sequences. The arable weed species Amaranthus retroflexus, Selosia cristata, Sonchus oleraceus and Sonchus sp. were identified as potential BPYV reservoirs.

Impact of Twospotted Spider Mite (Acari: Tetranychidae) on Growth and Productivity of Glasshouse Cucumbers

Experiments were conducted to assess the damage of the glasshouse cucumber by twospotted spider mite, Tetranychus urticae Koch, and to investigate when the economic yield begins to decrease after T. urticae infestations. To assess the damage, dry matter partitioning in the cucumber plant was quantified and plant growth analyses were conducted at four different T. urticae infestation levels. T. urticae infestations decreased leaf productivity by reducing the total number of leaves per plant. Approximately 14% reductions of total leaf areas could result in significant yield loss. The decreased leaf productivity by T. urticae feeding caused biomass reductions and altered the pattern of dry matter partitioning in the plant; damaged plants accumulated more dry matter in the leaf, and partitioning of dry matter to fruits was hindered. The economic yield of cucumber began to significantly decrease as early as 4 wk after heavy mite infestations. This study also showed the seasonal differences in T. urticae-cucumber damage interactions among mite infestation levels.

Impact of Twospotted Spider Mite (Acari: Tetranychidae) on Growth and Productivity of Glasshouse Cucumbers

Experiments were conducted to assess the damage of the glasshouse cucumber by twospotted spider mite, Tetranychus urticae Koch, and to investigate when the economic yield begins to decrease after T. urticae infestations. To assess the damage, dry matter partitioning in the cucumber plant was quantified and plant growth analyses were conducted at four different T. urticae infestation levels. T. urticae infestations decreased leaf productivity by reducing the total number of leaves per plant. Approximately 14% reductions of total leaf areas could result in significant yield loss. The decreased leaf productivity by T. urticae feeding caused biomass reductions and altered the pattern of dry matter partitioning in the plant; damaged plants accumulated more dry matter in the leaf, and partitioning of dry matter to fruits was hindered. The economic yield of cucumber began to significantly decrease as early as 4 wk after heavy mite infestations. This study also showed the seasonal differences in T. urticae–cucumber damage interactions among mite infestation levels.

Cucurbits under protected cultivation

Cucurbits under protected cultivation

Genetic diversity in African cucumber (Cucumis sativus L.) provides potential for germplasm enhancement

Genetic diversity among 26 cucumber (Cucumis sativus L. var. sativus) accessions from five African countries [Algeria (1), Egypt (21), Ethiopia (2), Kenya (1), and Libya (1)] present in the U.S. National Plant Germplasm System (NPGS) were examined by assessing variation at 71 polymorphic random amplified polymorphic DNA (RAPD) loci. Genetic distances (GD; simple matching coefficient) were estimated among these African accessions and a reference array (RA) of 21 accessions representative of the genetic variation in cucumber. GD among African accessions ranged between 0.41 and 0.97. GD among accessions in the reference array ranged between 0.36 and 0.88. Multivariate analysis identified three distinct groupings (1–3) of African accessions; Group 1 contained 21 accessions (Egypt, Ethiopia and Libya), Group 2 consisted of two accessions (Kenya, Algeria), and Group 3 possessed three accessions (Egypt). These groupings were distinct from each other (P > 0.001). Accessions in Group 1 differed genetically from all other accessions examined (P > 0.01), and accessions in Groups 2 and 3 were uniquely associated with several RA accessions. While GD among accessions in Group 1 ranged between 0.52 and 0.90, distances among Group 2 accessions varied between 0.93 and 0.97. The GD between the two accessions in Group 3 was 0.65. An accession from Syria (PI 181874) and from one Turkey (PI 199383) were genetically more similar to accessions in Group 1 than to other accessions in the RA. Likewise, accessions in Group 2 were genetically similar to two RA accessions from China and a European glasshouse cucumber line, and Group 3 accessions showed genetic affinities with the U.S. market class cultivar Dasher II. Data suggest that some Egyptian accessions (Group 1) possess unique genetic variation, that this germplasm has potential for broadening the genetic base of commerical cucumber, and that further collection of African germplasm is likely to enhance genetic diversity of cucumber in NPGS.

Occurrence of Beet pseudo-yellows virus in cucumber in New Zealand

In May 2001, unusual symptoms were observed on fewer than 1% of cucumber plants (Cucumis sativus) growing in a glasshouse in Tuakau, south Auckland, New Zealand. These symptoms, which included leaf chlorotic spotting and interveinal chlorosis, resembled those induced in cucumber elsewhere by Beet pseudo-yellows virus (BPYV), the vector of which, Trialeurodes vaporariorum (greenhouse whitefly), also occurred on the plants. Flexuous, filamentous virus particles resembling those of BPYV were observed in sap from affected plants using electron microscopy. Testing of these plants by indirect ELISA (Liu & Duffus, 1990) using specific polyclonal antiserum diluted 1/1000 (v/v) and antirabbit conjugate diluted 1/8000 (v/v) revealed that the plants were infected by BPYV. This diagnosis was confirmed by RT–PCR using specific primers which yielded a single band of 450 bp with nucleic acid extracted from the diseased, but not healthy, plants (Rubio et al., 1999). The sequence of the specific product of the BPYV isolate was almost identical to that of the isolate previously sequenced by Tian et al. (1996). No other viruses were detected in affected plants by electron microscopy or mechanical inoculation of common herbaceous indicator plant species, and specific tests for other cucumber pathogens (including Cucumber mosaic virus and Potato spindle tuber viroid) were negative. The distribution of BPYV in New Zealand is unknown, but similar symptoms in cucumber have been observed for a number of years in this region and around Nelson. It is also not known how the virus was introduced, but viruliferous T. vaporariorum may have been inadvertently imported with plant material. This outbreak is the first confirmed occurrence of BPYV in New Zealand, and also of a virus of the genus Crinivirus in the country. Glasshouse cucumbers are of some importance in New Zealand where an area of 499 000 m2 was cultivated in the year to March 2001. Severely affected cucumber plants may not yield at all (Liu & Duffus, 1990). More significantly, the virus also has the potential to infect a number of other crops grown in New Zealand, including sugar beet, lettuce, endive, squash and melon. The authors thank Dr Hsing-Yeh Liu, USDA-ARS, Salinas, USA for providing specific antiserum to Beet pseudo-yellows virus.

Effects of plant tissue factors on the acceptance of four greenhouse vegetable host plants by the greenhouse whitefly: an Electrical Penetration Graph (EPG) study

A combination of biological control and host-plant resistance is needed to control greenhouse whitefly, Trialeurodes vaporariorum (Westwood). The high level of susceptibility of several host plants to whitefly, based on their performance on these plants, is well documented. These studies only provide information on the overall host-plant acceptance by whiteflies. Here, we use a method that allows an examination of the different tissue layers in the overall acceptance. The effects of plant tissue factors on whitefly probing profiles were monitored using the electrical penetration graph (EPG) method. The EPGs of whitefly originating from a culture on glasshouse cucumber, were recorded for 8 hours on sweet pepper, tomato, gerbera and cucumber plants produced in a glasshouse. On sweet pepper the graphs showed that whitefly made many short probes, had long xylem phases, short phloem phases, and the shortest duration of first probes. An opposite probing profile was found on cucumber: longer probes, shorter xylem phases, fewer phloem phases but of longer duration, and longer first probes. The values of these parameters for gerbera and tomato were intermediate. Whiteflies encountered the greatest stimulation or the least resistance in the tissues of cucumber, and the least stimulation or the greatest resistance in the tissues of sweet pepper. Rejection of host plants probably occurred before the phloem tissue was reached, as the probes prior to a whitefly leaving a host plant were so short that the stylets cannot have reached the phloem. But phloem factors also determine host-plant rejection, as phloem probing on sweet pepper - a poor host plant - was much shorter than on the other host plants. Resistance factors seem, therefore, to be located both in the epidermis/mesophyll and in the phloem. We hypothesize that the factors encountered by whitefly in the different tissue layers during probing contribute to the acceptance or rejection of a host plant. Based on the performance of whitefly on these plants, which is also reflected in the values of the EPG parameters, the order of acceptance ranked from high to low is cucumber > tomato = gerbera > sweet pepper.

Life history of Aphis gossypii on cucumber: influence of temperature, host plant and parasitism

AbstractLife table data for Aphis gossypii Glover (Homoptera: Aphididae), an important pest in glasshouse cucumber crops, were studied at 20, 25 and 30 °C on two cucumber cultivars (Cucumis sativus L.) in controlled climate cabinets. The development time on the cucumber cv. ‘Sporu’ ranged from 4.8 days at 20 °C to 3.2 days at 30 °C. Immature mortality was approximately 20% and did not differ between temperatures. Most mortality occurred during the first instar. Reproduction periods did not differ among temperatures, but at 25 and 30 °C more nymphs were produced (65.9 and 69.8 nymphs/♀, respectively) than at 20 °C (59,9 nymphs/♀) because of a higher daily reproduction. Intrinsic rate of increase was greatest at 25 °C (rm = 0.556 day−1). At 20 and 30 °C the intrinsic rate of increase was 0.426 and 0.510, respectively. On cv. ‘Aramon’, the development time of A. gossypii was approximately 20% longer at all temperatures. Immature mortality did not differ between the two cultivars. The intrinsic rate of increase on cv. ‘Aramon’ was 15% smaller than on cv. ‘Sporu’. The use of cucumber cultivars partially resistant to aphids is discussed in relation to biological control of cotton aphid in glasshouses. Development time and immature mortality on leaves of the middle and upper leaf layer of glasshouse grown cucumber plants (cv. ‘Aramon’) were comparable to development in the controlled climate cabinets. On the lower leaves immature mortality was much higher (approximately 82%) than on leaves of the middle (24.0%) and upper leaf layer (24.5%). Reproduction was less on the lower leaf layer (45.9, 70.5 and 70.1 nymphs/♀ on leaves of the lower, middle and upper leaf layer, respectively).Aphids, successfully parasitized by Aphidius colemani Viereck (Hymenoptera: Braconidae) only reproduced when they were parasitized after the third instar. Fecundity was 0.1 to 0.9 and 10.5 to 13.3 nymphs/♀ for aphids parasitized in the fourth instar or as adults, respectively. Reproduction of aphids that were stung but survived the attack was lower than for aphids not stung. Average longevity of these aphids was equal to the longevity of aphids not stung by A. colemani.

Evaluation of four aphidiine parasitoids for biological control of Aphis gossypii

AbstractFour aphidiine parasitoid species (Hymenoptera: Braconidae) were evaluated with respect to their potential to control Aphis gossypii Glover (Homoptera: Aphididae) in glasshouse cucumbers. In a laboratory experiment thirty cotton aphids were offered to individual females for two hours. Aphidius matricariae Haliday parasitized less than six percent of the aphids and was ruled out as potential biological control agent. Ephedrus cerasicola Starý and Lysiphlebus testaceipes Cresson parasitized 23 and 26 percent of the aphids, respectively. Aphidius colemani Viereck parasitized 72 to 80 percent of the aphids.With the latter three species, experiments were performed in small glasshouses with cucumbers (Cucumis sativus L. cv. ‘Aramon’). As in the laboratory test A. colemani performed best; significantly more colonies were found and parasitization rates in the colonies were higher by A. colemani than by E. cerasicola and L. testaceipes.Because of the good correspondence between laboratory and glasshouse experiments, it is suggested that bad performance of an aphid parasitoid species in a simple laboratory trial might be sufficient evidence to disregard this species for further tests.

The relationship between powdery mildew (Sphaerotheca fuliginea) resistance and leaf chlorosis sensitivity in cucumber (Cucumis sativus) studied in single seed descent lines

The genetic relation between powdery mildew resistance and sensitivity for leaf chlorosis of glasshouse cucumber was investigated. The powdery mildew resistant, leaf chlorosis sensitive hybrid variety ‘Profito’ was crossed with the powdery mildew susceptible, non chlorosis sensitive hybrid variety ‘Corona’. Forty four F6 inbred lines of this cross, produced by single seed descent, were tested for powdery mildew resistance (PMR) and leaf chlorosis sensitivity (LCS). PMR and LCS were positively correlated (r=0.59). One or more of the PMR genes probably causes LCS as a pleiotropic effect or is closely linked to LCS, but also other factors, not genetically linked to PMR can cause LCS. Five F6 lines combined a significantly higher level of PMR than ‘Corona’ with a significantly lower LCS than ‘Profito’. Three of these lines could hardly be distinguished from ‘Corona’ for the level of LCS.

Control of root-knot nematodes (Meloidogyne spp.) in Hungary1

Under Hungarian climatic conditions, root-knot nematodes, and other phytoparasitic nematodes, generally cause damage in certain plant growing areas. These pests are present in glasshouses throughout the country. In the field the nematodes occur in sandy soil in the vegetable-growing areas of southern and central Hungary. The following species of root-knot nematodes have so far been reported to occur in Hungary: Meloidogyne incognita, M. arenaria, M. hapla, M. javanica, M. incognita acrita, M. thamesi and M. naasi. There are 10 specific nematicides registered for nematode control in the country. These chemicals are mainly applied in glasshouses where their use produces most economic return. Nematoderesistant cultivars are only available in the case of tomato. The nematodes cause the heaviest damage on glasshouse cucumber.

Light interception by a row crop of glasshouse peppers

Commercial crops of glasshouse cucumbers, peppers and tomatoes are normally trained into a highly artificial canopy of parallel hedgerows for easy access combined with effective interception of incident light. This study of a sweet pepper canopy with the plants in north-south rows shows that: (a) interception of light increased from a low value at planting to about 92% at maturity in early June and remained at this level throughout the fruiting period which coincided with high daily light integrals, (b) under overcast skies, light transmission beneath the rows was about a quarter of that in the intervening gaps, (c) under clear skies, transmission of light by the canopy varied with solar azimuth, increasing to over 20% around noon and falling to a minimum of about 2% a few hours away from noon, (d) interception of light differed little between the two cultivars and training systems examined, (e) the amount of light incident on the sides of the canopy in this large glasshouse was relatively unimportant, at...