Search

A SLAF-BSA approach was used to locate the RPF1 locus. The three most likely candidate genes were identified which provide a basic for cloning the resistance gene at the RPF1 locus. Spinach downy mildew is a globally devastating oomycete disease. The use of downy mildew resistance genes constitutes the most effective approach for disease management. Hence, the objective of the present study was to fine map the first-reported resistance locus RPF1. The resistance allele at this resistance locus was effective against races 1-7, 9, 11, 13, and 15 of Peronospora farinosa f. sp. spinaciae (P. effusa). The approach fine mapped RPF1 using specific-locus amplified fragment sequencing (SLAF-Seq) technology combined with bulked segregant analysis. A 1.72 Mb region localized on chromosome 3 was found to contain RPF1 based on association analysis. After screening recombinants with the SLAF markers within the region, the region was narrowed down to 0.89 Mb. Within this region, 14 R genes were identified based on the annotation information. To identify the genes involved in resistance, resequencing of two resistant inbred lines (12S2 and 12S3) and three susceptible inbred lines (12S1, 12S4, and 10S2) was performed. The three most likely candidate genes were identified via amino acid sequence analysis and conserved domain analysis between resistant and susceptible inbred lines. These included Spo12729, encoding a receptor-like protein, and Spo12784 and Spo12903, encoding a nucleotide-binding site and leucine-rich repeat domains. Additionally, based on the sequence variation in the three genes between the resistant and susceptible lines, molecular markers were developed for marker-assisted selection. The results could be valuable in cloning the RPF1 alleles and improving our understanding of the interaction between the host and pathogen.

Ratification of appointment of repositories by the International Mycological Congress is reported. The following two family names are recommended for conservation: Chrysotrichaceae against Pulverariaceae; and the teleomorph-typified Erysiphaceae against the anamorph-typified Oidiaceae. The following family name is not recommended for conservation: Dothioraceae against Saccotheciaceae. The following 10 generic names are recommended for conservation: the teleomorph-typified name Blumeria against the conserved anamorph-typified name Oidium; Catenaria Sorokīn (Fungi) against Catenaria Roussel (Algae); Chrysothrix, nom. cons., against an additional name, Alysphaeria; Flammula (Fr. : Fr.) P. Kumm. (Fungi) against Flammula (Webb ex Spach) Fourr. (Spermatophyta) with a conserved type; Fuscopannaria against Moelleropsis; Geastrum with a conserved type; Hebeloma with a conserved type; Polycaryum with that spelling; Pseudocyphellaria with a conserved type; and Talaromyces against Lasioderma. Conservation of Detonia Freng. (Algae) against Detonia Sacc. (Fungi) is not opposed. The following generic name is not recommended for conservation: Catillaria with a conserved type. The proposal to conserve the generic name Wickerhamomyces against Hansenula was withdrawn. The following 17 species names are recommended for conservation: Agaricus laterinus (Hebeloma laterinum) against the sanctioned A. fastibilis (H. fastibile); Agaricus tabescens against A. socialis; Alectoria fuscescens (Bryoria fuscescens) against Lichen chalybeiformis and A. subcana; Armillariella ostoyae (Armillaria ostoyae) against Agaricus obscurus, A. occultans, and Armillaria solidipes; Ganoderma camphoratum with a conserved type; Hebeloma fragilipes against Hebelomina domardiana (Hebeloma domardianum); Helminthosporium maydis Y. Nisik. & C. Miyake (Bipolaris maydis) against H. maydis Brond. and Ophiobolus heterostrophus; Lecidea oederi (Rhizocarpon oederi) against L. koenigii; Lichen fuscatus Schrad. (Acarospora fuscata) against L. fuscatus Lam. with a conserved type; Lichen leucomelos (Heterodermia leucomelos) with that spelling; Lichen muralis (Lecanora muralis, Protoparmeliopsis muralis) with a conserved type; Lichen vulgatus (Opegrapha vulgata) with a conserved type; Morchella semilibera against Phallus crassipes, P. gigas and P. undosus; Peziza ammophila Durieu & Lév. against P. ammophila Saut.; Polycaryum branchipodianum with that spelling; Stereocaulon pileatum with a conserved type; and Torula stilbospora with a conserved type. The following 22 species names (teleomorph-typified) are recommended for conservation against anamorph-typified names: Erysiphe arcuata against Oidium carpini; Erisyphe biocellata against Oidium erysiphoides; Erysiphe buhrii against Oidium dianthi; Erysiphe catalpae against Oidium bignoniae; Erysiphe celosiae against Oidium amaranthi; Erisyphe magnicellulata against O. drummondii; Erysiphe quercicola against Oidium anacardii; Erisyphe verbasci against Oidium balsamii; Golovinomyces sonchicola against Oidium sonchi-arvensis; Leveillula rutae against Oidium haplophylli; Microsphaera azaleae against O. ericinum; Microsphaera oehrensii against Oidium robustum; Phyllactinia alni against Ovulariopsis alni-formosanae; Phyllactinia ampelopsidis against Ovulariopsis ampelopsidis-heterophyllae; Phyllactinia chubutiana against Oidium insolitum; Phyllactinia dalbergiae against P. subspiralis; Phyllactinia gmelinae against Ovulariopsis gmelinae-arboreae; Phyllactinia populi against Ovulariopsis salicis-warburgii; Podosphaera solanacearum against Oidium saeforthiani; Sphaerotheca euphorbiae-hirtae against Oidium pedilanthi; Sphaerotheca filipendulae against Torula botryoides; and Sphaerotheca leucotricha against Oidium farinosum. The following two species names are not recommended for conservation: Cylindrocladium buxicola against C. pseudonaviculatum; and Verrucaria subcerasi (Arthopyrenia subcerasi) against A. subalbicans. It is recommended that the generic name Aspidelia and the species name Lichen quisquiliaris not be rejected under Art. 56. The following two species names are recommended for rejection under Art. 56: Botrytis farinosa (Peronospora farinosa) and Saccharomyces sphaericus. As a result of reference under Art. 53.5, it is recommended that the following two pairs of names are not to be treated as homonyms: Bertia De Not. and Bertya Planch.; and Otidea (Pers.) Bonord. and Otidia Sweet.

Six isolates of spinach downy mildew fungus, Peronospora farinosa f. sp. spinaciae, collected from Saitama and Ibaraki Prefectures in 2017 were identified. Three isolates collected from Saitama Prefecture in January differed from all the known races described by the International Seed Federation but their virulence was similar to that of strain UA1014 sampled in the USA in 2014. Isolate Iba17-2, collected from Ibaraki Prefecture in April, was identified as race 10; isolates Iba17-1 and Iba17-3, collected from the same region in February and May, did not match any known races and were coded as novel races, J17-1 and J17-2, respectively.

Chenopodium quinoa is a pseudocereal species identified as a potential crop to mitigate world food security. It has the ability to adapt to diverse agro-ecosystems ranging from sea level to over 4000 masl. Its cultivation in Morocco began in 1999, as it is tolerance to drought, salinity, and frost, and it can grow on marginal soils. It has exceptional nutritional value, as it is rich in proteins, essential amino acids, mineral nutrients, trace elements, vitamins, and unsaturated fatty acids. The present study aims to evaluate the adaptation of 14 quinoa varieties and lines from four different origins through fourteen agro-morphological characters. The experimental trials were conducted at five contrasted agro-climatic sites across the central part of Morocco. The data analysis showed high variability among the tested varieties and between sites for all assessed traits. The Meknes (foot-hill plain) site was the most productive, its grain yield reached 78.6 qx/ha. At the Rabat (coastal land) and Berrechid (continental plain) sites, grain production was respectively 56.4 and 45.9 qx/ha. The SW2 Moroccan line produced the highest grain yield that reached 78.3 qx/ha across sites. The Danish variety Titicaca presented the best harvest index (HI = 0.69) as well as the best “thousand kernel weight” (TGW = 3.4 g). As the mildew infection evaluation, the Vikinga and Titicaca varieties ranked the most sensitive to Peronospora farinosa. The germination rates of the harvested seeds were prejudiced by the sites’ high temperatures and were low in Tinejdad (oases site) and El Kbab (mountain plateau). The best average germination rate across sites was that of the Puno variety (84.5%). According to the Additive Main effects and Multiplicative Interaction analysis (AMMI), 23% of the grain yield variability is due to the genotype, while 32% is due to the site by the variety interaction contribution to the production variability. AMMI analysis also ranked the varieties according to their productivity and stability value. Accordingly, two varieties that have yielded above the overall average (42.7 qx/ha) are considered stable, those are Riobamba and W11, which is a local selected line. Titicaca, ILLPA, Atlas cultivars and the SW2 local line presented the best grain yield in one of the experimental sites but performed not as well on the others.

Isolates of spinach downy mildew fungus, Peronospora farinosa f. sp. spinaciae, collected at seven sites in Japan from December 2013 to March 2016, were identified as belonging to races 8, 10, 12 and 13, and one was unauthorized. Races 10, 12, 13 and the unauthorized were first found in Japan.

Downy mildew, caused by Peronospora farinosa (Fr.) Fr. f. sp. chenopodii Byford, is the most important disease of quinoa (Chenopodium quinoa Willd.) in the high mountainous areas of the Andes in South America (1), where the crop originated. While quinoa is not well known outside its traditional growing area, interest in this crop is increasing rapidly due to its high nutrient quality, many uses for human consumption, and agronomic characteristics of the plant; it is one of the most drought, salt, and frost tolerant crops known (2). From 1990 to 2001, several field trials were conducted in Denmark to study the performance of quinoa germ plasm of different origin under Danish conditions. Natural infection by downy mildew was observed each year on a range of cultivars, as well as on the common weed species, C. album L., which was observed growing near the quinoa. In 2001, 25 isolates of P. farinosa were collected from a field trial at the experimental station of the Royal Veterinary and Agricultural University in Taastrup, Denmark, from two Dutch quinoa cultivars (Carmen and Atlas) and one Danish breeding line (G205). Plants showed typical downy mildew symptoms: chlorotic lesions on the upper leaf surface and grayish spore masses on the lower leaf surface. Microscopic examination of the material showed the presence of dichotomously branched sporangiophores (200 to 400 μm long), which tapered to a blunt point and produced ellipsoidal, light brown sporangia with mean dimensions of 22 × 18 μm. The isolates were propagated and maintained by inoculation of detached quinoa leaves of two highly susceptible Peruvian cultivars (Toledo and Pandela) with a sporangium suspension (105 sporangia per ml), followed by incubation on water agar plates (10 to 15 leaves per plate) at 15°C and 12 h light/dark for 9 to 11 days. All isolates grew readily on these cultivars, and microscopic examination of the pathogen showed the same morphology as the original isolate. When the isolates were tested for their virulence on a range of quinoa cultivars with different geographic origin, specific interactions between host genotype and pathogen isolate were observed, measured as the degree of sporulation in the detached leaf assay, suggesting the presence of several pathotypes. To our knowledge, this is the first report of P. farinosa on quinoa in Denmark. Downy mildew should be considered as a potential problem for future large-scale quinoa production in Europe. References: (1) S. Danielsen. (Abstr.) Phytopathology 90(suppl):S17, 2000. (2) N. W. Galwey. Biologist 36:267, 1989.

Spinach downy mildew disease, caused by the obligate pathogen Peronospora farinosa f. sp. spinaciae, is the most economically important spinach (Spinacia oleracea) disease. New races of this pathogen have been emerging at a rapid rate over the last 15 years. This is likely due to production changes, particularly in California, such as high-density plantings and year-round spinach production. As of 2004, 10 races of P. farinosa f. sp. spinaciae had been identified, and the spinach resistance locus RPF2 provided resistance to races 1 to 10. Based on disease reactions on a set of spinach differentials containing six hypothesized resistance loci (RPF1-RPF6), races 11, 12, 13, and 14 of P. farinosa f. sp. spinaciae were characterized based on samples collected in the past 5 years as part of this study. Race 11, identified in 2008, could overcome the resistance of spinach cultivars resistant to races 1 to 10. Spinach resistance loci RPF1, RPF3, and RPF6 provided resistance to race 11. Race 12 was identified in 2009 and could overcome the resistances of the RPF1 and RPF2 loci. The RPF3 locus was effective against race 12. Race 13 was identified in 2010 and could overcome the resistance imparted by the RPF2 and RPF3 loci, whereas the RPF1 locus was effective against race 13. Race 14 was similar to race 12 and caused identical disease responses on the standard differentials but could be distinguished from race 12 by its ability to cause disease on a number of newly released cultivars, including ‘Pigeon’, ‘Cello’, and ‘Celesta’. Five novel strains of P. farinosa f. sp. spinaciae were also identified. For example, isolate UA4711 of the pathogen, collected from Spain in 2011, was able to overcome the resistance imparted by the RPF1 and RPF3 loci, while RPF2 and RPF4 were effective against this strain. A total of 116 spinach cultivars, including 103 commercial lines and 13 differential cultivars, were evaluated for resistance to race 10 and the newly designated races 11, 12, 13, and 14.

Spinach (Spinacae oleracae) is a nutritious vegetable and an economically important crop worldwide. Spinach is threatened by a number of diseases, and the most significant of which is downy mildew, caused by Peronospora farinosa f. sp. spinaciae (Pfs). The spinach locus RPF1 confers resistance to 11 of the 15 known races of Pfs. To study the RPF1 locus in depth, a BAC library was constructed from DNA of a single spinach plant that was homozygous at the RPF1 locus. The BAC library contained 73,728 clones, with an average insert size of 183 kb, which represented approximately 13 spinach genome equivalents (989 Mb). The ends of 1920 BAC clones were sequenced from both directions, and 3405 BAC end sequences (BESs) ranging from 100 to 935 bp were obtained. About 38.59 % of the BESs contained repetitive sequences, including 363 copies of retrotransposable elements and 32 copies of transposable elements. Less than 3 % of the clones originated from chloroplasts or mitochondria. Various categories of protein-encoding genes, including transcription factors, stress responsive genes, and reproduction-associated genes, were identified. Putative disease resistance genes containing nucleotide binding site-leucine-rich repeat (NBS-LRR) domains were also identified, one of which was closely linked to the RPF1 locus. Simple sequence repeat (SSR) motifs were identified from 154 BESs, including various di-, tri-, tetra-, and penta-nucleotide repeats. One hundred pairs of SSR primers and 24 retrotransposon primers were designed from BESs, all of which successfully amplified spinach DNA. This spinach BAC library will provide a useful resource for spinach genetic studies and breeding efforts.

Aims To develop multiplex TaqMan real-time PCR assays for detection of spinach seedborne pathogens that cause economically important diseases on spinach. Methods and Results Primers and probes were designed from conserved sequences of the internal transcribed spacer (for Peronospora farinosa f. sp. spinaciae and Stemphylium botryosum), the intergenic spacer (for Verticillium dahliae) and the elongation factor 1 alpha (for Cladosporium variabile) regions of DNA. The TaqMan assays were tested on DNA extracted from numerous isolates of the four target pathogens, as well as a wide range of nontarget, related fungi or oomycetes and numerous saprophytes commonly found on spinach seed. Multiplex real-time PCR assays were evaluated by detecting two or three target pathogens simultaneously. Singular and multiplex real-time PCR assays were also applied to DNA extracted from bulked seed and single spinach seed. Conclusions The real-time PCR assays were species-specific and sensitive. Singular or multiplex real-time PCR assays could detect target pathogens from both bulked seed samples as well as single spinach seed. Significance and Impact of the Study The freeze-blotter assay that is currently routinely used in the spinach seed industry to detect and quantify three fungal seedborne pathogens of spinach (C. variabile, S. botryosum and V. dahliae) is quite laborious and takes several weeks to process. The real-time PCR assays developed in this study are more sensitive and can be completed in a single day. As the assays can be applied easily for routine seed inspections, these tools could be very useful to the spinach seed industry.

In the Andean region of South America downy mildew, caused by Peronospora farinosa, is the most important disease of quinoa (Chenopodium quinoa). Peronospora farinosa, a highly polyphyletic species, occurs on quinoa and wild relatives on all continents. However, very little is known about the geographic diversity of the pathogen. As the interest in quinoa as a novel crop is increasing worldwide, geographical differences in the population structure of the downy mildew pathogen must be taken into consideration in order to design appropriate control strategies under a variety of circumstances. As a step towards understanding the geographic diversity of P. farinosa from quinoa, 40 downy mildew isolates from the Andean highlands and Denmark were characterized using universally primed PCR (UP-PCR). Eight UP-PCR primers were tested. A combined analysis of markers separated the Danish and Andean isolates in two distinct clusters. This study raises new questions about the origin and spread of P. farinosa on quinoa, its geographic diversity and host specificity. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Downy mildew is an economically important and widespread disease in quinoa (Chenopodium quinoa) growing areas. Although in many studies Peronospora farinosa is most commonly regarded as the causal agent of the disease, identification and classification of the pathogen remain still uncertain due to its taxonomic confusion. Thirty-six Peronospora isolates from quinoa with different geographic origins including Argentina, Bolivia, Denmark, Ecuador, and Peru were morphologically and molecularly compared with Peronospora species from other Chenopodium species. The morphology of three herbarium specimens was similar to that of P. variabilis, which originated from C. album, characterized by flexuous to curved ultimate branchlets and pedicellated conidia. Phylogenetic analysis based on ITS rDNA sequences also placed the quinoa pathogen within the same clade as P. variabilis. Within the ITS rDNA sequences of the quinoa pathogens, two base substitutions were found, which separated the majority of the Danish isolates from isolates from South America, but no sequence difference was found among the isolates from different cultivars of quinoa. The present results indicate that the pathogen responsible for the quinoa downy mildew is identical to Peronospora variabilis and that it should not be lumped with P. farinosa as claimed previously by most studies.

Spinach downy mildew, caused by Peronospora farinosa f. sp. spinaciae, is the most economically important disease of spinach worldwide. During the past few years, spinach cultivars resistant to the seven previously described races of P. farinosa f. sp. spinaciae were observed to be severely affected by downy mildew in both the United States and the European Union. Four new isolates of P. farinosa f. sp. spinaciae were collected from California and The Netherlands and characterized based on disease reactions on two modified sets of spinach differentials. The results led to the description of three new races of the downy mildew pathogen, designated races 8, 9, and 10. Four differential cultivars with resistance to races 1 to 7 were used to distinguish the three new races. Dolphin was susceptible to races 8 and 10 but resistant to race 9; Lion was susceptible to race 10 but resistant to races 8 and 9; Lazio was resistant to races 1 to 7 as well as races 8, 9, and 10; and Tarpy was susceptible to all three new races. The three new races also were used to evaluate the disease reactions on 43 contemporary commercial spinach cultivars in greenhouse trials. A survey of 58 isolates of P. farinosa f. sp. spinaciae collected in California and Arizona between 2004 and 2006 revealed that race 10 predominated in the areas sampled.

The present study includes a first report of downy mildew caused by Peronospora farinosa f.sp. chenopodii Byford on Chenopodium quinoa Willd. from India. Thirty-four exotic accessions of Chenopodium spp. comprising seven of wild type and 27 accessions of C. quinoa of different origin were evaluated and screened for downy mildew disease resistance under natural epiphytotic field conditions in the sub-tropical climate of mid-eastern India. To achieve the desired objective, two methods of disease assessment were tested and compared based on area under disease progress curve (AUDPC). In the first method, AUDPC(cal) was calculated utilizing all data points gathered over the entire epidemic, while in the second method, AUDPC(est) was estimated using only two assessment dates. The accessions were adequately resolved by both methods into highly susceptible to immune classes suggesting the presence of both major gene resistance and rate reducing resistance among them. The two-point method of disease assessment was found suitable and easy and could be employed for future screening programs. Out of 34 accessions, all seven accessions of wild types and four accessions PI 510532, CHEN 67/78, Ames 22158 and CHEN 7/81 of C. quinoa were found immune/resistant suggesting physiological specialization of current pathotypes for C. quinoa. The identification of the critical growth period attaining peak severity/epidemic has been solved through a disease severity–temporal relationship model at flower bud initiation stage in C. quinoa. The utilization of resistant accessions in the breeding program is also discussed.

Seven disease assessment methods to measure severity of downy mildew (Peronospora farinosa f.sp. chenopodii) were tested in eight cultivars of quinoa (Chenopodium quinoa) in two field experiments in Peru, one at low (Lima) and one at high (Huancayo) disease pressure. Two levels of downy mildew were established by means of fungicide treatments. Area under disease progress curve (AUDPC) values were calculated for each method and correlated to the grain yield. In addition to the severity measurements, spectral reflectance was measured throughout the growth season in Huancayo and area under reflectance curve (AURC) values calculated and correlated to yield. The disease level was ten-fold higher in Huancayo compared to Lima. AUDPC based on the Three-leaf method (mean disease severity of three leaves per plant selected randomly from the lower, middle and upper part of the plant), showed the highest negative correlation to yield (r=−0.736) and is regarded as the best method to predict yield loss caused by downy mildew. In addition, this method proved to be the quickest and easiest compared to the other six methods included in the study, which were based on assessments of disease severity of the entire plant or parts of the plant. Yield losses recorded in the tested cultivars ranged from 33% to 99% under the high-disease conditions. The reflectance method was superior to all other methods by showing a higher correlation between AURC and yield (r=0.853), which is explained by its ability to measure pathogen-induced defoliation. Remote sensing is an excellent tool to compare the effect of treatments on disease severity within a cultivar. However, the method does not allow for comparison of disease severity among cultivars as the spectral reflectance is determined by size, shape and colour of the plant. The Three-leaf method provides an easy, cheap and readily applicable tool for researchers and plant breeders to study downy mildew of quinoa, characterise germplasm for resistance and compare results across regions and years.

O balãozinho (Cardiospermum halicacabum), planta daninha introduzida recentemente no Paraná, tem causado perdas econômicas em lavouras de soja no Sul do Brasil. O objetivo deste trabalho foi determinar época e taxa de emergência, competição e sobrevivência de balãozinho na cultura da soja cultivar Embrapa 62, em dois sistemas de manejo. O experimento foi instalado em Londrina, PR, em maio de 1997, e conduzido por três anos consecutivos. Cinco densidades de semeadura de balãozinho (0, 60, 120, 240 e 480 sementes/m²) foram estabelecidas na cultura da soja sob semeadura convencional e direta. O delineamento experimental foi em blocos casualizados, com parcelas subdivididas e quatro repetições. A redução média anual do banco de sementes foi de 61,6% e 56,4%, em relação às semeaduras convencional e direta, correspondendo às sobrevivências de seis e sete anos, respectivamente. Taxas anuais de emergência, na ausência de reinfestações, foram maiores em semeadura direta (42,6%, 32,0% e 5,0%) do que na convencional (29,9%, 10,9% e 0,7%), nos três anos. Perdas de produtividade de soja foram estimadas em 8,1% com a presença de 10 plantas/m² de balãozinho, em 3.549 kg/ha de soja. O balãozinho apresenta significativa capacidade de infestação e competição com a soja, tendendo a ser eliminado por condições ambientais que favoreçam o ataque de míldio (Peronospora farinosa).

Since 1996, commercial spinach cultivars with resistance to four previously described races of Peronospora farinosa f. sp. spinaciae (races 1, 2, 3, and 4) were observed with high incidences of downy mildew both in California and Europe. Isolates of P. farinosa f. sp. spinaciae collected in California between 1997 and 2001, Arizona in 1999, and a single isolate collected in the Netherlands in 1996 were examined for their disease reaction on differential spinach cultivars and a set of commercial spinach cultivars. Disease reactions on the differential cultivars indicated the occurrence of three new races of P. farinosa f. sp. spinaciae. Two newly identified races, designated race 5 (isolate CA1) and race 6 (isolate SP1), were detected in the United States. The isolate from the Netherlands also was distinct and designated race 7 (isolate JVN7). Some cultivars with resistance to races 1, 2, 3, and 4 were susceptible to race 5, whereas others were resistant, indicating that resistance to a given race may be governed by different genes (or alleles) depending on the source of resistance. A survey of races in California indicated that races 5 and 6 predominated. Although the majority of the cultivars examined were susceptible to race 6 based on the traditional qualitative cotyledon inoculation assay, significant quantitative differences in resistance to race 6 were observed using a true-leaf greenhouse screening procedure. Although more work is needed to confirm the results of the true-leaf assays, the quantitative resistance observed using this procedure appears to be race specific.

The race of field isolates of Peronospora farinosa f. sp. spinaciae (Pfs), causal agent of spinach downy mildew, were identified using race-differential cultivars. One isolate was similar to race Pfs:6. Three isolates were identified as race Pfs:8, the first time the race has been reported in Japan as far as we know. The differential reaction caused by the other two isolates did not match any known to be caused by races Pfs:1 through Pfs:11; thus, this strain appears to a new pathogenic strain in Japan.

Twenty downy mildew isolates were collected in south, central and north Ecuador and inoculated on seedlings of 60 quinoa lines. A scale for scoring quinoa downy mildew infections was developed. Four virulence groups and three resistance factors were identified. In southern Ecuador only isolates of virulence group 2 were collected, while in the central region only virulence group 4 was found. In the north of Ecuador isolates of all four virulence groups were collected. Resistance factor R3 was found most frequently in seedlings of 13 high-yielding Ecuadorian quinoa lines. No effective resistance against group 4, the most virulent group, was observed. Lines ECU-288 (susceptible), ECU-291(R1), ECU-470 (R2) and ECU-379 (R3) could be used as a preliminary quinoa differential set for identifying downy mildew virulence groups.

Wageningen UR Greenhouse Horticulture, together with Syngenta Seeds performed field trials with fungicides and fertilizing products to prolong the consumer value of Impatiens walleriana (busy lily). This project was funded by the Dutch Horticultural Board. The plants were situated on two field locations, both in the field and in pots to follow the natural disease development with and without interaction with soil pathogens (e.g. downy mildew). The results of this study show that Ridomil Gold is effective against early infestation from soil propagules of downy mildew, but there is no effectivity against leaf infections. Products based on phoshite (potassium phosphite, product X of Everris) slow down the infection process with a few weeks. Especially, later in the season when the conidia are most dominantly present. It is recommended to screen multiple products which are effective against resting spores of downy mildew. Sensitive Impatiens species should preferably be planted early in the season and not directly in soil with high risk of surviving propagules.

Wageningen UR Greenhouse Horticulture, together with Syngenta Seeds performed field trials with fungicides and fertilizing products to prolong the consumer value of Impatiens walleriana (busy lily). This project was funded by the Dutch Horticultural Board. The plants were situated on two field locations, both in the field and in pots to follow the natural disease development with and without interaction with soil pathogens (e.g. downy mildew). The results of this study show that Ridomil Gold is effective against early infestation from soil propagules of downy mildew, but there is no effectivity against leaf infections. Products based on phoshite (potassium phosphite, product X of Everris) slow down the infection process with a few weeks. Especially, later in the season when the conidia are most dominantly present. It is recommended to screen multiple products which are effective against resting spores of downy mildew. Sensitive Impatiens species should preferably be planted early in the season and not directly in soil with high risk of surviving propagules. Referaat Wageningen UR Glastuinbouw heeft met Syngenta Seeds gewerkt aan voorkomen van uitval in Impatiens walleriana (vlijtig liesje). Dit project is gefinancierd door Productschap Tuinbouw. Doel van het onderzoek is om de consumentwaarde van Impatiens te verlengen door het voorkomen van uitval door bodemschimmels (oa. valse meeldauw) onder veldcondities. Tijdens de opkweekperiode zijn de planten behandeld met producten die eerder al een werking vertoonden tegen bodemsporen van valse meeldauw en producten met een verwachte werking tegen zoösporen en combinaties daarvan. De planten zijn op twee veldlocaties uitgezet, zowel in het veld als in potten om de natuurlijke ziekteontwikkeling te volgen. De uitkomsten van dit onderzoek laten zien dat Ridomil Gold een werking vertoont tegen vroege infecties van valse meeldauw vanuit rustsporen, maar dat er resistentie is opgetreden tegen zoösporen. Producten op basis van fosfiet-achtige verbindingen (kaliumfosfiet, product X van Everris) vertragen de uitval met enkele weken; vooral later in het seizoen als de uitval veroorzaakt wordt door bladinfecties. Eén behandeling één week voor aflevering werkt afdoende. Het verdient aanbeveling om meerdere middelen te screenen met een werking tegen rustsporen van valse meeldauw, gevoelige Impatiens soorten bij voorkeur vroeg uitleveren in het seizoen en niet in grond uitplanten met een historie van uitval. Abstract Wageningen UR Greenhouse Horticulture, together with Syngenta Seeds performed field trials with fungicides and fertilizing products to prolong the consumer value of Impatiens walleriana (busy lily). This project was funded by the Dutch Horticultural Board. The plants were situated on two field locations, both in the field and in pots to follow the natural disease development with and without interaction with soil pathogens (e.g. downy mildew). The results of this study show that Ridomil Gold is effective against early infestation from soil propagules of downy mildew, but there is no effectivity against leaf infections. Products based on phoshite (potassium phosphite, product X of Everris) slow down the infection process with a few weeks. Especially, later in the season when the conidia are most dominantly present. It is recommended to screen multiple products which are effective against resting spores of downy mildew. Sensitive Impatiens species should preferably be planted early in the season and not directly in soil with high risk of surviving propagules.

Quinoa, Chenopodium quinoa Willd., is an Andean crop prized for its high nutritional value and adaptability to harsh environments. Quinoa is plagued by downy mildew caused by Peronospora variabilis Gäum (formerly Peronospora farinosa f. sp. chenopodii Byford) (1). Quinoa production has spread beyond native Andean ranges and quinoa downy mildew has been reported in India, Canada, and Denmark (1). During the summer of 2011, quinoa trials were established to determine the ability of quinoa to grow under Mid-Atlantic conditions and monitor for regional disease problems. In July, after cool, rainy conditions, downy mildew-like symptoms were observed on quinoa at research plots in Centre and Lancaster counties of Pennsylvania. Symptoms and signs consisted of irregularly shaped areas of foliar chlorosis or pink discoloration accompanied by dense, gray sporulation on both leaf surfaces. Sporangia were tan to gray-brown, semi-ovoid, often with a pedicel, mean length of 31 μm, and mean width of 23 μm. Sporangiophores branched dichotomously, and the terminal branchlets curved and tapered to a point. Orange oospores were present in field samples of leaf tissue. DNA was extracted from infected foliar tissue and sporangial suspensions. A seminested PCR protocol (2) was used to obtain partial internal transcribed spacer (ITS) sequences of six Peronospora isolates. The sequences shared 99% maximum identity to a known P. variabilis accession (FM863721.2) in GenBank. A voucher specimen was deposited into the U.S. National Fungus Collections (BPI 882064). Pathogenicity of each of two strains of P. variabilis was confirmed by inoculating quinoa with sporangia (4). Sporangia were shaken from leaves in sterile distilled water and the suspension was filtered through cheesecloth. A 0.01% Tween solution was added and the suspension diluted to 103 sporangia/ml. With an atomizer, a 10-ml sporangial suspension (or sterile water for noninoculated control plants) was sprayed onto one flat of 18 2-week-old quinoa plants, and relative humidity was increased to saturation using a humidity dome for 24 h. After 1 week, chlorosis and pink discoloration were noted on leaves of inoculated quinoa, and after 18 h of subsequent increased humidity (>95% relative humidity), dense gray sporulation was observed. No symptoms were noted on noninoculated control plants. Sporangia and sporangiophores were examined morphologically and confirmed to be P. variabilis, confirming Koch's postulates. For culture maintenance, 2-week-old quinoa leaves were placed onto a sporangial suspension on top of 1% water agar and maintained in a growth chamber at 20°C with 16 h of light per day. Quinoa downy mildew is seedborne (3) and initial infections may have occurred from oospores in the pericarp, despite intensive processing of consumable quinoa seeds to remove saponins. To our knowledge, this is the first report of quinoa downy mildew in the United States and also the first report of P. variabilis in the United States. References: (1) Y. Choi et al. Mycopathologia 169:403, 2010. (2) D. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (3) S. Danielson et al. Seed Sci. Technol. 32:91, 2004. (4) J. Ochoa et al. Plant Pathol. 48:425, 1999.

Een goede bodemstructuur die onderdak biedt aan microbieel bodemleven dat vervolgens voldoende voedsel heeft, maakt de grond weerbaar. Daar begint het voorkomen van valse meeldauw bij zonnebloemen. Gecoat zaad biedt bescherming en tijdens de teelt wordt deze keuze in chemische bespuitingen iets groter.

De éénjarige zomerbloeier Impatiens walleriana is een belangrijk onderdeel in het perkgoedassortiment. De grote problemen met aantasting door valse meeldauw hebben de laatste jaren geresulteerd in een fikse omzetdaling. Er is daarom op korte termijn behoefte aan duurzame bestrijdingsmiddelen, die tenminste drie maanden effectief blijven. Dat laatste is ook de vraag van de begeleidingscommissie.

De éénjarige zomerbloeier Impatiens walleriana is een belangrijk onderdeel in het perkgoedassortiment. De grote problemen met aantasting door valse meeldauw hebben de laatste jaren geresulteerd in een fikse omzetdaling. Er is daarom op korte termijn behoefte aan duurzame bestrijdingsmiddelen, die tenminste drie maanden effectief blijven. Dat laatste is ook de vraag van de begeleidingscommissie.

Valse meeldauw is een probleem in een groot aantal glastuinbouwgewassen. De symptomen bij aantasting door de schimmel lijken soms op die van echte meeldauw, maar het gaat hier om een heel andere groep van schimmels die zich anders gedraagt en lastig te bestrijden is. Valse meeldauw kan veel glasgroenten, snijbloemen en potplanten aantasten.

Valse meeldauw is een probleem in een groot aantal glastuinbouwgewassen. De symptomen bij aantasting door de schimmel lijken soms op die van echte meeldauw, maar het gaat hier om een heel andere groep van schimmels die zich anders gedraagt en lastig te bestrijden is. Valse meeldauw kan veel glasgroenten, snijbloemen en potplanten aantasten.

The introduction of a new technology of sugar‐beet seed production (summer direct sown) gets the young plants into the environment ecologically suitable for infection and development of Peronospora farinosa f. sp. betae. The results of developing investigation dynamics in experimental plots and field stands (very low occurrences of disease in autumn and rapid increase in spring), and the intensity of occurrences in field stands (up to 45% destroyed plants) are given. The stronger winter significantly reduces the occurrence and harmfulness of the pathogen. The second part speaks about the effect of industrial crops as a source of infection, and of the importance of dominant wind direction on the occurrence of the disease. The third part evaluates the effect of nutrients in soil, especially potassium and phosphorus which increase the incidence of disease. In the concluding part there are recommendations for sugar‐beet seed cultivators.

Quinoa (Chenopodium quinoa Willd.) is a grain crop grown primarily for its edible seeds. The plant has originated in the Andean region of South America, where it was domesticated 3,000-4,000 years ago for human consumption. Because quinoa has a high nutritive value and desirable agricultural traits as tolerance to drought and salinity, it has gained increased demand in recent years. The winter climate in Egypt favors good production of quinoa and it has already been cultivated in saline soils in Upper Egypt. More, recently in 2014, downy mildew was recognized in plants of two Egyptian quinoa trials at Giza and Ismaeliya governorates. Infected plants showed small to large irregular chlorotic lesions with grey mildew on leaves (Fig.1), often leading to early leaf defoliation. Light microscopy revealed presence of colorless dichotomously branched sporangiophores (2-3.2μ width), slightly curved at the far point bearing hyaline sporangia (Fig.2). Spores are deciduous, mostly ovoid, 11.0- 15.6μ x 20.0-25.5μ (Fig.2). Dark brownish oospores were observed embedded into leaf tissues. The disease is caused by Peronospora variabilis Gaum, formerly Peronospora farinosa f.sp. chenopodii Byford, (Choi et al., 2010). It is expected that this disease could be a potential constraint for quinoa production in Egypt. To minimize the effect of downy mildew on the seed yield, in depth studies are to be done to develop control measures and accumulate information about disease parameters under local conditions.

Valse meeldauw is het grootste ziekteprobleem in de zonnebloementeelt. Het wordt veroorzaakt door de oömyceet Plasmopara halstedii, een bodemgebonden ziekte. Valse meeldauw kan tot tien jaar in de grond overleven als rustspore. In de bodem kan valse meeldauw onder natte omstandigheden via de jonge wortels van een kiemplant infecteren. Bij infectie vanuit de bodem, de zogenaamde systemische infectie, zijn er verschillende symptomen zichtbaar. De planten blijven achter in groei, bladeren vergelen en bij een zware aantasting kan de plant afsterven. Als een plant is aangetast en op de bladeren nieuwe sporen worden gevormd verspreiden deze sporen zich via de lucht. Ze veroorzaken een bovengrondse aantasting waarbij bladvlekken ontstaan. Beide soorten infecties leiden tot verminderde kwaliteit van de bloemen en met name de systemische infectie leidt tot verminderde productie. Meer dan 50% uitval is meermalen voorgekomen. Zowel in de gangbare teelt, als in de biologische teelt waarbij geen chemische ingreep mogelijk is, wordt het probleem steeds groter. Werkzame fungiciden zijn vooralsnog in de teelt niet toegelaten en coaten van zaad met fungiciden werkt niet afdoende. Er is daarom gezocht naar een geïntegreerde aanpak voor valse meeldauw in zonnebloem met de nadruk op preventieve maatregelen.

De éénjarige zomerbloeier Impatiens walleriana vormt een belangrijk onderdeel in het assortiment van perkgoed. Ondermeer in 2007 waren er door de natte weersomstandigheden grote problemen met uitval door valse meeldauw in de consumentfase. Hierdoor kwam de vraag of er tijdens de opkweek niet meer preventieve maatregelen genomen kunnen worden om infectie door valse meeldauw onder vochtige omstandigheden te verminderen of te voorkomen. Daarnaast was het onbekend of de besmetting met valse meeldauw op Nederlandse locaties veroorzaakt wordt door één soort of meerdere soorten. In een literatuurstudie is alle beschikbare informatie over valse meeldauw en mogelijkheden voor beheersen/ bestrijding samengevat

Rassenproef komkommer op praktijkbedrijven

Uit onderzoek is gebleken dat valse meeldauw in zonnebloem het beste kan worden bestreden met een grondmiddel. De nog niet toegelaten middelen konden de aantasting met 25% terugdringen.

Valse meeldauw is het grootste ziekteprobleem in de zonnebloementeelt. Het wordt veroorzaakt door de oömyceet Plasmopara halstedii, een bodemgebonden ziekte. Valse meeldauw kan tot tien jaar in de grond overleven als rustspore. In de bodem kan valse meeldauw onder natte omstandigheden via de jonge wortels van een kiemplant infecteren. Bij infectie vanuit de bodem, de zogenaamde systemische infectie, zijn er verschillende symptomen zichtbaar. De planten blijven achter in groei, bladeren vergelen en bij een zware aantasting kan de plant afsterven. Als een plant is aangetast en op de bladeren nieuwe sporen worden gevormd verspreiden deze sporen zich via de lucht. Ze veroorzaken een bovengrondse aantasting waarbij bladvlekken ontstaan. Beide soorten infecties leiden tot verminderde kwaliteit van de bloemen en met name de systemische infectie leidt tot verminderde productie. Meer dan 50% uitval is meermalen voorgekomen. Zowel in de gangbare teelt, als in de biologische teelt waarbij geen chemische ingreep mogelijk is, wordt het probleem steeds groter. Werkzame fungiciden zijn vooralsnog in de teelt niet toegelaten en coaten van zaad met fungiciden werkt niet afdoende. Er is daarom gezocht naar een geïntegreerde aanpak voor valse meeldauw in zonnebloem met de nadruk op preventieve maatregelen.

De éénjarige zomerbloeier Impatiens walleriana vormt een belangrijk onderdeel in het assortiment van perkgoed. Ondermeer in 2007 waren er door de natte weersomstandigheden grote problemen met uitval door valse meeldauw in de consumentfase. Hierdoor kwam de vraag of er tijdens de opkweek niet meer preventieve maatregelen genomen kunnen worden om infectie door valse meeldauw onder vochtige omstandigheden te verminderen of te voorkomen. Daarnaast was het onbekend of de besmetting met valse meeldauw op Nederlandse locaties veroorzaakt wordt door één soort of meerdere soorten. In een literatuurstudie is alle beschikbare informatie over valse meeldauw en mogelijkheden voor beheersen/ bestrijding samengevat

Valse meeldauw is het grootste ziekteprobleem in de zonnebloementeelt. Het wordt veroorzaakt door de oömyceet Plasmopara halstedii, een bodemgebonden ziekte. Valse meeldauw kan tot tien jaar in de grond overleven als rustspore. In de bodem kan valse meeldauw onder natte omstandigheden via jonge wortels de kiemplant infecteren. Bij infectie vanuit de bodem, de zogenaamde systemische infectie, zijn er verschillende symptomen zichtbaar. De planten blijven achter in groei, bladeren vergelen en bij een zware aantasting kan de plant afsterven. Als een plant is aangetast en op de bladeren nieuwe sporen worden gevormd verspreiden deze sporen zich via de lucht. Ze veroorzaken een bovengrondse aantasting waarbij onregelmatige bladvlekken ontstaan. Beide soorten infecties leiden tot verminderde kwaliteit van de bloemen en met name de systemische infectie leidt tot verminderde productie. Meer dan 50% uitval is meermalen voorgekomen. Zowel in de gangbare teelt, als in de biologische teelt waarbij geen chemische ingreep mogelijk is, wordt het probleem steeds groter. Werkzame fungiciden zijn vooralsnog in de teelt niet toegelaten en coaten van zaad met fungiciden werkt niet afdoende. Er is daarom gezocht naar een geïntegreerde aanpak voor valse meeldauw in zonnebloem met de nadruk op niet-chemische maatregelen.

Valse meeldauw is het grootste ziekteprobleem in de zonnebloementeelt. Het wordt veroorzaakt door de oömyceet Plasmopara halstedii, een bodemgebonden ziekte. Valse meeldauw kan tot tien jaar in de grond overleven als rustspore. In de bodem kan valse meeldauw onder natte omstandigheden via jonge wortels de kiemplant infecteren. Bij infectie vanuit de bodem, de zogenaamde systemische infectie, zijn er verschillende symptomen zichtbaar. De planten blijven achter in groei, bladeren vergelen en bij een zware aantasting kan de plant afsterven. Als een plant is aangetast en op de bladeren nieuwe sporen worden gevormd verspreiden deze sporen zich via de lucht. Ze veroorzaken een bovengrondse aantasting waarbij onregelmatige bladvlekken ontstaan. Beide soorten infecties leiden tot verminderde kwaliteit van de bloemen en met name de systemische infectie leidt tot verminderde productie. Meer dan 50% uitval is meermalen voorgekomen. Zowel in de gangbare teelt, als in de biologische teelt waarbij geen chemische ingreep mogelijk is, wordt het probleem steeds groter. Werkzame fungiciden zijn vooralsnog in de teelt niet toegelaten en coaten van zaad met fungiciden werkt niet afdoende. Er is daarom gezocht naar een geïntegreerde aanpak voor valse meeldauw in zonnebloem met de nadruk op niet-chemische maatregelen.

Valse meeldauw is het grootste ziekteprobleem in de zonnebloementeelt. Het wordt veroorzaakt door de oömyceet Plasmopara halstedii. In de bodem vormt de oömyceet rustsporen die aan het begin van het groeiseizoen de primaire infectiebron zijn omdat de sporen zeer lang kunnen overleven in de grond. De secundaire infectie van valse meeldauw ontstaat gedurende het gehele groeiseizoen. Door valse meeldauw systemisch aangetaste zonnebloemen produceren onderaan hun bladeren zoösporangia met daarin zoösporen. Deze sporen kunnen door de lucht verspreid worden en zodra ze bijvoorbeeld met regen in de bodem terecht komen zijn ze in staat om jonge zonnebloem plantjes te infecteren. Daarnaast kunnen ze ook bladvlekken op oudere zonnebloemen veroorzaken. In dit project is gezocht naar nieuwe (chemische) middelen om valse meeldauw te bestrijden. Om een eerste selectie te maken uit een hele lijst van potentiële chemische gewasbeschermingsmiddelen is een biotoets uitgevoerd. Met deze biotoets kan in een kort tijdsbestek de effectiviteit van veel middelen worden bepaald. Er is gekeken naar middelen met verschillende toepassingen als bespuiten, grondtoepassing en zaadcoating. Helaas is er door onbekende redenen niet voldoende ziekte ontstaan in de biotoets. Hierdoor kon geen goede selectie van middelen worden gemaakt voor de veldproef. De veldproef is toch ingezet met een aantal chemische middelen geselecteerd op basis van verschillende werkingsmechanismen en toepassingen. Uit de veldproef bleek dat vijf verschillende middelen effectief waren tegen valse meeldauw. In een opvolgende biotoets zijn deze vijf middelen opnieuw getest en drie bleken wederom een positief effect te hebben op de bestrijding van valse meeldauw in zonnebloem. Door het inzetten van grootschalige praktijkproeven in 2009 met één van deze middelen of een combinatie van middelen zal worden vastgesteld of deze middelen perspectief bieden voor een goede bestrijding van valse meeldauw in zonnebloemen.

Valse meeldauw is het grootste ziekteprobleem in de zonnebloementeelt. Het wordt veroorzaakt door de oömyceet Plasmopara halstedii. In de bodem vormt de oömyceet rustsporen die aan het begin van het groeiseizoen de primaire infectiebron zijn omdat de sporen zeer lang kunnen overleven in de grond. De secundaire infectie van valse meeldauw ontstaat gedurende het gehele groeiseizoen. Door valse meeldauw systemisch aangetaste zonnebloemen produceren onderaan hun bladeren zoösporangia met daarin zoösporen. Deze sporen kunnen door de lucht verspreid worden en zodra ze bijvoorbeeld met regen in de bodem terecht komen zijn ze in staat om jonge zonnebloem plantjes te infecteren. Daarnaast kunnen ze ook bladvlekken op oudere zonnebloemen veroorzaken. In dit project is gezocht naar nieuwe (chemische) middelen om valse meeldauw te bestrijden. Om een eerste selectie te maken uit een hele lijst van potentiële chemische gewasbeschermingsmiddelen is een biotoets uitgevoerd. Met deze biotoets kan in een kort tijdsbestek de effectiviteit van veel middelen worden bepaald. Er is gekeken naar middelen met verschillende toepassingen als bespuiten, grondtoepassing en zaadcoating. Helaas is er door onbekende redenen niet voldoende ziekte ontstaan in de biotoets. Hierdoor kon geen goede selectie van middelen worden gemaakt voor de veldproef. De veldproef is toch ingezet met een aantal chemische middelen geselecteerd op basis van verschillende werkingsmechanismen en toepassingen. Uit de veldproef bleek dat vijf verschillende middelen effectief waren tegen valse meeldauw. In een opvolgende biotoets zijn deze vijf middelen opnieuw getest en drie bleken wederom een positief effect te hebben op de bestrijding van valse meeldauw in zonnebloem. Door het inzetten van grootschalige praktijkproeven in 2009 met één van deze middelen of een combinatie van middelen zal worden vastgesteld of deze middelen perspectief bieden voor een goede bestrijding van valse meeldauw in zonnebloemen.

Downy mildew is a destructive disease of spinach worldwide. There have been 10 races described since 1824, six of which have been identified in the past 10 years. Race identification is based on qualitative disease reactions on a set of diverse host differentials which include open-pollinated cultivars, contemporary hybrid cultivars, and older hybrid cultivars that are no longer produced. The development of a set of near-isogenic open-pollinated spinach lines (NILs), having different resistance loci in a susceptible and otherwise common genetic background, would facilitate identification of races of the downy mildew pathogen, provide a tool to better understand the genetics of resistance, and expedite the development of molecular markers linked to these disease resistance loci. To achieve this objective, the spinach cv. Viroflay, susceptible to race 6 of Peronospora farinosa f. sp. spinaciae, was used as the recurrent susceptible parent in crosses with the hybrid spinach cv. Lion, resistant to race 6. Resistant F1 progeny were subsequently backcrossed to Viroflay four times with selection for race 6 resistance each time. Analysis of the segregation data showed that resistance was controlled by a single dominant gene, and the resistance locus was designated Pfs-1. By bulk segregant analysis, an amplified fragment length polymorphism (AFLP) marker (E-ACT/M-CTG) linked to Pfs-1 was identified and used to develop a co-dominant Sequence characterized amplified region (SCAR) marker. This SCAR marker, designated Dm-1, was closely linked (≈1.7 cM) to the Pfs-1 locus and could discriminate among spinach genotypes that were homozygous resistant (Pfs-1Pfs-1), heterozygous resistant (Pfs-1pfs-1), or homozygous susceptible (pfs-1pfs-1) to race 6 within the original mapping population. Evaluation of a wide range of commercial spinach lines outside of the mapping population indicated that Dm-1 could effectively identify Pfs-1 resistant genotypes; the Dm-1 marker correctly predicted the disease resistance phenotype in 120 out of 123 lines tested. In addition, the NIL containing the Pfs-1 locus (Pfs-1Pfs-1) was resistant to multiple races of the downy mildew pathogen indicating Pfs-1 locus may contain a cluster of resistance genes.

Trips, zwartnervigheid, bladvlekkenziekte en valse meeldauw: het zijn een paar van de ziekten en plagen die de teelt van kwalitatief goede kool en goed zaaizaad belemmeren. Kennis over de plaag of de schimmel levert aanwijzingen voor bestrijding.

Valse meeldauw is een toenemend probleem in de zomerbloementeelt. Onderzoek naar de biologie van valse meeldauw is op dit moment noodzakelijk om effectieve aangrijpingspunten voor bestrijding te vinden. WUR Glastuinbouw verricht onderzoek naar bestrijdingsmaatregelen van valse meeldauw in zomerbloemgewassen. PPO bollenteelt, boomkwekerij en fruit (PPO-BBF) doet onderzoek naar de biologie van en beheersmaatregelen tegen valse meeldauw in zonnebloemen