scholarly journals Resistance of Cucumber Cultivars to a New Strain of Cucurbit Downy Mildew

HortScience ◽  
2012 ◽  
Vol 47 (2) ◽  
pp. 171-178 ◽  
Author(s):  
Adam D. Call ◽  
Adam D. Criswell ◽  
Todd C. Wehner ◽  
Kaori Ando ◽  
Rebecca Grumet
Keyword(s):  
North Carolina ◽  
Downy Mildew ◽  
The United States ◽  
Leaf Damage ◽  
High Yield ◽  
Breeding Lines ◽  
Yield And Quality ◽  
Resistant Lines ◽  
High Level ◽  
Moderately Resistant

Downy mildew, a foliar disease caused by the oomycete Pseudoperonospora cubensis (Berk. and Curt.) Rostow, is one of the most destructive pathogens of cucurbits. From 1961 to 2003, resistant cucumber cultivars in the United States had sufficient resistance to grow a successful crop without the use of fungicides. The pathogen resurged as a major problem in 2004. Since then, the dm-1 gene has not been effective against the new strain of downy mildew, and yield losses are high without the use of fungicides. The objective of this experiment was to identify cultivars having high yield and resistance to the new downy mildew. The experiment had 86 cultivars and breeding lines (hereafter collectively referred to as cultigens) and was conducted in Clinton, NC, in 2007 and 2009, in Castle Hayne, NC, in 2008 and 2009, and in Bath, MI, in 2007 to 2009. Plots were rated weekly on a 0 to 9 scale (0 = none, 1–2 = trace, 3–4 = slight, 5–6 = moderate, 7–8 = severe, and 9 = dead). Mean ratings for downy mildew leaf damage ranged from 2.9 to 5.7 in Michigan in 2008 and 2009 and from 3.8 to 6.8 in North Carolina in 2007 to 2009. None of the cultigens tested in this study showed a high level of resistance, although differences in resistance were detected. Lines WI 2757 and M 21 and cultivar Picklet were consistently among the top resistant lines in North Carolina and Michigan. The cultivars Coolgreen, Wis. SMR 18, and Straight 8 were identified as moderately to highly susceptible. An unreleased hybrid, ‘Nun 5053 F1’, and the cultivar Cates were the top yielding lines overall. The highest yield in a single year and location was from the cultivar Cates in Clinton, NC, in 2009, with 25.6 Mg·ha−1. The best cultivars in this study were only moderately resistant and would likely require fungicide applications to achieve high yield and quality in the presence of downy mildew. Until high resistance becomes available, growers would benefit by using fungicides in combination with tolerant and moderately resistant cultigens.

scholarly journals Downy Mildew Resistance of the Cucumber Germplasm Collection in North Carolina Field Tests

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 450B-450
Author(s):  
Todd C. Wehner ◽  
Nischit V. Shetty
Keyword(s):  
North Carolina ◽  
Downy Mildew ◽  
Germplasm Collection ◽  
Field Tests ◽  
Plant Introduction ◽  
Leaf Damage ◽  
Downy Mildew Resistance ◽  
Mildew Resistance ◽  
Breeding Lines ◽  
Production Areas

Downy mildew [Pseudoperonospora cubensis (Berk. & Curt.) Rostov] is an important disease in most cucumber (Cucumis sativus L.) production areas of the world. Resistant cultivars are available, but higher levels are needed if yield losses are to be avoided. The objective of this experiment was to test all available plant introduction accessions, cultivars, and breeding lines (collectively referred to as cultigens) of cucumber for downy mildew resistance under field conditions in North Carolina. Cultigens were tested in 2 years and two replications under natural field epidemics of the disease. Mean ratings for downy mildew leaf damage ranged from 1.3 to 9.0 on a 0 to 9 scale. The most resistant nine cultigens originated from the U.S., and were primarily adapted cultivars or breeding lines. The most-resistant cultigens, for which multiple-year data were available, were Gy 4, `Clinton', PI 234517, `Poinsett 76', Gy 5, `Addis', M 21, M 27, and `Galaxy'. The most-susceptible cultigens for which multiple year data were available, were PI 288995, PI 176952, PI 178886, and PI 211985. We classified 17 cultigens as highly resistant (1.3 to 3.0), 87 as moderately resistant (3.3 to 5.0), 311 as moderately susceptible (5.3 to 7.0), and 248 as highly susceptible (7.3 to 9.0) for the 663 cultigens with multiple-year data. No plant introduction accessions were found to be more resistant than the most-resistant elite cultivars and breeding lines tested.

Susceptibility of Hop Cultivars to Downy Mildew: Associations with Chemical Characteristics and Region of Origin

2016 ◽  
Vol 17 (1) ◽  
pp. 42-48 ◽  
Author(s):  
Joanna L. Woods ◽  
David H. Gent
Keyword(s):  
United States ◽  
Downy Mildew ◽  
The United States ◽  
High Yield ◽  
Downy Mildew Resistance ◽  
Region Of Origin ◽  
Mildew Resistance ◽  
The United Kingdom ◽  
Pseudoperonospora Humuli ◽  
High Level

Hop downy mildew (caused by Pseudoperonospora humuli) is a yield-limiting disease in many hop-production regions of the world. In this research, 110 cultivars that are or were widely grown in the United States, Europe, or Australasia were evaluated in western Oregon over three years for their reaction to the shoot infection phase of downy mildew and vigor. There was a large range of downy mildew susceptibility and vigor amongst commercial cultivars, with some cultivars possessing a very high level of resistance. Overall, however, disease resistance and vigor were significantly greater in cultivars originating from Europe than those originating from the United States, Japan, and Australia/New Zealand. Amongst a subset of 79 cultivars, vigor was negatively correlated with levels, in cones, of cohumulone, a chemical constitute of bittering acids typically found in germplasm derived from North America. The generally poor vigor observed in cultivars derived outside of Europe likely is indicative of a lack of tolerance to the crown infection phase of the disease. Thus, the best sources of downy mildew resistance seems to be found in cultivars from the United Kingdom and continental Europe, and such cultivars are typically lower yielding and lack distinctive aroma and flavor characteristics presently desired by craft brewers. Introgression of downy mildew resistance into North American germplasm with high yield and desirable brewing characteristics is needed. Accepted for publication 3 March 2016. Published 7 March 2016.

scholarly journals KEMAJUAN GENETDX PADA DUA VARIETAS BARU KAPAS, KANESIA 8 DAN KANESIA

2020 ◽  
Vol 10 (2) ◽  
pp. 66
Author(s):  
. HASNAM ◽  
EMY SULISTYOWATI ◽  
SIWI SUMARTINI ◽  
FITRINTNGDYAH TRI KADARWATI ◽  
PRIMA D. RIAJAYA
Keyword(s):  
Gossypium Hirsutum ◽  
Competitive Ability ◽  
Fiber Strength ◽  
Fiber Quality ◽  
Insect Pest ◽  
Leaf Damage ◽  
High Yield ◽  
Good Tolerance ◽  
Breeding Lines ◽  
South Sulawesi

<p>Tujuan utama pemuliaan kapas di Indonesia adalah meningkatkan produktivitas dan kualitas serat dalam upaya meningkatkan pendapatan petani dan memperbaiki mutu benang tcnun seta kualitas tekstil yang harus bersaing di pasar internasional. Scjumlah enam persilangan telah dilakukan antara dua varietas dai India. I.RA 5166 dan SRT-1 dengan dua varietas dai Amerika Serikat, Dcltapine 55 dan Deltapinc Acala 90 dan satu vaietas dai Australia, Siokra. Seleksi individu, seleksi galur dan seleksi individu dalam galur dilaksanakan pada generasi F2 sampai F5 berdasarkan jumlah buah, tingkat kerusakan daun terhadap Sundapteryx biguttula. dan mutu serat; semua proses di atas dilakukan pada kondisi lahan tadah hujan, dan tanpa penggunaan insektisida terhadap tanaman; dari proses di atas diperoleh 12 galur harapan. Sejumlah 13 percobaan dilakukan antara tahun 1993 sampai dengan 2001 untuk mengamati kcragaan galur-galur baru tersebut; pengujian dilakukan di Jawa Timur dan Sulawesi Selatan, menggunakan teknik-teknik penelitian standar. Dengan proscdur ini dapat diidcntifikasi beberapa galur yang menunjuk¬ kan perbaikan serenlak hasil dan kualitas serat kapas. Beberapa penelitian juga dilakukan untuk mcngcvaluasi tanggap galur-galur tersebut pada tumpangsari dengan kedelai dan kacang hijau di Jawa Timur. Dua galur, 88003/16/2 dan 92016/6 (sudah dilepas dengan nama vaietas Kanesia 8 dan Kanesia 9 pada bulan Juni 2003), menunjukkan produktivitas dan kualitas serai yang lebih linggi. Rata-rata, kedua vaietas menghasilkan 1.85 ton dan 191 ton kapas berbiji per hektar atau 8-12% lebih tinggi dai hasil vaietas Kanesia 7 yang sudah dilepas sebelumnya. Persentase serat 35.2%, kekuatan serat berkisar antara 22.6-24.7 gram tex'1, serat lebih panjang dan berkisar 29.2-30.3 mm sedangkan angka mikroncr lebih rendah yang menyatakan bahwa serat lebih halus. Semua perbaikan di atas menunjukkan perbaikan mutu serat. Kanesia 8 dan Kanesia 9 juga menunjukkan peningkatan ketahanan terhadap Sundapteryx biguttula dan komplcks hama kapas. Kanesia 8 dan Kanesia 9 kurang kompctitif dalam tumpang sari dengan kedelai jika dibandingkan dengan Kanesia 7. Pada tumpang sari dengan kacang hijau Kanesia 8 juga mengalami kehilangan hasil yang tinggi, sedangkan Kanesia 9 menunjukkan toleransi yang tinggi dalam kompctisi dengan kacang hijau. Pelepasan Kanesia 8 dan Kanesia 9 akan memberikan pilihan varietas yang lebih banyak bagi petani dan perusahaan pemintalan untuk menyesuaikan dengan produk akhirnya.</p><p>Kata kunci : Gossypium hirsutum, prosedur pemuliaan, produktivitas, kualitas serat, Sundapteryx biguttula, tumpangsari</p><p> </p><p><strong>ABSTRACT </strong></p><p><strong>Genetic improvement on two new cotton varieties, Kanesia 8 and Kanesia 9</strong></p><p>The main objective of cotton breeding in Indonesia is to improve productivity and fiber quality which is aimed to increase farmers' income and to make beter yam and textile quality that has to compete in international market Six crosses were made between two Indian varieties, LRA 5166 and SRT-1 with two USA vaieties, Deltapine 55 and Deltapinc Acala 90 and one Australian variety, Siokra. Individual plants, lines and individual within lines were selected on F2-F5 generations based on boll- counts, leaf-damage by jassids and fiber traits, those were conducted under rainfed and insecticide-ree condition; twelve promising lines were produced from this process. A total of 13 trials were carried out to observe performance of these new lines during 1993 to 2001; those were located in East Java and South Sulawesi using the standardized experimental techniques. By these procedures make it possible to identify several breeding lines showing simultaneous improvement in yield and fiber quality. Several tests were also made to evaluate response of those lines under intercropping with soybean and mungbean, which were located in East Java. Two breeding lines, 88003/16/2 and 92016/6 (those have been released as Kanesia 8 and Kanesia 9 in 2003), showed higher productivity and fiber quality. In average, these new vaieties produced 1.85 and 1.91 ton ha'1 seed cotton respectively or 8 to 12% higher than those on Kanesia 7, the previously released vaiety. Lint turn-out was 35.2% fiber-strength was varied from 22.6 to 24.7 gram tex'1 , fiber lengths ranged from 29.2 to 30.3 mm with lower micronaire-valucs indicating better fiber-ineness. All of those improvements represented a trend toward a higher quality iber. Kanesia 8 and Kanesia 9 also showed a slight improvement in resistance to jasssids and insect pest-complex. Kanesia 8 and Kanesia 9 performed lower competitive ability under intercropping with soybean in comparison with Kanesia 7. Under intercropping with mungbean Kanesia 8 also suffered high yield loss, wherein Kanesia 9 showed good tolerance to mungbean. The release of Kanesia 8 and Kanesia 9 is expected to give a broader choice for the cotton growers and spinning-mills to match with their inal product.</p><p>Key words: Coton (Gossypium hirsutum), breeding procedure, productivity, liber quality, Sundapteryx bigullul. inter¬ cropping.</p>

scholarly journals Application of Plasmid Engineering to Enhance Yield and Quality of Plasmid for Vaccine and Gene Therapy

2019 ◽  
Vol 6 (2) ◽  
pp. 54
Author(s):  
Folarin ◽  
Nesbeth ◽  
Ward ◽  
Keshavarz-Moore
Keyword(s):  
Plasmid Dna ◽  
Downstream Processing ◽  
Point Of View ◽  
High Yield ◽  
Bacteriophage Mu ◽  
E Coli ◽  
Yield And Quality ◽  
Superhelical Density ◽  
High Level ◽  
Binding Sequence

There is an increased interest in plasmid DNA as therapeutics. This is evident in the number of ongoing clinical trials involving the use of plasmid DNA. In order to be an effective therapeutic, high yield and high level of supercoiling are required. From the bioprocessing point of view, the supercoiling level potentially has an impact on the ease of downstream processing. We approached meeting these requirements through plasmid engineering. A 7.2 kb plasmid was developed by the insertion of a bacteriophage Mu strong gyrase-binding sequence (Mu-SGS) to a 6.8 kb pSVβ-Gal and it was used to transform four different E. coli strains, and cultured in order to investigate the Mu-SGS effect and dependence on strain. There was an increase of over 20% in the total plasmid yield with pSVβ-Gal398 in two of the strains. The supercoiled topoisomer content was increased by 5% in both strains leading to a 27% increase in the overall yield. The extent of supercoiling was examined using superhelical density (σ) quantification with pSVβ-Gal398 maintaining a superhelical density of −0.022, and pSVβ-Gal −0.019, in both strains. This study has shown that plasmid modification with the Mu-phage SGS sequence has a beneficial effect on improving not only the yield of total plasmid but also the supercoiled topoisomer content of therapeutic plasmid DNA during bioprocessing.

scholarly journals Resurgence of Cucurbit Downy Mildew in the United States: A Watershed Event for Research and Extension

Plant Disease ◽  
2015 ◽  
Vol 99 (4) ◽  
pp. 428-441 ◽  
Author(s):  
Gerald J. Holmes ◽  
Peter S. Ojiambo ◽  
Mary K. Hausbeck ◽  
Lina Quesada-Ocampo ◽  
Anthony P. Keinath
Keyword(s):  
United States ◽  
North Carolina ◽  
Downy Mildew ◽  
The United States ◽  
Crop Loss ◽  
Eastern United States ◽  
Cucumis Sativus L ◽  
Cucurbit Downy Mildew ◽  
Control Programs ◽  
Rapid Spread

In 2004, an outbreak of cucurbit downy mildew (CDM) caused by the oomycete Pseudoperonospora cubensis (Berk. & M. A. Curtis) Rostovzev resulted in an epidemic that stunned the cucumber (Cucumis sativus L.) industry in the eastern United States. The disease affects all major cucurbit crops, including cucumber, muskmelon, squashes, and watermelon. Although the 2004 epidemic began in North Carolina, the cucumber crop from Florida to the northern growing regions in the United States was devastated, resulting in complete crop loss in several areas. Many cucumber fields were abandoned prior to harvest. The rapid spread of the disease coupled with the failure of fungicide control programs surprised growers, crop consultants, and extension specialists. The epidemic raised several fundamental questions about the potential causes for the resurgence of the disease. Some of these questions revolved around whether the epidemic would recur in subsequent years and the possible roles that changes in the host, pathogen, and environment may have played in the epidemic.

scholarly journals First Report of Pseudoperonospora cubensis Causing Downy Mildew on Momordica balsamina and M. charantia in North Carolina

Plant Disease ◽  
2014 ◽  
Vol 98 (9) ◽  
pp. 1279-1279 ◽  
Author(s):  
E. Wallace ◽  
M. Adams ◽  
K. Ivors ◽  
P. S. Ojiambo ◽  
L. M. Quesada-Ocampo
Keyword(s):  
United States ◽  
North Carolina ◽  
Downy Mildew ◽  
Leaf Surface ◽  
The United States ◽  
Pseudoperonospora Cubensis ◽  
Post Inoculation ◽  
Bitter Melon ◽  
First Report ◽  
C Cycle

Momordica balsamina (balsam apple) and M. charantia L. (bitter melon/bitter gourd/balsam pear) commonly grow in the wild in Africa and Asia; bitter melon is also cultivated for food and medicinal purposes in Asia (1). In the United States, these cucurbits grow as weeds or ornamentals. Both species are found in southern states and bitter melon is also found in Pennsylvania and Connecticut (3). Cucurbit downy mildew (CDM), caused by the oomycete Pseudoperonospora cubensis, was observed on bitter melon and balsam apple between August and October of 2013 in six North Carolina sentinel plots belonging to the CDM ipmPIPE program (2). Plots were located at research stations in Johnston, Sampson, Lenoir, Henderson, Rowan, and Haywood counties, and contained six different commercial cucurbit species including cucumbers, melons, and squashes in addition to the Momordica spp. Leaves with symptoms typical of CDM were collected from the Momordica spp. and symptoms varied from irregular chlorotic lesions to circular lesions with chlorotic halos on the adaxial leaf surface. Sporulation on the abaxial side of the leaves was observed and a compound microscope revealed sporangiophores (180 to 200 μm height) bearing lemon-shaped, dark sporangia (20 to 35 × 10 to 20 μm diameter) with papilla on one end. Genomic DNA was extracted from lesions and regions of the NADH dehydrogynase subunit 1 (Nad1), NADH dehydrogynase subunit 5 (Nad5), and internal transcribed spacer (ITS) ribosomal RNA genes were amplified and sequenced (4). BLAST analysis revealed 100% identity to P. cubensis Nad1 (HQ636552.1, HQ636551.1), Nad5 (HQ636556.1), and ITS (HQ636491.1) sequences in GenBank. Sequences from a downy mildew isolate from each Momordica spp. were deposited in GenBank as accession nos. KJ496339 through 44. To further confirm host susceptibility, vein junctions on the abaxial leaf surface of five detached leaves of lab-grown balsam apple and bitter melon were either inoculated with a sporangia suspension (10 μl, 104 sporangia/ml) of a P. cubensis isolate from Cucumis sativus (‘Vlaspik' cucumber), or with water as a control. Inoculated leaves were placed in humidity chambers to promote infection and incubated using a 12-h light (21°C) and dark (18°C) cycle. Seven days post inoculation, CDM symptoms and sporulation were observed on inoculated balsam apple and bitter melon leaves. P. cubensis has been reported as a pathogen of both hosts in Iowa (5). To our knowledge, this is the first report of P. cubensis infecting these Momordica spp. in NC in the field. Identifying these Momordica spp. as hosts for P. cubensis is important since these cucurbits may serve as a source of CDM inoculum and potentially an overwintering mechanism for P. cubensis. Further research is needed to establish the role of non-commercial cucurbits in the yearly CDM epidemic, which will aid the efforts of the CDM ipmPIPE to predict disease outbreaks. References: (1) L. K. Bharathi and K. J. John. Momordica Genus in Asia-An Overview. Springer, New Delhi, India, 2013. (2) P. S. Ojiambo et al. Plant Health Prog. doi:10.1094/PHP-2011-0411-01-RV, 2011. (3) PLANTS Database. Natural Resources Conservation Service, USDA. Retrieved from http://plants.usda.gov/ , 7 February 2014. (4) L. M. Quesada-Ocampo et al. Plant Dis. 96:1459, 2012. (5) USDA. Index of Plant Disease in the United States. Agricultural Handbook 165, 1960.

scholarly journals Effects of microwave and ultrasound on the extraction of pectin and its chemical characterisation of banana (Musa sapientum L.) peels

Food Research ◽  
2020 ◽  
Vol 4 (6) ◽  
pp. 2030-2036
Author(s):  
A. Phaiphan ◽  
S. Churat ◽  
T. Dougta ◽  
P. Wichalin ◽  
W. Khanchai ◽  
...  
Keyword(s):  
Microwave Power ◽  
Extraction Time ◽  
High Yield ◽  
Chemical Characteristics ◽  
Ultrasound Assisted Extraction ◽  
Degree Of Esterification ◽  
Yield And Quality ◽  
Assisted Extraction ◽  
High Level

Pectin is a polysaccharide that is widely used as a food additive in food industries. Banana peels that are discarded by vendors after processing bananas for food products contain a high level of pectin. The pectin can be extracted from the plant cell walls whereas the conventional method for extraction would normally take some time to get a high yield. This research was conducted to explore the effects of microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) on the extraction of pectin and its chemical characteristics found in banana peels. For MAE, the effects of microwave power and extraction time on the yield and quality of extracted pectin was studied. It was found that the pectin yield and chemical characteristics increased with the increase of microwave power and extraction time. The percentage yield ranged from 20.93% to 22.91% for microwave power of 300 W for 5-15 mins. The moisture, ash, degree of esterification, methoxyl, and galacturonic content of extracted pectin by MAE had 8.98%, 5.40%, 75.50%, 12.00%, and 57.80%, respectively. For UAE, the effects of temperature and sonication time on the pectin yield and quality of the extracted pectin were also studied. The pectin yields ranged from 1.81% to 3.49% and the moisture, ash, degree of esterification, methoxyl, and galacturonic content of extracted pectin by UAE had 8.00%, 3.39%, 88.83%, 14.50%, and 90.07%, respectively. Although the use of MAE promoted a high pectin yield it had a lower purity level when compared to UAE. Besides, the chemical characteristics of the extracted pectin by UAE is more comparable with commercial citrus pectin than the pectin extracted by MAE.

Cucurbit Downy Mildew ipmPIPE: A Next Generation Web-based Interactive Tool for Disease Management and Extension Outreach

2011 ◽  
Vol 12 (1) ◽  
pp. 26 ◽  
Author(s):  
P. S. Ojiambo ◽  
G. J. Holmes ◽  
W. Britton ◽  
M. Babadoost ◽  
S. C. Bost ◽  
...  
Keyword(s):  
North Carolina ◽  
Downy Mildew ◽  
Monitoring Network ◽  
The United States ◽  
United States Department ◽  
Environmental Implications ◽  
North Carolina State University ◽  
Cucurbit Downy Mildew ◽  
National Monitoring ◽  
The Usa

Cucurbit downy mildew (CDM), caused by Pseudoperonospora cubensis, is one of the most important diseases affecting cucurbits worldwide. In the USA, host resistance in cucumber had adequately controlled the disease with very minimal application of fungicides from the late 1960s to 2004. In 2004, there was a resurgence of the disease that devastated the cucumber crop in several states in the eastern USA. Since then, host plant resistance alone has not been sufficient to adequately control the disease and now control relies heavily on application of fungicides. To effectively apply fungicides in a timely manner, cucurbit growers, extension personnel, and crop consultants and advisors can now utilize information on disease occurrence and predicted spread disseminated through the United States Department of Agriculture's CDM ipmPIPE decision support system developed by scientists at North Carolina State University. Based on a survey conducted in Georgia, North Carolina, and Michigan, the CDM ipmPIPE resulted in an average reduction of 2 to 3 fungicide applications in 2009 compared to calendar-based fungicide sprays. With approximately 122,000 acres of cucurbits in these three states, this translates to more than $6 million in savings to the producers in these three states. Economic savings and positive environmental implications of reduced fungicide applications demonstrate the value of a coordinated national monitoring network for management of a plant disease that is disseminated aerially over long distances. Accepted for publication 31 January 2011. Published 11 April 2011.

scholarly journals Inheritance of Resistance to Cucurbit Powdery Mildew in Bitter Gourd

HortScience ◽  
2019 ◽  
Vol 54 (6) ◽  
pp. 1013-1016 ◽  
Author(s):  
Narinder P.S. Dhillon ◽  
Supannika Sanguansil ◽  
Supornpun Srimat ◽  
Suwannee Laenoi ◽  
Roland Schafleitner ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Bitter Gourd ◽  
Inheritance Of Resistance ◽  
Breeding Lines ◽  
Resistant Lines ◽  
Recessive Genes ◽  
High Level ◽  
Important Disease ◽  
Level Resistance ◽  
Cucurbit Powdery Mildew

Cucurbit powdery mildew (CPM) caused by Podosphaera xanthii (Px) is an economically important disease of bitter gourd (BG; Momordica charantia) in Asia. High-level resistance to CPM is known in various BG accessions that have been used to develop BG breeding lines that originated in different countries. BG breeding lines THMC 113 (Belize), THMC 143 (India), THMC 153 (Thailand), THMC 167 (India), and THMC 170 (Taiwan) possess high-level resistance to BG Px race (BG-CPM), designated Mc-1 from a field at Kamphaeng Saen, Thailand, whereas THMC 144 (India) is susceptible. Our objective was to determine the inheritance of resistance to BG-CPM race Mc-1. To that end, THMC 144 (India) was crossed with the five resistant lines. The parents and their respective F1, F2, backcross progenies were evaluated for BG-CPM disease severity in inoculated field and growth chamber tests. Resistance to BG-CPM race Mc-1 in the five resistant lines was controlled by at least two independent, recessive genes. Intercrosses of the BG-CPM–resistant lines revealed allelic resistances in four of the breeding lines: THMC 113, THMC 153, THMC 167, and THMC 170. Resistance in THMC 143 was clearly non-allelic for resistance to BG-CPM with the other four BG-CPM–resistant lines.

scholarly journals Effects of Host Plant Resistance and Fungicides on Severity of Cucumber Downy Mildew

HortScience ◽  
2013 ◽  
Vol 48 (1) ◽  
pp. 53-59 ◽  
Author(s):  
Adam D. Call ◽  
Todd C. Wehner ◽  
Gerald J. Holmes ◽  
Peter S. Ojiambo
Keyword(s):  
Host Plant ◽  
Downy Mildew ◽  
Plant Resistance ◽  
Host Plant Resistance ◽  
Maximum Yield ◽  
Plant Size ◽  
High Yield ◽  
High Yields ◽  
A Minor ◽  
Moderately Resistant

Cucurbit downy mildew caused by the oomycete Pseudoperonospora cubensis (Berk. And Curt) Rostov is a major disease of cucumber (Cucumis sativus L.) (Palti and Cohen, 1980) globally. Chemical control of downy mildew is necessary to achieve high yields in the absence of adequate host plant resistance. Most of the currently grown cultivars have some resistance to downy mildew. Before the resurgence of the disease in 2004, host plant resistance was sufficient to control the disease without fungicide use, and downy mildew was only a minor problem on cucumber. There are currently no cultivars that show resistance at a level equal to that observed before 2004. However, differences in resistance exist among cultivars, ranging from moderately resistant to highly susceptible. In this study, we evaluated the disease severity and yield of four cucumber cultivars that differed in disease resistance and were treated with fungicide programs representing a range of efficacy levels. The experiment was a split plot design with six replications and four years. Disease was evaluated as chlorosis, necrosis, and reduction in plant size on a 0 to 9 scale. Cultigen had a large effect in all four years. Fungicide has a smaller effect on resistance component traits and a larger effect on yield traits. The effects of cultivar resistance and fungicides appear to be additive until a threshold where maximum yield is reached. Highly resistant cultigens such as PI 197088 required only the least effective fungicides to achieve highest yields, whereas moderately resistant cultigens required a more effective fungicide to reach a similar level of yield. Susceptible cultigens did not achieve high yield even with the most effective fungicide treatments. It is likely that, even as highly resistant cultivars are released, growers will need to continue a minimal fungicide program to achieve maximum yield.

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