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Charles C. Block and Kathleen R. Reitsma

Nine hundred and seventy-seven (977) cucumber (Cucumis sativus L.) accessions from the U.S. National Plant Germplasm System (NPGS) collection were tested for resistance to powdery mildew, caused by the fungus Podosphaera xanthii (Castagne) Braun and Shishkoff, formerly known as Sphaerotheca fuliginea (Schlecht.) Poll. Plants from each accession were evaluated in the greenhouse following inoculation with field isolates of P. xanthii. Each plant was placed into one of three susceptibility classes based on the amount of fungal growth and sporulation on the hypocotyl, stem, petioles and leaves - susceptible (S), intermediate (I) or resistant (R). Of the 977 accessions (9.6%), 94 contained at least one I or R-type plant. Seventeen of the 20 most-resistant accessions came from Asian sources, including China (PIs 418962, 418964, 432860, and 432870), India (PIs 197085, 197088, and 605930), Japan (PIs 279465, 288238, 390258, and 390266), Pakistan (PI 330628), the Philippines (PIs 426169 and 426170), and Taiwan (PIs 321006, 321009, and 321011). A quantitative study was conducted to compare mildew reproduction on S, I, and R-type cucumbers in the greenhouse and under field conditions in Ames, Iowa. Leaf disks were removed weekly and microscopic counts made of spore populations. The leaf disk method was superior to visual rating for ranking and differentiating intermediate from resistant accessions. Both the intermediate (moderately resistant) and highly resistant accessions provided excellent protection against powdery mildew in the field.

Open access

Wenjing Guan, Elizabeth T. Maynard, Bronwyn Aly, Julie Zakes, Daniel S. Egel, and Laura L. Ingwell

Fresh-consumed parthenocarpic cucumbers (Cucumis sativus) are a popular and high-value crop sold in local food markets. The parthenocarpic plant characteristics and climbing growth habit make cucumbers an ideal crop for high-tunnel production. Major types of parthenocarpic cucumbers include Beit alpha and mini, Dutch greenhouse, American slicer, and Japanese. Information regarding yield performance, plant growth, and disease resistance of the four types grown in high-tunnel conditions is limited. In this study, 16 parthenocarpic cucumber cultivars from the four major types were evaluated in high tunnels at three locations in Indiana and Illinois during Spring 2018. Plants were pruned to a single stem that was supported on a string. At all locations, the cultivars that had the most total yields were Beit alpha and mini, although their total yields were not always significantly higher than that of all the others. However, Beit alpha and mini cucumbers had high percentages of unmarketable fruit, mainly because of insect feeding damage and mechanical injuries on the skins that led to scarred fruit. Dutch greenhouse cultivars had relatively lower marketable yields at two of the three locations where there was a high percentage of misshaped fruit. ‘Tasty Green’ Japanese cucumber consistently had the lowest yields at all three locations. This cultivar also produced the most side shoot growth and, therefore, more pruning waste. The Japanese types ‘Tasty Jade’ and ‘Taurus’ had yields comparable to those of other cultivars, and they were more tolerant to two-spotted spider mites (Tetranychus urticae). However, ‘Tasty Jade’ was the cultivar most susceptible to powdery mildew (Podosphaera xanthii and Golovinomyces cichoracearum). ‘Corinto’ American slicer cucumber had relatively high yields at two of the three locations. This cultivar also had the highest percentage of marketable fruit. Information provided in the study is readily useful for growers using high tunnels when selecting parthenocarpic cucumber cultivars. It is also valuable for seed companies wishing to breed new cultivars adaptive for high-tunnel production.

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Wenjing Guan, Xin Zhao, Danielle D. Treadwell, Michael R. Alligood, Donald J. Huber, and Nicholas S. Dufault

Interest in producing specialty melons (Cucumis melo) is increasing in Florida, but information on yield performance, fruit quality, and disease resistance of specialty melon cultivars grown in Florida conditions is limited. In this study conducted at Citra, FL, during the 2011 Spring season, 10 specialty melon cultivars were evaluated, in both certified organic and conventionally managed fields, including: Creme de la Creme and San Juan ananas melon (C. melo var. reticulatus), Brilliant and Camposol canary melon (C. melo var. inodorus), Ginkaku and Sun Jewel asian melon (C. melo var. makuwa), Arava and Diplomat galia melon (C. melo var. reticulatus), and Honey Pearl and Honey Yellow honeydew melon (C. melo var. inodorus). ‘Athena’ cantaloupe (C. melo var. reticulatus) was included as a control. ‘Sun Jewel’, ‘Diplomat’, ‘Honey Yellow’, and ‘Honey Pearl’ were early maturing cultivars that were harvested 10 days earlier than ‘Athena’. ‘Athena’ had the highest marketable yield in the conventional field (10.7 kg/plant), but the yield of ‘Camposol’, ‘Ginkaku’, ‘Honey Yellow’, and ‘Honey Pearl’ did not differ significantly from ‘Athena’. Under organic production, ‘Camposol’ showed a significantly higher marketable yield (8.3 kg/plant) than ‘Athena’ (6.8 kg/plant). ‘Ginkaku’ produced the largest fruit number per plant in both organic (10 fruit/plant) and conventional fields (12 fruit/plant) with smaller fruit size compared with other melon cultivars. Overall, the specialty melon cultivars, except for asian melon, did not differ significantly from ‘Athena’ in terms of marketable fruit number per plant. ‘Sun Jewel’, ‘Diplomat’, and ‘San Juan’ showed relatively high percentages of cull fruit. ‘Honey Yellow’, ‘Honey Pearl’, and ‘Sun Jewel’ exhibited higher soluble solids concentration (SSC) than ‘Athena’ in both organic and conventional fields, while ‘Brilliant’, ‘San Juan’, and ‘Ginkaku’ also had higher SSC than ‘Athena’ under organic production. ‘Honey Yellow’, ‘Sun Jewel’, ‘Brilliant’, and ‘Camposol’ were less affected by powdery mildew (caused by Podosphaera xanthii) and downy mildew (caused by Pseudoperonospora cubensis) in the conventional field. ‘Honey Yellow’ and ‘Camposol’ also had significantly lower aboveground disease severity ratings in the organic field compared with ‘Athena’, although the root-knot nematode (RKN) (Meloidogyne sp.) gall rating was higher in ‘Honey Yellow’ than ‘Athena’.

Free access

Chandrasekar S. Kousik, Jennifer Ikerd, Mihir Mandal, Scott Adkins, and William W. Turechek

Podosphaera xanthii (Castagne) U. Braun & Shishkoff (syn. Sphaerotheca fuliginea ). Specifically, the hypocotyls, cotyledons, and true leaves of these four PMR lines are highly resistant to PM compared with the susceptible watermelon line USVL677-PMS

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Rachel L. Hultengren, Lindsay Wyatt, and Michael Mazourek

was echoed in a recently conducted needs assessment of organic vegetable growers in the Northeast ( Hultengren et al., 2016 ). In the United States, infection by powdery mildew ( Podosphaera xanthii, syn. Sphaerotheca fuliginea ) causes yield losses

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Kyle E. LaPlant, Lindsay E. Wyatt, George Moriarty, Maryann Fink-Brodnicki, Molly Jahn, and Michael Mazourek

is put into controlling diseases that could decrease the value of the crop. Powdery mildew, caused by Podosphaera xanthii and Erysiphe cichoracearum , is one of the major diseases that reduce the yield of susceptible pumpkins ( McGrath and Thomas

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George E. Boyhan, Gerard Krewer, Darbie M. Granberry, C. Randell Hill, and William A. Mills

) resistance and tolerance for powdery mildew [ Podosphaera xanthii (Castag.) U. Braun and N. Shish. (formerly known as Sphaerotheca fuliginea ) or Golovinomyces cichoracearum (D.C.) Huleta (formerly known as Erysiphe cichoracearum )] and downy mildew

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James D. McCreight and William M. Wintermantel

leaf crumple virus (CuLCrV; Geminiviridae, Begomovirus ) in the fall ( Guzman et al., 2000 ) and Podosphaera xanthii (Castagne) Braun & Shishkoff, a causal agent of melon powdery mildew ( McCreight, 2006 ) in the spring and fall. Observation of

Open access

Fulya Baysal-Gurel and Ravi Bika

multiple applications of this treatment, and it is suggested to use lower rates due to the risk of developing pathogen resistance. Lebeda et al. (2010 ) reported that cucurbit powdery mildew ( Podosphaera xanthii ) had developed resistance to seven

Open access

Prabin Tamang, Kaori Ando, William M. Wintermantel, and James D. McCreight

, Podosphaera xanthii races 1, 2, 2U.S., 3, 3.5, 4.5, 5, and S ( McCreight, 2003 ; McCreight and Coffey, 2011 ; Pitrat and Besombes, 2008 ; Shishkoff, 2000 ), Cucurbit leaf crumple virus (CuLCrV) ( McCreight et al., 2008 ), as well as other insect pests