scholarly journals Mechanisms of different cultivars of Cucurbita pepo in resistance to Podosphaera xanthii infection through improvement of antioxidative defense system and gene expression

2020 ◽  
Author(s):  
Shuwu Zhang ◽  
Bingliang Xu ◽  
Jia Liu
Keyword(s):  
Gene Expression ◽  
Powdery Mildew ◽  
Cucurbita Pepo ◽  
Total Phenolics ◽  
Disease Incidence ◽  
Podosphaera Xanthii ◽  
Defense System ◽  
Pal Activity ◽  
Disease Occurrence ◽  
Ros Accumulation

Abstract Background: Powdery mildew is one of the world’s most destructive diseases of cucurbit and the major cause of losses in its production worldwide. A number of strategies have been developed and applied to discover some suitable and alternative safe methods to manage the powdery mildew disease occurrence, but little information is regarding to screen of resistant pumpkins (Cucurbita pepo L.) germplasm and explore the mechanisms of their preventing the disease occurrence at physiological, biochemical, and molecular levels. Therefore, we evaluated and determined the ability and mechanisms of two commercial pumpkin cultivars in resistance to Podosphaera xanthii infection. Results: Compared with mock-inoculated seedlings, small and sparse spots were observed on the cultivar of Sixing F1 leaves at the 13th day after inoculation with P. xanthii, whereas a large number of disease spots or a layer of white powdery mildew were observed on the surface of Jin12 F1 leaves. Increased the inoculation time (7, 9, 11 and 13 days) significantly and continuously increased the disease incidence and index of pumpkin seedlings after inoculation. The disease incidence and index of Jin12 F1 were significantly higher than the cultivar of Sixing F1. At Day 13, the disease incidence and index of Jin12 F1 were 80.0% and 72.6, whereas the cultivar of Sixing F1 was 22.3% and 17.7, respectively. The contents of H2O2, MDA, lignin and total phenolics in the leaves of Sixing F1 and Jin12 F1 were markedly accelerated after inoculation with P. xanthii. However, the cultivar of Sixing F1 exhibited less reactive oxygen species (ROS) accumulation, a lower rate of lipid peroxidation and higher level of lignin and total phenolics contents after inoculation, whereas the cultivar of Jin12 F1 exhibited higher level of ROS accumulation and rates of lipid peroxidation, and lower level of lignin and total phenolics contents. Higher activity and transcript level of antioxidant enzymes and gene of PAL expression were observed on different tissues of both cultivars after inoculated with P. xanthii. Compared with pumpkin seedlings that were inoculated with sterile water but not P. xanthii, the level of PAL activity and gene expression in leaves, petioles and stems of Sixing F1 and Jin12 F1 were upregulated and increased significantly at different time points after inoculation. The enhancement expression of PAL activity and gene in different tissues of Sixing F1 was significantly higher than Jin12 F1, and higher in leaves, lower in petioles and stems. Conclusions: Our results indicate that the cultivar of Sixing F1 exhibited the highest ability in resistance to P. xanthii infection in comparison to Jin12 F1, and one novel possible mechanism is related to the cultivars in resistance to P. xanthii infection by activating and enhancing the antioxidative defense system and gene expression to prevent the pathogens infection.

scholarly journals Differential Responses of Cucurbita pepo to Podosphaera xanthii Reveal the Mechanism of Powdery Mildew Disease Resistance in Pumpkin

2021 ◽  
Vol 12 ◽  
Author(s):  
Shuwu Zhang ◽  
Jia Liu ◽  
Bingliang Xu ◽  
Jingjiang Zhou
Keyword(s):  
Gene Expression ◽  
Disease Resistance ◽  
Powdery Mildew ◽  
Signaling Pathway ◽  
Cucurbita Pepo ◽  
Total Phenolics ◽  
Defense Enzymes ◽  
Podosphaera Xanthii ◽  
Ros Scavenging ◽  
Powdery Mildew Disease

Powdery mildew is one of the most destructive diseases and the major cause to the production losses of cucurbit worldwide. A number of strategies have been developed and applied to discover suitable and safer methods to manage the occurrence of powdery mildew disease in pumpkins (Cucurbita pepo L.), but information is limited in screening tolerant germplasms and exploring their mechanisms in preventing the disease occurrence at physiological, biochemical, and molecular levels. Therefore, we investigated the responses of two commercial pumpkin cultivars to Podosphaera xanthii infection. Compared with mock-inoculated seedlings, few small and sparse powdery areas were observed on the leaves of the Sixing F1 cultivar on the 13th day after inoculation with P. xanthii, whereas a large number of diseased powdery areas and a layer of white powdery mildew were observed on the surface of Jin12 F1 leaves. The inoculation duration (7, 9, 11, and 13 days) significantly and continuously increased the disease incidence and index of pumpkin seedlings. The contents of H2O2, MDA, lignin, and total phenolics in the leaves of Sixing F1 and Jin12 F1 cultivars were markedly increased after inoculation with P. xanthii. However, the Sixing F1 cultivar exhibited much less reactive oxygen species (ROS) accumulation, a lower rate of lipid peroxidation, and a higher level of lignin and total phenolics contents after inoculation than the Jin12 F1 cultivar. Compared with untreated control pumpkin seedlings, significantly higher activities and gene expressions of the phenylpropanoids pathway enzymes (PAL and PPO), ROS scavenging defense enzymes (SOD, CAT, POD, and APX), and other salicylic acid (SA) signaling pathway marker genes were observed in the leaves of both cultivars after P. xanthii inoculation at different inoculation time points. These enhancements were significantly higher in Sixing F1 than Jin12 F1. Our results indicate that the Sixing F1 cultivar exhibited a much stronger ability in resistance to P. xanthii infection than the Jin12 F1 cultivar. Our results suggest that one possible mechanism of C. pepo cultivars to prevent the pathogen P. xanthii infection is by activating and enhancing the activity and gene expression of the phenylpropanoids pathway to synthesize phenolic substances and lignin, ROS scavenging defense enzymes to eliminate the harmful effects of ROS, and signaling pathway marker gene expression to improve plant disease resistance.

scholarly journals First Report of Powdery Mildew Caused by Podosphaera xanthii on Cucurbita argyrosperma in Mexico

Plant Disease ◽  
2021 ◽  
Author(s):  
José Francisco Díaz-Nájera ◽  
Sergio Ayvar-Serna ◽  
Antonio Mena-Bahena ◽  
Guadalupe Arlene Mora-Romero ◽  
Karla Yeriana Leyva-Madrigal ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Microscopic Examination ◽  
Disease Incidence ◽  
Phylogenetic Analyses ◽  
Its Region ◽  
Likelihood Method ◽  
28S Rrna ◽  
Podosphaera Xanthii ◽  
Voucher Specimen ◽  
First Report

Cucurbita argyrosperma, commonly named as winter or cushaw squash, is highly sought for its seeds, which have important uses in culinary arts. During the autumn 2021, powdery mildew-like signs and symptoms were observed on cushaw squash in several commercial fields located in Cocula, Guerrero, Mexico. Signs were initially appeared as whitish powdery patches on both sides of leaves and then covering entire leaves and causing premature senescence. The disease incidence was estimated to be 80% in about 1000 plants in two fields. The mycelium was amphigenous, persistent, white in color, and occurred in dense patches. A voucher specimen was deposited in the Herbarium of the Colegio Superior Agropecuario del Estado de Guerrero under the accession number CSAEG22. For the morphological characterization by light microscopy, fungal structures were mounted in a drop of lactic acid on a glass slide. Microscopic examination showed nipple-shaped hyphal appressoria. Conidiophores (n = 30) were straight, 100 to 190 × 10 to 12 μm and produced 2 to 6 conidia in chains. Foot-cells were cylindrical, 41 to 78 μm long, followed by 1 to 2 shorter cells. Conidia (n = 100) were ellipsoid-ovoid to barrel-shaped, 29.5 to 39.1 × 19.4 to 22.7 μm, and contained conspicuous fibrosin bodies. Germ tubes were produced from a lateral position on conidia. Chasmothecia were not observed during the growing season. The morphological characters were consistent with those of the anamorphic state of Podosphaera xanthii (Braun and Cook 2012). For further confirmation, total DNA was extracted from conidia and mycelia following the CTAB method (Doyle and Doyle 1990), and the internal transcribed spacer (ITS) region and part of the 28S gene were amplified by PCR, and sequenced. The ITS region of rDNA was amplified using the primers ITS5/ITS4 (White et al. 1990). For amplification of the 28S rRNA partial gene, a nested PCR was performed using the primer sets PM3 (Takamatsu and Kano 2001)/TW14 (Mori et al. 2000) and NL1/TW14 (Mori et al. 2000) for the first and second reactions, respectively. Phylogenetic analyses using the Maximum Likelihood method, including ITS and 28S sequences of isolates of Podosphaera spp. were performed and confirmed the results obtained in the morphological analysis. The isolate CSAEG22 grouped in a clade with isolates of Podosphaera xanthii. The ITS and 28S sequences were deposited in GenBank under accession numbers OL423329 and OL423343, respectively. Pathogenicity was confirmed by gently dusting conidia from infected leaves onto ten leaves of healthy C. argyrosperma plants. Five non-inoculated leaves served as controls. The plants were maintained in a greenhouse at 25 to 35 ºC, and relative humidity of 60 to 70%. All inoculated leaves developed similar signs to the original observation after 10 days, whereas control leaves remained symptomless. Microscopic examination of the fungus on inoculated leaves showed that it was morphologically identical to that originally observed on diseased plants, fulfilling Koch’s postulates. Podosphaera xanthii has been previously reported on C. maxima, C. moschata, and C. pepo in Mexico (Yañez-Morales et al. 2009; Farr and Rossman 2021). To our knowledge, this is the first report of P. xanthii causing powdery mildew on C. argyrosperma in Mexico. This pathogen is a serious threat to C. argyrosperma production in Mexico and disease management strategies should be developed.

scholarly journals First Report of Powdery Mildew Caused by Podosphaera xanthii on Hulless Cucurbita pepo of Western District in China

Plant Disease ◽  
2020 ◽  
pp. PDIS-04-20-0703
Author(s):  
Q. L. Liang ◽  
L. X. Wei ◽  
B. L. Xu ◽  
L. L. Liu ◽  
A. Calderón-Urrea
Keyword(s):  
Powdery Mildew ◽  
Cucurbita Pepo ◽  
Podosphaera Xanthii ◽  
First Report

scholarly journals First Report of Powdery Mildew Caused by Podosphaera xanthii on Cuphea hyssopifolia (Lythraceae) in Mainland China

Plant Disease ◽  
2021 ◽  
Author(s):  
Irum Mukhtar ◽  
Ruiting Li ◽  
IBATSAM KHOKHAR ◽  
Ruanni Chen ◽  
Yunying Cheng ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Disease Incidence ◽  
Large Subunit ◽  
Mainland China ◽  
Lsu Rdna ◽  
Podosphaera Xanthii ◽  
Powdery Mildew Fungus ◽  
Potential Threat ◽  
First Report ◽  
Plant Pathol

Cuphea hyssopifolia (Mexican heather) is a popular evergreen perennial shrub used for ornamental and medicinal purposes. Due to its high ornamental value, it is often used as a ground cover in parks and gardens in China. During February and March 2019 & 2020, powdery mildew was observed on C. hyssopifolia in the districts of Minhou and Jinshan of Fuzhou, China. Disease incidence was 70% but of low severity with only a few older leaves showing yellowing and wilting. Sparse irregular patches of white superficial powdery mildew observed on both sides of mature and young leaves. The powdery mildew fungal appressoria that occurred on epigenous hyphae, were indistinct to nipple-shaped, hyaline, and smooth. Conidiophores were erect, smooth, 80 to 210 × 10 to 12 µm, and produced two to eight crenate-shaped conidia in chains. Foot-cells of conidiophores were straight, cylindric, and 30 to 65 × 10 to12 µm. Conidia were hyaline, smooth, ellipsoid-ovoid to barrel-shaped, 25 to 38 × 16 to 20 µm with distinct fibrosin bodies. Germ tubes were simple to forked and produced from the lateral position of the germinating conidia. No chasmothecia were observed on the surface of infected leaves. Based on the morphology of the imperfect state, the powdery mildew fungus was identified as Podosphaera xanthii (Castagne) U. Braun & N. Shishkoff (Braun and Cook 2012). To confirm fungal identification, total DNA was extracted (Mukhtar et al., 2018) directly from epiphytic mycelia on infected leaves collected from both districts. Internal transcribed spacer (ITS) regions and the partial large subunit (LSU) rDNA were amplified using primers ITS1/ITS4 and LSU1/LSU2 (Scholin et al. 1994, White et al. 1990), respectively. The sequences were deposited in GenBank (ITS: MW692364, MW692365; LSU: MW699924, MW699925). The ITS and LSU sequences were 99 to 100 % identical to those of P. xanthii in GenBank, (ITS: MT568609, MT472035, MT250855, and AB462800; LSU: AB936276, JX896687, AB936277, and AB936274). Koch’s postulates were completed by gently pressing diseased leaves onto leaves of five healthy potted C. hyssopifolia plants that were held in a greenhouse at 24 to 30°C without humidity control. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 6 to 10 days, whereas the controls remained symptomless. The morphology of the fungus on the inoculated leaves was identical to that observed on the originally diseased leaves. Previously, Podosphaera sp. has been reported on C. rosea in the United Kingdom (Beales & Cook 2008) and P. xanthii on C. hyssopifolia in Taiwan (Yeh et al. 2021). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on C. hyssopifolia in mainland China. Our field observations suggest that the P. xanthii infections would be a potential threat to the health of C. hyssopifolia in China. References: Beales, P. A., and Cook, R. T. A. 2008. Plant Pathol. 57:778. Braun, U., Cook, R. T. A. 2012. The Taxonomic Manual of the Erysiphales (Powdery Mildews). CBS Biodiversity Series 11: CBS. Utrecht, The Netherlands. Mukhtar, I., et al. 2018. Sydowia.70:155. Scholin, C. A., et al. 1994. J. Phycol. 30:999. White, T. J., et al. 1990. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA. Yeh, Y. W., et al. 2021. Trop. Plant Pathol. 46:44.

scholarly journals First Report of Powdery Mildew on Leucophyllum frutescens Caused by Podosphaera xanthii in Mexico

Plant Disease ◽  
2020 ◽  
Author(s):  
Hugo Beltrán-Peña ◽  
Ruben Felix-Gastelum ◽  
Moises Camacho-Tapia ◽  
Kamila C. Correia ◽  
Gabriel Herrera-Rodriguez ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Urban Areas ◽  
Disease Incidence ◽  
Phylogenetic Analyses ◽  
Morphological Characteristics ◽  
Podosphaera Xanthii ◽  
Monitoring And Control ◽  
Voucher Specimen ◽  
First Report ◽  
Initial Symptoms

Leucophyllum frutescens (Scrophulariaceae family), commonly known as Texas sage or cenizo, is an evergreen shrub native to southwestern United States and northern Mexico. This plant is commercially sold as a native, drought-tolerant ornamental. During the spring of 2019 and 2020, typical symptoms of powdery mildew were found on cenizo plants growing as ornamentals in urban areas in the municipality of Ahome, Sinaloa, Mexico. Disease incidence was 95% from a sampled population of 120 plants. Initial symptoms of powdery mildew developed as irregular white colonies on upper leaf surfaces which expanded as infections progressed. In severe infections, leaves became distorted, exhibiting premature defoliation. Microscopic examination showed nipple-shaped appressoria. Conidiophores (n= 30) were hyaline, cylindrical, erect, 89.4 to 134.2 μm long, and forming catenescent conidia. Foot-cells were cylindrical, 35.7 to 65.3 × 10.2 to 13.5 μm, followed by 1–3 shorter cells. Conidia (n= 100) were hyaline, ellipsoid to ovoid, 27.9 to 40.5 × 13.8 to 18.9 μm, containing distinct fibrosin bodies. Germ tubes were simple to forked and laterally produced from the middle of conidia. Chasmothecia were not found during the sampling period on the infected leaves. Based on morphological characteristics, the fungus was identified as Podosphaera xanthii (Braun and Cook 2012). A voucher specimen (accession no. FAVF219) was deposited in the Herbarium of the Faculty of Agronomy of El Fuerte Valley at the Autonomous University of Sinaloa (Juan Jose Rios, Sinaloa, Mexico). To further confirm the identification, total DNA was extracted, and the internal transcribed spacer (ITS) region was amplified by PCR using the primers ITS5/ITS4 (White et al. 1990) and sequenced. The resulting 503 bp sequence (GenBank accession no. MT624793) had 100% coverage and 100% identity to those of P. xanthii (MT568609–MT568611, MT472035, MT309699, MT250855, MT242593). A phylogenetic tree using the maximum parsimony (MP) and maximum likelihood (ML) methods and including published ITS sequences for Podosphaera species was obtained. Phylogenetic analyses revealed that ITS sequence from FAVF219 isolate was grouped into a clade with P. xanthii. Pathogenicity was demonstrated by gently dusting conidia from infected leaves onto 50 leaves of five healthy plants. Five non-inoculated plants served as controls. All plants were covered with polyethylene bags for 48 h to maintain high humidity and were maintained in a greenhouse at temperatures ranging from 20 to 35ºC. All inoculated plants developed similar symptoms to the original observations after 19 days, whereas no symptoms of powdery mildew were observed on control plants. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants, fulfilling Koch’s postulates. This fungus has been reported infecting members of the Cucurbitaceae in Mexico (Félix-Gastélum et al. 2017; Farr and Rossman 2020). However, to our knowledge, this is the first report of P. xanthii causing powdery mildew on a member of Scrophulariaceae, specifically L. frutescens in Mexico and worldwide. Further studies for monitoring and control strategies of powdery mildew on Texas sage are required.

scholarly journals First Report of Powdery Mildew Caused by Podosphaera xanthii on Benincasa hispida in Korea

Plant Disease ◽  
2021 ◽  
Author(s):  
In-Young Choi ◽  
Ho-Jong Ju ◽  
Kui-Jae Lee ◽  
Hyeon-Dong Shin
Keyword(s):  
Powdery Mildew ◽  
Disease Incidence ◽  
28S Rdna ◽  
Podosphaera Xanthii ◽  
Poor Growth ◽  
Voucher Specimen ◽  
First Report ◽  
Rdna Gene ◽  
Benincasa Hispida ◽  
Wax Gourd

Benincasa hispida (Thunb.) Cogn. (syn. B. cerifera Savi, Cucurbita hispida Thunb.), called wax gourd or ash gourd, is a cucurbitaceous vine grown for medicinal purposes and commercial values of its large fruits in Southeast Asia (Al-Snafi 2013). During the summer and autumn of 2020, leaves of wax gourd were observed to be affected by powdery mildew with 100% disease incidence in an experimental plot of Jeonbuk National University (35°50′55″N, 127°07′48″E), Korea. Fungal colonies were initially circular to irregular, forming white patches on both sides of the leaves and young stems, finally covering entire leaves and causing premature senescence of the leaves and poor growth. A representative voucher specimen was deposited in the Korea University herbarium (KUS-F32171). At least 30 measurements were taken for each asexual diagnostic features. Conidiophores arising from superficial hyphae were straight, 100 to 210 μm long, and produced 3 to 7 immature conidia in chains with a crenate outline. Foot-cells were cylindrical, 46 to 74 ×10 to 12 μm, followed by 1 to 2 shorter cells. Conidia were ellipsoid-ovoid to barrel-shaped, 30 to 40 × 18 to 23 μm with a length/width ratio of 1.4 to 2.0 and contained conspicuous fibrosin bodies. Germ tubes were produced from a lateral position on conidia. Sexual stage was not observed during the growing season. The morphological characteristics of the fungus were compatible with those of Podosphaera xanthii (Castagne) U. Braun & Shishkoff (Braun and Cook 2012), a well-known cucurbitaceous powdery mildew. DNA was extracted from mycelium, and primer sets ITS1F/PM6 and PM3/TW14 were used for amplification of ITS1-5.8S-ITS2 regions and 5´-end of 28S rDNA gene, respectively (Takamatsu and Kano 2001). Sequences determined in this study were deposited to the GenBank under the accession numbers MW559231 and MW559420, respectively. The sequences for ITS regions and 28S rDNA gene showed 99.78% and 99.07% similarity respectively with those of P. xanthii (MH465242, MH465243, MT250855 for ITS, and MK357436, MT826247 for LSU). Pathogenicity was confirmed twice by pressing a diseased leaf onto young leaves of five wax gourd plants. Five non-inoculated plants were used as controls. Inoculated leaves developed symptoms after 5 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Sphaerotheca fuliginea (syn. P. xanthii) on B. hispida has been listed in Hungary, India, Japan, Singapore, and Taiwan so far (Farr and Rossman 2021). Recently, the identity of P. xanthii on B. hispida in Taiwan was confirmed with morphological examination and molecular analysis by Wu and Kirschner (2017). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on B. hispida in Korea. Since wax gourd production is only recently started on a commercial scale in the southern part of Korea, powdery mildew infections pose a serious threat to the safe production of the fruits, especially in organic farming where chemical control options are limited.

scholarly journals Genotyping-by-Sequencing for Analysis of the Genetic Variation of Podosphaera xanthii, Incitant of Cucurbit Powdery Mildew

Plant Disease ◽  
2020 ◽  
Vol 104 (3) ◽  
pp. 951-957 ◽  
Author(s):  
Y. Xiang ◽  
A. N. Miller ◽  
M. McGrath ◽  
M. Babadoost
Keyword(s):  
United States ◽  
New York ◽  
Powdery Mildew ◽  
Cucumis Melo ◽  
Cucurbita Pepo ◽  
Genotyping By Sequencing ◽  
The United States ◽  
Podosphaera Xanthii ◽  
Internal Transcribed Spacer Region ◽  
Significant Difference

This research was conducted to identify species causing powdery mildew on cucurbits and to determine genetic variations among isolates of the pathogen. We collected 109 isolates from six cucurbit species hosts (Cucumis melo, Cucumis sativus, Cucurbita maxima, Cucurbita moschata, Cucurbita pepo, and Lagenaria siceraria) in California, Illinois, Indiana, Michigan, New York, Texas, Washington, and Wisconsin in the United States and in Italy. By sequencing the internal transcribed spacer region of the nuclear rDNA of these 109 isolates, Podosphaera xanthii was found as the only species causing powdery mildew on cucurbits in the United States. Genotyping-by-sequencing was applied to these 109 isolates to investigate their genetic diversity, which showed a trend of isolates clustering from New York and Italy. In addition, the virulence of 36 isolates was compared and a significant difference (P < 0.0001) was found among them. Furthermore, results of the virulence tests of 28 isolates from Illinois showed significant effects of collection years, hosts, and locations on the virulence of the isolates.

scholarly journals Impact of Fungicide Program and Powdery Mildew Resistance in Three Varieties of Pumpkin

2011 ◽  
Vol 21 (5) ◽  
pp. 533-538 ◽  
Author(s):  
Timothy Coolong ◽  
Kenneth Seebold
Keyword(s):  
Powdery Mildew ◽  
Cucurbita Pepo ◽  
Powdery Mildew Resistance ◽  
Fruit Weight ◽  
Podosphaera Xanthii ◽  
Varietal Resistance ◽  
High Input ◽  
Yield Parameters ◽  
Progress Curve ◽  
Different Levels

The effects of fungicide program and varietal resistance on the development of cucurbit powdery mildew [PM (Podosphaera xanthii)] in pumpkin (Cucurbita pepo) were tested in 2009 and 2010 in Lexington, KY. Three fungicide programs consisted of a no-fungicide control, low input (chlorothalonil), and high input (chlorothalonil alternated with myclobutanil) were applied to three varieties of pumpkin with different levels of cucurbit PM resistance. Varieties tested were Howden, Aladdin, and Camaro, which had no, moderate, and high levels of cucurbit PM resistance, respectively. There were no significant variety by fungicide program interactions for yield, number fruit per acre, and average fruit weight in both years. In 2009 and 2010, variety significantly affected yield. Yield increases corresponded to the level of cucurbit PM resistance. The high-resistance variety, Camaro, had the greatest yields in both years, while Howden, with no PM resistance, had the lowest yields. In 2010, yield significantly increased with the intensity of fungicide program. With the exception of cull percentage in 2009, there were no fungicide program by variety interactions for yield parameters. In both years, PM disease severity, characterized by the area under the disease progress curve (AUDPC), was lowest on ‘Camaro’ and highest on ‘Howden’. In 2009, unsprayed ‘Camaro’ had similar AUDPC values as ‘Aladdin’ and ‘Howden’ treated with low- or high-input fungicide programs. In 2010, unsprayed ‘Camaro’ had less disease than ‘Aladdin’ or ‘Howden’ that had received the high-intensity fungicide program. These results suggest that yields can be maintained with a minimal fungicide program when using a variety with high cucurbit PM resistant in some environments. A high-input fungicide program may be necessary to maintain yields of varieties with low cucurbit PM resistance.

scholarly journals Evaluation of biological control agents for managing squash powdery mildew under greenhouse conditions

2019 ◽  
Vol 29 (1) ◽  
Author(s):  
Ahmed A. Elsisi
Keyword(s):  
Powdery Mildew ◽  
Disease Severity ◽  
Cucurbita Pepo ◽  
Disease Incidence ◽  
Paenibacillus Polymyxa ◽  
Fruit Weight ◽  
Vegetable Crops ◽  
Fruit Number

AbstractSquash (Cucurbita pepo L.), is one of the most important vegetable crops for human nutriment in Egypt and the world. One of the most serious diseases that infect squash and cause yield losses was powdery mildew, caused by Podosphaera xanthisii. The aim of this study was to investigate the role of Bacillus subtilis, Paenibacillus polymyxa (109 cell ml/1), Trichoderma harzianum, T. album, T. viride and T. hamatum (107 spore ml/l) for controlling disease under greenhouse conditions. Results indicated that all treatments significantly inhibited the conidial germination of P. xanthii than control in vitro and decreased the incidence and disease severity after spraying with the bio-agents on squash plants under greenhouse conditions. The fungicide, Topas-100 (10.0% penconazole “w/v” [(R,S-1-(2-(2,4-dichlorophenyl)-Q pentyl)-1H-1,2,4-triazole]), followed by B. subtilis was highly significant for decreasing disease incidence (2.8 and 5.3%, respectively) and disease severity percentage (3.5 and 4.8%, respectively) than the control. The activities of biochemical changes, i.e., peroxidase, polyphenol oxidase, and total phenols, were significantly upregulated as results of most treatments. Also, bio-agent treatments caused significant increase in yield characteristics of squash plants such as fruit number/plant and fruit weight/plant than control. B. subtilis recorded the highest increase (110.9% and 98.7%) in fruit number and fruit weight/plant than control.

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