scholarly journals Resistance to Phytophthora citrophthora and P. parasitica and Nursery Characteristics of Several Citrus Rootstocks

Plant Disease ◽  
1998 ◽  
Vol 82 (11) ◽  
pp. 1217-1225 ◽  
Author(s):  
M. E. Matheron ◽  
G. C. Wright ◽  
M. Porchas
Keyword(s):  
Weight Reduction ◽  
Root Rot ◽  
Root Weight ◽  
Phytophthora Citrophthora ◽  
Phytophthora Root Rot ◽  
Rough Lemon ◽  
Vigorous Growth ◽  
Shoot Weight ◽  
Citrus Macrophylla ◽  
Stem Lesions

Studies were conducted to compare existing and potential citrus rootstocks with respect to resistance to root rot and gummosis caused by Phytophthora citrophthora and P. parasitica in greenhouse and growth chamber experiments and horticultural performance under simulated nursery conditions. Depending upon rootstock and experiment, mean root weights resulting from inoculation with P. citrophthora were 27 to 96% lower than the comparable controls. In similar experiments with the same rootstocks, inoculation with P. parasitica resulted in root weights that were 38 to 95% less than weights of the noninoculated controls. During 1994 or 1995, mean root weight reduction compared with noninoculated plants among Citrus macrophylla, rough lemon, C. volkameriana, and Sunki mandarin × Flying Dragon trifoliate (62-109-19) attributable to P. citrophthora and mean root weight reduction among C. macrophylla, C. volkameriana, rough lemon, Sacaton citrumelo, Sunki mandarin × Flying Dragon trifoliate (62-109-19), African shaddock × Rubidoux trifoliate, and Shekwasha mandarin × English trifoliate attributable to P. parasitica were significantly less than those recorded for all other tested rootstocks. Rootstocks that sustained a low percentage of root weight reduction generally experienced a low percentage of shoot weight reduction and survived longer as well. In evaluation of resistance to gummosis, depending on rootstock and experiment, the mean length of stem lesions caused by P. citrophthora on rootstocks ranged from 0.2 to 25.0 mm, whereas values for P. parasitica ranged from 0.2 to 18.5 mm. Stem lesions smaller than 5 mm in length were recorded for 21 and 14 of 36 different rootstocks inoculated with P. citrophthora and P. parasitica, respectively. On the other hand, P. citrophthora and P. parasitica caused stem lesions of at least 10 mm in length on 8 and 16 citrus rootstocks, respectively. Desirable nursery characteristics, including vigorous growth, minimal branching, and high leaf chlorophyll content, were demonstrated most prominently by Gomiri rough lemon, C. volkameriana, and Benton citrange, and to a lesser degree by some other rootstocks. Possible factors that could account for inconsistent classification of some citrus rootstocks as susceptible or resistant to Phytophthora root rot and gummosis are discussed.

scholarly journals The effect of mangroves amendments to soil on root rot and root knot of potato (Solanum tuberosum L.)

2012 ◽  
Vol 61 (1) ◽  
pp. 115-121 ◽  
Author(s):  
Marium Tariq ◽  
Shahnaz Dawar ◽  
Fatima S. Mehdi ◽  
Muhammad J. Zaki
Keyword(s):  
Root Rot ◽  
Solanum Tuberosum L ◽  
Organic Amendments ◽  
Avicennia Marina ◽  
Root Weight ◽  
Complete Suppression ◽  
Root Knot Nematode ◽  
Mangrove Plant ◽  
Plant Parts ◽  
Shoot Weight

Leaves, stem and pneumatophore of <i>Avicennia marina</i> and leaves and stem of <i>Rhizophora mucronata</i> were used as the organic amendments at 0.1, 1 and 5% concentrations in the control of root rot fungi like (<i>Fusarium</i> spp., <i>Rhizoctonia solani</i> and <i>Macrophomina phasoelina</i>) and root knot nematode <i>Meloidogyne javanica</i> on potato. In pot experiments, germination of seeds, shoot length, shoot weight, root length, root weight and number of knots were significantly increased when plant parts like leaves, stem and pneumatophore of <i>A. marina</i> and <i>R. mucronata</i> were used at 1 and 5% concentrations. There was a complete suppression in infection of <i>R. solani</i> and <i>M. phaseolina</i> when <i>A. marina</i> and <i>R. mucronata</i> were used at 5% concentration on potato. Maximum inhibition of knots of <i>M. javanica</i> was observed when powder made from mangrove plant parts was used at 1 and 5% concentrations. Powder from all plant parts, like leaves, stem and pneumatophore, was effective in suppression of root infecting fungi and root knot nematode.

scholarly journals Synergism of citrus nematode (Tylenchulus semipenetrans Cobb.) and Colletotrichum gloeosporioides plays a major role in citrus dieback

2021 ◽  
Vol 58 (04) ◽  
pp. 1291-1299
Author(s):  
Muhammad Usman Afzal
Keyword(s):  
Plant Growth ◽  
Colletotrichum Gloeosporioides ◽  
Growth Parameters ◽  
Shoot Length ◽  
Root Weight ◽  
Rough Lemon ◽  
Tylenchulus Semipenetrans ◽  
Significant Difference ◽  
Shoot Weight ◽  
Citrus Nematode

Citrus is known as a major fruit due to its high nutritional value and adaptability in tropical and sub-tropical regions. Among diseases, citrus dieback is one of the most threatening diseases in which overall plant growth is reduced. Major causes are Colletotrichum gloeosporioides and citrus nematode (Tylenchulus semipenetrans) with 15-35% losses all over the world. Plant material was established adopting sanitary measures in earthen pots (12-inch diameter). Fresh culture of C. gloeosporioides and T. semipenetrans was prepared for the inoculation by following the standard procedures. In the first set, rootstocks were inoculated with 200mL of water having spore suspension of C. gloeosporioides while in in the second set, inoculation of T. semipenetrans was done by using 45 mL of water suspension having 2000 freshly hatched juveniles per pot, while at the rate of 1 × 107 spores/mL per plant. In the third set, the interaction of C. gloeosporioides and T. semipenetrans was studied by inoculating selected citrus rootstocks by both pathogens. After four months of inoculation, data were recorded on plant disease index (PDI) along with plant growth parameters (root weight, shoot weight, shoot weight, shoot length and number of leaves). Trifoliate orange and cox mandarin hybrid showed resistance against the development of T. semipenetrans while rough lemon, C-35 Citrange and sour orange were found susceptible. There was a significant difference in plant growth parameters between inoculated and healthy plants. Root weight and shoot weight decreased by 8.98g and 11.53g, while root length and shoot length decreased by 7.29cm and 13.5cm respectively as compared to control treatments in most susceptible rootstocks. Per cent Branch Infection (PBI) and per cent Disease Index (PDI) were maximum (71.52, 37) per cent on rough lemon respectively. Results regarding combined inoculation of C. gloeosporioides and T. semipenetrans showed that there was a significant difference in plant growth parameters between inoculated and healthy plants. In rough lemon, Root weight and shoot weight decreased by 13.86 and 20.57g respectively in diseased and healthy plants. Root length and shoot length decreased by 8.37 and 20.04cm respectively as compared to control treatments in most susceptible rootstocks. Overall results depicted that inoculation of both pathogens reduced plant growth more severely as compared to their individual application.

scholarly journals Comparative Performance of Fungicides, Biofungicides, and Host Plant Defense Inducers in Suppression of Phytophthora Root Rot in Flowering Dogwood During Simulated Root Flooding Events

Plant Disease ◽  
2019 ◽  
Vol 103 (7) ◽  
pp. 1703-1711 ◽  
Author(s):  
Matthew S. Brown ◽  
Fulya Baysal-Gurel ◽  
Jason B. Oliver ◽  
Karla M. Addesso
Keyword(s):  
Plant Defense ◽  
Host Plant ◽  
Disease Severity ◽  
Root Rot ◽  
Positive Control ◽  
Root Weight ◽  
Phytophthora Root Rot ◽  
Plant Weight ◽  
Flowering Dogwood ◽  
Flooding Events

During flooding events in nurseries, Phytophthora root rot caused by Phytophthora cinnamomi Rands often causes damage that leads to complete crop loss. In this study, we evaluated the efficacy of fungicides, biofungicides, and host plant defense inducers for preventive and curative control of Phytophthora root rot on flowering dogwood (Cornus florida L.) seedlings exposed to a simulated flood event of 1, 3, or 7 days. In two greenhouse trials, preventive (7 days before flooding) or curative (1 day after flooding) drench treatments were applied to dogwood seedlings artificially inoculated with P. cinnamomi. The plants were flooded by maintaining standing water for 1, 3, or 7 days. After the trials, plant growth data (total plant weight, root weight, plant height, and plant width) were recorded, and root systems were assessed for disease severity using a scale of 0 to 100% of roots affected, and subsamples were plated on PARPH-V8 medium to determine the percent recovery of the Phytophthora pathogen. Plants preventively treated with Subdue MAXX had reduced disease severity relative to the nontreated, inoculated plants (positive control) flooded 1, 3, or 7 days in both trials. Pageant Intrinsic and Segovis treatments also had lower disease severity than the positive control at all flooding durations in trial two, but not trial one. In trial one, preventive and curative treatments of Orkestra Intrinsic had reduced disease severity compared with the positive control at 1 and 3 days of flooding, whereas curative treatments of Empress Intrinsic and Tartan Stressgard also were effective at 1 and 3 days of flooding in trial one. The host plant defense inducers (Aliette 80 WDG, Signature Xtra, and Actigard) were inconsistent and ineffective at reducing disease severity when applied as preventive or curative treatments. Preventive treatments of the biofungicides RootShield Plus+and MBI-110 had consistently lower disease severity than the positive control at 1 day of flooding but not 3 or 7 days of flooding. Potentially, growers can use information from this study to manage Phytophthora root rot during flooding or in areas of the nursery that often experience high soil moisture levels.

scholarly journals Assessing the Resistance of Red Raspberry (Rubus idaeus L.) Genotypes to Phytophthora fragariae var. rubi in Hydroponic Culture

HortScience ◽  
2004 ◽  
Vol 39 (7) ◽  
pp. 1553-1556 ◽  
Author(s):  
J.A. Pattison ◽  
W.F. Wilcox ◽  
C.A. Weber
Keyword(s):  
Root Rot ◽  
Screening Method ◽  
Rubus Idaeus ◽  
Root Tissue ◽  
Red Raspberry ◽  
Phytophthora Root Rot ◽  
Multiple Observations ◽  
Leaf Chlorosis ◽  
Phytophthora Fragariae ◽  
Stem Lesions

A hydroponic method was developed and tested for screening red raspberry genotypes for resistance to Phytophthora fragariae var. rubi, the most common causal agent of Phytophthora root rot in raspberry. Plants of `Titan' and `Encore' exhibited typical disease symptoms, with the latter developing significantly smaller stem lesions and fewer petiole lesions. The resistant cultivar, `Latham', regenerated healthy root tissue from the crown and older-order roots after initial infection and necrosis of young roots and exhibited no other symptoms beyond minor leaf chlorosis. This component of the resistance reaction has not been documented previously. A segregating F1 population from the cross of `Latham' × `Titan' had a survival rate of 56% with 42% classified as resistant, exhibited minimal symptoms, and produced varying amounts of healthy root tissue. This screening method allows multiple observations of all plant tissues, including roots, under repeatable and definable growth chamber conditions. It should be useful for classifying the phenotype of individuals in segregating red raspberry populations to investigate the inheritance of Phytophthora root rot resistance using molecular markers.

scholarly journals Protection of Citrus Rootstocks Against Phytophthora spp. with a Hypovirulent Isolate of Phytophthora nicotianae

2007 ◽  
Vol 97 (8) ◽  
pp. 958-963 ◽  
Author(s):  
G. C. Colburn ◽  
J. H. Graham
Keyword(s):  
Poncirus Trifoliata ◽  
Phytophthora Nicotianae ◽  
Root Weight ◽  
Post Inoculation ◽  
Phytophthora Root Rot ◽  
Phytophthora Spp ◽  
Naturally Occurring ◽  
Fibrous Roots ◽  
Cleopatra Mandarin ◽  
Swingle Citrumelo

Phytophthora root rot of citrus in Florida is caused by Phytophthora nicotianae and P. palmivora. A naturally occurring isolate of P. nicotianae (Pn117) was characterized as hypovirulent on citrus roots. Pn117 infected and colonized fibrous roots, but caused significantly less disease than the virulent isolates P. nicotianae Pn198 and P. palmivora Pp99. Coincident inoculation of rootstock seedlings of Cleopatra mandarin (Citrus reticulata) or Swingle citrumelo (C. paradisi × Poncirus trifoliata) with the hypovirulent Pn117 and the virulent isolates Pn198 and Pp99 did not reduce the severity of disease caused by the virulent Phytophthora spp. When either rootstock was inoculated with the hypovirulent Pn117 for 3 days prior to inoculation with virulent isolates, preinoculated seedlings had significantly less disease and greater root weight compared with seedlings inoculated with the virulent isolates alone. Recovery of the different colony types of Phytophthora spp. from roots of sweet orange (C. sinensis) or Swingle citrumelo was evaluated on semiselective medium after sequential inoculations with the hypovirulent Pn117 and virulent Pp99. Pn117 was isolated from roots at the same level as the Pp99 at 3 days post inoculation. Preinoculation of Pn117 for 3 days followed by inoculation with Pp99 resulted in greater recovery of the hypovirulent isolate and lower recovery of the virulent compared with coincident inoculation.

scholarly journals Cellulase Activity as a Mechanism for Suppression of Phytophthora Root Rot in Mulches

2011 ◽  
Vol 101 (2) ◽  
pp. 223-230 ◽  
Author(s):  
Brantlee Spakes Richter ◽  
Kelly Ivors ◽  
Wei Shi ◽  
D. M. Benson
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Cellulase Activity ◽  
Enzyme Concentration ◽  
Disease Suppression ◽  
In Vitro Assays ◽  
Infested Soil ◽  
Phytophthora Root Rot ◽  
Standard Curve

Wood-based mulches are used in avocado production and are being tested on Fraser fir for reduction of Phytophthora root rot, caused by Phytophthora cinnamomi. Research with avocado has suggested a role of microbial cellulase enzymes in pathogen suppression through effects on the cellulosic cell walls of Phytophthora. This work was conducted to determine whether cellulase activity could account for disease suppression in mulch systems. A standard curve was developed to correlate cellulase activity in mulches with concentrations of a cellulase product. Based on this curve, cellulase activity in mulch samples was equivalent to a cellulase enzyme concentration of 25 U ml–1 or greater of product. Sustained exposure of P. cinnamomi to cellulase at 10 to 50 U ml–1 significantly reduced sporangia production, but biomass was only reduced with concentrations over 100 U ml–1. In a lupine bioassay, cellulase was applied to infested soil at 100 or 1,000 U ml–1 with three timings. Cellulase activity diminished by 47% between 1 and 15 days after application. Cellulase applied at 100 U ml–1 2 weeks before planting yielded activity of 20.08 μmol glucose equivalents per gram of soil water (GE g–1 aq) at planting, a level equivalent to mulch samples. Cellulase activity at planting ranged from 3.35 to 48.67 μmol GE g–1 aq, but no treatment significantly affected disease progress. Based on in vitro assays, cellulase activity in mulch was sufficient to impair sporangia production of P. cinnamomi, but not always sufficient to impact vegetative biomass.

Assessment of tolerance for reducing yield losses in field pea caused by Aphanomyces root rot

2013 ◽  
Vol 93 (3) ◽  
pp. 473-482 ◽  
Author(s):  
R. L. Conner ◽  
K. F. Chang ◽  
S. F. Hwang ◽  
T. D. Warkentin ◽  
K. B. McRae
Keyword(s):  
Disease Severity ◽  
Root Rot ◽  
Weight Ratio ◽  
Field Pea ◽  
Control Measures ◽  
Effective Control ◽  
Yield Losses ◽  
Plant Vigour ◽  
Shoot Weight ◽  
High Yields

Conner, R. L., Chang, K. F., Hwang, S. F., Warkentin, T. D. and McRae, K. B. 2013. Assessment of tolerance for reducing yield losses in field pea caused by Aphanomyces root rot. Can. J. Plant Sci. 93: 473–482. Aphanomyces root rot, caused by Aphanomyces euteiches Drechs., is a serious disease of peas (Pisum sativum) that can severely reduce seed yield, and few effective control measures are available. The development of pea cultivars with tolerance or partial resistance to Aphanomyces root rot is generally considered to be one of the best options to reduce yield loss. A 4-yr field study was conducted at disease-free sites and at an Aphanomyces root rot site to compare the responses of cultivars and lines in the presence and absence of Aphanomyces root rot, identify breeding lines with tolerance and to evaluate the effects of tolerance on plant growth, disease severity and yield. At the Aphanomyces root rot site, a second test was established in which the phosphite fungicide Phostrol™ was applied as a soil drench treatment to the pea cultivars and lines. Aphanomyces root rot reduced seedling emergence, biomass production and yield in the susceptible pea genotypes. However, line 00-2067 consistently produced relatively high yields at all the field sites. At the Aphanomyces root rot site, yield was closely associated with plant vigour and shoot weight. Small, but significant, differences (P<0.05) in disease severity were observed between susceptible cultivars and tolerant lines indicating that the lines producing high yields at the Aphanomyces root rot site are tolerant rather than partially resistant. The root/shoot weight ratio was very low in the tolerant lines, indicating that even though their root systems were reduced and severely damaged by root rot, they were still able to produce high yields under favourable conditions for the disease. Drench application of the fungicide Phostrol™ did not significantly reduce root rot severity or improve the performance of any of the pea cultivars or lines.

Isolation, identification and characterization of native plant growth promoting bacteria and their plant growth promotion in Zea mays

2021 ◽  
Vol 16 (8) ◽  
pp. 75-80
Author(s):  
Pitchaiah Pelapudi ◽  
Sasikala Ch ◽  
Swarnabala Ganti
Keyword(s):  
Plant Growth ◽  
Plant Growth Promotion ◽  
Root Length ◽  
Growth Promotion ◽  
Shoot Length ◽  
Root Weight ◽  
Plant Growth Promoting Bacteria ◽  
Plant Growth Promoting ◽  
Growth Promoting ◽  
Shoot Weight

In the present rapid growing world, need for a sustainable agricultural practice which helps in meeting the adequate food demand is much needed. In this context, plant growth promoting bacteria were brought into the spot light by the researchers. Though the plant growth promoting bacteria have several beneficial applications, due to some of the disadvantages in the field conditions, they lagged behind. In the current research work, native PGPR were isolated from the rhizosphere soil samples of maize with an aim to isolate the nitrogen fixing, phosphate solubilising and potash solubilising bacteria. Out of the several isolates, potent PGPR isolates viz., Paenibacillus durus PCPB067, Bacillus megaterium PCBMG041 and Paenibacillus glucanolyticus PCPG051 were isolated and identified by using the 16 S rRNA gene sequencing studies. Genomic DNA sequences obtained were deposited in the NCBI Genbank and accession numbers were assigned as MW793452, MW793456 and MW843633. In order to check the efficacy of the PGPR isolates, pot trials were conducted by taking maize as the host plant. Several parameters viz. shoot length, shoot weight, root length, root weight and weight of the seeds were tested in which PGP treatment showed good results (shoot length - 187±3.5 cm, shoot weight - 31±4 g, root length - 32±3.6 cm, root weight - 17±2 g, yield- 103.3±6.1 g) when compared to the chemical fertilizer treatment (shoot length - 177±3.5 cm, shoot weight - 25±3.6 g, root length - 24±3.5 cm, root weight - 14.6±1.52 g, yield- 85.6±7.6 g). Based on the results, it can be stated that these native PGPR isolates can be effectively used in the plant growth promotion of maize.

scholarly journals Phytophthora Root Rot Resistance in Soybean E00003

Crop Science ◽  
2014 ◽  
Vol 54 (2) ◽  
pp. 492-499 ◽  
Author(s):  
Zhongnan Zhang ◽  
Jianjun Hao ◽  
Jiazheng Yuan ◽  
Qijian Song ◽  
David L. Hyten ◽  
...  
Keyword(s):  
Root Rot ◽  
Phytophthora Root Rot

scholarly journals Evaluation of Organic Amendments against Rice Root-KnotNematode at Seedling Stage of Rice

1970 ◽  
Vol 9 ◽  
pp. 21-27 ◽  
Author(s):  
Nabin Kumar Dangal ◽  
D. Sharma Poudyal ◽  
S. M. Shrestha ◽  
C. Adhikari ◽  
J. M. Duxbury ◽  
...  
Keyword(s):  
Block Design ◽  
Organic Amendments ◽  
Severity Index ◽  
Rice Root ◽  
Chicken Manure ◽  
Root Weight ◽  
Root Knot Nematode ◽  
Meloidogyne Graminicola ◽  
Shoot Weight ◽  
Lesion Severity

Pot experiment was conducted during July-September 2006 to evaluate some organic amendments such as sesame (Sesamum indicum) biomass, buckwheat (Fagopyrum esculentum) biomass, neem (Azadirachta indica) leaves, chinaberry (Melia azedarch) leaves and chicken manure @ 1, 2 and 3 t ha-1 each against the rice root-knot nematode (Meloidogyne graminicola Golden & Birchfield) in direct seeded rice. The treatments were replicated five times in a randomized complete block design. The number of second stage juveniles (J2) of M. graminicola was significantly low in chicken manure @ 3 t ha-1. The root knot severity index was significantly low in sesame @ 3 t ha-1, chinaberry @ 3, 2 or 1 t ha-1, neem @ 3 t ha-1 and chicken manure @ 2 or 3 t ha-1 amended soil but root lesion severity index was lower only in chicken manure @ 2 t ha-1 treated plots. The fresh shoot weight and length were significantly high in chicken manure amendment @ 2 or 3 t ha-1 at 45th day after seeding. However, the fresh root weight, length, number of leaves and number of J2 recovered from the roots were non-significant. Key words: biomass; juveniles; Meloidogyne graminicola; root-knot severity index; root lesion severity index DOI: 10.3126/njst.v9i0.3160 Nepal Journal of Science and Technology 9 (2008) 21-27

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