Relative Resistance of Four Peach Rootstocks to Phytophthora cactorum and Phytophthora megasperma

Many species of Phytophthora de Bary are important pathogens of cultivated Prunus L. species worldwide, often invading the trees via their rootstocks. In a series of greenhouse trials, resistance to Phytophthora was tested in new and standard rootstocks for cultivated stone fruits, including almond. Successive sets of the rootstocks, propagated as hardwood cuttings or via micropropagation, were transplanted into either noninfested potting soil or potting soil infested with Phytophthora cactorum (Lebert & Cohn) J. Schöt., Phytophthora citricola Sawada, Phytophthora megasperma Drechs, or Phytophthora niederhauserii Z.G. Abad & J.A. Abad. Soil flooding was included in all trials to facilitate pathogen infection. In some trials, soil flooding treatments were varied to examine their effects on the rootstocks in both the absence and presence of Phytophthora. Two to 3 months after transplanting, resistance to the pathogens was assessed based on the severity of root and crown rot. ‘Hansen 536’ was consistently more susceptible than ‘Lovell’, ‘Nemaguard’, ‘Atlas’, ‘Viking’, ‘Citation’, and ‘Marianna 2624’ to root and/or crown rot caused by P. cactorum, P. citricola, and P. megasperma. By contrast, susceptibility to P. niederhauserii was similarly high among all eight tested genotypes of peach, four genotypes of peach × almond, two genotypes of (almond × peach) × peach, and one genotype of plum × almond. Most plum hybrids were highly and consistently resistant to crown rot caused by P. niederhauserii, but only ‘Marianna 2624’ was highly resistant to both crown and root rot caused by all of the Phytophthora species. The results indicate that there is a broad tendency for susceptibility of peach × almond rootstocks and a broad tendency for resistance of plum hybrid rootstocks to multiple species of Phytophthora.

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In Vitro Fungicidal Activity of Calcium and Potassium Salts on Several Commercially Significant Plant Pathogens

HortScience ◽

10.21273/hortsci.46.6.913 ◽

2011 ◽

Vol 46 (6) ◽

pp. 913-916 ◽

Cited By ~ 2

Author(s):

Clive Kaiser ◽

Philip B. Hamm ◽

Stacy Gieck ◽

Nicholas David ◽

Lynn Long ◽

...

Keyword(s):

Plant Pathogens ◽

Phytophthora Cinnamomi ◽

Pythium Ultimum ◽

Calcium Acetate ◽

Potassium Silicate ◽

Phytophthora Cactorum ◽

Potassium Salts ◽

Phytophthora Megasperma ◽

Calcium Propionate

In vitro dose responses of several calcium and potassium salts were determined on some commercially significant plant pathogens, including: Helminthosporium solani, Fusarium oxysporum f. sp. pisi race 2, Colletotricum coccodes, Phytophthora cactorum, Phytophthora cinnamomi, Phytophthora erythroseptica, Phytophthora infestans, Phytophthora megasperma, Pythium ultimum, and Venturia inaequalis. Mycelial growth inhibition was both salt-specific and dose-related. Pythium ultimum was completely inhibited by 75 mg·L−1 or greater calcium propionate, but needed 300 mg·L−1 or greater of calcium acetate and 40 mL·L−1 or greater of potassium silicate for complete inhibition. Phytophthora infestans was completely inhibited by 150 mg·L−1 or greater calcium acetate, 150 mg·L−1 or greater calcium propionate, or 5 mL·L−1 or greater potassium silicate. Phytophthora cactorum was completely inhibited by 300 mg·L−1 or greater calcium propionate, but required 600 mg·L−1 or greater calcium acetate and 10 mL·L−1 or greater potassium silicate for complete inhibition. Phytophthora cinnamomi was completely inhibited by calcium propionate at 600 mg·L−1 or greater or by 10 mL·L−1 or greater potassium silicate. Only potassium silicate inhibited Phytophthora megasperma, Phytophthora erthroseptica, V. inequalis, and H. solani at concentrations of 5 mL·L−1 or greater, 20 mL·L−1 or greater, 40 mL·L−1 or greater, or 80 mL·L−1 or greater, respectively. Potassium acetate did not completely inhibit any of the pathogens in this study when tested at concentrations 1200 mg·L−1 or less.

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Canavanine utilization by Phytophthora sp.

Canadian Journal of Botany ◽

10.1139/b77-153 ◽

1977 ◽

Vol 55 (10) ◽

pp. 1322-1327 ◽

Cited By ~ 2

Author(s):

T. E. Weaks ◽

F. L. Binder

Keyword(s):

Amino Acid ◽

Trichloroacetic Acid ◽

Basal Medium ◽

Labeled Compounds ◽

Phytophthora Cactorum ◽

Phytophthora Megasperma ◽

Total Uptake ◽

Low Degree ◽

Race 1

Three isolates of Phytophthora that are pathogens of legumes and three that are nonpathogens were tested for sensitivity to L-canavanine. Growth of only one pathogen was affected by this amino acid. Phytophthora megasperma var. sojae race 1 was inhibited by canavanine when cultured in the basal medium. When starved mycelium of this isolate was treated with canavanine, total uptake of [H3] uridine and L-[H3] leucine and incorporation of these labeled compounds into insoluble fractions of trichloroacetic acid were enhanced. This demonstrated that under these conditions, canavanine supported some synthetic processes in the fungus.Of the Phytophthora sp. tested that are nonpathogens of legumes, one was affected by canavanine. Growth of P. cactorum was enhanced to a low degree. When asparagine (1.5 × 102 M) was replaced by canavanine (1.8 × 10−4 M) in the basal medium, growth was significantly higher than that in the asparagine-deficient basal medium. Labeling experiments with P. cactorum demonstrated that canavanine enhanced incorporation of [H3]uridine and L-[H3]leucine into insoluble fractions of trichloroacetic acid. Phytophthora cactorum apparently detoxifies canavanine and utilizes it in growth-supporting activities.

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Variability in pathogenicity among Greek isolates of Phytophthora cactorum to four peach rootstocks

Australian Journal of Experimental Agriculture ◽

10.1071/ea01203 ◽

2003 ◽

Vol 43 (1) ◽

pp. 99 ◽

Cited By ~ 4

Author(s):

T. Thomidis

Keyword(s):

Phytophthora Cactorum ◽

Strawberry Plant ◽

Apple Trees ◽

Laboratory Techniques ◽

Peach Rootstocks

Studies on 8 isolates of Phytophthora cactorum recovered from different plants identified the presence of diversity in pathogenicity. All isolates appeared pathogenic to tested peach rootstocks but with variable levels of aggressiveness. The peach and almond isolates were the most aggressive. In contrast, the apple and strawberry isolates were least aggressive. Generally, the aggressiveness of P. cactorum isolates did not differ among peach rootstocks. The weak aggressiveness of isolates of P. cactorum from apple trees and strawberry plant suggests that these isolates are not a serious threat to peach rootstocks. This study also confirms that laboratory techniques, such as the excised-twig assay, correlate well with field evaluations.

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Relative resistance of newly released apple rootstocks to Phytophthora cactorum

Canadian Journal of Plant Science ◽

10.4141/p04-176 ◽

2006 ◽

Vol 86 (1) ◽

pp. 199-204 ◽

Cited By ~ 6

Author(s):

O. Carisse ◽

S. Khanizadeh

Keyword(s):

Root Rot ◽

Cultural Practices ◽

Integrated Approach ◽

Crown Rot ◽

Lesion Length ◽

Phytophthora Cactorum ◽

High Susceptibility ◽

Apple Rootstocks ◽

Relative Resistance ◽

Moderate Susceptibility

New rootstocks from series SJM (St-Jean-Morden) and SJP84 (ST-Jean-1984) have been evaluated for agronomic qualities since 1970 and 1975, respectively. As a result of the evaluation, seven and nine rootstocks from the SJM and SJP84 series, respectively, were selected. However, these were not evaluated for crown rot resistance. Excised shoot assay was used to evaluate resistance of 22 apple rootstocks to crown rot caused by Phytophthora cactorum (Leb. and Cohn.) Schroet. The pathogenicity of four isolates of P. cactorum to apple rootstocks was confirmed using the same excised twig assay. For both tests, relative lesion length was used as a measure of susceptibility. The analysis of variance showed that there was a significant effect of rootstocks, isolate and the interaction between rootstock and isolate. In general, apple rootstocks were more susceptible to isolate PC04-02 followed by isolates PC04-03 and PC04-01 and less susceptible to isolate PC04-04. The selection SJM189 was the least susceptible to P. cactorum and SJP84-5162 and SJM15 were the most susceptible suggesting that these rootstocks may not be suitable in orchards with favourable conditions to P. cactorum infection. Excised twigs of the SJP84-5180, SJP84-5189, SJP845174, O.3, SJP84-5230, O.3A, SJP84-5198, SJM167 and M.44 showed low to moderate susceptibility, whereas, rootstocks SJP845231, SJM150 and M.26 showed moderate susceptibility to P. cactorum. Rootstocks SJM188, SJP84-5217, MM.111, SJM127, SJP84-5218 and MM.106 showed high susceptibility to P. cactorum. The present results confirmed that none of the released or commercial rootstocks are completely resistant to P. cactorum and an integrated approach including resistance, chemical control and cultural practices is recommended to manage P. cactorum in apple orchards. Key words: Apple breeding, crown rot, Malus domestica Borkh., root rot

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Relative Resistance of Cotton Lines to Pink Bollworm

Crop Science ◽

10.2135/cropsci1990.0011183x003000030004x ◽

1990 ◽

Vol 30 (3) ◽

pp. 500-504 ◽

Cited By ~ 7

Author(s):

F. Douglas Wilson

Keyword(s):

Pink Bollworm ◽

Relative Resistance

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Growth Characteristics of Activated Sludges Acclimated to para-Nitrophenol in Batch and Continuous Modes

Water Science & Technology ◽

10.2166/wst.1994.0359 ◽

1994 ◽

Vol 29 (7) ◽

pp. 327-333

Author(s):

Y. Matsui ◽

F. Yamaguchi ◽

Y. Suwa ◽

Y. Urushigawa

Keyword(s):

Growth Characteristics ◽

The Other ◽

Operational Mode ◽

Continuous Mode ◽

Relative Resistance ◽

Batch Mode ◽

The Given ◽

Operational Modes ◽

Very High ◽

Sensitive Group

Activated sludges were acclimated to p-nitrophenol (PNP) in two operational modes, a batch and a continuous. The operational mode of the PNP acclimation of activated sludges strongly affected the physiological characteristics of predominant microorganisms responsible for PNP degradation. Predominant PNP degraders in the sludge in batch mode (Sludge B) had lower PNP affinity and were relatively insensitive to PNP concentration. Those of the sludge in continuous mode (Sludge C), on the other hand, had very high PNP affinity and were sensitive to PNP. MPN enumeration of PNP degraders in sludge B and C using media with different PNP concentrations (0.05, 0.2,0.5 and 2.0 mM) supported the above results. Medium with 0.2 mM of PNP did not recover PNP degraders in sludge C well, while it recovered PNP degraders in sludge B as well as the medium with 0.05 mM did. When switching from one operational mode to the other, the predominant population in sludge B shifted to the sensitive group, but that of sludge C did not shift at the given loading of PNP, showing relative resistance to inhibitive concentration.

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Survey of Glyphosate-Resistant Junglerice Accessions in Dicamba-Resistant Crops in Tennessee

Weed Technology ◽

10.1017/wet.2020.131 ◽

2020 ◽

pp. 1-31

Author(s):

Clay M. Perkins ◽

Thomas C. Mueller ◽

Lawrence E. Steckel

Keyword(s):

Resistance Factor ◽

Relative Resistance ◽

Roundup Ready ◽

The Past ◽

Growing Seasons ◽

The Poor

Abstract Junglerice has become a major weed in Tennessee cotton and soybean fields. Glyphosate has been relied upon to control these accessions over the past two decades but in recent years cotton and soybean producers have reported junglerice escapes after glyphosate + dicamba and/or clethodim applications. In the growing seasons of 2018 and 2019, a survey was conducted of weed escapes in dicamba-resistant crops. Junglerice was the most prevalent weed escape in these dicamba-resistant (Roundup Ready Xtend®) cotton and soybean fields in both years of the study. In 2018 and 2019, junglerice was found 76% and 64% of the time in dicamba-resistant cotton and soybean fields, respectively. Progeny from junglerice seeds collected during this survey was screened for glyphosate and clethodim resistance. Seventy percent of the junglerice accessions tested had an effective relative resistance factor (RRF) of 3.1 to 8.5 to glyphosate. In all, 13% of the junglerice accessions could no longer be effectively controlled with glyphosate. This research also showed that all sampled accessions could still be controlled with clethodim in a greenhouse environment but less control was observed in the field. These data would also suggest that another cause for the poor junglerice control is dicamba antagonizing the glyphosate and clethodim activity.

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