EFFECT OF OXYGEN SUPPLY ON PHYTOPHTHORA ROOT ROT OF AVOCADO IN NUTRIENT SOLUTION

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.

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Phytophthora Root Rot Resistance in Soybean E00003

Crop Science ◽

10.2135/cropsci2012.11.0631 ◽

2014 ◽

Vol 54 (2) ◽

pp. 492-499 ◽

Cited By ~ 9

Author(s):

Zhongnan Zhang ◽

Jianjun Hao ◽

Jiazheng Yuan ◽

Qijian Song ◽

David L. Hyten ◽

...

Keyword(s):

Root Rot ◽

Phytophthora Root Rot

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Influence of Pure Mulches on Suppressing Phytophthora Root Rot Pathogens

Journal of Environmental Horticulture ◽

10.24266/0738-2898.31.4.221 ◽

2013 ◽

Vol 31 (4) ◽

pp. 221-226 ◽

Cited By ~ 1

Author(s):

G.C. Percival

Keyword(s):

Root Rot ◽

Crop Production ◽

Prunus Avium ◽

European Beech ◽

Dry Weight ◽

Urban Trees ◽

Horse Chestnut ◽

Phytophthora Root Rot ◽

Tree Vitality ◽

Lesion Severity

Mulching as a means of controlling Phytophthora root rot pathogens has become recognised as a potential cultural management system within the arboricultural, nursery and landscape industry. The influence of a pure mulch, i.e., mulch derived solely from one tree species, on reducing Phytophthora root rot severity has received little study. The purpose of the conducted research was to determine if a range of pure mulches derived from European beech (Fagus sylvatica L.), common hawthorn (Crataegus monogyna JACQ), silver birch (Betula pendula ROTH.), common cherry (Prunus avium L.), evergreen oak (Quercus ilex L.) and English oak (Q. robur L.) could reduce the development and impact of pathogen severity caused by Phytophthora cactorum and P. criticola on containerised horse chestnut (Aesculus hippocastanum). Irrespective of Phytophthora pathogen, leaf area, leaf, shoot, root and total plant dry weight following application of a pure mulch was higher than non-mulched controls. Likewise, leaf chlorophyll content, chlorophyll fluorescence Fv/Fm ratios, photosynthetic rates and root carbohydrate concentration as measures of tree vitality were higher in pure mulched compared to non-mulched control trees. Application of a pure mulch had a significant influence on Phytophthora root rot lesion severity. In the case of P. cactorum root rot lesion severity was reduced by 39–63%. In the case of P. criticola root rot lesion severity was reduced by 33–61%. In conclusion, pure mulches offer positive benefits for those involved in the care and maintenance of urban trees as well as nursery, forestry, orchard and horticultural crop production where Phytophthora pathogens are problematic.

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Evaluating the Efficacy of the Systems Approach at Mitigating Five Common Pests in Oregon Nurseries

Journal of Environmental Horticulture ◽

10.24266/0738-2898.32.1.1 ◽

2014 ◽

Vol 32 (1) ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

Nancy K. Osterbauer ◽

Melissa Lujan ◽

Gary McAninch ◽

S. Lane ◽

Aaron Trippe

Keyword(s):

Root Rot ◽

Systems Approach ◽

Phytophthora Root Rot ◽

Potted Plants ◽

Foliar Blight ◽

Total Percentage ◽

Phytophthora Spp ◽

Root Weevils ◽

Pest Incidence ◽

Point Inspection

In Oregon, the U.S. Nursery Certification (USNCP), Grower Assisted Inspection (GAIP), and Shipping Point Inspection (SPI) programs are used to certify nursery plants as pest free. To compare the programs' effectiveness for mitigating pest risk, potted plants grown within two USNCP, two GAIP, and two SPI nurseries were surveyed for Phytophthora root rot (Phytophthora spp.), Phytophthora foliar blight (Phytophthora spp.), bittercress (Cardamine spp.), snails and slugs (Class Gastropoda), and root weevils (Otiorhynchus spp.). A total of 1,635 plots were surveyed in the nurseries, with one or more pests detected in 1,003 plots. Based on the total percentage of plots found infested with a pest, significantly fewer were detected in the GAIP nurseries (55%) than in the USNCP nurseries (68%). However, bittercress incidence was significantly higher in GAIP nurseries (21%), while snails and slugs incidence was significantly higher in USNCP nurseries (49%), and Phytophthora root rot incidence was significantly higher in SPI nurseries (31%). Also, the plant families grown by the nurseries had a significant impact on pest incidence for two of the target pests, Phytophthora root rot and root weevils. While the GAIP seemed the best at mitigating pest incidence overall, none of the certification programs was consistently the most effective against all five target pests.

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Limitation of theophylline elimination by reduced oxygen availability in mouse hepatocytes and rat isolated livers

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y85-149 ◽

1985 ◽

Vol 63 (8) ◽

pp. 903-907 ◽

Cited By ~ 10

Author(s):

Kanji Nakatsu

Keyword(s):

Oxygen Supply ◽

Correlation Coefficients ◽

Oxygen Availability ◽

Isolated Perfused Rat Liver ◽

Mouse Hepatocyte ◽

Mouse Hepatocytes ◽

Per Se ◽

Theophylline Metabolism ◽

Effect Of Oxygen ◽

Rat Livers

The effect of oxygen availability on theophylline metabolism by mouse hepatocytes and rat isolated livers was examined. The elimination of theophylline by mouse hepatocytes and the metabolism of theophylline to dimethyluric acid by isolated, perfused rat livers was seriously impaired when the gas mixture supplied contained less than 28% oxygen. The correlation coefficients relating oxygen supply and the concentration of theophylline remaining in mouse hepatocyte suspensions were −0.74 to −0.84. In the isolated, perfused rat liver experiments, the correlation coefficient relating oxygen availability and dimethyluric acid production was 0.87. These observations are interpreted as supporting the hypothesis that oxygen availability per se is an important factor in determining the rate of theophylline metabolism.

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