Glasshouse and field screening of chickpea cultivars for resistance to Phytophthora megasperma f.sp. medicaginis

1991 ◽  
Vol 31 (5) ◽  
pp. 663 ◽  
Author(s):  
ML Dale ◽  
JAG Irwin
Keyword(s):  
Disease Incidence ◽  
Field Trials ◽  
Field Resistance ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
Progress Curve ◽  
Susceptible Control ◽  
Epidemic Development ◽  
Compound Interest ◽  
Chickpea Cultivars

The resistance expressed by a range of chickpea cultivars to phytophthora root rot in glasshouse and field trials was examined. Van der Plank's compound interest equation was the most suitable transformation for providing parameters to describe epidemic development for most of the cultivars when compared to the simple interest equation by plotting residuals and coefficients of determination. The area under the disease progress curve (AUDPC) was significantly correlated with the final disease incidence (FDI), which was also significantly correlated with the apparent infection rate (r), but r and AUDPC were not significantly correlated. The AUDPC proved to be relatively indiscriminate in this study for selecting resistant cultivars, since the value for the susceptible control cultivar was high, and many cultivars therefore had statistically lower AUDPC values. Several cultivars (i.e. CQ1591, ICC7568 and 232-4) were resistant on the basis of both the FDI and r parameters in the field trial and considered worthy of further investigation. When the parameters FDI or r were used to categorise the disease reactions of cultivars in the field, only half of the 30 cultivars assessed showed similar responses in both the glasshouse and field trials. The glasshouse assay used here does not allow the detection of all potentially useful forms of field resistance, and further work is needed in the development of a glasshouse assay which gives an accurate representation of field response to Phytophthora megasperma Drechs. f. sp. medicaginis Kuan and Erwin.

Effects of systemic fungicidal seed dressings on the incidence of Phytophthora megasperma, nodulation, and nitrogen fixation in two soybean cultivars

1983 ◽  
Vol 23 (120) ◽  
pp. 87 ◽  
Author(s):  
A Diatloff ◽  
JAG Irwin ◽  
JL Rose
Keyword(s):  
Nitrogen Fixation ◽  
Root Rot ◽  
Disease Incidence ◽  
Resistance Mechanisms ◽  
Field Resistance ◽  
Nitrogen Fixing ◽  
Phytophthora Megasperma ◽  
Phytophthora Root Rot ◽  
High Level ◽  
Root Health

Two cultivars of soybeans, Davis and Ross, resistant and susceptible to Phytophthora root rot, respectively, were grown in a field trial where there was a moderately high level of Phytophthora megasperma f. sp. glycinea. The efficacy of metalaxyl and Dowco 444 as fungicidal seed dressings, their interaction with host resistance and the effect of plant health on nodulation and nitrogen fixing activity (acetylene reduction) were assessed. The cultivar Davis showed a relatively high level of field resistance in the absence of fungicidal protection; this was manifest in increased emergence and a lower incidence of disease in the surviving plants. In contrast cv. Ross had virtually no field resistance. In both cultivars, disease incidence was lower where fungicides were used. Metalaxyl was more effective than Dowco 444 on cv. Ross but not on cv. Davis. This suggests that the better performance of Dowco 444 on Davis was through an enhancement of existing resistance mechanisms of the host. Nitrogen fixing activity was generally higher in Davis than in Ross with a positive correlation between nitrogen fixing activity and nodule number. Disease incidence was negatively correlated with nitrogen fixing activity indicating the dependence of nitrogen fixation on root health. Neither fungicides suppressed nitrogen fixing activity at the rates used.

scholarly journals Field Response of New Peanut Cultivar UF 91108 to Tomato Spotted Wilt Virus

Plant Disease ◽  
1997 ◽  
Vol 81 (12) ◽  
pp. 1410-1415 ◽  
Author(s):  
A. K. Culbreath ◽  
J. W. Todd ◽  
D. W. Gorbet ◽  
F. M. Shokes ◽  
H. R. Pappu
Keyword(s):  
Disease Incidence ◽  
Field Resistance ◽  
Individual Plant ◽  
Breeding Line ◽  
Oil Composition ◽  
Tomato Spotted Wilt ◽  
Progress Curve ◽  
Rating Method ◽  
Epidemic Development ◽  
Highly Correlated

Epidemics of spotted wilt, caused by tomato spotted wilt tospovirus (TSWV), were monitored in field plots of the new runner-type peanut (Arachis hypogaea) cv. UF 91108, in advanced breeding line F 84 × 9B-4-2-1-1-2-b2-B, in runner-type peanut cvs. Southern Runner and Florunner, and in Virginia-type cv. NC-V11 at two locations in 1994 and 1995. Epidemics of spotted wilt were suppressed in UF 91108 compared to the standard runner-type cv. Florunner. Final disease incidence, standardized area under the disease progress curve values, and final disease intensity ratings were lower in UF 91108 than in Florunner and were similar to those in the moderately resistant cv. Southern Runner. Results indicate that new cv. UF 91108 represents a new potential tool for management of spotted wilt in peanut production areas of the southeastern United States. UF 91108 is the first peanut cultivar in which an oil composition of approximately 65% oleic acid is combined with a moderate level of field resistance to TSWV. Epidemics of spotted wilt also were suppressed in breeding line F 84 × 9B-4-2-1-1-2-b2-B. Across the four tests, the effects of NC-V11 on epidemic development, final incidence, and spotted wilt intensity ratings were not consistent relative to the other genotypes. Use of final disease intensity ratings provided separation of the genotypes similar to use of final incidence of spotted wilt. Assessment values by these two methods were highly correlated. In three of four experiments, final disease intensity ratings were more closely correlated with pod yield than was final incidence. The new intensity rating method described in this paper requires much less time and effort than determining disease incidence and may be a practical alternative to individual plant assessment for characterization of genotype responses to TSWV.

Yield losses of soybeans due to Phytophthora megasperma f.sp. Glycinea

1989 ◽  
Vol 40 (6) ◽  
pp. 1161 ◽  
Author(s):  
MJ Ryley ◽  
HF Mosetter ◽  
JL Rose
Keyword(s):  
The United States ◽  
Field Trials ◽  
Field Resistance ◽  
Growth Stages ◽  
Yield Losses ◽  
Phytophthora Megasperma ◽  
High Death Rate ◽  
High Death ◽  
Soybean Genotypes ◽  
Seed Yields

Field trials were conducted in two seasons to determine the influence of Phytophthora megasperma f.sp. glycinea on seed yields of soybean genotypes with different levels of resistance. The fungicide metalaxyl, applied as a seed dressing and soil drenches, was used to control the disease. The cultivar Davis, which has high field resistance, did not suffer significant losses in either year. whereas the yield depression of less resistant genotypes ranged up to 72%, depending on the genotype and year. In 198 1 - 82 high death rate of plants occurred early in the season, but yield losses were less than in 1982-83 when mortality occurred late in the season. The declining ability of surviving plants to compensate for disease losses during the latter growth stages may account for the differences in yield losses between seasons.Genotypes with immunity to P. megasperma f.sp. glycinea have been widely grown in the United States because they offer complete protection against some races. However, new pathogenic races have developed quickly, and previously immune genotypes have then suffered severe yield losses. The results of these trials demonstrate that yield losses can be prevented without resorting to fungicide treatments. It is likely that a stable long-term solution to phytophthora root and stem rot will be conferred by field resistance.

Reaction of soybean cultivars to races of Phytophthora megasperma f.sp. glycinea present in Queensland

1982 ◽  
Vol 33 (5) ◽  
pp. 763 ◽  
Author(s):  
JL Rose ◽  
JAG Irwin ◽  
MJ Ryley ◽  
PW Langdon ◽  
LB Jenner
Keyword(s):  
Disease Incidence ◽  
Field Resistance ◽  
The Other ◽  
Stem Rot ◽  
Breeding Line ◽  
Phytophthora Megasperma ◽  
Breeding Lines ◽  
The North ◽  
Race 1 ◽  
Race 2

Phytophthora megasperma f.sp, glycinea, the cause of phytophthora root and stem rot of soybeans, was found to be widespread in southern Queensland. Race determinations on 56 isolates were made at 26�C using the North American differential set. Thirty isolates resembled race 1 (virulent only on Harosoy), while the remaining isolates killed varying proportions of the other six differentials. Two of these isolates most closely resembled race 15. When race determinations were repeated for four isolates at 31�C, each isolate was more virulent on most of the differentials. One isolate resembling race 1 at 26�C would have been classified as race 2 at 31�C. All of the cultivars grown in Queensland were susceptible to hypocotyl inoculation, indicating the absence of genes conditioning resistance to races 1 and 15. Small proportions of plants in some cultivars, including Davis and Bragg were resistant to hypocotyl inoculation. The field resistances of 21 cultivars and breeding lines were assessed in a disease nursery. Progressive assessments of disease incidence were significantly correlated with grain yield and plant height. Davis had the highest level of field resistance while Ross and Semstar had the lowest. A breeding line (HS 1115) was identified as highly resistant to the fungus, both in the field and following hypocotyl inoculation. Three F6 lines from the cross Davis x Bragg showed a range of disease reactions, with the best showing an equivalent level of resistance to that of Davis.

scholarly journals Temporal Dynamics of Brown Rot in Different Apple Management Systems and Importance of Dropped Fruit for Disease Development

2007 ◽  
Vol 97 (9) ◽  
pp. 1104-1111 ◽  
Author(s):  
I. J. Holb ◽  
H. Scherm
Keyword(s):  
Management System ◽  
Temporal Dynamics ◽  
Management Practice ◽  
Disease Incidence ◽  
Brown Rot ◽  
Tree Canopy ◽  
Apple Orchards ◽  
Progress Curve ◽  
Epidemic Development ◽  
Organic Orchards

Epidemic development of brown rot, caused by Monilinia fructigena, was monitored in integrated and organic apple orchards at two locations in eastern Hungary between 2002 and 2005 on three cultivars with early, midseason, and late ripening periods. Disease incidence and severity measures were affected significantly (P < 0.05) by management system (organic versus integrated) and cultivar, but there was no significant management system–cultivar interaction. Epidemics started 2 to 4 weeks earlier in organic orchards and on the early cv. Prima compared with integrated orchards and the late cv. Mutsu. Disease intensity increased markedly in the final 3 to 5 weeks before harvest and was considerably lower in integrated than in organic orchards. Final brown rot incidence on fruit in the tree was correlated with incidence on dropped fruit on the orchard floor (r > 0.75, P < 0.05), whereby the lag period from the appearance of the first symptomatic fruit on the ground to the occurrence of the first symptomatic fruit in the tree ranged from 2 weeks to 2 months, depending on the cultivar. The inflection point of the disease progress curve was attained first by fruit on the ground, followed successively by fruit in the lower, middle, and upper thirds of the tree canopy. This may indicate that dropped fruit that became infected early provided a source of inoculum for subsequent epidemics by serving as a bridge between sporulation from overwintered fruit mummies in the spring and the first fruit with sporulating lesions in the tree in midsummer. Removal of dropped fruit from the orchard floor resulted in a significantly lower disease incidence on fruit in the tree on all cultivars; thus, drop-removal may be useful as a brown rot management practice in apple orchards.

scholarly journals Epidemic Development of Bacterial Blight on Rice Carrying Resistance Genes Xa-4, Xa-7, and Xa-10

Plant Disease ◽  
1998 ◽  
Vol 82 (12) ◽  
pp. 1337-1340 ◽  
Author(s):  
I. Oña ◽  
C. M. Vera Cruz ◽  
Rebecca J. Nelson ◽  
Jan E. Leach ◽  
T. W. Mew
Keyword(s):  
Resistance Genes ◽  
Bacterial Blight ◽  
Disease Incidence ◽  
Xanthomonas Oryzae ◽  
Diseased Leaf ◽  
Near Isogenic Lines ◽  
Bacterial Blight Resistance ◽  
Progress Curve ◽  
Diseased Leaf Area ◽  
Epidemic Development

Epidemic development of bacterial blight caused by Xanthomonas oryzae pv. oryzae on three near-isogenic lines (IRBB lines) carrying bacterial blight resistance genes Xa-4 (IRBB4), Xa-7 (IRBB7), and Xa-10 (IRBB10) was studied in two farmers' fields located in Calauan and Mabi-tac, Phillipines, during 1993, 1994, and 1995. The plots were planted continuously during dry and wet seasons, with disease assessments done during the wet seasons, when weather was conducive to bacterial blight development. Disease incidence (number of hills infected) and severity (diseased leaf area) were assessed and area under the disease progress curve (AUDPC) values were computed. Mean disease incidence and severity in Calauan (AUDPC = 3,241.5 and 716.7, respectively) were significantly higher than in Mabitac (AUDPC = 2,431.2 and 558.0, respectively). In Calauan, AUDPC values for disease incidence and severity on IRBB4, IRBB10, and IR24 did not differ significantly during the three years of testing. In Mabitac, the AUDPC values for disease incidence and severity were not significantly different among IRBB4, IRBB10, and IR24 in 1993 and in 1995. However, in 1994, disease incidence (AUDPC = 3,037.7) and severity (AUDPC = 891.0) on IRBB4 were significantly lower than on IRBB10 and IR24. Bacterial blight was lowest on IRBB7 at both sites and throughout 1993 to 1995, indicating that this genotype is effective in suppressing the disease even with the presence of an indigenous virulent population of X. oryzae pv. oryzae.

scholarly journals Epidemiology and management of bacterial leaf spot on watermelon caused byPseudomonas syringae

Plant Disease ◽  
2017 ◽  
Vol 101 (7) ◽  
pp. 1222-1229 ◽  
Author(s):  
E. A. Newberry ◽  
L. Ritchie ◽  
B. Babu ◽  
T. Sanchez ◽  
K. A. Beckham ◽  
...  
Keyword(s):  
Disease Severity ◽  
Pseudomonas Syringae ◽  
Leaf Spot ◽  
Negative Relationship ◽  
Disease Outbreaks ◽  
Field Trials ◽  
Multiple Regression Model ◽  
Bacterial Leaf Spot ◽  
Progress Curve ◽  
Cool Conditions

Bacterial leaf spot of watermelon caused by Pseudomonas syringae has been an emerging disease in the southeastern United States in recent years. Disease outbreaks in Florida were widespread from 2013 to 2014 and resulted in foliar blighting at the early stages of the crop and transplant losses. We conducted a series of field trials at two locations over the course of two years to examine the chemical control options that may be effective in management of this disease, and to investigate the environmental conditions conducive for bacterial leaf spot development. Weekly applications of acibenzolar-S-methyl (ASM) foliar, ASM drip, or copper hydroxide mixed with ethylene bis-dithiocarbamate were effective in reducing the standardized area under the disease progress curve (P < 0.05). Pearson’s correlation test demonstrated a negative relationship between the average weekly temperature and disease severity (–0.77, P = 0.0002). When incorporated into a multiple regression model with the square root transformed average weekly rainfall, these two variables accounted for 71% of the variability observed in the weekly disease severity (P < 0.0001). This information should be considered when choosing the planting date for watermelon seedlings as the cool conditions often encountered early in the spring season are conducive for bacterial leaf spot development.

scholarly journals In-Furrow Applications of Metalaxyl and Phosphite for Control of Pink Rot (Phytophthora erythroseptica) of Potato in New Brunswick, Canada

Plant Disease ◽  
2007 ◽  
Vol 91 (10) ◽  
pp. 1305-1309 ◽  
Author(s):  
Khalil I. Al-Mughrabi ◽  
Rick D. Peters ◽  
H. W. (Bud) Platt ◽  
Gilles Moreau ◽  
Appanna Vikram ◽  
...  
Keyword(s):  
New Brunswick ◽  
Disease Incidence ◽  
Field Trials ◽  
Russet Burbank ◽  
Viable Option ◽  
Potato Plants ◽  
Pink Rot ◽  
Phytophthora Erythroseptica ◽  
Sensitive Isolate ◽  
The Mean

The efficacy of metalaxyl-m (Ridomil Gold 480EC) and phosphite (Phostrol) applied at planting in-furrow against pink rot (Phytophthora erythroseptica) of potato (Solanum tuberosum) ‘Shepody’ and ‘Russet Burbank’ was evaluated in field trials conducted in 2005 and 2006 in Florenceville, New Brunswick, Canada. Inoculum made from a metalaxyl-m-sensitive isolate of P. erythroseptica from New Brunswick was applied either in-furrow as a vermiculite slurry at planting or as a zoospore drench in soils adjacent to potato plants in late August. After harvest, the number and weight of tubers showing pink rot symptoms were assessed and expressed as percentages of the total tuber number and total weight of tubers. Metalaxyl-m applied in-furrow was significantly more effective against pink rot than phosphite. The mean percentage of diseased tubers as a percentage of total tuber weight was 1.5% (2005) and 1.2% (2006) for metalaxyl-m-treated plots and 9.6% (2005) and 2.8% (2006) for phosphite-treated plots, a percentage similar to that obtained in inoculated control plots with no fungicide treatment. The mean percentage of diseased tubers expressed as a percentage of the total number of tubers was 1.7% (2005) and 1.3% (2006) for metalaxyl-m-treated plots and 10.1% (2005) and 3.1% (2006) for phosphite-treated plots. Disease incidence was significantly higher using the late-season inoculation technique (respective means in 2005 and 2006 were 9.9 and 3.8% diseased tubers, by weight, and 10.6 and 3.9%, by number) than with the in-furrow inoculation method (respective means in 2005 and 2006 were 3.3 and 0.7% by weight, and 3.7 and 1.3%, by number). The potato cv. Shepody was significantly more susceptible to pink rot (9.9 and 3.3% diseased tubers, by weight, in 2005 and 2006, respectively, and 10.6 and 3.9%, by number) than Russet Burbank (respective means in 2005 and 2006 were 3.4,% and 1.2%, by weight, and 3.7,% and 1.2%, by number). Our findings indicate that metalaxyl applied in-furrow at planting is a viable option for control of pink rot caused by metalaxyl-sensitive strains of P. erythroseptica, whereas phosphite was ineffective.

scholarly journals Field Evaluations of Leaf Spot Resistance and Yield in Peanut Genotypes in the United States and Bolivia

Plant Disease ◽  
2011 ◽  
Vol 95 (3) ◽  
pp. 263-268 ◽  
Author(s):  
S. K. Gremillion ◽  
A. K. Culbreath ◽  
D. W. Gorbet ◽  
B. G. Mullinix ◽  
R. N. Pittman ◽  
...  
Keyword(s):  
United States ◽  
Disease Resistance ◽  
Leaf Spot ◽  
Field Experiments ◽  
Disease Incidence ◽  
The United States ◽  
Yield Potential ◽  
Cercospora Arachidicola ◽  
Breeding Lines ◽  
Progress Curve

Field experiments were conducted in 2002 to 2006 to characterize yield potential and disease resistance in the Bolivian landrace peanut (Arachis hypogaea) cv. Bayo Grande, and breeding lines developed from crosses of Bayo Grande and U.S. cv. Florida MDR-98. Diseases of interest included early leaf spot, caused by the fungus Cercospora arachidicola, and late leaf spot, caused by the fungus Cercosporidium personatum. Bayo Grande, MDR-98, and three breeding lines, along with U.S. cvs. C-99R and Georgia Green, were included in split-plot field experiments in six locations across the United States and Bolivia. Whole-plot treatments consisted of two tebuconazole applications and a nontreated control. Genotypes were the subplot treatments. Area under the disease progress curve (AUDPC) for percent defoliation due to leaf spot was lower for Bayo Grande and all breeding lines than for Georgia Green at all U.S. locations across years. AUDPC for disease incidence from one U.S. location indicated similar results. Severity of leaf spot epidemics and relative effects of the genotypes were less consistent in the Bolivian experiments. In Bolivia, there were no indications of greater levels of disease resistance in any of the breeding lines than in Bayo Grande. In the United States, yields of Bayo Grande and the breeding lines were greater than those of the other genotypes in 1 of 2 years. In Bolivia, low disease intensity resulted in the highest yields in Georgia Green, while high disease intensity resulted in comparable yields among the breeding lines, MDR-98, and C-99R. Leaf spot suppression by tebuconazole was greater in Bolivia than in the United States. This result indicates a possible higher level of fungicide resistance in the U.S. population of leaf spot pathogens. Overall, data from this study suggest that Bayo Grande and the breeding lines may be desirable germplasm for U.S. and Bolivian breeding programs or production.

scholarly journals Spatial Distribution of Green Mold Foci in 30 Commercial Mushroom Crops

Plant Disease ◽  
1999 ◽  
Vol 83 (1) ◽  
pp. 71-76 ◽  
Author(s):  
D. J. Royse ◽  
K. Boomer ◽  
Y. Du ◽  
M. Handcock ◽  
P. S. Coles ◽  
...  
Keyword(s):  
Cultural Practices ◽  
Disease Incidence ◽  
Spatial Distributions ◽  
Trichoderma Spp ◽  
Nutrient Supplementation ◽  
Green Mold ◽  
Factors Influencing ◽  
Airborne Contamination ◽  
Epidemic Development ◽  
Surface Covering

Statistical analyses were performed on spatial distributions of mushroom green mold foci caused by Trichoderma spp. in 30 standard Pennsylvania doubles (743 m2 production surface) selected at random from over 900 total crops mapped. Mapped production houses were divided into four tiers of six beds each with 16 sections per bed (total = 384 sections per double). Each section contained approximately 2 m2. Green mold foci were mapped according to presence or absence in each section as they became visible during the course of the mushroom production. There was a trend toward higher disease incidence at the ends of the doubles, although this was not consistent from level to level. Spatial analysis revealed that green mold foci were more likely to occur in neighboring sections along the beds rather than above, below, or across from each other. Cultural practices that were associated with movement along the beds, i.e., nutrient supplementation, spawning, bed tamping, surface covering, etc., were considered the most likely factors influencing the incidence of green mold in spawned compost. Airborne contamination was considered a less likely source of inocula contributing to epidemic development. Sanitation practices that reduce spore loads along the beds are expected to provide the greatest degree of green mold control.

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