Effect of frequency of defoliation of 40 Stylosanthes guianensis genotypes on field reaction to anthracnose caused by Colletotrichum gloeosporioides

1987 ◽  
Vol 38 (2) ◽  
pp. 309 ◽  
Author(s):  
JW Miles ◽  
JM Lenne
Keyword(s):  
Colletotrichum Gloeosporioides ◽  
Genetic Resistance ◽  
Field Trials ◽  
Reproductive Stage ◽  
Frequency Interaction ◽  
Field Reaction ◽  
Defoliation Frequency ◽  
Degree Of Association ◽  
Main Effects ◽  
Moderate Magnitude

Four different defoliation frequency treatments (uncut, or cut to approx, 10 cm every 4, 8, or 12 weeks) were imposed over 40 weeks on 40 S. guianensis genotypes to determine whether defoliation frequency can reliably be used to alter reproductive stage (as measured by visual score of flowering abundance) of the host plant and to determine the degree of association between anthracnose severity and reproductive stage. Flowering was more abundant and anthracnose more severe with less frequent defoliation. Flowering abundance was closely related with weeks of uninterrupted regrowth. Anthracnose severity was not closely associated either with weeks of uninterrupted regrowth nor with flowering abundance. The genotype-defoliation frequency interaction effect on anthracnose severity was very small compared to the main effects. Thus defoliation frequency of field trials should not affect reliability of estimation of relative genetic resistance to anthracnose. Flowering abundance was positively correlated with anthracnose susceptibility across genotypes, but the correlation was generally of only moderate magnitude.

scholarly journals Effect of mancozeb on the control of mycosphaerella blight of field pea

2000 ◽  
Vol 80 (2) ◽  
pp. 403-406 ◽  
Author(s):  
T. D. Warkentin ◽  
A. G. Xue ◽  
D. W. McAndrew
Keyword(s):  
Yield Loss ◽  
Foliar Application ◽  
Genetic Resistance ◽  
Similar Efficacy ◽  
Field Trials ◽  
Field Pea ◽  
Mycosphaerella Pinodes ◽  
Western Canada ◽  
Flowering Stage ◽  
Plot Design

Mycosphaerella blight (MB) [Mycosphaerella pinodes (Berk. & Blox.)Vestergr.] causes substantial yield loss to field pea in western Canada in most seasons and is a disease for which genetic resistance is lacking. The objective of this research was to evaluate the effectiveness of foliar application of mancozeb for the control of MB of field pea. Field trials of split-plot design were conducted at two sites per year from 1996 to 1998 in southern Manitoba, with cultivars as main-plots and fungicide treatments as sub-plots. In most site-years, a single application of mancozeb at the early flowering stage was effective in reducing MB severity and in increasing yield. Mancozeb had similar efficacy to chlorothalonil, the only currently registered fungicide for control of MB in field pea. The beneficial effect of both fungicides was greater for the highly MB susceptible cultivars AC Tamor and Carrera than the moderately MB susceptible cultivar Radley. Key words: Pisum sativum, field pea, mycosphaerella blight, mancozeb, chlorothalonil

Corroboration That Highly Resistant Impatiens Cultivars Are Not Immune to Downy Mildew Disease: A Report of Crop Losses from Two California Producers

2020 ◽  
Vol 21 (3) ◽  
pp. 214-216
Author(s):  
Margery Daughtrey ◽  
Janna Beckerman ◽  
William J. Davis ◽  
Karen Rane ◽  
Jo Anne Crouch
Keyword(s):  
United States ◽  
Downy Mildew ◽  
Genetic Resistance ◽  
Disease Outbreaks ◽  
The United States ◽  
Field Trials ◽  
Commercial Production ◽  
Impatiens Walleriana ◽  
Action Groups ◽  
Downy Mildew Disease

Two new series of Impatiens walleriana (impatiens) cultivars, Beacon and Imara XDR, were released to commercial growers in the United States in 2019 to 2020. Field trials show these new cultivar series are highly resistant to impatiens downy mildew (IDM). However, neither of these two impatiens series are completely immune to the disease, and preventive fungicide programs are still recommended for use throughout production to maintain plant health. Here we report two destructive outbreaks of IDM from Imara XDR in two commercial production facilities in California, one in 2019 and one in 2020. The disease outbreaks were caused by a known rDNA genotype of Plasmopara destructor (synonym = P. obducens). Modified Koch’s postulates showed that the pathogen could infect and cause disease in both Beacon and Imara XDR plants. Mefenoxam applied by both growers may have been ineffective due to resistance in P. destructor populations, which has been demonstrated on several previous occasions. Given these findings, fungicide programs intended to supplement genetic resistance should not be overly reliant upon application of mefenoxam and should utilize effective materials from different mode of action groups, in rotation. Fungicides to supplement genetic resistance are particularly appropriate in frost-free areas or in any circumstances that provide a potential inoculum source.

Characterization of flowering time response among recombinant inbred lines of WAB638-1/PRIMAVERA rice under reproductive stage drought stress

2021 ◽  
pp. 1-8
Author(s):  
Kehinde A. Adeboye ◽  
Olusegun A. Oduwaye ◽  
Isaac O. Daniel ◽  
Mamadou Fofana ◽  
Mande Semon
Keyword(s):  
Drought Stress ◽  
Flowering Time ◽  
Recombinant Inbred ◽  
Root Length ◽  
Recombinant Inbred Lines ◽  
Block Design ◽  
Field Trials ◽  
Inbred Lines ◽  
Reproductive Stage ◽  
Time Response

Abstract Ninety-eight high-yielding recombinant inbred lines (RILs) of WAB638-1/PRIMAVERA rice were evaluated with the parents under reproductive stage drought stress. The study aimed at characterizing flowering time response under drought stress and consequently classifying the genetic resources for efficient use in breeding programmes. Two field trials were conducted during the 2016 and 2017 dry seasons using the randomized complete block design with two replications. In 2016, 12 RILs were evaluated with the parents for the rooting attributes under drought stress and well-watered treatments. Analysis of variance revealed a significant (P < 0.05) variation among the genotypes for the traits evaluated. Drought stress reduced most of the characters in this study, including grain yield. However, the inbred lines exhibited considerable tolerance to drought stress as indicated by yield-related stress indexes, including stress susceptibility and drought tolerance indexes. Delayed flowering (FD) was recorded in 75 genotypes (including WAB638-1), while 25 genotypes (including PRIMAVERA) had no delay under drought stress compared to the control. The genotypes were grouped into flowering delay (D) genotypes (FD > 1 d) and no delay (N) genotypes (FD < 1 d), which significantly differ (P ⩽ 0.05) for numbers of days to 50% flowering. The flowering delay genotypes may be suitable for intermittent drought, while genotypes with little or no delay may be selected for terminal drought conditions. There was a significant correlation (r > 0.5) between the root length and number of days to 50% flowering. The study indicated that root parameters, such as the root length, may contribute to the drought adaptation mechanisms of the RILs.

scholarly journals Pelargonic Acid for Weed Control in Organic Vidalia® Sweet Onion Production

2014 ◽  
Vol 24 (6) ◽  
pp. 696-701 ◽  
Author(s):  
Wiley Carroll Johnson ◽  
Jerry W. Davis
Keyword(s):  
Weed Control ◽  
Winter Season ◽  
Field Trials ◽  
Pelargonic Acid ◽  
Yield Response ◽  
Clove Oil ◽  
Cool Season ◽  
Control Efficacy ◽  
Natural Sources ◽  
Main Effects

Cultivation using a tine weeder is a proven means to manage weeds in organic Vidalia® sweet onion (Allium cepa) production. If the initial cultivation is delayed, emerged weeds are not controlled. In these cases, herbicides derived from natural products could be used to control the emerged weeds before the initial cultivation. Clove oil has been evaluated for this use, but cool-season weed control is inconsistent during the winter season when Vidalia® sweet onion are grown. Pelargonic acid is a herbicide that can be derived from natural sources or synthesized. Field trials were conducted from 2011 through 2013 to determine the efficacy of pelargonic acid for cool-season weed control in organic Vidalia® sweet onion. All possible combinations of four herbicides and three cultivation regimes using a tine weeder were evaluated. Herbicides evaluated were pelargonic acid (3% and 5% by vol.), clove oil [10% by vol. (2011 and 2012)], d-limonene [14% (2013 only)], and a nontreated control. Cultivation regimes were twice (2×) and four times (4×) at 2-week intervals, and a noncultivated control. Main effects of cultivation and herbicides were independent for all parameters, with no improvement when used in combination. Cultivation 2× and 4× controlled cool-season weeds and improved onion yields, which is consistent with previous research. Pelargonic acid (5%) controlled weeds similar to clove oil (2011 and 2012) and d-limonene (2013), with cool-season weed control efficacy being inconsistent among all herbicides. Onion yield response to weed control from any of the herbicides, including pelargonic acid, also was inconsistent. In organic onion production, inconsistent cool-season performance using pelargonic acid is similar to other herbicides derived from natural sources.

A Temperature-Controlled Water Bath Method for Evaluating Soybean Reaction to Sudden Death Syndrome (SDS)

2005 ◽  
Vol 6 (1) ◽  
pp. 5 ◽  
Author(s):  
R. Y. Hashmi ◽  
J. P. Bond ◽  
M. E. Schmidt ◽  
J. H. Klein
Keyword(s):  
Sudden Death ◽  
Temperature Control ◽  
Field Trials ◽  
Sudden Death Syndrome ◽  
Water Bath ◽  
Screening Methods ◽  
Soil Medium ◽  
Soybean Genotypes ◽  
Field Reaction ◽  
Efficiency Of Selection

Many greenhouse screening methods have been tested to evaluate soybean genotypes for reaction to sudden death syndrome (SDS) caused by Fusarium solani f. sp. glycines. These methods generally have proven disappointing in that results are not consistent among methods or do not correlate with field reaction. In the present study, SDS foliar symptom severity among 24 soybean genotypes was compared using three inoculation methods in the greenhouse. The pathogen inoculum was either mixed (seedbed mixing) or layered (seedbed layering) in the soil medium prior to planting seed and then kept on a greenhouse bench or the inoculum was layered in the soil medium and kept in a temperature control water bath. The water bath method was similar to the layering method with the addition of precise temperature control. The water bath method was superior to the other methods in consistency of SDS symptoms among genotypes among trials and in agreement with SDS field reaction. When disease severity data obtained in the greenhouse were regressed with foliar disease data obtained in field trials, R2 values were 0.56, 0.60, and 0.81 for the seedbed mixing, seedbed layering, and water bath methodS, respectively. The improved ability to predict field response using the water bath method likely results from precise control of the temperature in the rhizosphere. The water bath method described herein will increase the efficiency of selection for highly adapted SDS resistant cultivars by reducing the number of genotypes that must be evaluated under field conditions. Accepted for publication 2 August 2005. Published 6 September 2005.

scholarly journals Evaluating Quantitative Trait Locus Resistance in Tomato to Multiple Xanthomonas spp.

Plant Disease ◽  
2020 ◽  
Vol 104 (2) ◽  
pp. 423-429
Author(s):  
Eduardo Bernal ◽  
Debora Liabeuf ◽  
David M. Francis
Keyword(s):  
Quantitative Trait ◽  
Major Gene ◽  
Genetic Resistance ◽  
Field Trials ◽  
Chromosome 11 ◽  
Sources Of Resistance ◽  
Xanthomonas Perforans ◽  
Independent Field ◽  
Xanthomonas Species ◽  
Trait Locus

Bacterial spot of tomato is a foliar disease caused by four Xanthomonas species. Identifying genetic resistance in wild tomatoes and subsequent breeding of varieties has been a strategy to reduce the loss from this disease because control using pesticides has been ineffective. Three independent sources of resistance have been identified with quantitative trait loci (QTL) mapping to the centromeric region on chromosome 11. These sources are derived from Hawaii 7998 (QTL-11A), PI 114490 (QTL-11B), and LA2533 (QTL-11C). To determine which QTL introgression from chromosome 11 provides the greatest resistance to multiple species, we developed near-isogenic lines (NILs) using marker-assisted backcrossing. In parallel, we developed an NIL that contains Rx-4/Xv3, which provides major gene resistance to Xanthomonas perforans. Additionally, we combined Rx-4/Xv3 resistance with QTL-11A. These sources of resistance were independently introduced into the susceptible parent, OH88119. During a 3-year period from 2016 to 2018, we evaluated backcross-derived families and NILs from each source in independent field trials inoculated with X. perforans, X. euvesicatoria, or X. gardneri. Our results suggest that both QTL-11C and QTL-11A combined with Rx-4/Xv3 provide effective genetic resistance against multiple Xanthomonas species. In addition, we provide evidence for additive to dominant genetic action for the QTL introgressions.

scholarly journals Seed Dressing Maize with Imazapyr to Control Striga hermonthica in Farmers’ Fields in the Savannas of Nigeria

Agriculture ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 83
Author(s):  
Alpha Yaya Kamara ◽  
Abebe Menkir ◽  
David Chikoye ◽  
Reuben Solomon ◽  
Abdullahi Ibrahim Tofa ◽  
...  
Keyword(s):  
Effective Means ◽  
Genetic Resistance ◽  
Integrated Approach ◽  
Field Trials ◽  
Striga Hermonthica ◽  
Seasonal Effects ◽  
Seed Coating ◽  
Maize Hybrids ◽  
Maize Seeds ◽  
Hybrid Maize

Use of small doses of imazapyr and pyrithiobac for seed coatings of imazapyr-resistant maize hybrids (IR-Maize) offers an effective means to control Striga hermonthica. Field trials were conducted in Bauchi and Kano States of Nigeria in 2014 and 2015 under heavy Striga infestation to evaluate the potential effectiveness of herbicide coated hybrids maize on Striga control in farmers’ field. Results showed that herbicide coated seeds reduced number of emerged Striga per m2 and Striga damage symptoms in farmers’ fields in all the locations. In Kano the number of emerged Striga was 4.9 to 7.9 times less in herbicide treated hybrids in comparison with those of the same hybrids planted without herbicide treatment. The Striga-resistant open pollinated variety (OPV) (TZL COMP1 SYN) had 6.7 to 8.0 times more Striga than the treated hybrids. In Bauchi, the number of emerged Striga on the untreated IR-maize hybrids were over four-times higher on the treated IR-maize hybrids than on the untreated hybrids. The Striga-resistant OPV check had four-times more Striga than the treated IR-maize hybrids and twice more than the untreated IR-maize hybrids across the two years. However, the effects of herbicide seed coating on grain yields were not consistent because of strong seasonal effects. The result revealed that coating of imazapyr-resistant hybrid maize seeds with imazapyr was effective in reducing Striga infestation in farmers’ fields. Although herbicide seed coating did not give consistent yield advantages of the hybrids over the untreated checks, a combination of herbicide seed treatment and genetic resistance to Striga would serve as an effective integrated approach that could significantly reduce the parasite seed bank from the soil and prevent production of new seeds. The IR-hybrids and the OPV checks contained Striga resistance/tolerant genes that protected them against drastic yield loss in the Striga infested fields in both Bauchi and Kano.

scholarly journals Antifungal activity of some alternative control against mango anthracnose in Senegal

2021 ◽  
Vol 9 (2) ◽  
pp. 239-246
Author(s):  
Yaya Diallo ◽  
P. M. Diedhiou ◽  
Elisabeth Bush ◽  
Mizuho Nita ◽  
Anton Baudoin
Keyword(s):  
Colletotrichum Gloeosporioides ◽  
Sodium Molybdate ◽  
Field Trials ◽  
Control Measures ◽  
Fruit Rot ◽  
The South ◽  
Significant Control ◽  
Fruit Drop ◽  
Short Rainy Season ◽  
Set Up

Mango production in the South of Senegal is exposed to intensive rainfall from late May to October, with high temperature and moisture levels. These conditions are conducive for the development of anthracnose caused by Colletotrichum gloeosporioides (sensu lato) and leading to an absolute necessity for adequate control measures for good quality mango production. Anthracnose disease causes both pre- and postharvest fruit spots and fruit rot as well as premature fruit drop. The purpose of this study was to test the efficacy of several fungicide alternatives (fertilizers and biological control agents) against mango anthracnose in Senegal comparatively to standard fungicides. Field trials were set up in contrasting climates conditions and involved three orchards in the Northern part of the country with a short rainy season and dry climate over 9 to 10 months a year and three other orchards in the Southern part of Senegal with in a humid tropic environment. No anthracnose was recorded in the orchards in northern Senegal. In the south, in contrast, the disease was actual. Among the treatments tested for the control of anthracnose, Sodium molybdate were found effective after fungicides (azoxystrobin and thiophanate methyl). All the alternative treatments to fungicides provided a statistically significant control to the disease as compared to the control

Fungicide Efficacy and Specificity Toward Fungi in the Cranberry Fruit Rot Disease Complex

2014 ◽  
Vol 15 (1) ◽  
pp. 31-35 ◽  
Author(s):  
Lindsay D. Wells ◽  
Robert S. Perry ◽  
Patricia S. McManus
Keyword(s):  
Colletotrichum Gloeosporioides ◽  
Field Trials ◽  
Fruit Rot ◽  
Colletotrichum Acutatum ◽  
Disease Complex ◽  
Industry Standards ◽  
Dmi Fungicides ◽  
Phomopsis Vaccinii ◽  
Rot Disease ◽  
Important Disease

Cranberry fruit rot is an economically important disease complex comprised of as many as 15 different fungi that destroy cranberries in the field and/or after harvest. We evaluated fungicides in six field trials over 3 years for their ability to reduce the incidence of cranberry fruit rot and for their specificity in controlling six principal pathogens in the complex: Coleophoma empetri, Colletotrichum acutatum, Colletotrichum gloeosporioides, Phomopsis vaccinii, Phyllosticta vaccinii, and Physalospora vaccinii. Fruit rot incidence and efficacy of fungicides varied greatly among replicate plots within trials and among trials, often making it difficult to discern significant differences among treatments. However, in general, the newer strobilurin and sterol demethylation inhibitor (DMI) fungicides were at least as effective as the industry standards, chlorothalonil and mancozeb. An exception was the DMI fungicide fenbuconazole, which was ineffective in three of five trials. Compared to other fungicides, fenbuconazole was weak in controlling Colletotrichum gloeosporioides, which along with Coleophoma empetri, dominated among fungi isolated from rotten berries. The results are being used to develop disease management programs that control the key fruit rot pathogens with reduced reliance on environmentally risky and potentially carcinogenic fungicides. Accepted for publication 21 January 2014. Published 14 March 2014.

scholarly journals On-field phenotypic evaluation of sunflower populations for broad-spectrum resistance to Verticillium leaf mottle and wilt

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Juan F. Montecchia ◽  
Mónica I. Fass ◽  
Ignacio Cerrudo ◽  
Facundo J. Quiroz ◽  
Salvador Nicosia ◽  
...  
Keyword(s):  
Broad Spectrum ◽  
Linear Models ◽  
Disease Incidence ◽  
Genetic Resistance ◽  
Field Trials ◽  
Agricultural Technology ◽  
Phenological Stages ◽  
Broad Spectrum Resistance ◽  
Growing Conditions ◽  
Mapping Populations

AbstractSunflower Verticillium Wilt and Leaf Mottle (SVW), caused by Verticillium dahliae (Kleb.; Vd), is a soil-borne disease affecting sunflower worldwide. A single dominant locus, known as V1, was formerly effective in controlling North-American Vd races, whereas races from Argentina, Europe and an emerging race from USA overcome its resistance. This emphasizes the need for identifying broad-spectrum genetic resistance (BSR) sources. Here we characterize two sunflower mapping populations (MPs) for SVW resistance: a biparental MP and the association MP from the National Institute of Agricultural Technology (INTA), under field growing conditions. Nine field-trials (FTs) were conducted in highly infested fields in the most SVW-affected region of Argentina. Several disease descriptors (DDs), including incidence and severity, were scored across four phenological stages. Generalized linear models were fitted according to the nature of each variable, adjusting mean phenotypes for inbred lines across and within FTs. Comparison of these responses allowed the identification of novel BSR sources. Furthermore, we present the first report of SVW resistance heritability, with estimates ranging from 35 to 45% for DDs related to disease incidence and severity, respectively. This study constitutes the largest SVW resistance characterization reported to date in sunflower, identifying valuable genetic resources for BSR-breeding to cope with a pathogen of increasing importance worldwide.

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