scholarly journals Effect of Phosphonate Applications, for Phytophthora Brown Rot Control, on ‘Nadorcott’ Mandarin External Fruit Quality

2018 ◽  
Vol 28 (4) ◽  
pp. 470-475
Author(s):  
Jan van Niekerk ◽  
Charl Kotze ◽  
Jade North ◽  
Paul Cronje
Keyword(s):  
Fruit Development ◽  
Brown Rot ◽  
Citrus Reticulata ◽  
Green Color ◽  
Full Color ◽  
Commercial Harvest ◽  
Citrus Production ◽  
The Mean ◽  
Production Areas ◽  
Percentage Incidence

Phosphonate foliar applications in the period before harvest are routinely used in citrus (Citrus sp.) production for the control of phytophthora brown rot (Phytophthora sp.) control. However, several grower reports indicated that these applications caused phytotoxic damage on ‘Nadorcott’ mandarin (Citrus reticulata hybrid) fruit. To investigate this, trials were conducted over two seasons (2016 and 2017) in two climatically different citrus production areas of South Africa. These trials consisted of ammonium and potassium phosphite foliar applications (at full dose or half dose) at green, color break, or full color stages of fruit development. At commercial harvest, fruit was sampled from the different treatments and the incidence of the phytotoxic damage was documented as both percentage incidence and a phytotoxic index (PI). Results indicated that, regardless of the type of phosphonate or dosage applied, phytotoxic damage was observed at harvest if foliar applications were carried out at color break or full color stage of fruit development. The same results were observed in the different climatic areas, although the mean percentage of damaged fruit varied between the areas. Based on these results it is recommended that skirt pruning be used to mitigate phytophthora brown rot on ‘Nadorcott’ mandarin fruit.

Field assessment of partial resistance to mycosphaerella blight in Pisum subspecies accessions

2012 ◽  
Vol 92 (2) ◽  
pp. 289-296 ◽  
Author(s):  
R. L. Conner ◽  
B. D. Gossen ◽  
S. F. Hwang ◽  
K. F. Chang ◽  
K. B. McRae ◽  
...  
Keyword(s):  
Partial Resistance ◽  
Field Trials ◽  
Field Pea ◽  
Mycosphaerella Pinodes ◽  
Detached Leaf ◽  
High Severity ◽  
Field Assessment ◽  
Ascochyta Pinodes ◽  
The Mean ◽  
Production Areas

Conner, R. L., Gossen, B. D., Hwang, S. F., Chang, K. F., McRae, K. B. and Penner, W. C. 2012. Field assessment of partial resistance to mycosphaerella blight in Pisum subspecies accessions. Can. J. Plant Sci. 92: 289–296. Mycosphaerella blight, caused by Mycosphaerella pinodes (Berk. & Bloxam) Vestergr., the teleomorph of Ascochyta pinodes Jones, is an important foliar disease of field pea in the major production areas of the world. Partial resistance to mycosphaerella blight has been reported in some field pea cultivars, but, at best, they are only moderately susceptible. A 3-yr field study was conducted to evaluate the mycosphaerella blight reactions of 28 accessions from a number of subspecies of Pisum sativum L. and one accession of P. fulvum Sibth. A few of the accessions carried mutations for the genes af, tl, and st that affect the morphology of the leaflets, stipules and tendrils. Reactions to mycosphaerella blight were characterized based on the mean of the severity ratings taken on the two final assessment dates before the crop matured and also on the change in mycosphaerella blight severity between these two dates. In many of the accessions, severity ratings were similar to that of the moderately susceptible check cultivar, CDC Peko, while a few had high severity ratings similar to those of the susceptible check cultivars. The accession PI 512079, which has small stipules, branched petioles with many leaflets but no tendrils, had the lowest ratings for mycosphaerella blight severity. Four other accessions exhibited the smallest change in mycosphaerella blight severity at the end of the growing season. Differences in leaf morphology likely influenced the change in disease severity, since all the semi-leafless and leafless accessions had smaller changes in mycosphaerella blight severity than the susceptible check cultivars. In a detached leaf assay with two isolates of Mycosphaerella pinodes (Berk. & Bloxam) Vestergr., the smallest lesions formed on PI 512079, but otherwise the results failed to show a relationship with the observed severity values in the field trials.

scholarly journals A Survey for ‘Candidatus Liberibacter’ Species in South Africa Confirms the Presence of Only ‘Ca. L. africanus’ in Commercial Citrus

Plant Disease ◽  
2010 ◽  
Vol 94 (2) ◽  
pp. 244-249 ◽  
Author(s):  
G. Pietersen ◽  
E. Arrebola ◽  
J. H. J. Breytenbach ◽  
L. Korsten ◽  
H. F. le Roux ◽  
...  
Keyword(s):  
South Africa ◽  
Western Cape ◽  
Chain Reaction ◽  
Citrus Production ◽  
Candidatus Liberibacter ◽  
Citrus Orchards ◽  
Polymerase Chain ◽  
Serious Disease ◽  
Production Areas ◽  
Representative Samples

Greening disease of citrus is a serious disease known in South Africa since the late 1920s. In South Africa, it is associated with infection by ‘Candidatus Liberibacter africanus’, a heat sensitive, phloem-limited, noncultured alpha-proteobacterium. Huanglongbing (HLB), a similar, but more devastating disease that was described initially from China but which now occurs in several citrus producing countries, is associated with a different Liberibacter species, ‘Ca. L. asiaticus’. A ‘Ca. L. africanus’ subspecies, ‘Ca. L. africanus subsp. capensis’, has been found only in South Africa infecting an indigenous Rutaceous species, Calodendrum capense (Cape Chestnut), in the Western Cape in 1995. The discovery of a new Liberibacter species in Brazil, ‘Ca. L. americanus’, and the spread of ‘Ca. L. asiaticus’ to a number of additional countries over the last few years prompted us to assess whether only ‘Ca. L. africanus’ is present in commercial citrus orchards in South Africa. Samples displaying greening or similar symptoms were collected from 249 citrus trees from 57 orchards distributed throughout the greening affected citrus production areas of South Africa. Multiplex polymerase chain reaction (PCR) was performed on DNA extracts to detect the known citrus Liberibacters. Amplicons were obtained from 197 samples. None of the samples yielded a 1,027-bp amplicon indicative of ‘Ca. L. americanus’ infection. The amplicons of 84 samples were sequenced, and all were identical to the cognate ‘Ca. L. africanus’ Nelspruit sequence in GenBank. No instance of ‘Ca. L. asiaticus’ or ‘Ca. L. africanus subsp. capensis’ sequence was found. Geographically representative samples that tested negative for Liberibacter also tested negative for phytoplasmas based on real-time PCR results. Based on the results of this survey, it is concluded that to date only ‘Ca. L. africanus’ is associated with citrus greening in commercial citrus in South Africa.

scholarly journals Apple, Campylomma Control on ‘Golden Delicious’, 1994

1995 ◽  
Vol 20 (1) ◽  
pp. 30-30
Author(s):  
M. E. Reding ◽  
E. H. Beers
Keyword(s):  
Experimental Design ◽  
Single Tree ◽  
Application Rates ◽  
Commercial Harvest ◽  
Golden Delicious ◽  
The Mean ◽  
Fruit Damage

Abstract The experiment was performed in a ‘Golden Delicious’ orchard containing trees 4 to 5 m tall. The experimental design was a randomized complete block with seven treatments and four single-tree replicates. All treatments were applied with a handgun sprayer to point of drip at 300 psi. Application rates were based on 400 gpa. The Lorsban 4E + dormant oil treatment was applied at half-inch green (29 Mar). All other treatments were applied at pink (7 Apr). MPB nymphs were sampled from 2 limbs of each replicate tree on each sampling date with the mean of the 2 samples representing that replication. A beating tray with black cloth (45 cm × 45 cm) was held beneath a limb that was struck sharply three times and the number of nymphs was then counted. Fruit damage evaluations were conducted 16 Jun and 2 Sep, just before commercial harvest. Eighty fruit per replicate were examined visually on the tree for MPB damage. Fruit with one or more stings were classed as damaged.

scholarly journals Factors Affecting Latent Infection of Prune Fruit by Monilinia fructicola

2001 ◽  
Vol 91 (9) ◽  
pp. 864-872 ◽  
Author(s):  
Yong Luo ◽  
Themis J. Michailides
Keyword(s):  
Growth Stage ◽  
Latent Infection ◽  
Developmental Stages ◽  
Seasonal Pattern ◽  
Brown Rot ◽  
Effect Of Temperature ◽  
Monilinia Fructicola ◽  
Inoculum Concentration ◽  
Factors Affecting ◽  
Commercial Harvest

Experiments were conducted in three prune orchards in California. In each orchard, inoculations with Monilinia fructicola, the causal agent of brown rot of stone fruits, were performed on branches of trees at bloom and fruit developmental stages. Five inoculum concentrations were used in each inoculation. Six and four wetness durations were created for each inoculum concentration at bloom and fruit developmental stages, respectively. Fruit were harvested 3 weeks before commercial harvest. The overnight freezing incubation technique was used to promote sporulation and to determine incidence of latent infection (ILI) of fruit brown rot. No differences in ILI among locations were found. A seasonal pattern of bloom and fruit susceptibility to latent infection was determined. Susceptibility to latent infection at bloom stage was at a moderate level and increased to reach the highest level at pit hardening stage. Subsequently, fruit susceptibility to latent infection decreased, reaching the lowest level in early June at embryo growth stage. Thereafter, the susceptibility increased again with fruit development and maturity until harvest. Linear relationships between ILI and inoculum concentration were obtained for most combinations of growth stage and wetness duration. Incidence of latent infection increased linearly with increased wetness duration at bloom stage and increased exponentially with increased wetness duration at early and late fruit developmental stages. The optimum temperatures for latent infection at pit hardening stage ranged from 14 to 18°C, but the effect of temperature on latent infection was reduced at resistant stages. The temperature range favorable to latent infection varied for different wetness durations.

In-Season Monitoring of Postharvest Rot Pathogens on European Pears (Pyrus communis) in Southern Oregon and Subsequent Management Strategies

2020 ◽  
pp. 1-11
Author(s):  
Achala N. KC ◽  
Ann L. Rasmussen
Keyword(s):  
Fruit Development ◽  
Fungal Pathogens ◽  
Management Strategies ◽  
Penicillium Expansum ◽  
Separate Experiment ◽  
Full Bloom ◽  
Postharvest Decay ◽  
Commercial Harvest ◽  
Postharvest Application ◽  
Postharvest Rot

Postharvest decay in pears is a disease complex caused by several fungal pathogens. To understand the presence of these pathogens on flower and fruit tissues at early stages of fruit development, we collected samples from two commercial pear orchards in southern Oregon at five stages of fruit development: cluster bud, full bloom, petal fall, fruitlets, and field bins during commercial harvest. We recovered four common postharvest decay pathogens, Alternaria spp., Botrytis cinerea, Cladosporium herbarum, and Penicillium expansum, which varied in frequency across these stages, suggesting that pathogens may initially infect flowers and fruitlets well before conventional preharvest fungicide sprays. In a separate experiment, we applied four fungicides early in the growing season and/or shortly before harvest to determine when treatment was most effective in reducing the recovery rate of these pathogens and reducing storage rot. The recovery of Alternaria spp., B. cinerea, and P. expansum from flowers and fruitlets was reduced by 33, 47, and 33%, respectively, with bloom-time fungicide applications compared with nontreated control treatments. In addition, the fungicide program that included bloom-time application, preharvest application, and postharvest application resulted in significantly lower storage rot incidence compared with preharvest and postharvest application only. Syllit (dodine) reduced the storage rot incidence by 71%, Inspire Super (difenoconazole + cyprodinil) by 52%, Nevado (iprodione) by 36%, and Merivon (fluxapyroxad + pyraclostrobin) by 33% compared with nontreated control treatments.

scholarly journals Virulence Frequencies in Oat Crown Rust in the United States from 2001 Through 2005

Plant Disease ◽  
2008 ◽  
Vol 92 (3) ◽  
pp. 379-384 ◽  
Author(s):  
M. L. Carson
Keyword(s):  
United States ◽  
The United States ◽  
Crown Rust ◽  
Upper Midwest ◽  
Oat Crown Rust ◽  
Oat Cultivars ◽  
The Mean ◽  
Production Areas ◽  
The U.S ◽  
Virulence Diversity

In all, 680 single-pustule isolates of the oat crown rust pathogen, Puccinia coronata f. sp. avenae, were collected from cultivated and wild oat (Avena sativa and A. fatua, respectively) in the major oat-production areas of the United States from 2001 through 2005. They were tested for virulence on seedlings of differential oat lines in the greenhouse. In all, 171 races were found among the 357 isolates from the winter oat region of the United States, whereas 212 races were found among 323 isolates from the spring oat region. The crown rust population derived from winter oat in the southern United States was distinct from the spring oat population in the upper Midwest, although there was no virulence unique to either population. Virulence to Pc48 and Pc52 increased significantly in both regions during 2001 to 2005. Virulence to Pc59 increased and virulence to Pc53 decreased in the winter oat region during the same period. Many of the virulence associations previously reported in the U.S. oat crown rust population in the early 1990s also were found in both regions in this survey. Associations between virulence to the Pc genes were predominately positive in both regions; however, both positive and negative associations occurred more frequently in the winter oat region. Much of the virulence diversity in the oat crown rust population in the United States can be related to the deployment of resistance genes in commercial oat cultivars and virulence associations existing in the oat crown rust population. The mean virulence of the U.S. populations of crown rust continued to increase from 2001 to 2005. Genes for crown rust resistance derived from A. sterilis appear to be rapidly defeated, as has happened to Pc genes from A. sativa.

Genetic variation in the decay resistance of Scots pine wood against brown rot fungus

2001 ◽  
Vol 31 (7) ◽  
pp. 1244-1249 ◽  
Author(s):  
Anni M Harju ◽  
Martti Venäläinen ◽  
Egbert Beuker ◽  
Pirkko Velling ◽  
Hannu Viitanen
Keyword(s):  
Genetic Variation ◽  
Mass Loss ◽  
Scots Pine ◽  
Brown Rot ◽  
Decay Resistance ◽  
Phenotypic Variance ◽  
Increment Core ◽  
Genetic Components ◽  
Brown Rot Fungus ◽  
The Mean

The role of genotype in the durability of Scots pine (Pinus sylvestris L.) wood against decay by brown rot fungus (Coniophora puteana (Schum. ex Fr.) Karst. (strain Bam EBW 15)) was studied in a laboratory test. The wood material was obtained from 32-year-old half-sib progenies of Scots pine. The increment core samples of sapwood and juvenile heartwood were decayed using a modification of the standardized EN 113 method. The mean densities of the sapwood and heartwood samples were 391 and 337 mg·cm–3, respectively, and the mean mass losses were 114 and 80 mg·cm–3, respectively. The additive genetic components were small compared with the total phenotypic variance, which resulted in small narrow-sense heritabilities in mass loss. The most marked feature was the wide phenotypic variation in mass loss observed in heartwood (range 199 mg·cm–3) compared with sapwood (range 72 mg·cm–3) samples. Low heritability, together with the relatively high coefficient of additive genetic variation (CVA) in heartwood mass loss, suggests that advances in breeding can only be made through intensive testing in the environments which the studied experiment represents.

scholarly journals Transcriptome Analyses throughout Chili Pepper Fruit Development Reveal Novel Insights into the Domestication Process

Plants ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 585
Author(s):  
Octavio Martínez ◽  
Magda L. Arce-Rodríguez ◽  
Fernando Hernández-Godínez ◽  
Christian Escoto-Sandoval ◽  
Felipe Cervantes-Hernández ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Fruit Development ◽  
Time Course ◽  
Expression Profiles ◽  
Fruit Size ◽  
Gene Expression Profiles ◽  
Chili Pepper ◽  
Time Shift ◽  
The Mean

Chili pepper (Capsicum spp.) is an important crop, as well as a model for fruit development studies and domestication. Here, we performed a time-course experiment to estimate standardized gene expression profiles with respect to fruit development for six domesticated and four wild chili pepper ancestors. We sampled the transcriptomes every 10 days from flowering to fruit maturity, and found that the mean standardized expression profiles for domesticated and wild accessions significantly differed. The mean standardized expression was higher and peaked earlier for domesticated vs. wild genotypes, particularly for genes involved in the cell cycle that ultimately control fruit size. We postulate that these gene expression changes are driven by selection pressures during domestication and show a robust network of cell cycle genes with a time shift in expression, which explains some of the differences between domesticated and wild phenotypes.

scholarly journals A Review on the Role of Silicon Treatment in Biotic Stress Mitigation and Citrus Production

Agronomy ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2198
Author(s):  
Mireille Asanzi Mvondo-She ◽  
Auges Gatabazi ◽  
Mark Delmege Laing ◽  
Ashwell Rungano Ndhlala
Keyword(s):  
Biotic Stress ◽  
Brown Rot ◽  
Biotic Stresses ◽  
Post Harvest ◽  
Citrus Production ◽  
Biochemical Mechanisms ◽  
The Impact ◽  
Soluble Silicon ◽  
Post Harvest Disease

This paper reviews the threat of citrus pathogens during citrus production, with a focus on two pre-harvest diseases, citrus leaf spot, caused by Alternaria alternata (Fr.) Keissl. (1912) and brown rot, caused by Phytophthora citrophthora (R.E. Sm. and E.H. Sm.) Leonian, (1906) as well as green and blue mold post-harvest disease, caused by Penicillium digitatum (Pers.) Sacc. and P. italicum Wehmer, (1894), respectively. Furthermore, it reviews the role of soluble silicon, Si nutrition in biotic stress mitigation and potential mitigation mechanisms. Previous studies on the use of Si fertilizers have focused on high accumulator Si crops. These have demonstrated the potential of Si to reduce the occurrence of biotic stresses, which takes place through both physical and biochemical mechanisms. However, few studies have demonstrated the potential of Si to mitigate biotic stress in citrus, or the mechanisms involved. There is a clear need for studies on the impact of Si on various stress biochemical pathways in plants generally, and specifically for citrus due to the huge loss caused by pre- and post-harvest pathogens. This will assist in deepening our understanding of the pathophysiology which is essential to develop resistant cultivars.

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