scholarly journals Evaluation of Leaf Spot Resistance in Wild Arachis Species of Section Arachis

2021 ◽  
Author(s):  
Alicia N Massa ◽  
Renee S Arias ◽  
Ronald B Sorensen ◽  
Victor S Sobolev ◽  
Shyamalrau P Tallury ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Fungal Pathogens ◽  
Germplasm Collection ◽  
Limited Information ◽  
Cercospora Arachidicola ◽  
Sources Of Resistance ◽  
Arachis Species ◽  
Leaf Spots ◽  
Predominant Pathogen ◽  
Selection Of

Wild diploid Arachis species are potential sources of resistance to early (ELS) and late (LLS) leaf spot diseases caused by Passalora arachidicola (syn. Cercospora arachidicola Hori), and Nothopassalora personata (syn. Cercosporidium personatum (Berk. & Curt.) Deighton), respectively. Within section Arachis, limited information is available on the extent of genetic variation for resistance to these fungal pathogens. A collection of 78 accessions representing 15 wild species of Arachis section Arachis from the U.S peanut germplasm collection was evaluated for resistance to leaf spots. Screening was conducted under field (natural inoculum) conditions in Dawson, Georgia, during 2017 and 2018. Accessions differed significantly (P < 0.01) for all three disease variables evaluated, which included final defoliation rating, ELS lesion counts, and LLS lesion counts. Relatively high levels of resistance were identified for both diseases, with LLS being the predominant pathogen during the two years of evaluation. This research documents new sources of resistance to leaf spot diseases selected from an environment with high inoculum pressure. The presence of ELS and LLS enabled the selection of resistant germplasm for further introgression and pre-breeding.

Geographical Distribution of Genetic Diversity in Arachis hypogaea

2001 ◽  
Vol 28 (2) ◽  
pp. 80-84 ◽  
Author(s):  
C. C. Holbrook ◽  
T. G. Isleib
Keyword(s):  
Disease Resistance ◽  
Arachis Hypogaea ◽  
Leaf Spot ◽  
Germplasm Collection ◽  
Cercospora Arachidicola ◽  
Root Knot Nematode ◽  
Sources Of Resistance ◽  
Arachis Hypogaea L ◽  
Race 1 ◽  
The U.S

Abstract The U.S. maintains a large (> 8000 accessions) and genetically diverse collection of peanut (Arachis hypogaea L.) germplasm. It is costly to screen all accessions within this collection for traits that could be useful in cultivar development. The objective of this research was to identify countries of origin that are rich sources of resistance to important peanut diseases. This would allow peanut breeders to focus their efforts on smaller subsets of the germplasm collection. Accessions in the peanut core collection were evaluated for resistance to late (Cercosporidium personatum Berk. & M. A. Curtis) and early (Cercospora arachidicola Hori) leaf spot, tomato spotted wilt Tospovirus (TSWV), the peanut root-knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1], and Cylindrocladium black rot (CBR)[Cylindrocladium crotalarie (Loos) Bell & Sobers]. These data then were examined to determine if genes for resistance clustered geographically. Several geographical areas that appear to be rich sources for disease-resistant genes were identified. China had a relatively large number of accessions with resistance to the peanut root-knot nematode. Peru appeared to be a rich source of material with resistance to CBR. Resistance to late leaf spot was more frequent than expected in accessions from Bolivia and Ecuador. Bolivia was also a valuable source of resistance to early leaf spot. Early leaf spot resistance also was more prevalent than expected in accessions from India, Nigeria, and Sudan. India, Israel, and Sudan were valuable origins for material with resistance to TSWV. Accessions with multiple disease resistance were most common in India, Mozambique, and Senegal. This information should enable plant breeders to utilize more efficiently the genes for disease resistance that are available in the U.S. germplasm collection.

scholarly journals Host–pathogen interactions in relation to management of light leaf spot disease (caused by Pyrenopeziza brassicae) on Brassica species

2018 ◽  
Vol 69 (1) ◽  
pp. 9 ◽  
Author(s):  
Chinthani S. Karandeni Dewage ◽  
Coretta A. Klöppel ◽  
Henrik U. Stotz ◽  
Bruce D. L. Fitt
Keyword(s):  
Leaf Spot ◽  
Fungal Pathogens ◽  
Molecular Mechanisms ◽  
Brassica Species ◽  
Leaf Spot Disease ◽  
Yield Losses ◽  
Sources Of Resistance ◽  
Management Tools ◽  
Brussels Sprouts ◽  
Main Component

Light leaf spot, caused by Pyrenopeziza brassicae, is the most damaging disease problem in oilseed rape (Brassica napus) in the United Kingdom. According to recent survey data, the severity of epidemics has increased progressively across the UK, with yield losses of up to £160M per annum in England and more severe epidemics in Scotland. Light leaf spot is a polycyclic disease, with primary inoculum consisting of airborne ascospores produced on diseased debris from the previous cropping season. Splash-dispersed conidia produced on diseased leaves are the main component of the secondary inoculum. Pyrenopeziza brassicae is also able to infect and cause considerable yield losses on vegetable brassicas, especially Brussels sprouts. There may be spread of light leaf spot among different Brassica species. Since they have a wide host range and frequent occurrence of sexual reproduction, P. brassicae populations are likely to have considerable genetic diversity, and evidence suggests population variations between different geographic regions, which need further study. Available disease-management tools are not sufficient to provide adequate control of the disease. There is a need to identify new sources of resistance, which can be integrated with fungicide applications to achieve sustainable management of light leaf spot. Several major resistance genes and quantitative trait loci have been identified in previous studies, but rapid improvements in the understanding of molecular mechanisms underpinning B. napus–P. brassicae interactions can be expected through exploitation of novel genetic and genomic information for brassicas and extracellular fungal pathogens.

Inheritance of Resistance to Cercospora arachidicola and Cercosporidium personatum in Six Virginia-type Peanut Lines1,3

1980 ◽  
Vol 7 (1) ◽  
pp. 4-9 ◽  
Author(s):  
Julia L. Kornegay ◽  
M. K. Beute ◽  
J. C. Wynne
Keyword(s):  
Combining Ability ◽  
Leaf Spot ◽  
Resistance Breeding ◽  
Diallel Cross ◽  
General Combining Ability ◽  
Leaf Spot Disease ◽  
Inheritance Of Resistance ◽  
Cercospora Arachidicola ◽  
Cercosporidium Personatum ◽  
Leaf Spots

Abstract The inheritance of resistance to two cercospora leaf-spots, Cercospora arachidicola (early leafspot) and Cercosporidium personatum (late leafspot) in Virginia-type peanuts (Arachis hypogaea L.), was determined using F1 and F2 generations and parental lines from a six parent diallel cross under natural field conditions. Two techniques for rating disease severity were employed. General combining ability, determined from both rating techniques, was significant for both F1 and F2 generations, indicating that resistance to both fungi and tolerance to infection i. e., minimal leaf defoliation, was primarily due to additive genetic effects. The six parents produced offspring with different levels of resistance to both fungi. From the estimates of general combining ability effects, only NC-GP 343 and NC 5 produced progeny resistant to both early and late leaf-spot. NC 3033 was resistant to early leafspot, but susceptible to late leafspot. NC-Ac 3139, Florigiant and NC 2 were resistant to late leafspot, but susceptible to early leaf-spot. Disease indices ranked NC 3033 and NC-GP 343 as, overall, the most resistant of the six lines and the most useful to include in a cercospora leafspots resistance breeding program.

Combination of Early Maturity and Leaf Spot Tolerance Within an Advanced Georgia Peanut Breeding Line1

1995 ◽  
Vol 22 (2) ◽  
pp. 106-108 ◽  
Author(s):  
W. D. Branch ◽  
A. K. Culbreath
Keyword(s):  
Leaf Spot ◽  
Genetic Resistance ◽  
Field Tests ◽  
Cercospora Arachidicola ◽  
Early Maturity ◽  
The Past ◽  
Leaf Spots ◽  
Arachis Hypogaea L ◽  
Cultivated Peanut ◽  
Efficient Alternative

Abstract In the past, genetic resistance to both early and late leaf spots [Cercospora arachidicola Hori and Cercosporidiumpersonatum (Berk. & Curt.) Deighton] has been found to be negatively or inversely correlated with early maturity in the cultivated peanut (Arachis hypogaea L.). For example, the late leaf spot resistant cultivar Southern Runner is approximately 2 wk later in maturity than the susceptible Florunner cultivar. Recently, an advanced runner-type breeding line (GA T-2844) has been developed by the Georgia peanut breeding program which combines early maturity and leaf spot tolerance. For the past 3 yr (1991–1993), GA T-2844 has been evaluated in replicated field tests without fungicides. Results show that GA T-2844 has on the average >30% yield advantage and a 30-d earlier maturity than Southern Runner. Leaf spot ratings also showed GA T-2844 to be intermediate between Southern Runner and Florunner. Such a combination of early maturity and leaf spot tolerance could significantly enhance U.S. peanut production by providing an environmentally safer and efficient alternative to costly pesticides not previously available among runner-type cultivars.

scholarly journals Determining the Sources of Primary and Secondary Inoculum and Seasonal Inoculum Dynamics of Fungal Pathogens Causing Fruit Rot of Deciduous Holly

Plant Disease ◽  
2019 ◽  
Vol 103 (5) ◽  
pp. 951-958
Author(s):  
Shan Lin ◽  
Francesca Peduto Hand
Keyword(s):  
Leaf Spot ◽  
Fungal Pathogens ◽  
Disease Incidence ◽  
Fruit Rot ◽  
Plant Production ◽  
Mature Fruit ◽  
Average Temperature ◽  
Leaf Spots ◽  
Maximum Minimum

Fruit rot of deciduous holly, caused by species of the genera Alternaria, Colletotrichum, Diaporthe, and Epicoccum, is affecting plant production in Midwestern and Eastern U.S. nurseries. To determine the sources of inoculum, dormant twigs and mummified fruit were collected, and leaf spot development was monitored throughout the season from three Ohio nurseries over two consecutive years. Mummified fruit was the main source of primary inoculum for species of Alternaria and Epicoccum, whereas mummified fruit and bark were equally important for species of Colletotrichum and Diaporthe. Brown, irregular leaf spots developed in the summer, and disease incidence and severity increased along with leaf and fruit development. Coalesced leaf spots eventually resulted in early plant defoliation. When tested for their pathogenicity on fruit, leaf spot isolates were able to infect wounded mature fruit and induce rot symptoms, which indicated that leaf spots could serve as a source of secondary inoculum for fruit infections. In addition, spore traps were used to monitor seasonal inoculum abundance in the nurseries. Fruit rot pathogens were captured by the spore traps throughout the season, with peak dissemination occurring during flowering. In this study, we also attempted to understand the role of environmental factors on leaf spot development. Although leaf spot incidence and severity were negatively correlated to mean maximum, minimum and average temperature, a decrease in temperature also coincided with leaf senescence. The role of temperature on leaf spot development should be further studied to fully interpret these results.

scholarly journals Sources and Nature of Resistance to Cercospora Arachidicola Hori and Cercosporidium Personatum (Beck & Curtis) Deighton in Arachis Species1

1974 ◽  
Vol 1 (1) ◽  
pp. 6-11 ◽  
Author(s):  
Yousef A-M. Abdou ◽  
W. C. Gregory ◽  
W. E. Cooper
Keyword(s):  
Cell Walls ◽  
Host Response ◽  
Cercospora Arachidicola ◽  
Sources Of Resistance ◽  
Arachis Species ◽  
Arachis Hypogaea L ◽  
In The Wild ◽  
Directed Growth ◽  
High Degree ◽  
Germ Tubes

Abstract Various subspecies, botanical varieties and cultivars of peanuts (Arachis hypogaea L.) from widely separated areas of South America and Africa were evaluated for resistance to C. personatum and C. arachidicola. All cultivated peanuts tested were highly susceptible to both fungi except one collection from Peru, which showed a high degree of tolerance to defoliation. Sources of resistance were found in the wild Arachis species. Several immune and many highly resistant collections of Arachis were found in the sections Erectoides, Rhizomatosae, and Extranervosae. In section Axonomorphae, A. chacoense (10602 GKP) was highly resistant to C. arachidicola but susceptible to C. personatum, and C. cardenasii (10017 GKP) was susceptible to C. arachidicola but immune to C. personatum. Both Arachis species are cross-compatible with A. hypogaea. Host response in terms of pathogen penetration was classified into: immune, moderately and highly susceptible; and the reactions after penetration were: highly resistant, moderately and highly susceptible. On highly susceptible peanuts, the germ-tubes showed directed growth toward open stomata through which these fungi penetrate. On moderately susceptible peanuts a few germ-tubes grew toward the stomata, and on the immune entries no directed growth of the germ-tubes was observed. Resistance after penetration was associated with the formation of a barrier in advance of and around the infection site in the form of cell wall swelling and thickening, and the deposition of pectic substances on the cell walls and in intercellular spaces.

scholarly journals Mangrove Dieback and Leaf Disease in Sonneratia apetala and Sonneratia caseolaris in Vietnam

Forests ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1273 ◽  
Author(s):  
Huong Thi Thuy Nguyen ◽  
Giles E. St. J. Hardy ◽  
Tuat Van Le ◽  
Huy Quoc Nguyen ◽  
Duc Hoang Le ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Fungal Pathogens ◽  
Survival Rates ◽  
Tree Decline ◽  
Mangrove Restoration ◽  
Sonneratia Caseolaris ◽  
Leaf Spots ◽  
Black Leaf Spot ◽  
Stem Lesions

Even though survival rates for mangrove restoration in Vietnam have often been low, there is no information on fungal pathogens associated with mangrove decline in Vietnam. Therefore, this research was undertaken to assess the overall health of mangrove afforestation in Thanh Hoa Province and fungal pathogens associated with tree decline. From a survey of 4800 Sonneratia trees, the incidence of disorders was in the order of pink leaf spot > shoot dieback > black leaf spot for S. caseolaris and black leaf spot > shoot dieback > pink leaf spot for S. apetala. Approximately 12% of S. caseolaris trees had both pink leaf spot and shoot dieback, while only 2% of S. apetala trees had black leaf spot and shoot dieback. Stem and leaf samples were taken from symptomatic trees and fungi were cultured in vitro. From ITS4 and ITS5 analysis, four main fungal genera causing leaf spots and shoot dieback on the two Sonneratia species were identified. The most frequently isolated fungal taxa were Curvularia aff. tsudae (from black leaf spot),Neopestalotiopsis sp.1 (from stem dieback), Pestalotiopsis sp.1 (from pink leaf spot), and Pestalotiopsis sp.4a (from black leaf spot). The pathogenicity of the four isolates was assessed by under-bark inoculation of S. apetala and S. caseolaris seedlings in a nursery in Thai Binh Province. All isolates caused stem lesions, and Neopestalotiopsis sp.1 was the most pathogenic. Thus, investigation of fungal pathogens and their impact on mangrove health should be extended to other afforestation projects in the region, and options for disease management need to be developed for mangrove nurseries.

scholarly journals Selection of tomato breeding lines with resistance to Tomato yellow vein streak virus

2015 ◽  
Vol 33 (3) ◽  
pp. 345-351
Author(s):  
Jean CS Santos ◽  
Walter J Siqueira ◽  
Paulo CT Melo ◽  
Addolorata Colariccio ◽  
André L Lourenção ◽  
...  
Keyword(s):  
Virus Transmission ◽  
Virus Detection ◽  
Germplasm Collection ◽  
Yellow Vein ◽  
Streak Virus ◽  
Sources Of Resistance ◽  
Breeding Lines ◽  
Determinate Growth ◽  
Tomato Breeding ◽  
Selection Of

The study aimed to assess the reaction to Tomato yellow vein streak virus (ToYVSV) of determinate-growth tomato breeding lines of the Instituto Agronomico de Campinas (Campinas Agronomic Institute) germplasm collection and to select resistant plants. The experiment was carried out from August 2008 to February 2009 in greenhouse conditions. The geminivirus isolate used was collected in a tomato commercial field, in Sumaré, São Paulo State, Brazil. The experimental design was completely ramdomized blocks, with 25 treatments, four replications, and 30-plant plots. Virus transmission was carried out in cages containing viruliferous whiteflies (Bemisia tabaci B biotype). Plant reaction to the pathogen was evaluated by means of the percentage of symptomless plants 40, 50, 57 and 64 days after transplanting. Virus detection in each genotype was carried out using PCR. Although all genotypes showed plants with and without ToYVSV symptoms, lines IAC-TG 17 and LA 462 (Solanum peruvianum) stood out due to the highest percentage of symptomless plants in the four evaluation dates. Therefore, considering the genotypes evaluated and the edaphoclimatic conditions in which this work was carried out, lines IAC-TG 17 and LA 462 can be used as sources of resistance to ToYVSV.

Peanut (Arachis hypogaea L.) Cultivar Response to Leaf Spot Disease Development Under Four Disease Management Programs1

1998 ◽  
Vol 25 (1) ◽  
pp. 35-39 ◽  
Author(s):  
W. J. Grichar ◽  
B. A. Besler ◽  
A. J. Jaks
Keyword(s):  
Arachis Hypogaea ◽  
Leaf Spot ◽  
Leaf Spot Disease ◽  
Cercospora Arachidicola ◽  
Spot Disease ◽  
Pod Yield ◽  
Leaf Spots ◽  
Arachis Hypogaea L ◽  
Yield Difference ◽  
Disease Pressure

Abstract Peanut (Arachis hypogaea L.) pod yield and response to early and late leaf spots [caused by Cercospora arachidicola S. Hori and Cercosporidium personatum (Berk. & M. A. Curtis) Deighton, respectively] were evaluated on six runner-type cultivars under four leaf spot spray programs using tebuconazole at 0.23 kg ai/ha and chlorothalonil at 1.26 kg ai/ha. The four leaf spot spray programs included unsprayed, 14-d schedule, 21-d schedule, and 28-d schedule. With the 14- and 21-d schedule, chlorothalonil was applied at the first and last applications with a maximum of four tebuconazole applications for the middle sprays. On the 28-d schedule, tebuconazole was applied four times. Under conditions of heavy leaf spot disease pressure where no fungicide was applied, Southern Runner and Georgia Browne were slightly less susceptible (although not significantly) to early or late leaf spot than Florunner, GK-7, Georgia Runner, or Sunrunner. Less leaf spot was present in the 14-d schedule compared to 21- or 28-d schedules. Although there was no yield difference between the 14-, 21-, or 28-d schedules, the plots sprayed on a 14-d schedule yielded 43% more than the unsprayed. When averaged across all spray schedules, Georgia Browne yielded 15% more peanuts than Georgia Runner.

Variability in Field Response of Peanut Genotypes from the U.S. and China to Tomato Spotted Wilt Virus and Leaf Spots

2012 ◽  
Vol 39 (1) ◽  
pp. 30-37 ◽  
Author(s):  
Yan Li ◽  
Albert K. Culbreath ◽  
Charles Y. Chen ◽  
Steve J. Knapp ◽  
C. Corley Holbrook ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Tomato Spotted Wilt Virus ◽  
Field Trials ◽  
Breeding Lines ◽  
Leaf Spots ◽  
Tomato Spotted Wilt ◽  
Total Incidence ◽  
Wilt Virus ◽  
Selection Of

Abstract Tomato spotted wilt, caused by Tomato spotted wilt virus (TSWV) and transmitted by thrips, and early leaf spot and late leaf spot are among the most important diseases of peanut in the southeastern United States. The objective of this study was to compare field susceptibility of diverse peanut lines to TSWV and leaf spot pathogens for selection of lines for mapping population development. In field trials in 2007 and 2008, 22 genotypes were evaluated for reactions to TSWV and leaf spots. Early leaf spot was the predominate pathogen in both years. There was a near-continuous range of spotted wilt from 18% to 79% for the total incidence rating with any symptoms caused by TSWV. In general, NC94022, ‘Georganic’, C689-6-2, ‘Georgia-01R’, C724-19-25, TifGP-1, C11-154-61, C12-3-114-58, and ‘Tifguard’ were among the most resistant genotypes to TSWV, whereas GT-C20, GT-C9 and PE-2 were the most susceptible. Final percentage of defoliation by leaf spots ranged from 10% to 97% for both years. Genotypes C689-2, Georgia-01R, C12-3-114-58, C11-154-61, Tifguard and Georganic showed resistance to leaf spots, whereas ‘NC-6’, ‘Spancross’, GT-C9, GT-C20 and PE-2 were susceptible to leaf spots. There were 3 cultivars and 3 breeding lines classified as resistant to both TSWV and leaf spots; and there were 3 genotypes from China susceptible to both TSWV and leaf spots. These phenotypic disease reaction data can be used in conjunction with genetic characterization of these genotypes for development of recombinant inbred line populations in efforts to develop markers for resistance to TSWV and leaf spots.

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