scholarly journals Relationship Between Avirulence Gene (avrA) Diversity in Ralstonia solanacearum and Bacterial Wilt Incidence

2004 ◽  
Vol 17 (12) ◽  
pp. 1376-1384 ◽  
Author(s):  
Alison E. Robertson ◽  
W. Patrick Wechter ◽  
Timothy P. Denny ◽  
Bruce A. Fortnum ◽  
Daniel A. Kluepfel
Keyword(s):  
United States ◽  
South Carolina ◽  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Disease Incidence ◽  
Southeastern United States ◽  
Avirulence Gene ◽  
Avirulent Strain ◽  
Wild Type ◽  
North And South

Bacterial wilt, caused by Ralstonia solanacearum, is a serious disease of tobacco in North and South Carolina. In contrast, the disease rarely occurs on tobacco in Georgia and Florida, although bacterial wilt is a common problem on tomato. We investigated whether this difference in disease incidence could be explained by qualitative characteristics of avirulence gene avrA in the R. solanacearum population in the southeastern United States. Sequence analysis established that wild-type avrA has a 792-bp open reading frame. Polymerase chain reaction (PCR) amplification of avrA from 139 R. solanacearum strains generated either 792-bp or ≈960-bp DNA fragments. Strains that elicited a hypersensitive reaction (HR) on tobacco contained the 792-bp allele, and were pathogenic on tomato and avirulent on tobacco. All HR-negative strains generated a ≈960-bp DNA fragment, and wilted both tomato and tobacco. The DNA sequence of avrA in six HR-negative strains revealed the presence of one of two putative miniature inverted-repeat transposable elements (MITEs): a 152-bp MITE between nucleotides 542 and 543, or a 170-bp MITE between nucleotides 461 and 462 or 574 and 575. Southern analysis suggested that the 170-bp MITE is unique to strains from the southeastern United States and the Caribbean. Mutated avrA alleles were present in strains from 96 and 75% of North and South Carolina sites, respectively, and only in 13 and 0% of the sites in Georgia and Florida, respectively. Introduction of the wild-type allele on a plasmid into four HR-negative strains reduced their virulence on both tobacco and tomato. Inactivation of avrA in an HR-positive, avirulent strain, resulted in a mutant that was weakly virulent on tobacco. Thus, the incidence of bacterial wilt of tobacco in the southeastern United States is partially explained by which avrA allele dominates the local R. solanacearum population.

scholarly journals Grafting Tomato to Manage Bacterial Wilt Caused by Ralstonia solanacearum in the Southeastern United States

Plant Disease ◽  
2012 ◽  
Vol 96 (7) ◽  
pp. 973-978 ◽  
Author(s):  
C. L. Rivard ◽  
S. O'Connell ◽  
M. M. Peet ◽  
R. M. Welker ◽  
F. J. Louws
Keyword(s):  
United States ◽  
North Carolina ◽  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Southeastern United States ◽  
The United States ◽  
Tomato Production ◽  
Progress Curve ◽  
Grafting Onto ◽  
Wilt Incidence

Bacterial wilt, caused by Ralstonia solanacearum, can result in severe losses to tomato (Solanum lycopersicum) growers in the southeastern United States, and grafting with resistant rootstocks may be an effective strategy for managing this disease. However, R. solanacearum populations maintain considerable diversity, and little information is known regarding the efficacy of commercially available rootstocks to reduce bacterial wilt incidence and subsequent crop loss in the United States. In this study, tomato plants grafted onto ‘Dai Honmei’ and ‘RST-04-105-T’ rootstocks had significantly lower area under the disease progress curve (AUDPC) values compared with nongrafted plants (P < 0.05). Across three locations in North Carolina, final bacterial wilt incidence for non- and self-grafted plants was 82 ± 14 to 100%. In contrast, bacterial wilt incidence for the grafted plants was 0 to 65 ± 21%. Final bacterial wilt incidence of plants grafted with Dai Honmei rootstock was 0 and 13 ± 3% at two locations in western North Carolina but 50 ± 3% at a third site in eastern North Carolina. Similarly, grafting onto RST-04-105-T rootstock significantly reduced AUDPC values at two of the three locations (P < 0.05) compared with that of the nongrafted plants, but performed poorly at the third site. Total fruit yields were significantly increased by grafting onto resistant rootstocks at all three sites (P < 0.05). Regression analyses indicated that yield was significantly negatively correlated with bacterial wilt AUDPC values (R2 was 0.4048 to 0.8034), and the use of resistant rootstocks enabled economically viable tomato production in soils naturally infested with R. solanacearum.

scholarly journals Diversity Among Ralstonia solanacearum Strains Isolated from the Southeastern United States

2012 ◽  
Vol 102 (10) ◽  
pp. 924-936 ◽  
Author(s):  
Jason C. Hong ◽  
David J. Norman ◽  
David L. Reed ◽  
M. Timur Momol ◽  
Jeffrey B. Jones
Keyword(s):  
United States ◽  
South Carolina ◽  
Ralstonia Solanacearum ◽  
Phylogenetic Analyses ◽  
Southeastern United States ◽  
The United States ◽  
Hypersensitive Reaction ◽  
Systemic Movement ◽  
Solanacearum Strain ◽  
Unique Banding Pattern

This is the first comprehensive study of a collection of Ralstonia solanacearum strains from the southeastern United States to be characterized based on biovar, pathogenicity, hypersensitive reaction on tobacco, and phylogenetic analyses of the egl sequence. Rigorous phylogenetic analysis of the commonly used egl gene produced robust phylogenies that differed significantly from a neighbor-joining tree differed from and previously published phylogenies for R. solanacearum strains. These robust trees placed phylotype IV within the phylotype I clade, which may suggest that phylogenies based solely on egl may be misleading. As a result of phylogenetic analyses in this study, we determined that U.S. strains from Georgia, North Carolina, South Carolina, and older Florida strains isolated from solanaceous crops all belong to phylotype II sequevar 7. However, many strains recently isolated in Florida from tomato and other crops were more diverse than the southeastern United States population. These unique Florida strains grouped with strains mostly originating from the Caribbean and Central America. One of the exotic strains, which in a previous study was determined to be established in northern Florida, was characterized more extensively. Upon using Musa-specific multiplex polymerase chain reaction, this strain produced a unique banding pattern, which has not previously been reported. Inoculation of this strain into Musa spp. did not result in wilt symptoms; however, the plants were stunted and root masses were significantly reduced. Furthermore, following root inoculation, the bacterium, unlike a typical Florida race 1 biovar 1 strain, was recovered from the roots and stems, indicating systemic movement. This is the first report of an R. solanacearum strain isolated in the United States that is deleterious to the growth of Musa plants.

Shell Mounds in the Southeast: Middens, Monuments, Temple Mounds, Rings, or Works?

2010 ◽  
Vol 75 (3) ◽  
pp. 551-570 ◽  
Author(s):  
William H. Marquardt
Keyword(s):  
United States ◽  
South Carolina ◽  
Climate Changes ◽  
Southeastern United States ◽  
Short Term ◽  
Mound Construction ◽  
Architectural Features ◽  
Shell Mounds ◽  
Shell Rings ◽  
Oriented Approach

Focusing on the southeastern United States, I provide some alternative perspectives on shell mounds previously interpreted as architectural features, temple mounds, and feasting sites. The same pattern of deposition often inferred to indicate mound construction—darker-colored, highly organic strata alternating with lighter-colored, shell-rich strata—can be accounted for by domestic midden accumulation and disposal of refuse away from living areas. Observed abundances of particular shell species can result from local or regional ecological conditions. Site complexes interpreted as architectural may have evolved largely in response to short-term climate changes. Shell rings on the Georgia and South Carolina coasts probably functioned to conserve and store unconfined water. To understand ancient shell mounds, we need a sediment-oriented approach to the study of mound deposits and more attention to the environmental contexts in which shell mounds accumulated.

scholarly journals Fungicide Rotation Programs for Managing Phytophthora Fruit Rot of Watermelon in Southeastern United States

2017 ◽  
Vol 18 (1) ◽  
pp. 28-34 ◽  
Author(s):  
Chandrasekar (Shaker) S. Kousik ◽  
Pingsheng Ji ◽  
Daniel S. Egel ◽  
Lina M. Quesada-Ocampo
Keyword(s):  
United States ◽  
South Carolina ◽  
Phytophthora Capsici ◽  
Southeastern United States ◽  
Heavy Rain ◽  
Integrated Approach ◽  
The United States ◽  
Fruit Rot ◽  
Management Options ◽  
Before And After

About 50% of the watermelons in the United States are produced in the southeastern states, where optimal conditions for development of Phytophthora fruit rot prevail. Phytophthora fruit rot significantly limits watermelon production by causing serious yield losses before and after fruit harvest. Efficacy of fungicide rotation programs and Melcast-scheduled sprays for managing Phytophthora fruit rot was determined by conducting experiments in Phytophthora capsici-infested fields at three locations in southeastern United States (North Carolina, South Carolina, and Georgia). The mini seedless cultivar Wonder and seeded cultivar Mickey Lee (pollenizer) were used. Five weekly applications of fungicides were made at all locations. Significant fruit rot (53 to 91%, mean 68%) was observed in the nontreated control plots in all three years (2013 to 2015) and across locations. All fungicide rotation programs significantly reduced Phytophthora fruit rot compared with nontreated controls. Overall, the rotation of Zampro alternated with Orondis was highly effective across three locations and two years. Rotations of Actigard followed by Ranman+Ridomil Gold, Presidio, V-10208, and Orondis, or rotation of Revus alternated with Presidio were similarly effective. Use of Melcast, a melon disease-forecasting tool, may occasionally enable savings of one spray application without significantly impacting control. Although many fungicides are available for use in rotations, under very heavy rain and pathogen pressure, the fungicides alone may not offer adequate protection; therefore, an integrated approach should be used with other management options including well-drained fields.

Recent Research Concerning the Freezing Point Value of Milk Produced in the Southeastern United States

1963 ◽  
Vol 46 (4) ◽  
pp. 732-736
Author(s):  
R W Henningson
Keyword(s):  
United States ◽  
South Carolina ◽  
Freezing Point ◽  
Southeastern United States ◽  
Fat Content ◽  
Extensive Survey ◽  
Milk Solids

Abstract In 1953 Dahlberg, et al. published the first information indicating that the freezing point value of milk produced in the Southeastern United States might be higher than commonly accepted values. An extensive survey of retail milk marketed in South Carolina during 1957 produced an unweighted average freezing point value of –0.529°C, and disclosed that the unweighted average milk solids-not-fat content of retail milk marketed in South Carolina was 8.88%. Other surveys revealed such freezing point values as –0.537, –0.540, –-0.533, –0.528, and –0.532°C. Custer and Cardwell found freezing point depressions averaging 0.025—0.030°C less for reconstituted non-fat milks of southern origin than for similar milks of northern origin. The lactose and chloride contents of these milks were lower than those of the northern milks. Problems created by high freezing point values which are intensified by the effects of vacuum pasteurization, common in the Southeastern United States, on freezing point values will be discussed.

scholarly journals A cbb3-Type Cytochrome C Oxidase Contributes to Ralstonia solanacearum R3bv2 Growth in Microaerobic Environments and to Bacterial Wilt Disease Development in Tomato

2010 ◽  
Vol 23 (8) ◽  
pp. 1042-1052 ◽  
Author(s):  
Jennifer Colburn-Clifford ◽  
Caitilyn Allen
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Wilt Disease ◽  
Wild Type ◽  
Low Oxygen ◽  
Tomato Root ◽  
Bacterial Wilt Disease ◽  
Oxygen Conditions

Ralstonia solanacearum race 3 biovar 2 (R3bv2) is an economically important soilborne plant pathogen that causes bacterial wilt disease by infecting host plant roots and colonizing the xylem vessels. Little is known about R3bv2 behavior in the host rhizosphere and early in bacterial wilt pathogenesis. To explore this part of the disease cycle, we used a novel taxis-based promoter-trapping strategy to identify pathogen genes induced in the plant rhizosphere. This screen identified several rex (root exudate expressed) genes whose promoters were upregulated in the presence of tomato root exudates. One rex gene encodes an assembly protein for a high affinity cbb3-type cytochrome c oxidase (cbb3-cco) that enables respiration in low-oxygen conditions in other bacteria. R3bv2 cbb3-cco gene expression increased under low-oxygen conditions, and a cbb3-cco mutant strain grew more slowly in a microaerobic environment (0.5% O2). Although the cco mutant could still wilt tomato plants, symptom onset was significantly delayed relative to the wild-type parent strain. Further, the cco mutant did not colonize host stems or adhere to roots as effectively as wild type. These results suggest that R3bv2 encounters low-oxygen environments during its interactions with host plants and that the pathogen depends on this oxidase to help it succeed in planta.

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