scholarly journals Progress in Developing Bacterial Spot Resistance in Tomato

Agronomy ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 26 ◽  
Author(s):  
Sadikshya Sharma ◽  
Krishna Bhattarai
Keyword(s):  
Gene Pyramiding ◽  
Weather Conditions ◽  
Disease Spread ◽  
Bacterial Spot ◽  
Hypersensitive Resistance ◽  
Solanum Lycopersicum L ◽  
Industry Standard ◽  
Bacterial Spot Resistance ◽  
Wild Accessions ◽  
Multiple Strains

Bacterial spot (BS), caused by four species of Xanthomonas: X. euvesicatoria, X. vesicatoria, X. perforans and X. gardneri in tomato (Solanum lycopersicum L.) results in severe loss in yield and quality by defoliation and the appearance of lesions on fruits, respectively. The combined industry standard for BS control (foliar applications Actigard® rotated with copper plus mancozeb) does not offer sufficient protection, especially when weather conditions favor disease spread. Development of tomato cultivars with BS resistance is thus an important measure to minimize losses. Hypersensitive and non-hypersensitive resistance has been identified in different wild accessions and cultivated tomato relatives and has been transferred to cultivated tomato. However, complete resistance is yet to be obtained. With the advent of next generation sequencing and precise genome editing tools, the genetic regions that confer resistance to bacterial spot can be targeted and enriched through gene pyramiding in a new commercial cultivar which may confer higher degree of horizontal resistance to multiple strains of Xanthomonas causing bacterial spot in tomato.

scholarly journals A Non-Hypersensitive Resistance in Pepper to the Bacterial Spot Pathogen Is Associated with Two Recessive Genes

2002 ◽  
Vol 92 (3) ◽  
pp. 273-277 ◽  
Author(s):  
J. B. Jones ◽  
G. V. Minsavage ◽  
P. D. Roberts ◽  
R. R. Johnson ◽  
C. S. Kousik ◽  
...  
Keyword(s):  
Electrolyte Leakage ◽  
Visual Assessment ◽  
Field Studies ◽  
Hypersensitive Reaction ◽  
Bacterial Spot ◽  
Similar Concentration ◽  
Hypersensitive Resistance ◽  
Growth Room ◽  
Recessive Genes ◽  
Bacterial Spot Resistance

The pepper genotype, ECW-12346, was developed with bacterial spot resistance derived from Pep13, PI 271322, and ECW123 (Early Calwonder containing Bs1, Bs2, and Bs3 genes). For genetic analysis of this resistance, ECW12346, ECW123, F1, F2, and backcrosses were inoculated with a pepper race 6 (P6) strain. Two recessive genes were identified that determined resistance. The genes are designated bs5 and bs6 for the resistance derived from PI 271322 and Pep13, respectively. In greenhouse and field studies, ECW12346 was highly resistant, whereas ECW123 had significant defoliation. In growth-room studies, electrolyte leakage and population dynamics were determined. Following infiltration of both genotypes with 108 CFU/ml of a P6 strain, there was no rapid increase in electrolyte leakage within 72 h, whereas a rapid increase in electrolyte leakage occurred within 24 h when a similar concentration of a P3 strain (containing the avrBs2 gene) was infiltrated into the intercellular spaces of the leaf. When 105 CFU/ml of a P6 strain was infiltrated into leaves, complete tissue collapse was evident in ECW123 10 days later as determined by visual assessment and electrolyte leakage data, but no confluent necrosis was detected in ECW12346. Internal populations were at least two logarithmic units higher in ECW123 than in ECW12346. Therefore, ECW12346 inhibits population build-up without inducing the typical hypersensitive reaction characterized by an increase in electrolyte leakage.

scholarly journals Protecting vegetable cultivars in Brazil: a chili pepper case-study research

2016 ◽  
Vol 34 (2) ◽  
pp. 161-167 ◽  
Author(s):  
Samy Pimenta ◽  
Rosana Rodrigues ◽  
Cláudia P Sudré ◽  
João GT Moraes ◽  
Cíntia S Bento ◽  
...  
Keyword(s):  
Recombinant Inbred Lines ◽  
Block Design ◽  
Case Study Research ◽  
Fruit Shape ◽  
Bacterial Spot ◽  
Randomized Block Design ◽  
Dus Testing ◽  
Bacterial Spot Resistance ◽  
Test Requirements ◽  
L1 And L2

ABSTRACT: In all countries, members of the UPOV (Union Internationale pour la Protection des Obtentions Végétales), of which Brazil is a signatory, to protect a new plant variety is necessary to carry out DUS (Distinctness, Uniformity and Stability) tests. DUS testing forCapsicum spp. is based on 48 descriptors, which involve qualitative and quantitative traits, observed from germination to fruit harvest. This paper describes the performance of DUS tests on lines of chili peppers, which are candidates for protection; we discuss the main aspects related to operational difficulties, the relevance of some descriptors for the protection process and highlight the importance of protecting new plant varieties as national intellectual property. Four C. annuum var.annuum recombinant inbred lines were tested. The Capsicum Breeding Program of the Universidade Estadual do Norte Fluminense Darcy Ribeiro developed the lines, which are resistant to bacterial spot. They were tested under greenhouse conditions from June to November 2013; and from January to July 2014 in Campos dos Goytacazes, Rio de Janeiro State, Brazil. The 'Jalapeño M' commercial genotype was used as control and treatments were arranged in a randomized block design with seven plants per plot with five replications. Besides the 48 descriptors, stipulated by legislation for Capsicum DUS testing, we included a descriptor for bacterial spot resistance. The descriptors that enabled distinction varied with each line. Although being distinctive for some descriptors, L1 and L2 lines were neither homogeneous nor stable. L6 and L8 recombined lines were characterized by homogeneity and stability. Fruit shape, capsaicin presence, number of days for flowering and bacterial spot resistance were descriptors that allowed for differentiation between treatments. In conclusion, the L6 and L8 recombined lines met the DUS test requirements; therefore, they may be subjected to the protection process with the Brazilian Ministry of Agriculture, Livestock and Food Supply.

scholarly journals Characterization of Hypersensitive Resistance to Bacterial Spot Race T3 (Xanthomonas perforans) from Tomato Accession PI 128216

2009 ◽  
Vol 99 (9) ◽  
pp. 1037-1044 ◽  
Author(s):  
Matthew D. Robbins ◽  
Audrey Darrigues ◽  
Sung-Chur Sim ◽  
Mohammed Abu Taher Masud ◽  
David M. Francis
Keyword(s):  
Gene Dosage ◽  
Hypersensitive Reaction ◽  
Recurrent Parent ◽  
Chromosome 6 ◽  
Chromosome 11 ◽  
Bacterial Spot ◽  
Hypersensitive Resistance ◽  
Xanthomonas Perforans ◽  
Additive Gene ◽  
Candidate Loci

Bacterial spot of tomato is caused by four species of Xanthomonas. The accession PI 128216 (Solanum pimpinellifolium) displays a hypersensitive reaction (HR) to race T3 strains (predominately Xanthomonas perforans). We developed an inbred backcross (IBC) population (BC2S5, 178 families) derived from PI 128216 and OH88119 (S. lycopersicum) as the susceptible recurrent parent for simultaneous introgression and genetic analysis of the HR response. These IBC families were evaluated in the greenhouse for HR to race T3 strain Xcv761. The IBC population was genotyped with molecular markers distributed throughout the genome in order to identify candidate loci conferring resistance. We treated the IBC population as a hypothesis forming generation to guide validation in subsequent crosses. Nonparametric analysis identified an association between HR and markers clustered on chromosome 11 (P < 0.05 to 0.0001) and chromosome 6 (0.04 > P > 0.002). Further analysis of the IBC population suggested that markers on chromosome 6 and 11 failed to assort independently, a phenomenon known as gametic phase disequilibrium. Therefore, to validate marker-trait linkages, resistant IBC plants were crossed with OH88119 and BC3F2 progeny were evaluated for HR in the greenhouse. In these subsequent populations, the HR response was associated with the chromosome 11 markers (P < 0.0002) but not with the markers on chromosome 6 (P > 0.25). Independent F2 families were developed by crossing resistant IBC lines to OH8245, OH88119, and OH7530. These populations were genotyped, organized into classes based on chromosome 11 markers, and evaluated for resistance in the field. The PI 128216 locus on chromosome 11 provided resistance that was dependent on gene dosage and genetic background. These results define a single locus, Rx-4, from PI 128216, which provides resistance to bacterial spot race T3, has additive gene action, and is located on chromosome 11.

scholarly journals Techniques for screening Cercospora leaf spot resistant fenugreek genotypes

2019 ◽  
Vol 99 (3) ◽  
pp. 324-337
Author(s):  
U. Subedi ◽  
S. Acharya ◽  
S. Chatterton ◽  
J. Thomas ◽  
D. Friebel
Keyword(s):  
Leaf Spot ◽  
Weather Conditions ◽  
Disease Spread ◽  
Temperature Sensitive ◽  
Cercospora Leaf Spot ◽  
Legume Crop ◽  
Whole Plant ◽  
Crop Field ◽  
Plant Assays ◽  
Trigonella Foenum Graecum L

Cercospora leaf spot (CLS) caused by Cercospora traversiana is an important phyto-pathological problem of fenugreek (Trigonella foenum-graecum L.), a multiuse legume crop. Field screenings for resistant plants, although accurate and effective, demand significant time and a sizable workforce to accomplish. Also, weather conditions in the field may not always be favourable for uniform disease spread, which eventually may lead to failure of the overall experiment. Whole-plant assays (WPA) and detached leaf assays (DLA) with artificial inoculation not only help in scaling up the number of plants screened but also reduce the space, time, and amount of inoculum needed for the experiment. The results from our two experiments indicate that both the WPA and DLA methods can be used reliably to differentiate resistant and susceptible genotypes of fenugreek. In addition, the correlation coefficient between WPA and DLA (r = 0.875, P < 0.01), derived from the mean disease score of each genotype, shows that they can be used interchangeably while screening fenugreek for CLS. DLA was found to be temperature-sensitive for the development of CLS symptoms and wounded leaves developed symptoms faster than non-wounded leaves. These indoor methods can be used for the development of CLS-resistant fenugreek cultivars in areas where disease development is difficult under field conditions.

scholarly journals Comparison of Resistant Cultivars for Management of Bacterial Spot in Peppers

1999 ◽  
Vol 9 (4) ◽  
pp. 645-655
Author(s):  
Brent Rowell ◽  
R. Terry Jones ◽  
William Nesmith ◽  
John C. Snyder
Keyword(s):  
Capsicum Annuum ◽  
Xanthomonas Campestris ◽  
Bell Pepper ◽  
Bacterial Spot ◽  
Eastern Kentucky ◽  
Breeding Lines ◽  
Resistant Cultivars ◽  
Bacterial Spot Resistance ◽  
Free Environment

Bacterial spot epidemics, caused by Xanthomonas campestris pv. vesicatoria (Doidge) Dye, continue to plague bell pepper (Capsicum annuum L.) growers in a number of southern and midwestern states. A 3-year study designed to compare cultivars and breeding lines under induced bacterial spot epidemic and bacterial spot-free conditions began soon after the first release of cultivars having the Bs2 gene for resistance to races 1 to 3 of the pathogen. Bacterial spot epidemics were created by transplanting `Merlin' plants (inoculated with races 1 to 3) into plots of each test cultivar at an isolated location in eastern Kentucky. Plots of the same trial entries at a second location were kept free of bacterial spot for 2 of the 3 years of trials; however, a moderate natural epidemic occurred at this location in 1996. Bacterial spot resistance had the greatest impact on yields and returns per acre in the inoculated trials. Cultivars with only Bs1 or a combination of Bs1 and Bs3 were highly susceptible in the inoculated trials. There were statistically significant and economically important differences in resistance among cultivars and breeding lines having the Bs2 gene; some were nearly as susceptible as susceptible checks. Although many Bs2-gene cultivars showed satisfactory levels of resistance, only a few were highly resistant, horticulturally acceptable, and comparable in yields to the best susceptible hybrids in a bacterial spot-free environment.

Association Analysis for Bacterial Spot Resistance in a Directionally Selected Complex Breeding Population of Tomato

2015 ◽  
Vol 105 (11) ◽  
pp. 1437-1445 ◽  
Author(s):  
Sung-Chur Sim ◽  
Matthew D. Robbins ◽  
Saranga Wijeratne ◽  
Hui Wang ◽  
Wencai Yang ◽  
...  
Keyword(s):  
Single Point ◽  
Breeding Population ◽  
Field Trials ◽  
Chromosome 11 ◽  
Bacterial Spot ◽  
Model Based Clustering ◽  
Breeding Populations ◽  
Q Matrix ◽  
Bacterial Spot Resistance ◽  
Genomic Regions

Bacterial spot of tomato is caused by at least four species of Xanthomonas with multiple physiological races. We developed a complex breeding population for simultaneous discovery of marker-trait linkage, validation of existing quantitative trait loci (QTL), and pyramiding of resistance. Six advanced accessions with resistance from distinct sources were crossed in all combinations and their F1 hybrids were intercrossed. Over 1,100 segregating progeny were evaluated in the field following inoculation with X. euvesicatoria race T1 strains. We selected 5% of the most resistant and 5% of the most susceptible progeny for evaluation as plots in two subsequent replicated field trials inoculated with T1 and T3 (X. perforans) strains. The estimated heritability of T1 resistance was 0.32. In order to detect previously reported resistance genes, as well as novel QTL, we explored methods to correct for population structure and analysis based on single markers or haplotypes. Both single-point and haplotype analyses identified strong associations in the genomic regions known to carry Rx-3 (chromosome 5) and Rx-4/Xv3 (chromosome 11). Accounting for kinship and structure generally improved the fit of statistical models. Detection of known loci was improved by adding kinship or a combination of kinship and structure using a Q matrix from model-based clustering. Additional QTL were detected on chromosomes 1, 4, 6, and 7 for T1 resistance and chromosomes 2, 4, and 6 for T3 resistance (P < 0.01). Haplotype analysis improved our ability to trace the origin of positive alleles. These results demonstrate that both known and novel associations can be identified using complex breeding populations that have experienced directional selection.

BACTERIAL SPOT RESISTANCE IN PEACH: FUNCTIONAL ALLELE DISTRIBUTION IN BREEDING GERMPLASM

2015 ◽  
pp. 69-74 ◽  
Author(s):  
K. Gasic ◽  
G. Reighard ◽  
W. Okie ◽  
J. Clark ◽  
T. Gradziel ◽  
...  
Keyword(s):  
Bacterial Spot ◽  
Allele Distribution ◽  
Functional Allele ◽  
Bacterial Spot Resistance ◽  
Breeding Germplasm
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