scholarly journals Advances and Challenges in Bacterial Spot Resistance Breeding in Tomato (Solanum lycopersicum L.)

2020 ◽  
Vol 21 (5) ◽  
pp. 1734
Author(s):  
Pragya Adhikari ◽  
Tika B. Adhikari ◽  
Frank J. Louws ◽  
Dilip R. Panthee
Keyword(s):  
Quantitative Resistance ◽  
Durable Resistance ◽  
Resistance Breeding ◽  
Field Resistance ◽  
Control Measures ◽  
Current Status ◽  
Linkage Drag ◽  
Bacterial Spot ◽  
Regulatory Processes ◽  
Solanum Lycopersicum L

Bacterial spot is a serious disease of tomato caused by at least four species of Xanthomonas. These include X. euvesicatoria (race T1), X. vesicatoria (race T2), X. perforans (races T3 and T4), and X. gardneri, with the distinct geographical distribution of each group. Currently, X. gardneri and X. perforans are two major bacterial pathogens of tomato in North America, with X. perforans (race T4) dominating in east-coast while X. gardneri dominating in the Midwest. The disease causes up to 66% yield loss. Management of this disease is challenging due to the lack of useful chemical control measures and commercial resistant cultivars. Although major genes for resistance (R) and quantitative resistance have been identified, breeding tomato for resistance to bacterial spot has been impeded by multiple factors including the emergence of new races of the pathogen that overcome the resistance, multigenic control of the resistance, linkage drag, non-additive components of the resistance and a low correlation between seedling assays and field resistance. Transgenic tomato with Bs2 and EFR genes was effective against multiple races of Xanthomonas. However, it has not been commercialized because of public concerns and complex regulatory processes. The genomics-assisted breeding, effectors-based genomics breeding, and genome editing technology could be novel approaches to achieve durable resistance to bacterial spot in tomato. The main goal of this paper is to understand the current status of bacterial spot of tomato including its distribution and pathogen diversity, challenges in disease management, disease resistance sources, resistance genetics and breeding, and future prospectives with novel breeding approaches.

scholarly journals Characterization and elimination of linkage-drag associated with Fusarium wilt race 3 resistance genes

2021 ◽  
Author(s):  
Jessica Chitwood-Brown ◽  
Gary E. Vallad ◽  
Tong Geon Lee ◽  
Samuel F. Hutton
Keyword(s):  
Fusarium Wilt ◽  
Host Resistance ◽  
Management Strategy ◽  
Durable Resistance ◽  
Fruit Size ◽  
Linkage Drag ◽  
Effective Management ◽  
Bacterial Spot ◽  
Breeding Lines ◽  
Increased Sensitivity

Abstract Key message Reducing the size of the I-3 introgression resulted in eliminating linkage-drag contributing to increased sensitivity to bacterial spot and reduced fruit size. The I-7 gene was determined to have no effect on bacterial spot or fruit size, and germplasm is now available with both the reduced I-3 introgression and I-7. Abstract Tomato (Solanum lycopersicum) production is increasingly threatened by Fusarium wilt race 3 (Fol3) caused by the soilborne fungus, Fusarium oxysporum f. sp. lycopersici. Although host resistance based on the I-3 gene is the most effective management strategy, I-3 is associated with detrimental traits including reduced fruit size and increased bacterial spot sensitivity. Previous research demonstrated the association with bacterial spot is not due to the I-3 gene, itself, and we hypothesize that reducing the size of the I-3 introgression will remedy this association. Cultivars with I-7, an additional Fol3 resistance gene, are available but are not widely used commercially, and it is unclear whether I-7 also has negative horticultural associations. To characterize the effect of I-3 on fruit size, segregating populations were developed and evaluated, revealing that the large I-3 introgression decreased fruit size by approximately 21%. We reduced the I-3 introgression from 5 to 140 kb through successive recombinant screening and crossing efforts. The reduced I-3 introgression and I-7 were then separately backcrossed into elite Florida breeding lines and evaluated for effects on bacterial spot sensitivity and fruit size across multiple seasons. The reduced I-3 introgression resulted in significantly less bacterial spot and larger fruit size than the large introgression, and it had no effect on these horticultural characteristics compared with Fol3 susceptibility. I-7 was also found to have no effect on these traits compared to Fol3 susceptibility. Together, these efforts support the development of superior Fol3-resistant cultivars and more durable resistance against this pathogen.

scholarly journals Qualitative and Quantitative Late Blight Resistance in the Potato Cultivar Sarpo Mira Is Determined by the Perception of Five Distinct RXLR Effectors

2012 ◽  
Vol 25 (7) ◽  
pp. 910-919 ◽  
Author(s):  
Hendrik Rietman ◽  
Gerard Bijsterbosch ◽  
Liliana M. Cano ◽  
Heung-Ryul Lee ◽  
Jack H. Vossen ◽  
...  
Keyword(s):  
Late Blight ◽  
Quantitative Resistance ◽  
Durable Resistance ◽  
Potato Cultivar ◽  
Field Resistance ◽  
R Gene ◽  
R Genes ◽  
Qualitative And Quantitative ◽  
Rxlr Effectors ◽  
Sarpo Mira

Potato defends against Phytophthora infestans infection by resistance (R)-gene-based qualitative resistance as well as a quantitative field resistance. R genes are renowned to be rapidly overcome by this oomycete, and potato cultivars with a decent and durable resistance to current P. infestans populations are hardly available. However, potato cultivar Sarpo Mira has retained resistance in the field over several years. We dissected the resistance of ‘Sarpo Mira’ in a segregating population by matching the responses to P. infestans RXLR effectors with race-specific resistance to differential strains. The resistance is based on the combination of four pyramided qualitative R genes and a quantitative R gene that was associated with field resistance. The qualitative R genes include R3a, R3b, R4, and the newly identified Rpi-Smira1. The qualitative resistances matched responses to avirulence (AVR)3a, AVR3b, AVR4, and AVRSmira1 RXLR effectors and were overcome by particular P. infestans strains. The quantitative resistance was determined to be conferred by a novel gene, Rpi-Smira2. It was only detected under field conditions and was associated with responses to the RXLR effector AvrSmira2. We foresee that effector-based resistance breeding will facilitate selecting and combining qualitative and quantitative resistances that may lead to a more durable resistance to late blight.

Current Status of Knowledge and Awareness of Diabetes Mellitus in Saudi Arabia

2020 ◽  
Vol 16 ◽  
Author(s):  
Asirvatham Alwin Robert ◽  
Ahmad Dakeel Al Awad ◽  
Mohamed Abdulaziz Al Dawish
Keyword(s):  
Diabetes Mellitus ◽  
Saudi Arabia ◽  
Disease Risk ◽  
Current Knowledge ◽  
Adult Population ◽  
Management Training ◽  
Control Measures ◽  
Current Status ◽  
Treatment Modalities ◽  
The Government

Abstract: Diabetes mellitus (DM) is a chronic disease, and the complications may be life-threatening; however, with proper treatment and control measures, it can be very well-managed. Self-management training and education of diabetes are critical in diabetes care and management. It is essential that patients with diabetes must have a comprehensive understanding of the nature of the disease, risk factors, complications, and possible treatment modalities to attenuate the complications. Over the last few years, DM in Saudi Arabia has been rapidly growing at an alarming rate. It has affected around one-fifth of the adult population, and by 2030, the numbers are predicted to rise further and exceed more than double the present number. An estimated tenfold increase has been reported over the past three decades in Saudi Arabia. However, there has not been much research focusing on understanding the knowledge and awareness of DM in Saudi Arabia as compared to developed nations. This review aims to present an overview of the current knowledge and awareness level of DM among the population of Saudi Arabia through an extensive review of the currently available literature. The review findings could be of immense assistance to the government, healthcare systems, educational institutions, and researchers to develop evidence-based programs, policies, and guidelines towards increasing the knowledge and awareness about diabetes and its management, so that early detection and management can be ensured to control the escalating burden of diabetes, in Saudi Arabia.

scholarly journals Leishmaniasis: Current Status of Vaccine Development

2001 ◽  
Vol 14 (2) ◽  
pp. 229-243 ◽  
Author(s):  
Emanuela Handman
Keyword(s):  
Dna Sequences ◽  
Vaccine Development ◽  
Development Program ◽  
Skin Lesions ◽  
Mononuclear Phagocytes ◽  
Control Measures ◽  
Host Susceptibility ◽  
Current Status ◽  
Dna Encoding ◽  
And Control

SUMMARY Leishmaniae are obligatory intracellular protozoa in mononuclear phagocytes. They cause a spectrum of diseases, ranging in severity from spontaneously healing skin lesions to fatal visceral disease. Worldwide, there are 2 million new cases each year and 1/10 of the world's population is at risk of infection. To date, there are no vaccines against leishmaniasis and control measures rely on chemotherapy to alleviate disease and on vector control to reduce transmission. However, a major vaccine development program aimed initially at cutaneous leishmaniasis is under way. Studies in animal models and humans are evaluating the potential of genetically modified live attenuated vaccines, as well as a variety of recombinant antigens or the DNA encoding them. The program also focuses on new adjuvants, including cytokines, and delivery systems to target the T helper type 1 immune responses required for the elimination of this intracellular organism. The availability, in the near future, of the DNA sequences of the human and Leishmania genomes will extend the vaccine program. New vaccine candidates such as parasite virulence factors will be identified. Host susceptibility genes will be mapped to allow the vaccine to be targeted to the population most in need of protection.

scholarly journals Analysis of Sequenced Genomes of Xanthomonas perforans Identifies Candidate Targets for Resistance Breeding in Tomato

2016 ◽  
Vol 106 (10) ◽  
pp. 1097-1104 ◽  
Author(s):  
Sujan Timilsina ◽  
Peter Abrahamian ◽  
Neha Potnis ◽  
Gerald V. Minsavage ◽  
Frank F. White ◽  
...  
Keyword(s):  
Resistance Breeding ◽  
Effector Protein ◽  
Bacterial Disease ◽  
Bacterial Spot ◽  
Genome Sequences ◽  
Xanthomonas Perforans ◽  
Modern Agriculture ◽  
Rapid Changes ◽  
Pathogen Populations ◽  
Race 4

Bacterial disease management is a challenge for modern agriculture due to rapid changes in pathogen populations. Genome sequences for hosts and pathogens provide detailed information that facilitates effector-based breeding strategies. Tomato genotypes have gene-for-gene resistance to the bacterial spot pathogen Xanthomonas perforans. The bacterial spot populations in Florida shifted from tomato race 3 to 4, such that the corresponding tomato resistance gene no longer recognizes the effector protein AvrXv3. Genome sequencing showed variation in effector profiles among race 4 strains collected in 2006 and 2012 and compared with a race 3 strain collected in 1991. We examined variation in putative targets of resistance among Florida strains of X. perforans collected from 1991 to 2006. Consistent with race change, avrXv3 was present in race 3 strains but nonfunctional in race 4 strains due to multiple independent mutations. Effectors xopJ4 and avrBs2 were unchanged in all strains. The effector avrBsT was absent in race 3 strains collected in the 1990s but present in race 3 strains collected in 2006 and nearly all race 4 strains. These changes in effector profiles suggest that xopJ4 and avrBsT are currently the best targets for resistance breeding against bacterial spot in tomato.

Genetic Diversity, Identification and Utilization of Novel Genetic Resources for Resistance to Meloidogyne incognita in Mulberry (Morus spp.)

Plant Disease ◽  
2021 ◽  
Author(s):  
Gondi S Arunakumar ◽  
Belaghihalli Nanjappa Gnanesh ◽  
Haniyambadi B Manojkumar ◽  
Doss S. Gandhi ◽  
Mogili Thallapally ◽  
...  
Keyword(s):  
Ssr Markers ◽  
Resistance Breeding ◽  
Field Resistance ◽  
Infested Soil ◽  
Root Knot Nematode ◽  
Sources Of Resistance ◽  
Molecular Variance ◽  
Morus Spp ◽  
Principle Coordinate Analysis ◽  
Germplasm Accessions

Mulberry (Morus spp.) is an important crop in the sericulture industry as the leaves constitute the primary feed for the silkworm. The availability of diverse genetic sources of resistance to root- knot nematode (RKN; Meloidogyne spp.) are very scanty and therefore, a set of 415 varied exotic and indigenous germplasm accessions were screened under glasshouse conditions. Twenty one accessions were identified as highly resistant and 48 were resistant, the highest numbers of highly resistant/resistant accessions were found in Morus alba. Further, thirty accessions based on rooting ability were evaluated for field resistance at four different locations with infested soil. Finally, eight germplasm accessions; BR-8, Karanjtoli-1, Hosur-C8, Nagalur Estate, Tippu, Calabresa, Thai Pecah and SRDC-3 were identified as potential genetic sources in RKN resistance breeding programs or as resistant rootstock for the establishment of mulberry gardens. Sixteen SSR markers analyzed among the 77 resistant and susceptible accessions, generated 55 alleles, ranging from 2 to 5 with an average of 3.43 alleles per locus. Principle coordinate analysis grouped the accessions on the basis of RKN susceptible and resistant to a greater extent. The RKN susceptible accessions exhibited higher variability as compared to resistant accessions and they were more dispersed. Analysis of molecular variance showed that maximum molecular variance (78%) within the population and 22% between populations. Results of this study indicate that SSR markers are reliable for assessing genetic variability among the RKN resistant and susceptible mulberry accessions.

scholarly journals The 12th I. E. Melhus Graduate Student Symposium: Host Plant Resistance and Disease Management, Current Status, and Future Outlook

2013 ◽  
Vol 14 (1) ◽  
pp. 28
Author(s):  
C. S. Kousik
Keyword(s):  
Disease Management ◽  
Host Plant ◽  
Annual Meeting ◽  
Graduate Student ◽  
Plant Resistance ◽  
Host Plant Resistance ◽  
Resistance Breeding ◽  
Current Status ◽  
American Phytopathological Society ◽  
Future Outlook

The 12th I. E. Melhus Graduate Student Symposium was held at the 2012 annual meeting of the American Phytopathological Society in Providence, RI. Its theme was “Host Plant Resistance and Disease Management: Current Status and Future Outlook.” The symposium featured four graduate student presentations highlighting research that leads to a better understanding of host plant resistance, resistance breeding, and disease management. Accepted for publication 6 November 2013. Published 25 November 2013.

scholarly journals Current status of major foodborne and waterborne viral infections and their prevention strategies

2021 ◽  
Vol 7 (3) ◽  
pp. 227-241
Author(s):  
Ahmet Gökhan Coşkun ◽  
Ayşegül Demircioğlu ◽  
Seran Temelli ◽  
Ayşegül Eyigör
Keyword(s):  
Viral Infections ◽  
Hemorrhagic Fever ◽  
Diagnostic Techniques ◽  
Control Measures ◽  
Current Status ◽  
Waterborne Diseases ◽  
Antiviral Compounds ◽  
Current Prevalence ◽  
Haccp System ◽  
Waterborne Viruses

Advances in diagnostic techniques and their widespread use for infectious agents revealed the considerably high current prevalence of viral agents in foodborne and waterborne diseases. Foodborne and waterborne viruses are indicated to cause not only gastroenteritis and hepatitis but also neurological disorders, respiratory tract diseases, myocarditis, glomerulonephritis and hemorrhagic fever, with a particularly high mortality rate in infants/children and in individuals with immune deficiency. Additionally, due to their resistance to environmental conditions and food processes compared to other microorganisms, elimination of these viruses by heat and high pressure applications, natural antiviral compounds, UV applications and conventional cleaning-disinfection remains difficult even inadequate. In protection from viral infections, vaccine applications together with GMP, GHP and HACCP system approaches in production seem to be the most effective approaches to ensure the minimization of viruses in food environment and in public. In this review article, up-to-date information is presented on the general characteristics and the diseases caused by enterotropic viruses; NoV, AstV, RoV, AdV and hepatotropic viruses; HAV and HEV, with a particularly high worldwide prevalence, as well as their epidemiology, prevention and their control measures.

Advances in breeding techniques for durable Septoria tritici blotch (STB) resistance in cereals

2021 ◽  
pp. 303-356
Author(s):  
Harsh Raman ◽  
Keyword(s):  
Quantitative Resistance ◽  
Durable Resistance ◽  
Genetic Resistance ◽  
Septoria Tritici Blotch ◽  
Septoria Tritici ◽  
Zymoseptoria Tritici ◽  
Winter Cereal ◽  
Cereal Breeding ◽  
Qualitative Resistance ◽  
Breeding Techniques

Septoria tritici blotch (STB), caused by the hemibiotrophic fungus Zymoseptoria tritici, is one of the most important foliar diseases of winter cereal crops. Recent advances are helping to understand the genetic basis and architecture of resistance to STB. To date, at least 22 genes for qualitative resistance and over 200 quantitative trait loci (QTL) for quantitative resistance have been identified in cereals. This knowledge is enabling cereal breeding programs to develop varieties with more durable resistance to STB. This chapter reviews recent research on genetic resistance loci and breeding strategies based on both conventional and biotechnology-based breeding approaches (molecular marker/genomic-assisted breeding, genetic transformation, and gene-editing) to achieve achieving durable resistance to STB infection and minimise grain yield losses.

scholarly journals Race structure of cowpea witchweed (Striga gesnerioides) in West Africa and its implications for Striga resistance breeding of cowpea

Weed Science ◽  
2020 ◽  
Vol 68 (2) ◽  
pp. 125-133 ◽  
Author(s):  
Erik W. Ohlson ◽  
Michael P. Timko
Keyword(s):  
West Africa ◽  
Resistance Genes ◽  
Broad Spectrum ◽  
Genetic Relatedness ◽  
Durable Resistance ◽  
Resistance Breeding ◽  
Differential Resistance ◽  
African Countries ◽  
Sources Of Resistance ◽  
Striga Gesnerioides

AbstractCowpea witchweed [Striga gesnerioides (Willd.) Vatke] is a primary constraint of cowpea [Vigna unguiculata (L.) Walp.] production in West Africa. Previously, seven S. gesnerioides races were classified based upon host specificity and genotypic profiling. Because race number and distribution are dynamic systems influenced by gene flow, genetic drift, and natural selection, a thorough investigation of S. gesnerioides diversity and the effectiveness of known sources of resistance in cowpea is needed to develop varieties with durable and broad-spectrum Striga resistance. In this study, we screened seven cowpea lines against 58 unique S. gesnerioides populations collected from across nine West African countries. Individuals from 10 S. gesnerioides populations were genotyped with simple sequence repeat (SSR) markers. We identified six races of S. gesnerioides based on their parasitism of the seven cowpea lines with known differential resistance genotypes. No cowpea line was resistant to all 58 Striga populations and none of the Striga populations were able to overcome the resistance of all seven lines. A novel race, SG6, of the parasite collected from Kudu, Nigeria, was found to overcome more cowpea resistance genes than any previously reported race. SSR analysis indicates that Striga populations are highly differentiated and genetic relatedness generally corresponds with geographic proximity rather than their host compatibility. Due to the dearth of broad-spectrum resistance found among Striga-resistant cowpea lines, there exists a need to stack multiple Striga resistance genes in order to confer broad-spectrum and durable resistance.

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