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Post by nathalia on Sept 7, 2015 17:06:43 GMT -6
www.sciencedaily.com/releases/2011/01/110118101606.htmThe above link to Science News released on February 17, 2011 that mentioned new breeding lines of Romaine lettuce developed in California to have disease resistance against Lettuce necrotic stunt virus. The article mentioned that California and Arizona together account for more than 95% of lettuce production in United States and the virus had been responsible for approx. 60% crop losses resulting in major setback to the growers. The work was published in HortScience: Ivan Simko, Ryan J. Hayes, Krishna V. Subbarao, and Rebecca Grube Sideman. SM09A and SM09B: Romaine Lettuce Breeding Lines Resistant to Dieback and with Improved Shelf Life. HortScience, 2010; 45: 670-672. I have a question about resistance. Since only romaine lettuce cultivars are resistant to lettuce die back disease and viruses are changing quite often, I was wondering if the resistance found in romaine lettuce can be considered durable resistance. Have you found anything about durable resistance to this disease? Is there any report of a cultivar that was resistant but resistance was broken? |
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Post by omararias on Sept 7, 2015 20:18:36 GMT -6
www.sciencedaily.com/releases/2011/01/110118101606.htmThe above link to Science News released on February 17, 2011 that mentioned new breeding lines of Romaine lettuce developed in California to have disease resistance against Lettuce necrotic stunt virus. The article mentioned that California and Arizona together account for more than 95% of lettuce production in United States and the virus had been responsible for approx. 60% crop losses resulting in major setback to the growers. The work was published in HortScience: Ivan Simko, Ryan J. Hayes, Krishna V. Subbarao, and Rebecca Grube Sideman. SM09A and SM09B: Romaine Lettuce Breeding Lines Resistant to Dieback and with Improved Shelf Life. HortScience, 2010; 45: 670-672. I have a question about resistance. Since only romaine lettuce cultivars are resistant to lettuce die back disease and viruses are changing quite often, I was wondering if the resistance found in romaine lettuce can be considered durable resistance. Have you found anything about durable resistance to this disease? Is there any report of a cultivar that was resistant but resistance was broken? Unfortunately, I haven't been able to find any information related to broken resistance, what I was able to find is that the feature can actually be inherited by a dominant allele at a single locus (gene Tvr1) with an offspring that hasn't shown any decreasing level of resistance. But I regard that eventually the virus will develop some way to overcome that difficulty and will modify its machinery in order to infect the host. Wintermantel, W., Hand, P., Aburomia, R., Pink, D., Ryder E. (2005). Genetic analysis and mapping of resistance to lettuce dieback: a soilborne disease caused by tombusviruses.Theor Appl Genet;110(2):259-68. |
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Post by ravendra on Sept 8, 2015 9:27:42 GMT -6
www.sciencedaily.com/releases/2011/01/110118101606.htmThe above link to Science News released on February 17, 2011 that mentioned new breeding lines of Romaine lettuce developed in California to have disease resistance against Lettuce necrotic stunt virus. The article mentioned that California and Arizona together account for more than 95% of lettuce production in United States and the virus had been responsible for approx. 60% crop losses resulting in major setback to the growers. The work was published in HortScience: Ivan Simko, Ryan J. Hayes, Krishna V. Subbarao, and Rebecca Grube Sideman. SM09A and SM09B: Romaine Lettuce Breeding Lines Resistant to Dieback and with Improved Shelf Life. HortScience, 2010; 45: 670-672. I have a question about resistance. Since only romaine lettuce cultivars are resistant to lettuce die back disease and viruses are changing quite often, I was wondering if the resistance found in romaine lettuce can be considered durable resistance. Have you found anything about durable resistance to this disease? Is there any report of a cultivar that was resistant but resistance was broken? Nathalia, it's not only Romaine lettuce but leafy lettuce cultivars are also resistant against the Lettuce necrotic stunt virus infection. The lines have been developed and commercialized in CA and AZ. I think the resistance developed in these breeding lines is durable and I havn't come across any reports So far that discusses breaking of resistance. The following link will direct you to the paper that identified a molecular marker that is tightly linked to the Tvr1 gene conferring durable resistance, a feature that reduces the need for field-based screening and would accelerate development of resistant cultivars (Ivan Simko et al. 2009, DOI: 10.1186/1471-2229-9-135). link.springer.com/article/10.1186/1471-2229-9-135/fulltext.html
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Post by nathalia on Sept 8, 2015 19:09:44 GMT -6
Awesome! Thank you Omar and Ravendra for the information.
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Post by gabriela on Sept 10, 2015 11:49:19 GMT -6
Is awesome that they have new lines that are resistant to the virus. The resistance was developed by natural breeding technologies. Such as pedigree selection and internal crosses between the population, preforming mechanisms and by infection-induced responses of the immune system of the plant. So that defense-activativation occurs and "defense compounds" can move cell-to-cell and systemically through the plant vascular system I will assume that the answer is yes, right?, because the incorporation of genes in lettuce will turn in the GMOs dilemma that occurs in banana crops as well.
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Post by dulanjani on Sept 12, 2015 21:53:23 GMT -6
Great job on the presentation! It was very interesting. This virus intrigued me because normally viruses survive in a vector or in a host. This one does not have a vector (identified so far). How long could this virus survive in the soil or in water in the absence of a susceptible lettuce cultivar. Also, is there any other host besides lettuce that has been reported? Yes, the Lettuce necrotic stunt virus has a wide host range similar to the other tombusviruses. The host range lies within multiple families including Amaranthaceae, Brassicaceae, Apiaceae, Chenopodiaceae, Compositae, Caryophyllaceae, and Cucurbitaceae. In most of the cases the virus produces local lesions in the inoculated leaves. One of the papers attached in above posts has all the detailed information on the host range studies carried out. Hi i am also very curious about the question that Nathalia asked, How can a virus survive in soil or water without a host? |
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Post by ravendra on Sept 13, 2015 6:15:11 GMT -6
Yes, the Lettuce necrotic stunt virus has a wide host range similar to the other tombusviruses. The host range lies within multiple families including Amaranthaceae, Brassicaceae, Apiaceae, Chenopodiaceae, Compositae, Caryophyllaceae, and Cucurbitaceae. In most of the cases the virus produces local lesions in the inoculated leaves. One of the papers attached in above posts has all the detailed information on the host range studies carried out. Hi i am also very curious about the question that Nathalia asked, How can a virus survive in soil or water without a host? Viruses usually survive outside their host for long periods of time and stay inactive. When viruses come in contact with host they become active because they hijack cellular machinery of the host to reproduce. In case of Lettuce necrotic stunt virus, this survives in soil and/or water in inactivated state for very long periods of time which is very typical to the virus survival outside their host. |
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Post by ravendra on Sept 13, 2015 6:35:20 GMT -6
As Dr. Verchot mentioned to not to refer to the published paper when discussing on the board rather provide information in our words, in that attempt, I am herewith providing information from a paper that identified and characterized Lettuce necrotic stunt virus for the first time....
A soilborne disease of lettuce characterized by chlorosis, mottling, and necrosis of older leaves, general stunting, and dieback was first reported from California and Arizona in the 1920s in crisphead lettuce cv. New York. This disease was referred to as “brown blight”, but the causal agent of this disease was not identified because it disappeared after introduction of resistant crisphead lettuce cv. Imperial. During the mid-1980s and early 1990s a soilborne disease with symptoms similar to brown blight appeared in the Salinas Valley and other lettuce growing areas in California and Arizona. The disease was called lettuce dieback disease. Affected fields in the Salinas Valley were mainly located close to the Salinas River in areas that, in recent years, had been flooded during the winter months. A disease of greenhouse-grown tomatoes, characterized by chlorosis and necrotic speckling of leaves, leaf curling and chlorosis, necrosis of inflorescence, flower abortion, and internal browning and necrosis of the fruit, has also been repeatedly observed in Colorado and New Mexico since 1997.
Since the tombusvirus group was established in 1971 with the TBSV tomato isolate as the type species, it has been argued whether other serologically related tombusvirus isolates from artichoke, carnation, petunia, pelargonium, and other crops are distinct tombusvirus species or strains of TBSV. Classification of a distinct tombusvirus species has been based mainly on differences in serology and electrophoretic mobilities of viral particles. However, serological criteria alone may not be sufficient for accurate tombusvirus classification because they were not always in agreement with results of nucleic acid hybridization studies and sequence analyses. The 3′-end sequences of the genomes of several tombusvirus isolates obtained from lettuce, tomato, eggplant, and sugar beet (Beta vulgaris L.) have been determined and serological properties of these isolates have been compared in order to better characterize
tombusviruses associated with different crops and geographical regions. On this basis, evidence that a new tombusvirus is the causal agent of lettuce dieback disease and the new tomato greenhouse disease is presented. The name of this virus is proposed to be Lettuce necrotic stunt virus (LNSV). The relationship of LNSV to other tombusvirus strains isolated from lettuce, tomato, sugar beet, and eggplant crops in California and the western part of the United States has been determined.
Reference:
C. Obermeier, J. L. Sears, H. Y. Liu, K. O. Schlueter, E. J. Ryder, J. E. Duffus, S. T. Koike, and G. C. Wisler (2001). Characterization of Distinct Tombusviruses that Cause Diseases of Lettuce and Tomato in the Western United States. Phytopathology, 91(8): 797-806.
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Post by ravendra on Sept 13, 2015 6:44:35 GMT -6
Great job on the presentation! It was very interesting. This virus intrigued me because normally viruses survive in a vector or in a host. This one does not have a vector (identified so far). How long could this virus survive in the soil or in water in the absence of a susceptible lettuce cultivar. Also, is there any other host besides lettuce that has been reported? Lettuce dieback disease symptoms include yellowing, necrosis, stunting and dieback of affected plants. The disease primarily affects romaine and leaf lettuce types, which have increased significantly in area cultivated in the late 1990s. Several isolates of Tomato bushy stunt 6irus (TBSV; family, Tombusviridae; genus, Tombusvirus) have been recovered from symptomatic romaine lettuce as well as from leaf lettuces and one crisphead lettuce variety from the Salinas Valley. Dieback is causing increased concern to growers and some have encountered 60% or more crop loss. The disease has been found primarily in low-lying areas near rivers, in areas where soil has been dredged from a drainage area and spread onto the field, or in flooded locations. Heavy rains and flooding of farmland in recent years and a shift in the lettuce varieties planted from primarily crisphead to 30% leafy types has contributed to the increasing incidence of lettuce dieback which is primarily associated with fields along the Salinas River. Reference: Gail C. Wisler, and James E. Duffus (2000). A century of plant virus management in the Salinas Valley of California, ‘East of Eden’. Virus Research 71, 161–169. |
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Post by ravendra on Sept 13, 2015 6:57:12 GMT -6
Lettuce is susceptible to dieback, a soilborne disease caused by two viruses from the family Tombusviridae. Susceptibility to dieback is widespread in romaine and leaf-type lettuce, while modern iceberg cultivars are resistant to this disease. Resistance in iceberg cultivars is conferred by Tvr1 - a single, dominant gene that provides durable resistance. Studies have been conducted that describe fine mapping of the resistance gene, analysis of nucleotide polymorphism and linkage disequilibrium in the Tvr1 region, and development of molecular markers for marker-assisted selection. A combination of classical linkage mapping and association mapping allows to pinpoint the location of the Tvr1 resistance gene on chromosomal linkage group 2. Nine molecular markers, based on expressed sequence tags (EST), were closely linked to Tvr1 in the mapping population, developed from crosses between resistant (Salinas and Salinas 88) and susceptible (Valmaine) cultivars. . The association mapping approach revealed that one of the nine markers (Cntg10192) in the Tvr1 region matched exactly with resistant and susceptible phenotypes when tested on a set of 200 L. sativa accessions from all horticultural types of lettuce. Marker-assisted selection for dieback resistance with HRM is now an integral part of the breeding program that is focused on the development of improved lettuce cultivars.
Reference:
Ivan Simko, Dov A Pechenick, Leah K McHale, María José Truco, Oswaldo E Ochoa, Richard W Michelmore and Brian E Scheffler (2009). Association mapping and marker-assisted selection of the lettuce dieback resistance gene Tvr1. BMC Plant Biology, 9:135.
DOI:10.1186/1471-2229-9-135
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Post by ravendra on Sept 13, 2015 7:03:32 GMT -6
This was in Research News- Science Daily...
California and Arizona, the two largest lettuce-producing states, account for more than 95% of the lettuce grown in the United States. Since the early 1990s, the states' lettuce crops have been subject to "dieback," a disease indicated by symptoms including mottling, yellowing, and death of older leaves, and stunting and eventual death of lettuce plants. Dieback disease, caused by two soil-borne viruses, affects romaine and leaf-type lettuce, often leading to crop loss of 60% or more. Most disturbing is the news that the virus is not effectively reduced using either chemical treatment or rotation with nonhost crops, and the virus can live on in infested soil.
In an effort to control looming economic losses to the region's vital lettuce industry, scientists are being challenged to develop new breeding lines that provide genetic resistance to the virus. Add in another challenge for researchers: some recently developed romaine cultivars that are resistant to dieback have limited shelf life, decaying quickly when processed for salad.
Three romaine-type breeding lines with resistance to the disease were previously released by the U.S. Department of Agriculture-Agricultural Research Service in Salinas, California. Now, the Salinas breeding program has introduced new romaine breeding lines that prove praiseworthy in terms of both disease resistance and shelf life. Ivan Simko and Ryan J. Hayes from the USDA-ARS in Salinas, Krishna V. Subbarao of the Department of Plant Pathology at the University of California, and Rebecca Grube from the University of New Hampshire introduced the new romaine lines in a recent issue of HortScience.
SM09A and SM09B are F8 romaine breeding lines of lettuce (Lactuca sativa L.) resistant to the dieback disease and with good shelf life. SM09B was selected from a cross between 'Darkland' and PI 491224. SM09A was developed from 'Green Towers' ('Darkland' x PI 491224). "In replicated field trials, the two breeding lines showed complete resistance to dieback. Testing of salad-cut lettuce in modified atmosphere packaging indicated slower decay in the two breeding lines compared with other dieback-resistant romaine varieties," noted Simko.
Story Source:
The above post is reprinted from materials provided by American Society for Horticultural Science.
Journal Reference:
Ivan Simko, Ryan J. Hayes, Krishna V. Subbarao, and Rebecca Grube Sideman. SM09A and SM09B: Romaine Lettuce Breeding Lines Resistant to Dieback and with Improved Shelf Life. HortScience, 2010; 45: 670-672.
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Post by JamesTat on Jan 21, 2022 2:27:11 GMT -6
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