Search for molecular markers linked to Liriomyza trifolii resistance in tomato

Resistance to many arthropods, including Liriomyza species, is known to be present in accessions of Lycopersicon hirsutum (f. typicum or f. glabratum). From the cross L. esculentum cv. Moneymaker and L. hirsutum f. glabratum G1561 100 F₂ plants were screened in a no-choice test for resistance to Liriomyza trifolii. The Bulked Segregant Analysis approach was used to find Random Amplified Polymorphic DNA markers linked to resistance. Two markers were located on chromosome 2. Restriction Fragment Length Polymorphisms constructed a more detailed genetic linkage map for part of chromosome 2. Kruskal-Wallis analysis showed that this chromosome harbored a Quantitative Trait Locus (QTL) for number of pupae, number of mines and damage. At least one major QTL is essential for resistance and this QTL is located on chromosome 2 nearby the location of the tomato probe TG451. This revised version was published online in July 2006 with corrections to the Cover Date.     

Virus-free plants of iris ‘wedgwood’ obtained by meristem culture

Some commercial varieties of Dutch (bulbous) iris such as ‘Wedgwood’ and ‘Imperator’ are wholly infected with a virus called latent mosaic virus in Israel or iris mosaic virus in the Netherlands. The aim of the investigation was to obtain virus-free plants of these varieties by culture of meristem tips excised from bulbs kept in their vegetative stage by storage at 25.5°C. Several media were used; those based on the medium ofMorel (personal communication) gave the best results. About 100 meristems were placed on each medium and on the best media about 30% started to grow. By transferring slowly growing meristems to the medium ofMurashige & Skoog (1962), growth improved greatly, though root formation remained poor. Twenty meristems developed into plants, of which ten were tested serologically. Eight plants of the variety ‘Wedgwood’ proved to be virus-free.     

Limited BVDV transmission and full protection against CSFV transmission in pigs experimentally infected with BVDV type 1b

Bovine viral diarrhea virus (BVDV) in pigs may interfere with the detection and epidemiology of classical swine fever virus (CSFV). To investigate the importance of BVDV infections in pigs, first we studied the transmission dynamics of a recent BVDV field isolate. Subsequently, the protection of BVD antibodies against transmission and clinical disease of CSF virus was studied. Only limited transmission of BVDV occurred (R = 0.20), while no CSFV transmission occurred in pigs with BVDV antibodies. We concluded that BVDV transmission among pigs is possible, but seems to be limited and thus the virus should disappear from a population if no new introductions occur. Furthermore, the presence of BVD antibodies may completely prevent the transmission of CSFV and therefore could protect pigs against classical swine fever. It was also noticed that double infections with BVDV and CSFV were incorrectly diagnosed using the neutralization peroxidase linked assay (NPLA), which is the golden standard for antibody detection. This might hamper the diagnosis of CSF in herds with a high BVD prevalence.     

Effect of heat treatment of young plants on freeing chrysanthemums from virus B by means of meristem culture

Meristem culture provides a means of obtaining virus-free plants from cultivars of chrysanthemum which are wholly infected with virus B. In an effort to improve the efficiency of the method plants were subjected to a temperature of 37 °C for periods of 0, 10, 20, 30, 40, 50 and 60 days, respectively, prior to isolation of the meristems. The three chrysanthemum cultivars used, Blanche Poitevine Suprême, Migoli and Chatsworth reacted differently both to heat treatment and to meristem culture. However, their reactions had two points in common. First, heat proved to be non-essential: even without heat plants could be produced in which virus B was no longer present. Secondly, with increasing increased; but since prolonged heat treatment had an unfavourable effect on the cultivation of the meristems, the absolute number of plants free from the virus eventually decreased.     

Genetic research in a public–private research consortium: prospects for indirect use of Elite breeding germplasm in academic research

The creation of a public–private research partnership between plant breeding industry and academia can be beneficial for all parties involved. Academic partners benefit from the material contributions by industry and a practically relevant research focus, while industry benefits from increased insights and methodology tailored to a relevant set of data. However, plant breeding industry is highly competitive and there are obvious limits to the data and material partners are willing and able to share. This will usually include current and historic released cultivated materials, but will very often not include the elite germplasm used in-house to create new cultivars. Especially for crops where hybrid cultivars dominate the market, parental lines of hybrid cultivars are considered core assets that are never provided to outside parties. However, this limitation often does not apply to DNA or genetic fingerprints of these parental lines. We developed a procedure to take advantage of elite breeding materials for the creation of new promising research populations, through indirect selection of parents. The procedure starts with the identification of a number of traits for further study based on the presence of marker-trait associations and a priori knowledge within the participating companies about promising traits for quality improvement. Next, regression-based multi-QTL models are fitted to hybrid cultivar data to identify QTLs. Fingerprint data of parental lines of a limited number of specific hybrids are then used to predict parental phenotypes using the multi-QTL model fitted on hybrid data. The specific hybrids spanned the whole of the sensory space adequately. Finally, a choice of parental lines is made based on the QTL model predictions and new promising line combinations are identified. Breeding industry is then asked to create and provide progeny of these line combinations for further research. This approach will be illustrated with a case study in tomato.     

Efficacy of a pandemic (H1N1) 2009 virus vaccine in pigs against the pandemic influenza virus is superior to commercially available swine influenza vaccines

In April 2009 a new influenza A/H1N1 strain, currently named "pandemic (H1N1) influenza 2009" (H1N1v), started the first official pandemic in humans since 1968. Several incursions of this virus in pig herds have also been reported from all over the world. Vaccination of pigs may be an option to reduce exposure of human contacts with infected pigs, thereby preventing cross-species transfer, but also to protect pigs themselves, should this virus cause damage in the pig population. Three swine influenza vaccines, two of them commercially available and one experimental, were therefore tested and compared for their efficacy against an H1N1v challenge. One of the commercial vaccines is based on an American classical H1N1 influenza strain, the other is based on a European avian H1N1 influenza strain. The experimental vaccine is based on reassortant virus NYMC X179A (containing the hemagglutinin (HA) and neuraminidase (NA) genes of A/California/7/2009 (H1N1v) and the internal genes of A/Puerto Rico/8/34 (H1N1)). Excretion of infectious virus was reduced by 0.5-3 log(10) by the commercial vaccines, depending on vaccine and sample type. Both vaccines were able to reduce virus replication especially in the lower respiratory tract, with less pathological lesions in vaccinated and subsequently challenged pigs than in unvaccinated controls. In pigs vaccinated with the experimental vaccine, excretion levels of infectious virus in nasal and oropharyngeal swabs, were at or below 1 log(10)TCID(50) per swab and lasted for only 1 or 2 days. An inactivated vaccine containing the HA and NA of an H1N1v is able to protect pigs from an infection with H1N1v, whereas swine influenza vaccines that are currently available are of limited efficaciousness. Whether vaccination of pigs against H1N1v will become opportune remains to be seen and will depend on future evolution of this strain in the pig population. Close monitoring of the pig population, focussing on presence and evolution of influenza strains on a cross-border level would therefore be advisable.     

Meristeemcultuur,gecombineerd met warmtebehandeling,voor het verkrijgen van virusvrije anjerplanten

Summary Of the carnation varieties Pink Sim and Harvest Moon no virus-free plants were known. As therapy by means of heat treatment gave no satisfactory results, this method was combined with applacation of meristem culture. From plants kept for 6–8 weeks at 40°C, small portions from the tips of the stems, consisting of the meristem and some leaf primordia, were isolated and cultured in a nutrient agar under sterile conditions. The small plants that developed were transferred to soil. They grew into normal carnation plants in which no virus could be demonstrated either by serological test or by local lesion assays. From these plants virus-free stocks of these two varieties will be raised.