Transmission of Tomato spotted wilt virus isolates able and unable to overcome tomato or pepper resistance by its vector Frankliniella occidentalis

[EN] Tomato spotted wilt virus (TSWV) causes serious diseases of many economically important crops. Disease control has been achieved by breeding tomato and pepper cultivars with the resistance genes Sw-5 and Tsw, respectively. However, TSWV isolates overcoming these genetic resistances have appeared in several countries. To evaluate the risk of spread of these resistance-breaking isolates, we tested their ability of transmission by the main vector of TSWV, the thrips Frankliniella occidentalis. We compared the transmission rate by thrips of six TSWV isolates of different biotype (able or unable to overcome this resistance in pepper and tomato), and with divergent genotype (A and B). Our results indicate that the transmission rate was related to the amount of virus accumulated in thrips but not to virus accumulation in the source plants on which thrips acquired the virus. No correlation was found between transmission efficiency by thrips and the genotype or between transmission efficiency and the ability of overcoming both resistances. This result suggests that resistance-breaking isolates have the same potential to be transmitted as the isolates unable to infect resistant tomato and pepper cultivars.This work was supported by grants RTA2008-00010-C03 and FEDER, and ACOMP/2009/103 financed by INIA and Generalitat Valenciana, respectively. D. E. D. was recipient of a FPU predoctoral fellowship from the Spanish Ministry of Science and Education and B. B. was supported by an INIA-CCAA contract. Fito´ and Seminis kindly provided the seeds of the tomato and pepper cultivars used in the experiment. We would like to thank Debora Mart ´ ´ınez and Dolores Com´ın for technical assistance, as well as Dr D. Peters (Wageningen University, the Netherlands) and Dr J. Contreras (Universidad Politecnica de Cartagena, Spain) ´ for kindly providing the TSWV isolate BR01 and a thrips colony, respectively. Drs E. Carbonell and J. Perez- Panades (IVIA) are thanked for statistical advice. Two anonymous referees improved a previous version of the manuscript.Debreczeni, DE.; Rubio, L.; Aramburu, J.; López Del Rincón, C.; Galipienso, L.; Soler Aleixandre, S.; Belliure, B. (2014). Transmission of Tomato spotted wilt virus isolates able and unable to overcome tomato or pepper resistance by its vector Frankliniella occidentalis. Annals of Applied Biology. 164:182-189. https://doi.org/10.1111/aab.12090S18218916

Herbivore benefits from vectoring plant virus through reduction of period of vulnerability to predation

Herbivores can profit from vectoring plant pathogens because the induced defence of plants against pathogens sometimes interferes with the induced defence of plants against herbivores. Plants can also defend themselves indirectly by the action of the natural enemies of the herbivores. It is unknown whether the defence against pathogens induced in the plant also interferes with the indirect defence against herbivores mediated via the third trophic level. We previously showed that infection of plants with Tomato spotted wilt virus (TSWV) increased the developmental rate of and juvenile survival of its vector, the thrips Frankliniella occidentalis. Here, we present the results of a study on the effects of TSWV infections of plants on the effectiveness of three species of natural enemies of F. occidentalis: the predatory mites Neoseiulus cucumeris and Iphiseius degenerans, and the predatory bug Orius laevigatus. The growth rate of thrips larvae was positively affected by the presence of virus in the host plant. Because large larvae are invulnerable to predation by the two species of predatory mites, this resulted in a shorter period of vulnerability to predation for thrips that developed on plants with virus than thrips developing on uninfected plants (4.4 vs. 7.9 days, respectively). Because large thrips larvae are not invulnerable to predation by the predatory bug Orius laevigatus, infection of the plant did not affect the predation risk of thrips larvae from this predator. This is the first demonstration of a negative effect of a plant pathogen on the predation risk of its vector

Vector-Virus Mutualism Accelerates Population Increase of an Invasive Whitefly

The relationships between plant viruses, their herbivore vectors and host plants can be beneficial, neutral, or antagonistic, depending on the species involved. This variation in relationships may affect the process of biological invasion and the displacement of indigenous species by invaders when the invasive and indigenous organisms occur with niche overlap but differ in the interactions. The notorious invasive B biotype of the whitefly complex Bemisia tabaci entered China in the late 1990s and is now the predominant or only biotype in many regions of the country. Tobacco curly shoot virus (TbCSV) and Tomato yellow leaf curl China virus (TYLCCNV) are two whitefly-transmitted begomoviruses that have become widespread recently in south China. We compared the performance of the invasive B and indigenous ZHJ1 whitefly biotypes on healthy, TbCSV-infected and TYLCCNV-infected tobacco plants. Compared to its performance on healthy plants, the invasive B biotype increased its fecundity and longevity by 12 and 6 fold when feeding on TbCSV-infected plants, and by 18 and 7 fold when feeding on TYLCCNV-infected plants. Population density of the B biotype on TbCSV- and TYLCCNV-infected plants reached 2 and 13 times that on healthy plants respectively in 56 days. In contrast, the indigenous ZHJ1 performed similarly on healthy and virus-infected plants. Virus-infection status of the whiteflies per se of both biotypes showed limited effects on performance of vectors on cotton, a nonhost plant of the viruses. The indirect mutualism between the B biotype whitefly and these viruses via their host plants, and the apparent lack of such mutualism for the indigenous whitefly, may contribute to the ability of the B whitefly biotype to invade, the displacement of indigenous whiteflies, and the disease pandemics of the viruses associated with this vector

Vector and virus induce plant responses that benefit a non-vector herbivore

The negative cross-talk between induced plant defences against pathogens and arthropod herbivores is exploited by vectors of plant pathogens: a plant challenged by pathogens reduces investment in defences that would otherwise be elicited by herbivores. This negative cross-talk may also be exploited by non-vector herbivores which elicit similar anti-herbivore defences in the plant. We studied how damage by the thrips Frankliniella occidentalis and/or infection with Tomato spotted wilt virus (TSWV) affect the performance of a non-vector arthropod: the two-spotted spider mite Tetranychus urticae, a parenchym feeder just like F. occidentalis. Juvenile survival of spider mites on plants inoculated with TSWV by thrips was higher than on control and on thrips-damaged plants. However, thrips damage did not reduce spider-mite survival as compared to the control, suggesting that the positive effect of TSWV on spider-mite survival is independent of anti-thrips defence. Developmental and oviposition rates were enhanced on plants inoculated with TSWV by thrips and on plants with thrips damage. Therefore, spider mites benefit from TSWV-infection of pepper plants, but also from the response of plants to thrips damage. We suggest that the positive effects of TSWV on this non-vector species cannot be explained exclusively by cross-talk between anti-herbivore and anti-pathogen plant defences

MITES AS MODELS FOR EXPERIMENTAL EVOLUTION STUDIES BelØn B , Marta M and Sara M

Belliure, B., Montserrat, M., Magalhaes, S. (2010): MITES AS MODELS FOR EXPERIMENTAL EVOLUTION STUDIES BelØn B , Marta M and Sara M. Acarologia 50 (4): 513-529, DOI: 10.1051/acarologia/20101985, URL: http://dx.doi.org/10.1051/acarologia/2010198

Determinación de los umbrales económicos de tratamiento contra "Aphis gossypii" (Hemiptera, Aphididae) y su parasitismo en clementinos

Se han mantenido diferentes cantidades de Aphis gossypii en varios grupos de clementinos por el método de aislarlos con jaulas de malla. La pérdida de producción de los árboles se ha correlacionado con el número de áfidos por m2 de copa, obteniéndose la fórmula correspondiente. A partir de ella se han obtenido el nivel de daño económico, el umbral económico, el nivel de daño económico ambiental y el umbral económico ambiental. También se han obtenido las fórmulas que relacionan el número de áfidos por m2 con otros índices más sencillos para expresar estos umbrales: porcentaje de brotes atacados, brotes atacados por aro de 0,25 m2, índice de ataque, porcentaje de aros ocupados y número de áfidos capturados por semana en una trampa amarilla ABSTRACT