| inventarisation of natural enemies in witloof chicory fields: preliminary results. | due to residues on the witloof chicory heads the use of insecticides is forbidden during forcing. at this moment a suitable chemical control of the leafminer napomyza cichorii is carried out in the field, based on the phenology and the population density and taking into account the economic threshold level. no chemical treatment is recognized against the root aphid pemphigus bursarius. for monitoring these pests during the growing season water traps were placed on observation fields, scattered o ... | 2007 | 18399482 |
| silencing of the major family of nbs-lrr-encoding genes in lettuce results in the loss of multiple resistance specificities. | the rgc2 gene cluster in lettuce (lactuca sativa) is one of the largest known families of genes encoding nucleotide binding site-leucine-rich repeat (nbs-lrr) proteins. one of its members, rgc2b, encodes dm3 which determines resistance to downy mildew caused by the oomycete bremia lactucae carrying the cognate avirulence gene, avr3. we developed an efficient strategy for analysis of this large family of low expressed genes using post-transcriptional gene silencing (ptgs). we transformed lettuce ... | 2007 | 17587302 |
| host-associated populations in the lettuce root aphid, pemphigus bursarius (l.). | pemphigus bursarius is a host-alternating aphid in which annual rounds of sexual reproduction on its primary host, populus nigra, are interspersed with parthenogenesis on a range of secondary hosts. evidence was sought for the existence of genetically distinct populations, associated with different secondary hosts, in p. bursarius. microsatellite markers revealed that genetically distinct populations were present on three different secondary host species. microsatellites were also used, in conju ... | 2005 | 15785781 |
| population genetic structure of the lettuce root aphid, pemphigus bursarius (l.), in relation to geographic distance, gene flow and host plant usage. | microsatellite markers were used to examine the population structure of pemphigus bursarius, a cyclically parthenogenetic aphid. substantial allele frequency differences were observed between populations on the primary host plant (collected shortly after sexual reproduction) separated by distances as low as 14 km. this suggested that migratory movements occur over relatively short distances in this species. however, the degree of allele frequency divergence between populations was not correlated ... | 2003 | 12939621 |
| overwintering adaptations in the lettuce root aphid pemphigus bursarius (l.). | pemphigus bursarius (l.) is a host alternating root-feeding aphid with a proportion of the population overwintering as asexual hiemalis in the soil. these hiemalis must be sufficiently cold tolerant to survive at the temperatures they would experience in winter, and also be able to overcome a period of prolonged starvation brought about by the absence of secondary host plants. cold tolerance experiments showed field collected hiemalis to be considerably more cold hardy than laboratory summer apt ... | 2000 | 12770240 |
| polymorphic microsatellite loci from the lettuce root aphid, pemphigus bursarius. | | 2000 | 11091347 |
| ultrastructure of the antennal sensilla of aphids. i. coeloconic and placoid sensilla. | an electron microscopical study was made of the coeloconic and placoid sensilla on the antennae of the aphids aphis pomi, macrosiphum euphorbiae, nasonovia ribis-nigri, and pemphigus bursarius. scanning electron microscopy revealed some variation in morphology which may be functionally important but is more likely to reflect the evolution of these species. the placoid sensilla were shown by tranwo or three neurons is surrounded by two ensheathing cells. the ciliary regions of the dendrites pass ... | 1979 | 519733 |