Transmission of ‘Candidatus Liberibacter solanacearum’ by Bactericera trigonica Hodkinson to vegetable hosts

Abstract

The bacterium 'Candidatus Liberibacter solanacearum' is a recent plant pathogen of several crops in Solanaceae and Apiaceae and is associated with economically important diseases. The bacterium is a carrot seed borne pathogen that can also be transmitted from potato mother tubers and by psyllid vectors. The psyllid Bactericera trigonica Hodkinson was described carrying CaLso associated with vegetative disorders in carrot and celery crops in Spain and its competence to transmit this phloem-limited bacterium among vegetables is currently being investigated. Here electrical penetration graphs showed that B. trigonica fed in the phloem of carrot and celery and probed the phloem in potato, but not in tomato plants. The bacterium was efficiently transmitted to carrot and celery plants when either single B. trigonica or groups of ten fed on these species. An inoculation access period of 24 hours was sufficient for a single B. trigonica to transmit the bacterium to carrot (67.8%), celery (21.1%) and eventually to potato and tomato (6.0%). Higher transmission rates were obtained with 10 individuals on celery (100%), carrot (80%), potato (10%) and tomato (10%). Bactericera trigonica laid eggs, and the hatched nymphs develop into adult on carrot and celery, but not on potato and tomato. CaLso was detected in 20% of the eggs laid by females carrying the bacterium. The results confirmed that B. trigonica is a vector of the bacterium to carrot and celery, and it is discussed the potential role of this psyllid in the transmission of the pathogen to potato and tomato plants.Additional keywords: electrical penetration graph; haplotype E; psyllids; real-time PCR; transovarial passage.

‘Candidatus Liberibacter Solanacearum’ Is Unlikely to Be Transmitted Spontaneously from Infected Carrot Plants to Citrus Plants by Trioza Erytreae

“…According to Catling [65], a high mortality of different juvenile stages in host plants was previously reported. Taken together, these results indicate a high survival of T. erytreae on a nonhost plant species, which contrasts with the results of previous studies conducted with B. trigonica, which was unable to lay eggs on tomato plants, and only five eggs were laid by a total of three pairs in potato plants, where the few hatched nymphs died during the first instar [54]. In the case of B. tremblayi, although it could settle and oviposit on carrot plants, it clearly preferred to oviposit in leek (its main host) [45].…”

“…In addition, previous studies using sampling methods at the level of the crop canopy have shown that the main psyllid species present in carrot fields is B. trigonica, followed by B. nigricornis in low proportions [27,29]. Several previous studies on bacterial transmission by psyllid species in nonhost plant species found that: T. apicalis (a vector of CaLsol in Apiaceae species in northern Europe) does not transmit the bacterium from carrot to potato [16], B. trigonica (a vector of CaLsol in Apiaceae species in southern Europe and North Africa) was able to transmit CaLsol at a low rate from carrot to potato or tomato [45,54], and the transmission of CaLsol to carrots by B. cockerelli (vector of CaLsol in Solanaceae species) was possible at a low rate and induced disease symptoms [62]. On the one hand, B. tremblayi could acquire CaLsol from infected carrot plants, but it could not transmit the bacterium to carrot plants, which might be because the bacterium was not able to complete circulation in the body of the psyllid to be ultimately inoculated from the salivary glands [45].…”

“…All in all, it would be interesting to perform new feeding behavior assays with other citrus species, such as lemon, sweet orange or mandarin trees, since certain preference of T. erytreae have been seen in the fields where the most frequently grown citrus species are: lime, lemon, mandarins, sweet orange and grapefruit trees [60][61][62]. For our study, eight hours of EPG recording time was used as this is the standard time used in many previous similar EPG studies, e.g., in those involving B. trigonica, B. tremblayi and D. citri [45,54,63]. However, EPG recordings of B. cockerelli were documented for 24 h [55,64] and in D. citri for 42 h [58]; if shorter EPG recording times are used, it could be problematic to quantify the first phloem ingestion phase by some psyllids [59].…”

“…On the one hand, B. tremblayi could acquire CaLsol from infected carrot plants, but it could not transmit the bacterium to carrot plants, which might be because the bacterium was not able to complete circulation in the body of the psyllid to be ultimately inoculated from the salivary glands [45]. On the other hand, Teresani et al [54], who investigated CaLsol transmission by B. trigonica from carrot to potato and tomato, reported a high detection of CaLsol in the leaves immediately after the insects were removed, which may be due to inoculation in phloem sieves, contamination of the tissue by psyllid activities or detection of nonviable bacteria. A similar situation could have happened with the detection of CaLsol in our assay.…”

New Ca. Liberibacter psyllaurous haplotype resurrected from a 49-year-old specimen of Solanum umbelliferum: a native host of the psyllid vector

“…The initial characterization of Ca. L. psyllaurous established that this pathogen is vertically transmitted in its vector, the native potato/tomato psyllid, Bactericera cockerelli, and subsequent work has shown that it is also harbored within and vectored by the native psyllids Trioza apicalis 21 , Trioza urticae 4 , and Bactericera trigonica 22,23 in Europe. Currently, a total of 7 Ca.…”