Seasonality, life cycle and vectorial capacity of Xylella fastidiosa insect vectors in the main crops of the Balearic Islands
[eng] Xylella fastidiosa (Wells et al. 1987) is a gram-negative Gammaproteobacterium pathogen of plants and limited to the xylem conduits. The bacterium is capable to infect more than 600 different plant species causing several types of diseases (i.e., Pierce's disease, citrus variegated chloro...
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| Format: | doctoral thesis |
| Status: | Published version |
| Publication Date: | 2022 |
| Country: | España |
| Institution: | CBUC, CESCA |
| Repository: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/675508 |
| Online Access: | http://hdl.handle.net/10803/675508 |
| Access Level: | Open access |
| Keyword: | Xylella fastidiosa Philaenus spumarius Neophilaenus campestris Seasonality Vector competence Mechanical control Entomologia aplicada 57 632 |
| Summary: | [eng] Xylella fastidiosa (Wells et al. 1987) is a gram-negative Gammaproteobacterium pathogen of plants and limited to the xylem conduits. The bacterium is capable to infect more than 600 different plant species causing several types of diseases (i.e., Pierce's disease, citrus variegated chlorosis, leaf scorch). It is transmitted by xylem sap feeder insects from the order Hemiptera and suborder Cicadomorpha. In Europe, the major vectors belong to the family Aphrophoridae. Xylella fastidiosa was detected in 2013 in Italy and in 2016 in the Balearic Islands. The general objectives of the thesis are i) macrocosm and microcosm studies of the vectors in the major agrosystems of the Balearic Islands; ii) Prevalence of X. fastidiosa in the vectors and vectorial capacity of potential vectors; iii) Test a cultural method against vectors. Nine organic farms (three olive, three vineyards and three almond) were selected in Majorca for conducting annual monitoring. The islands of Minorca, Ibiza and Formentera were sampled twice a year (summer and autumn). Insects were collected biweekly in each plot in Majorca by using a sweep net for adults and a wood frame of 0.25 m2 for nymphs. In the microcosm study, 50 cages containing one male and one female of Philaenus spumarius, one plant species per cage (Rosmarinus officinalis, Mentha x piperita, Ocimum basilicum, Pistacia lentiscus or Lavandula dentata) and substrate for oviposition (straw) were placed at field conditions. Insects were placed inside the cages from September to November, then cages were checked to detect egg batches and monitor nymphs’ development. From the adults collected from the field, the prevalence of X. fastidiosa was determined by qPCR. In a first approach, field collected insects were caged for the vector competence studies with X. fastidiosa free plants of Medicago sativa for 96 h. Then, insects were analysed by qPCR. Samples taken from plants were analysed 15, 30, 45 and 60d post inoculation. Moreover, in a second approach, nymphs were collected from the field, reared until adults and put in contact with vine and almond X. fastidiosa infected trees for 96 h acquisition access period. Then, adults were in contact with alfalfa plants for 96 h inoculation access period. Both adults and alfalfa plants were analysed by qPCR. Finally, for the mechanical control method test, the ground cover vegetation was mowed or tilled from olive and vineyard farms to assess the control of nymphs of X. fastidiosa vectors. Philaenus spumarius and Neophilaenus campestris (Aphrophoridae) were recorded in the Balearic Islands. Results indicated that nymphs were present from early-May to early-June. Philaenus spumarius nymphs were more abundant in the cover vegetation of olive crops, followed by vineyard and almond ones, while N. campestris was more abundant in olive and almond. The highest abundance of P. spumarius adults was recorded in May and October in the cover vegetation. Presence of adults increased in trees in June, while presence in the border vegetation of the crop increased in August and decreased around October. In the case of N. campestris, the highest abundance of adults was detected in the cover plants in May and November, however its presence in trees and border vegetation can be considered negligible. The prevalence of X. fastidiosa from the insects collected (1059 insects analysed) was 22.8 %; P. spumarius showed a prevalence of 23.6 % and N. campestris of 20.8 %. The island with the highest prevalence was Majorca reaching the 24 %, followed by Menorca (21.5 %) and Ibiza (21 %), Formentera remained free of X. fastidiosa. Xylella fastidiosa subsp. fastidiosa and multiplex were detected in insects form Majorca, X. fastidiosa subsp. multiplex was determined in Minorca and X. fastidiosa subsp. pauca was identified in Ibiza. The first approach of transmission test showed a 16.3 % of positive insects (N = 264). Inoculation to M. sativa was confirmed since the plants were positive by qPCR 15, 30, 45 and 60 days after inoculation. In the second approach, P. spumarius acquired the bacteria from almond (34.4 % of insects) and from vineyard (87.7 %). Only insects that acquired the bacterium from almond, transmitted X. fastidiosa to alfalfa plants. Results on the mechanical control test showed that mowing and tilling affect nymphs of X. fastidiosa vectors by reducing its density significantly below that of control zones. |
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