Enhanced biocontrol services in artificially selected strains of Orius laevigatus

Augmentative biological control in protected crops relies mainly on omnivorous predators. Their performance as biological control agents (BCA) depends on several characteristics of the species, which in turn may differ among strains within a species. We have recently reported the achievement of two Orius laevigatus (Hemiptera: Anthocoridae) strains showing a significant larger body size or better fitness when feeding on pollen, two characteristics having a key impact on field performance. However, selection towards a specific trait might result in trade-offs, such as reduced predation capacity, which may impair control efficiency. Therefore, the predation capacity of these selected populations was tested in laboratory as a first step prior to its field use. Functional response to different densities of Frankliniella occidentalis (Thysanoptera: Thripidae) (adults and larvae) and Myzus persicae (Hemiptera: Aphididae) (nymphs) were studied in the large-sized and pollen-tolerant O. laevigatus strains in comparison with commercial and wild populations. A type-II functional response was observed regardless of the population. Body size was significantly related to thrips but not to aphid predation. The large-sized strain showed a superior predation capacity, both on thrips larvae and especially on adult thrips, although not on aphids. Therefore, the larger body size of the selected strain may increase its effectiveness as BCA of thrips. Regarding the pollen-tolerant strain, no trade-offs were observed in predation rates on adults or larvae of thrips, but it showed higher predation capacity on aphid nymphs, suggesting an expanded prey range. Implications of such enhanced biocontrol services on crop protection are also discussed.We acknowledge anonymous referees for reviews and comments on an earlier version of the manuscript. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. Grant PID2020-116897RB-I00 funded by Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación MCIN/AEI/10.13039/501100011033. José Enrique Mendoza holds a Grant from the MSIU (FPU14/02932)

Artificial selection for emamectin benzoate resistance in the biological control agent Orius laevigatus

Biological control is occasionally supplemented with insecticides treatments, which may have a significant impact on natural enemies. Typically, selective compounds are chosen to overcome lack of compatibility, but an alternative approach is the use of biocontrol agents resistant to pesticides. Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) is the main predator used to control thrips and other small pests in greenhouses. The avermectin emamectin benzoate is a bioinsecticide developed for the control of lepidopteran pests, reported as moderately to highly toxic to O. laevigatus. Firstly, we studied the variation in susceptibility to emamectin benzoate in 32 wild and commercial populations of O. laevigatus. A 62.4-fold variation in response was found (LC50 from 0.8 mg L−1 to 49.9 mg L−1). The baseline LC50 was 4.8 mg L−1. Secondly, we exploited this intraspecific variation to select four distinct emamectin-resistant strains. After 41–47 selection cycles, four resistant strains were successfully obtained (LC50 = 104–203 mg L−1) compared to the reference population (LC50 = 4.7 mg L−1). The resistance was retained for 18 generations without insecticide exposure and was expressed in all life instars, especially from the 4th nymphal instar to adult. The emamectin-resistant strains did not show cross-resistance to abamectin. Inhibitors of the detoxification enzymes failed to restore susceptibility at the concentrations tested. Fecundity and predation capacity in the resistant strain was similar to those in a commercial population. The resistance obtained may be enough to allow survival of adults and nymphs of O. laevigatus exposed to treatments of emamectin benzoate across the crop season.We thank the editor and anonymous reviewers for their constructive comments on the manuscript. This research has been supported by the Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (773902-SuperPests). ARG contract is co-financed by Grant PID2020-116897RB-I00 funded by Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación MCIN/AEI/10.13039/501100011033 and the R&D Support Plan of the Polytechnic University of Cartagena

Inheritance of resistance to acrinathrin in Frankliniella occidentalis (Thysanoptera: Thripidae)

[SPA] Se investigó la base genética de la resistencia al acrinatrín para Frankliniella occidentalis. La población resistente, seleccionada en el laboratorio para la resistencia a acrinatrín, de un conjunto de poblaciones de trips recogidas en Almería (sureste de España), mostró una gran resistencia al acrinatrín (43 veces superior a la CL50) comparada con la población susceptible de laboratorio. Los datos de mortalidad de cruces recíprocos de trips resistentes y susceptibles indicaron que la resistencia era autosomal y no estaba influenciada por efectos maternos. El análisis de las líneas probit de las poblaciones parentales y los cruces recíprocos mostró que la resistencia se expresaba como un rasgo codominante. [ENG] The genetic basis of acrinathrin resistance was investigated in WFT. The resistant strain, selected in the laboratory for acrinathrin resistance from a pool of thrips populations collected in Almeria (south-eastern Spain), showed a high resistance to acrinathrin (43-fold based on LC50 values) compared with the laboratory susceptible strain. Mortality data from reciprocal crosses of resistant and susceptible thrips indicated that resistance was autosomal and not influenced by maternal effects. Analysis of probit lines fromthe parental strains and reciprocal crosses showed that resistance was expressed as a codominant trait

Genetic relationship among seven specialized forms of Fusarium oxysporum determined by DNA sequencing of the ITS region and AFLPs

[ENG] The fungus Fusarium oxysporum Sch.: Fr. present a high biological and genetic variability, manifested the exixtence of many specialized forms and races. With the goal of evaluating the genetic relationship among different specialized forms, an experiment was carried out involving the application of two types of molecular markers. One consisted of sequencing the internal transcribed spacer (ITS) region of the ribosomal DNA of 17 isolates belonging to seven forms: F.o. melonis (4 isolates), F.o. dianthi (2), F.O. niveum (4), F.o. lycopersici (2), F.o. radicis-lycopersici (3),F.o. lagenaria (1) and F.o. luffae (1). Analysis of these sequences revealed that isolates from different forms presentan identical sequence while isolates of the same form apper distributed in different groups of the dendrogram. This observation was confirmed by an AFLP analysis. In addition to the previously cited forms, ten more were studied in this esperiment, belonging to F.o. ciceris, F.o. cucumerinum, F. proliferatum and F.o. asparagi, as well as two non-pathogenic isolates.The dendrogram calculated with the AFLP markers did not reveal any genetic structuration of the 10 specialized forms. These data, in line with those obtained by other authors, seem to suggest that in general, the specialized forms of F. oxysporum do not constitute monophyletic lineages because they evolve in a divergent way. It rather seems that widely different genotypes could share similar genetic factors conferring pathogenic specificity. [ESP] El hongo Fusarium oxysporum Sch.:Fr. presenta una elevada variabilidad biológica y genética que se manifiesta por la existencia de numerosas formas especializadas y razas. Con el fin de evaluar la relación genética entre diferentes formas especializadas se aplicaron dos tipos de marcadores genéticos. En primer lugar se secuenció la región ITS (inyernal transcribed spacer) del ADN ribosomal de 17 aislados pertenecientes a siete de dichas formas: F.o. melonis (4 aislados), F.o. dianthi (2), F.o. niveum (4), F.o. lycopersici (2), F.o. radicis-lycopersici (3), F.o. lagenaria (1) y F.o. luffae (1). El análisis de estas secuencias reveló que aislados de diferentes formas presentan una secuencia idéntica, mientras que aislados de la misma familia forma a parecen en grupos diferentes del correspondiente dendograma. Esta observación se confirmó mediante marcadores AFLP de las mismas formas especializadas y 10 más pertenecientes a F.o. ciceres, F.o. cucumericum, F. proliferatum y F.o. asparagi, así como dos aislados no patogénicos. El dendograma obtenido no reveló ninguna estructuración genética de las 10 formas especializadas. Estos datos, que están en la línea de los obtenidos por otros autores, parecen indicar que algunas formas especializadas de F. oxysporum no constituyen linajes monofiléticos, ya que evolucionan de forma divergente. Oarece más bien que genotipos muy diferentes podrían compartie factores similares de especifidad y especialización patogénica.This work was financed by the project INIA SC93-135