Browsing by Author "Bueno-Pallero, Francisco Angel"
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- Cutaneous excreta of the earthworm Eisenia fetida (Haplotaxida: Lumbricidae) might hinder the biological control performance of entomopathogenic nematodesPublication . Chelkha, Maryam; Blanco-Perez, Ruben; Bueno-Pallero, Francisco Angel; Amghar, Souad; El Harti, Abdellatif; Campos-Herrera, RaquelEarthworms enhance soil structure, the decomposition of organic matter and the dissemination of beneficial soil organisms such as the entomopathogenic nematodes (EPNs). Nevertheless, the effects of earthworm feeding behavior or cutaneous excreta (CEx) on the performance of EPNs as biological control agents is poorly understood. We hypothesized that the presence of earthworms or their excreta reduces EPN fitness, measured in terms of pathogenicity and reproductive success. In laboratory experiments we first evaluated the killing ability of EPNs against Galleria mellonella (Lepidoptera: Pyralidae) larvae when inoculated in autoclaved soil alone or in combination with the earthworm Eisenia fetida (Haplotaxida: Lumbricidae) or their excreta. We also evaluated EPN efficacy and reproduction when exposed to CEx derived from E. fetida at two nematode concentrations (1.5 and 10 IJs/cm(2)). For both experiments, we tested four steinernematids (Steinernema carpocapsae, S. feltiae, S. glaseri, and S. khuongi) and two heterorhabditids (Heterorhabditis bacteriophora and H. zealandica). The presence of earthworms or their excreta resulted in significant reduction of the larval mortality caused by some of the steinernematids at certain timings depending of the species (P < 0.015), while heterorhabditids were mainly not affected. Both S. feltiae and H. zealandica progeny production was significantly reduced (P < 0.01) when exposed to CEx. Hence, we showed that the presence of CEx might alter the biocontrol performance of certain EPN species, especially steinernematids bigger than 600 mu m in size (S. feltiae, S. glaseri, and S. khoungi), by affecting their pathogenicity and reproductive success.
- First report of curvularia trifolii causing curvularia blight in agrostis stolonifera in South of PortugalPublication . Coelho, Luísa; Borrero, C.; Bueno-Pallero, Francisco Angel; Guerrero, Carlos; Fonseca, Filomena; Reis, Mário; Avilés, M.; Dionísio, LídiaAlgarve region (Portugal) has nearly 40 golf courses with a significant economic impact. Summer surveys on 10 golf courses detected an unknown disease on one course in 2009 and on another course in 2012 and 2013 at 29 to 30°C daily average. The second course had symptoms on about 25% of the turf of two putting greens. Diseased bentgrass (Agrostis stolonifera L.) had a green dappled pattern with irregular patches of turfgrass on yellowed leaves. Prior to decaying, affected leaves turned brown and then gray. Crown and leaf sheath infections resulted in dark brown dry rot. No lesions were observed on the roots. Leaves were surface disinfected with 5% commercial bleach (0.225% sodium hypochlorite) and cultured on potato dextrose agar (PDA). Ten fungal colonies grew from the leaf tissue, and brown mycelia, conidiophores, and conidia were observed under a microscope. Conidia were ventricose pyriform, mostly abruptly curved, 20 to 36 µm (30 µm, SD = 4) × 7 to 12 µm (10.5 µm, SD = 1.3) (n = 50), predominantly three-septate, with a prominent hilum and enlarged and darkened central cells. Colonies grown on PDA were black-brown with a black reverse side. Conidia differed in size, 15.4 to 24.6 µm (19.99 µm, SD = 3.00) × 6 to 11 μm (8.68 µm, SD = 1.54) (n = 50) and morphology (cylindrical or slightly curved). These characteristics were consistent with Curvularia trifolii (Kauffm.) Boedijn. (Ellis 1971; Falloon 1976; Khadka 2016). Species identification of the representative isolate A2 1.12 was confirmed by analysis of nucleotide sequences of the ITS1-5.8S-ITS2 region using primers ITS1 and ITS4 (White et al. 1990) and GPDH gene region with primer set gpd (Koike et al. 2013). BLAST searches of GenBank showed a high similarity of the isolate ITS sequence (MG029439) to the reference sequence JN712458 of C. trifolii (99% identity) and GPDH sequence (MK570108) with LT715803.1 (97.88% identity). The maximum likelihood phylogenetic tree showed that our isolate clustered with C. trifolii. The pathogenicity assay of this isolate was conducted in greenhouse on A. stolonifera ‘Penncross’. The isolate was grown on PDA (25°C, 10 days). Five pots (100 ml) were filled with a sand and peat mix (9:1 v/v) with 0.06 g of seeds per pot, covered with a fine sand layer. Turfgrass was cut once a week beginning 2 weeks after seeding and was fertigated with 0.5 g/liter of Peter’s foliar feed (27 + 15 + 12; N + P2O5 + K2O; and micronutrients; Scotts, Heerlen, The Netherlands). To obtain a conidial suspension for inoculation, cultured plates were scraped with a sterilized spreader and water. The suspension was filtered through a sterile gauze. Conidia were counted under a microscope (400×) with a hemocytometer. The suspension was adjusted to 8 × 103 conidia/ml, and 10 ml was sprayed per pot. Pots maintained humidity for 2 days under microtunnels. The first disease symptoms appeared 3 days after inoculation. Bentgrass from the five pots developed Curvularia blight and rotted crown symptoms. Control plants (five pots treated with water) did not display symptoms. This trial was repeated once. On PDA, C. trifolii was reisolated from leaf lesions and morphologically identified, confirming Koch’s postulates. Ellis (1971) referred to the presence of C. trifolii in Portugal, but no region, symptom description, or grass species was detailed. Sivanesan (1987) reported C. trifolii in Portugal only on Lolium multiflorum. Therefore, this is the first report of C. trifolii in Algarve, affecting A. stolonifera. This disease can increase maintenance costs in greens in this area.
- Scavenging behavior and interspecific competition decrease offspring fitness of the entomopathogenic nematode Steinernema feltiaePublication . PEREZ, RUBEN; Bueno-Pallero, Francisco Angel; Vicente-Diez, Ignacio; Santiago Marco-Mancebon, Vicente; Perez-Moreno, Ignacio; Campos-Herrera, RaquelEntomopathogenic nematodes (EPNs) are well-studied biocontrol agents of soilw-dwelling arthropod pests. The insecticidal efficiency of EPNs is modulated by food web dynamics. EPNs can reproduce in freeze-killed insect larvae, even in competition with free-living bacterivorous nematodes (FLBNs) in the genus Oscheius. The objective of this study was to assess the efficiency of EPNs as scavengers when competing with free-living saprophagous nematodes and fungi, and to determine the possible impact on subsequent EPN offspring fitness. Live and freeze-killed larvae of Galleria mellonella were used to evaluate the reproduction rate and progeny fitness of two EPN species, Heterorhabditis bacteriophora and Steinernema feltiae, applied individually or combined with the FLBN species Oscheius onirici or Pristionchus maupasi, or Aspergillus flavus, an opportunistic saprophytic fungus. We hypothesized that (1) EPN scavenging behaviors previously observed (for H. megidis and S. kraussei) apply to other EPN species, (2) infective juveniles (IJs) emerging from freeze-killed larvae will display reduced pathogenicity and reproduction, and (3) fitness reduction will be amplified by exposure to other organisms competing for the resources. The reproduction rate of S. feltiae was lower in freeze-killed larvae than in larvae infected and killed by the nematode, whereas H. bacteriophora failed to reproduce as a scavenger. The S. feltiae Fl IJs that emerged from freeze-killed larvae exhibited lower pathogenicity rates than Us resulting from entomopathogenic activity, and also lower reproductive rates if they experienced high FLBN competitive pressure during development. This study illustrates that scavenging is a suboptimal alternative pathway for EPNs, especially in the face of scavenger competition, even though it provides a means for some EPN species to complete their life-cycle.