Abstract
The Rio Grande Valley (RGV) in southern Texas is well-suited for vegetable production due to its relatively mild/warm weather conditions in the fall and winter. Consequently, insects inflict year-round, persistent damage to crops in the RGV and regions with similar climate. Bactericera cockerelli (Šulc) (Hemiptera: Triozidae), commonly known as the potato psyllid, is a known vector of Candidatus Liberibacter solanacearum (CLso) (Hyphomicrobiales: Rhizobiaceae), a fastidious phloem-limited bacterium associated to vein-greening in tomatoes and Zebra Chip in potatoes. Vector control is the primary approach of integrated pest management (IPM) strategies that aim to prevent plant diseases in commercial agricultural systems. However, resistance-selective pressures that decrease the effectiveness of chemical control (insecticide) applications over time are of increasing concern. Therefore, we explore an ecological approach to devising alternative IPM methodologies to manage the psyllid-transmitted CLso pathogen to supplement existing chemical products and application schedules without increasing resistance. In this study, our objective was to examine the effects of plant-growth promoting rhizobacteria (PGPR) on host-vector-pathogen interactions. Soil-drench applications of PGPRs to Solanum lycopersicum (Solanales: Solanaceae) seedlings revealed structural and possible physiological changes to the plant host and indirect changes on psyllid behavior: host plants had increased length and biomass of roots and exhibited delayed colonization by CLso, while psyllids displayed changes in parental (F0) psyllid behavior (orientation and oviposition) in response to treated hosts and in the sex ratio of their progeny (F1). Based on our results, we suggest that PGPR may have practical use in commercial tomato production.
Huanglongbing (HLB) is associated with Candidatus Liberibacter asiaticus (CLas). It is a destructive disease of citrus. The objective of this study was to determine the genetic diversity of 90 strains of CLas infecting eight citrus species trees from the Central Pacific in Mexico. Genetic diversity among CLas was estimated by fourteen variable numbers of tandem repeat (VNTRs) loci. Three loci were polymorphic, SSR00 and SSR077 amplified four alleles each, while the locus SSR-A amplified two alleles, and the other loci only one allele per locus, resulting in a total of 21 alleles. Dendrogram analysis showed two clusters. No clear genetic structure was found in relation to geographical origin or host. The cluster I was mostly constituted by the majority of CLas strains (82%), but the cluster II comprised twelve strains of CLas collected in Tecoman location, State of Colima, and were obtained from different citrus hosts species. The frequency of 17 haplotypes among strains of CLas from the states of Nayarit, Jalisco, Colima and Michoacán was analyzed; in Colima 14 haplotypes were determinated, while in Michoacan all strains were identified in one haplotype. These results indicate a large genetic diversity among the strains of CLas present in the Central Pacific region in Mexico.
In Mexico, Huanglongbing HLB has become endemic in all Mexican lime producing areas. This disease is transmitted by the insect Diaphorina citri (Hemiptera: Liviidae). The objective of the study was to evaluate different plant extracts and biorational products for the control of D. citri in mexican lime. Two evaluations were made under field conditions; the first one included five treatments, with previous sampling and at 8, 20 and 27 days after the application of the treatments. In the second, eight treatments were evaluated, with prior sampling and at 6, 21 and 27 days. The response variable was the number of D. citri. A completely randomized experimental design with ten repetitions was used. A test of normality and homogeneity of variances was applied to the data, and they were processed through an analysis of variance and separation of means using Tukey (p≤ 0.05). The sweet clover extract (6.0 mL L-1) at 20 days decreased the population density by 59.2%, and Pyrifluquinazon (0.58 mL L-1) at 6 days the decrease was 31.3%. All the extracts showed to be a sustainable alternative for the management of D. citri.
AbstractCandidatus Neoehrlichia mikurensis (CNM) and Hepatozoon spp. are important vector-borne parasites of humans and animals. CNM is a relatively recently discovered pathogen of humans. Hepatozoon are parasites of reptiles, amphibians and mammals, commonly found in rodents and carnivores worldwide. The present study aimed to determine the prevalence of CNM and Hepatozoon spp. in three species of Microtus and to assess the occurrence of vertical transmission in naturally-infected voles. Molecular techniques were used to detect pathogen DNA in blood and tissue samples of captured voles and their offspring. The prevalence of CNM in the vole community ranged 24–47% depending on Microtus species. The DNA of CNM was detected in 21% of pups from three litters of six infected Microtus dams (two Microtus arvalis and one M. oeconomus) and in 3/45 embryos (6.6%) from two litters of eight CNM-infected pregnant females. We detected Hepatozoon infection in 14% of M. arvalis and 9% of M. oeconomus voles. Hepatozoon sp. DNA was detected in 48.7% of pups from seven litters (6 M. arvalis and 1 M. oeconomus) and in two embryos (14.3%) obtained from one M. arvalis litter. The high prevalence of CNM infections in the Microtus spp. community may be a result of a relatively high rate of vertical transmission among naturally infected voles. Vertical transmission was also demonstrated for Hepatozoon sp. in M. arvalis and M. oeconomus. Our study underlines the significance of alternative routes of transmission of important vector-borne pathogens.