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San Rafael del Norte, Nicaragua

Blandon-Diaz J.U.,National University of Agriculture at Nicaragua | Blandon-Diaz J.U.,Swedish University of Agricultural Sciences | Widmark A.-K.,Swedish University of Agricultural Sciences | Hannukkala A.,Mtt Agrifood Research Finland | And 3 more authors.
Phytopathology | Year: 2012

Late blight caused by Phytophthora infestans (Mont.) de Bary is a constraint to both potato and tomato crops in Nicaragua. The hypothesis that the Nicaraguan population of P. infestans is genotypically and phenotypically diverse and potentially subdivided based on host association was tested. A collection of isolates was analyzed using genotypic markers (microsatellites and mitochondrial DNA haplotype) and phenotypic markers (mating type, virulence, and fungicide sensitivity). The genotypic analysis revealed no polymorphism in 121 of 132 isolates of P. infestans tested. Only the Ia haplotype and the A2 mating type were detected. Most of the tested isolates were resistant to metalaxyl. The virulence testing showed variation among isolates of P. infestans. No evidence was found of population differentiation among potato and tomato isolates of P. infestans based on the genotypic and phenotypic analysis. We conclude that the Nicaraguan population of P. infestans consists of a single clonal lineage (NI-1) which belongs to the A2 mating type and the Ia mitochondrial DNA haplotype. Moreover, based on the markers used, this population of P. infestans does not resemble the population in countries from which potato seed is imported to Nicaragua or the population in neighboring countries. The data presented here indicate that the NI-1 clonal lineage is the primary pathogen on both potato and tomato, and its success on both host species is unique in a South American context.© 2012 The American Phytopathological Society. Source

Miranda F.,Swedish University of Agricultural Sciences | Miranda F.,National University of Agriculture at Nicaragua | Bylund H.,Swedish University of Agricultural Sciences | Gronberg L.,Swedish University of Agricultural Sciences | And 2 more authors.
Environmental Entomology | Year: 2011

The diamondback moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) is a serious pest of economically important brassica crops such as cabbage (Brassica oleracea Linne). To address the current lack of baseline information concerning predators of P. xylostella, and their potential role as biological control agents, especially in Central America, we aimed to 1) identify predators in northern Nicaragua, and estimate their population densities; 2) assess their killing rate of eggs and larvae of P. xylostella; and 3) assess if predators feed more of smaller P. xylostella larvae. Individuals of selected predator groups were offered eggs, second-or third-instar larvae. Our results indicate that there exists a broad spectrum of predators, within and around cabbage fields in Nicaragua that have the capacity to feed on P. xylostella eggs and larvae under laboratory conditions. Predators with the highest killing rates were adult and larval rove beetles (Staphylinidae), sheet weaving spiders (Linyphiidae), and larger jumping spiders (Salticidae). Although all predator densities varied in space and time the consistently most abundant predator groups with the highest consumption or killing rate, and consequently the highest potential for suppressing P. xylostella populations were wolf spiders (Lycosidae) and rove beetles (Staphylinidae), although sheet weaving spiders, jumping spiders, assassin bugs (Reduviidae), and damsel bugs (Nabidae) also can be important. We conclude that those generalist predators exhibiting the highest killing rates in the laboratory should be considered for further study in the field as candidate species with a role in the management of pest P. xylostella. © 2011 Entomological Society of America. Source

Bommarco R.,Swedish University of Agricultural Sciences | Miranda F.,National University of Agriculture at Nicaragua | Bylund H.,Swedish University of Agricultural Sciences | Bjorkman C.,Swedish University of Agricultural Sciences
Journal of Economic Entomology | Year: 2011

Intensive use of pesticides is common and increasing despite a growing and historically well documented awareness of the costs and hazards. The benefits from pesticides of increased yields from sufficient pest control may be outweighed by developed resistance in pests and killing of beneficial natural enemies. Other negative effects are human health problems and lower prices because of consumers' desire to buy organic products. Few studies have examined these trade-offs in the field. Here, we demonstrate that Nicaraguan cabbage (Brassica spp.) farmers may suffer economically by using insecticides as they get more damage by the main pest diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), at the same time as they spend economic resources on insecticides. Replicated similarly sized cabbage fields cultivated in a standardized manner were either treated with insecticides according common practice or not treated with insecticides over two seasons. Fields treated with insecticides suffered, compared with nontreated fields, equal or, at least in some periods of the seasons, higher diamondback moth pest attacks. These fields also had increased leaf damage on the harvested cabbage heads. Weight and size of the heads were not affected. The farmers received the same price on the local market irrespective of insecticide use. Rates of parasitized diamondback moth were consistently lower in the treated fields. Negative effects of using insecticides against diamondback moth were found for the density of parasitoids and generalist predatory wasps, and tended to affect spiders negatively. The observed increased leaf damages in insecticide-treated fields may be a combined consequence of insecticide resistance in the pest, and of lower predation and parasitization rates from naturally occurring predators that are suppressed by the insecticide applications. The results indicate biological control as a viable and economic alternative pest management strategy, something that may be particularly relevant for the production of cash crops in tropical countries where insecticide use is heavy and possibly increasing. © 2011 Entomological Society of America. Source

Loaisiga C.H.,National University of Agriculture at Nicaragua | Loaisiga C.H.,Swedish University of Agricultural Sciences | Brantestam A.K.,Nordic Genetic Resource Center | Diaz O.,University of Los Lagos | And 2 more authors.
Genetic Resources and Crop Evolution | Year: 2011

Teosintes are the closest relatives to modern maize, Zea mays L. ssp. mays. They are wild grasses with a native distribution area from Mexico to Nicaragua and represent an important genetic resource. However, the genetic diversity of Nicaraguan teosinte (Zea nicaraguensis Iltis et Benz) has not yet been determined. This teosinte species has decreased in the last 25 years and now must be regarded as an endangered species. An analysis of the genetic diversity of Zea nicaraguensis was carried out in a total of 240 individuals from seven populations. Eleven Simple Sequences Repeat (SSR) primer pairs were used. A total of 42 alleles were found, the range of alleles per locus was 2-5 (mean 3.8) and the numbers of genotypes varied between primers. The primer Bnlg 1538 showed the highest value, with 45 genotypes through all populations. The genetic diversity observed (Ho) between all populations varied from 0.51 to 0.63, with an average of 0.563. One of the populations had as many as 40 alleles. Analysis of molecular variance (AMOVA) revealed that most of the variation was within population, at a significantly high level (P < 0.001). Rare alleles were detected in all populations, but unique alleles were only found in four populations. These results are highly relevant when developing conservation strategies and show that preserving populations in their natural habits is highly important. © 2010 Springer Science+Business Media B.V. Source

Mason M.,Alcorn State University | Cuadra E.J.,Alcorn State University | Elsasser T.H.,U.S. Department of Agriculture | Lopez J.,National University of Agriculture at Nicaragua | Yoonsung J.,Prairie View A&M University
Canadian Journal of Animal Science | Year: 2013

Fifty-eight non-lactating cows previously synchronized for estrus were assigned to two treatments to assess the effects of progesterone supplementation and its correlation with tumor necrosis factor-α (TNF-α) and cortisol on the survival of the transferred embryos. On day 7 after exhibiting estrus (day 0), cows in both groups received embryos. In contrast with the control group, animals in the CIDR-group had a controlled internal drug release (CIDR) additionally inserted. Blood samples for progesterone, TNF-α and cortisol analysis were taken immediately before insertion and removal of CIDRs and 7 d after insertion. Progesterone did not differ between the control and the CIDR animals at any day of the study; however, it significantly increased at 7 and 14 d after insertion of the embryos in the control animals, compared with the levels observed in that same experimental group at the time of the transfer. Regardless of the treatment, all pregnant cows experienced a significant increase in progesterone from day 0 to day 7. Progesterone on day 0 was correlated to itself (r =0.46) on day 14 and to TNF-α (r = -0.37) on day 0 in pregnant animals; TNF-α on day 7 was significantly higher in pregnant cows compared with non-pregnant and correlated between day 0 and day 14. These results suggest that high levels of progesterone during the first 14 d after the transfer are indicative of the survival of transferred embryos. Additionally, these data also indicate that the decrease in TNF-α concentration on day 7 after the transfer of embryos may be associated with the low concentrations of progesterone observed in the non-pregnant animals. Source

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