RESUMEN

Late blight, caused by the oomycete plant pathogen Phytophthora infestans, is a devastating disease of potato and was responsible for epidemics that led to the Irish potato famine in 1845 (refs 1,2,3,4,5). Before the 1980s, worldwide populations of P. infestans were dominated by a single clonal lineage, the US-1 genotype or Ib mitochondrial DNA (mtDNA) haplotype, and sexual reproduction was not documented outside Mexico, the centre of diversity of the pathogen. Here we describe the amplification and sequencing of 100-base-pair fragments of DNA from the internal transcribed spacer region 2 from 28 historic herbarium samples including Irish and British samples collected between 1845 and 1847, confirming the identity of the pathogen. We amplified a variable region of mtDNA that is present in modern Ib haplotypes of P. infestans, but absent in the other known modern haplotypes (Ia, IIa and IIb). Lesions in samples tested were not caused by the Ib haplotype of P. infestans, and so theories that assume that the Ib haplotype is the ancestral strain need to be re-evaluated. Our data emphasize the importance of using historic specimens when making inferences about historic populations.

Asunto(s)

Phytophthora/genética , Enfermedades de las Plantas/historia , Inanición/historia , Secuencia de Bases , Bancos de Muestras Biológicas , ADN Mitocondrial , ADN Ribosómico , Historia del Siglo XIX , Historia del Siglo XX , Humanos , Irlanda , Datos de Secuencia Molecular , Enfermedades de las Plantas/microbiología , Reacción en Cadena de la Polimerasa , Análisis de Secuencia de ADN , Solanum tuberosum/microbiología

RESUMEN

This study investigated the clinical relevance of heavy drinking during the college years and beyond on concurrent and prospective alcohol-related problems in a high-risk sample (N = 377). Measures of heavy drinking and alcohol-related problems were significantly correlated cross-sectionally over the study frame, regardless of how these constructs were operationalized. However, the magnitude of the association between heavy drinking and alcohol-related problems declined substantially over time, with the most pronounced decrease following the college years. Despite this cross-sectional decrease in the association between heavy drinking and alcohol-related problems over time, heavy drinking during the college years significantly and substantially predicted alcohol-use disorders up to 10 years later. Implications for assessment of heavy drinking as well as prevention of problematic alcohol use in college students are discussed.

Asunto(s)

Consumo de Bebidas Alcohólicas/epidemiología , Trastornos Relacionados con Alcohol/etiología , Adulto , Factores de Edad , Consumo de Bebidas Alcohólicas/efectos adversos , Trastornos Relacionados con Alcohol/genética , Trastornos Relacionados con Alcohol/psicología , Intoxicación Alcohólica/epidemiología , Estudios Transversales , Femenino , Estudios de Seguimiento , Predisposición Genética a la Enfermedad , Humanos , Estudios Longitudinales , Masculino , Medio Oeste de Estados Unidos/epidemiología , Pronóstico , Factores de Riesgo , Estudiantes/estadística & datos numéricos , Encuestas y Cuestionarios , Universidades

RESUMEN

ABSTRACT The effect of components of primary inoculum dispersal in soil on the temporal dynamics of Phytophthora blight epidemics in bell pepper was evaluated in field and growth-chamber experiments. Phytophthora capsici may potentially be dispersed by one of several mechanisms in the soil, including inoculum movement to roots, root growth to inoculum, and root-to-root spread. Individual components of primary inoculum dispersal were manipulated in field plots by introducing (i) sporangia and mycelia directly in soil so that all three mechanisms of dispersal were possible, (ii) a plant with sporulating lesions on the soil surface in a plastic polyvinyl chloride (PVC) tube so inoculum movement to roots was possible, (iii) a wax-encased peat pot containing sporangia and mycelia in soil so root growth to inoculum was possible, (iv) a wax-encased peat pot containing infected roots in soil so root-to-root spread was possible, (v) noninfested V8 vermiculite media into soil directly as a control, or (vi) wax-encased noninfested soil as a control. In 1995 and 1996, final incidence of disease was highest in plots where sporangia and mycelia were buried directly in soil and all mechanisms of dispersal were operative (60 and 32%) and where infected plants were placed in PVC tubes on the soil surface and inoculum movement to roots occurred with rainfall (89 and 23%). Disease onset was delayed in 1995 and 1996, and final incidence was lower in plants in plots where wax-encased sporangia (6 and 22%) or wax-encased infected roots (22%) were buried in soil and root growth to inoculum or root-to-root spread occurred. Incidence of root infections was higher over time in plots where inoculum moved to roots or all mechanisms of dispersal were possible. In growth-chamber studies, ultimately all plants became diseased regardless of the dispersal mechanism of primary inoculum, but disease onset was delayed when plant roots had to grow through a wax layer to inoculum or infected roots in tension funnels that contained small volumes of soil. Our data from both field and growth-chamber studies demonstrate that the mechanism of dispersal of the primary inoculum in soil can have large effects on the temporal dynamics of disease.