RÉSUMÉ
Cotton (Gossypium spp) is one of the most economically important crops that provide the world's most widely used natural fiber. Diseases such as Fusarium wilt and particularly Verticillium wilt seriously affect cotton production, and thus breeding for disease resistance is one of the most important goals of cotton breeding programs. Currently, potential exists to improve disease resistance in cultivated cotton. Increasing the understanding of the distribution, structure, and organization of genes or quantitative trait loci for disease resistance will help the breeders improve crop yield even in the event of disease. To facilitate the mapping of disease-resistance quantitative trait loci to achieve disease-resistant molecular breeding in cotton, it is necessary to develop polymorphic molecular markers. The objective of this study was to develop simple sequence repeat markers based on cotton expressed sequence tags for disease resistance. The efficacy of these simple sequence repeat markers, their polymorphisms, and cross-species transferability were evaluated. Their value was further investigated based on genetic diversity and evolution analysis. In this study, the unique sequences used to develop markers were compared with the G. arboretum and G. raimondii genome sequences to investigate their position, homology, and collinearity between G. arboretum and G. raimondii.
Sujet(s)
Chromosomes de plante/composition chimique , Résistance à la maladie/génétique , Gossypium/génétique , Maladies des plantes/génétique , Polymorphisme génétique/immunologie , Locus de caractère quantitatif , Séquence nucléotidique , Évolution biologique , Cartographie chromosomique , Résistance à la maladie/immunologie , Fusarium/pathogénicité , Fusarium/physiologie , Marqueurs génétiques , Gossypium/classification , Gossypium/immunologie , Gossypium/microbiologie , Répétitions microsatellites , Données de séquences moléculaires , Phylogenèse , Amélioration des plantes , Maladies des plantes/immunologie , Maladies des plantes/microbiologie , Alignement de séquences , Similitude de séquences d'acides nucléiques , Verticillium/pathogénicité , Verticillium/physiologieRÉSUMÉ
To understand the natural history of chronic hepatitis B virus infection in children, we studied factors affecting the clearance of hepatitis B e antigen (HBeAg). One hundred sixty-nine apparently healthy children whose sera were positive for HBeAg and hepatitis B surface antigen (HBsAg) and who were recruited by screening were followed prospectively to delineate the HBeAg clearance rate. Another 59 carrier children visiting the outpatient clinic because of symptoms or abnormal liver function were studied for comparison. The annual HBeAg clearance rate was low (less than 2%) during the first 3 years of life but increased with age. The HBeAg clearance rate in children older than 6 years of age was lower in those whose mothers had HBsAg positivity (14.3%) than in those whose mothers had no detectable HBsAg (35.3%). Children who were brought for medical care had higher HBeAg clearance rates (42.4%) than those who were recruited by screening (14.6%) because immune clearance of hepatitis B virus and hence HBeAg often led to hepatocellular damage manifested by abnormal liver function profiles or by symptoms that had caused the parents to seek medical care for their children. We conclude that age, source of subject recruitment, and maternal HBsAg status are important factors affecting HBeAg clearance rate in HBsAg carriers.