Sunflower domestication alleles support single domestication center in eastern North America.

Phylogenetic analyses of genes with demonstrated involvement in evolutionary transitions can be an important means of resolving conflicting hypotheses about evolutionary history or process. In sunflower, two genes have previously been shown to have experienced selective sweeps during its early domestication. In the present study, we identified a third candidate early domestication gene and conducted haplotype analyses of all three genes to address a recent, controversial hypothesis about the origin of cultivated sunflower. Although the scientific consensus had long been that sunflower was domesticated once in eastern North America, the discovery of pre-Columbian sunflower remains at archaeological sites in Mexico led to the proposal of a second domestication center in southern Mexico. Previous molecular studies with neutral markers were consistent with the former hypothesis. However, only two indigenous Mexican cultivars were included in these studies, and their provenance and genetic purity have been questioned. Therefore, we sequenced regions of the three candidate domestication genes containing SNPs diagnostic for domestication from large, newly collected samples of Mexican sunflower landraces and Mexican wild populations from a broad geographic range. The new germplasm also was genotyped for 12 microsatellite loci. Our evidence from multiple evolutionarily important loci and from neutral markers supports a single domestication event for extant cultivated sunflower in eastern North America.

Risk factors for pediatric tuberculosis infection and disease after household exposure to adult index cases in Alaska.

OBJECTIVES: To determine risk factors for pediatric tuberculosis infection and active tuberculosis. STUDY DESIGN: We examined medical records from multiple sources for all 282 children younger than 15 years in Alaska during the period 1987 to 1994 who were household contacts of an adult with culture-positive pulmonary tuberculosis. RESULTS: Infection developed in 25% of the children and progressed to active disease in 9.6%. Risk factors for pediatric infection included exposure to a parent who had active tuberculosis and exposure to any adult with active tuberculosis who had a cough, smear positivity, or a left upper lobe (LUL) chest lesion (odds ratios, 2.1 to 2.8). Among the 71 children in whom infection developed, Alaska Natives and younger children were more likely to progress to active tuberculosis, as were children exposed to a parent who had active tuberculosis and children exposed to any adult who had a LUL chest lesion (odds ratios, 1.5 to 12). CONCLUSIONS: Although all children with household exposure to adults with active tuberculosis have a high risk of contracting the infection and disease, specific risk factors can be identified and differ for infection and disease. Alaska Natives have an increased risk of progression to disease once infected.