Expanding Maize Genetic Resources with Predomestication Alleles: Maize-Teosinte Introgression Populations

Teosinte ( subsp. H. H. Iltis & Doebley) has greater genetic diversity than maize inbreds and landraces ( subsp. ). There are, however, limited genetic resources to efficiently evaluate and tap this diversity. To broaden resources for genetic diversity studies in maize, we developed and evaluated 928 near-isogenic introgression lines (NILs) from 10 teosinte accessions in the B73 background. Joint linkage analysis of the 10 introgression populations identified several large-effect quantitative trait loci (QTL) for days to anthesis (DTA), kernel row number (KRN), and 50-kernel weight (Wt50k). Our results confirm prior reports of kernel domestication loci and identify previously uncharacterized QTL with a range of allelic effects enabling future research into the genetic basis of these traits. Additionally, we used a targeted set of NILs to validate the effects of a KRN QTL located on chromosome 2. These introgression populations offer novel tools for QTL discovery and validation as well as a platform for initiating fine mapping.

Genetic properties of the maize nested association mapping population

Maize genetic diversity has been used to understand the molecular basis of phenotypic variation and to improve agricultural efficiency and sustainability. We crossed 25 diverse inbred maize lines to the B73 reference line, capturing a total of 136,000 recombination events. Variation for recombination frequencies was observed among families, influenced by local (cis) genetic variation. We identified evidence for numerous minor single-locus effects but little two-locus linkage disequilibrium or segregation distortion, which indicated a limited role for genes with large effects and epistatic interactions on fitness. We observed excess residual heterozygosity in pericentromeric regions, which suggested that selection in inbred lines has been less efficient in these regions because of reduced recombination frequency. This implies that pericentromeric regions may contribute disproportionally to heterosis.

Characteristics of nurse anesthetists working with and without anesthesiologists

All professionally active certified registered nurse anesthetists (CRNAs) in four geographically representative states were surveyed by mail and telephone in 1981, and response rate of greater than or equal to 70% was obtained for each state. CRNAs who worked with anesthesiologists (Group I) were compared with those who worked in hospitals with no anesthesiologists (Group II). More than 75% of both groups were employed by hospitals, but Group II CRNAs (15.5% of respondents) were nearly five times as likely to practice on an independent, fee-for-service basis. Members of Group II worked predominantly in hospitals in small or rural communities and, compared with those in Group I, were more likely to be male and older, less likely to hold a baccalaureate degree, and less likely to use invasive monitoring techniques. Nearly 50% of Group II had no standing consulting relationship with an anesthesiologist. A consultation network supported by telecommunications deserves consideration as a means of providing CRNAs who work independently in small rural hospitals with a cost-effective team approach to anesthesia care.