This study examines whether the length of the relationship between a company and an audit firm (audit‐firm tenure) is associated with financial‐reporting quality. Using two proxies for financial‐reporting quality and a sample of Big 6 clients matched on industry and size, we find that relative to medium audit‐firm tenures of four to eight years, short audit‐firm tenures of two to three years are associated with lower‐quality financial reports. In contrast, we find no evidence of reduced financial‐reporting quality for longer audit‐firm tenures of nine or more years. Overall, our results provide empirical evidence pertinent to the recurring debate regarding mandatory audit‐firm rotation — a debate that has, to date, relied on anecdotal evidence and isolated cases.

Genetic markers linked with quantitative trait loci (QTL) may enable indirect selection of complex disease resistance. Construction of separate linkage maps to identify QTL for each complex disease resistance trait of common bean (Phaseolus vulgaris L.) is unfeasible, however. We investigated whether selective mapping could be used to hasten identification of random amplified polymorphic DNA (RAPD) associated with QTL conditioning bean golden mosaic virus (BGMV) or common bacterial blight (CBB) resistance. The mapping population (‘Dorado’ × XAN 176) consisted of 79 F5:7 recombinant inbred lines. A bulked segregant analysis (BSA) of as few as three individuals and selective genotyping was used. The 101 RAPDs identified between the parents were tested across resistant vs. susceptible bulks for BGMV reaction, combined greenhouse (leaf) and field reactions to CBB, and pod (greenhouse) reaction to CBB. Fourteen of 22 RAPDs selectively mapped because they cosegregated among lines within bulks, were linked with seven of the nine QTL conditioning resistance as identified by QTL mapping using all 101 RAPDs. The two QTL not identified by this approach had minor effects. BSA and selective genotyping required only about one‐third the cost and labor of completely classifying the whole population with each marker and was similarly effective for identifying RAPD markers associated with major‐effect QTL that condition disease resistance in common bean. Two‐locus models (R2), for select environments, explained 60% of the phenotypic variation in BGMV reaction, and 65, 58, and 46% of the phenotypic variation in greenhouse‐leaf, ‐pod, and field reactions to CBB. Repulsion linkages between QTL for BGMV and CBB may complicate the combination of resistance alleles for these two traits.

Long-distance dispersal in microbial eukaryotes has been shown to result in the establishment of populations on continental and global scales. Such “ubiquitous dispersal” has been claimed to be a general feature of microbial eukaryotes, homogenising populations over large scales. However, the unprecedented sampling of opportunistic infectious pathogens created by the global AIDS pandemic has revealed that a number of important species exhibit geographic endemicity despite long-distance migration via aerially dispersed spores. One mechanism that might tend to drive such endemicity in the face of aerial dispersal is the evolution of niche-adapted genotypes when sexual reproduction is rare. Dispersal of such asexual physiological “species” will be restricted when natural habitats are heterogeneous, as a consequence of reduced adaptive variation. Using the HIV-associated endemic fungus Penicillium marneffei as our model, we measured the distribution of genetic variation over a variety of spatial scales in two host species, humans and bamboo rats. Our results show that, despite widespread aerial dispersal, isolates of P. marneffei show extensive spatial genetic structure in both host species at local and country-wide scales. We show that the evolution of the P. marneffei genome is overwhelmingly clonal, and that this is perhaps the most asexual fungus yet found. We show that clusters of genotypes are specific to discrete ecological zones and argue that asexuality has led to the evolution of niche-adapted genotypes, and is driving endemicity, by reducing this pathogen's potential to diversify in nature.

In order to preserve and exploit the valuable genetic resources of tropical forest trees, such as cocoa, a systematic assessment of the available genetic variability is necessary. The approach we have used is based on a simple mini-prep DNA extraction procedure together with a polymerase-chain-reaction- (PCR)-based polymorphic assay procedure (RAPD). Twenty-five cocoa accessions: IMCs and PAs collected from Peru and LCTEENs collected from Ecuador, which are difficult to distinguish using morphological or biochemical descriptors, were uniquely fingerprinted using a minimum of three oligonucleotide primers. Analysis of the variability detected using RAPDs clearly discriminated between the geographical origin of the three cocoa populations. Partitioning of variability into within and between population components revealed that most variation was detected within a population. The potential of RAPD analysis to facilitate the rationalization of field gene banks and provide accurate estimates of diversity to allow optimization of collecting strategies is discussed.

The Guatemalan black bean (Phaseolus vulgaris L.) plant introduction (PI) 181996 is resistant to all known US races of the bean rust fungus Uromyces appendiculatus (Pers. ex Pers.) Unger var. appendiculatus [syn. U. phaseoli (Reben) Wint.]. We report on two random amplified polymorphic DNA (RAPD) markers OAC20490 tightly linked (no recombinants) in coupling phase and OAE19890 linked in repulsion phase (at 6.2±2.8 cM) to PI 181996 rust resistance. These RAPDs, generated by single decamer primers in the polymerase chain reaction, were identified in near-isogenic bulks of non-segregating resistant and susceptible BC4F2 (NX-040*4/PI 181996) lines. Linkage of the RAPD markers was confirmed by screening 19 BC4F2 and 57 BC4F3 individuals segregating for PI 181996 resistance. Utility of the RAPDs OAC20490 and OAE19890 was investigated in a diverse group of common bean cultivars and lines. All cultivars into which the PI 181996 resistance was introgressed had the RAPD OAC20490. A RAPD similar in size to OAC20490, observed in some susceptible common bean lines, was confirmed by Southern blotting to be homologous to the RAPD OAC20490. Use of the RAPDs OAC20490 and OAE19890 in marker-assisted selection (MAS) is proposed. The coupling-phase RAPD is most useful for MAS of resistant BCnF1individuals during traditional backcross breeding. The repulsion-phase RAPD has greatest utility in MAS of homozygous-resistant individuals in F2 or later-segregating generations.