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Climate change presents new challenges for managing plant health. Simultaneously, the revolution in sequencing technologies offers an exciting new perspective on whole microbial communities – and on both microbial responses to climate and microbial effects on plant health. There is still the need for a comparable revolution in experimental approaches to understand the functional roles of microbial taxa within these communities. Two approaches leveraging advances in genomics tools and analyses may contribute. First, new soil mixing experiments may be developed, where analyses of quantitative trait taxa (QTT) may be analogous to analyses of quantitative trait loci (QTL). Second, new approaches for characterizing the extended phenotype or phenome of soil microbial communities may be developed, leveraging genomic tools for Arabidopsis and other model plant species through the construction of plant genotype panels in an ‘Arabidopsitron’. [ABSTRACT FROM PUBLISHER]

A detailed description of local population structure in Arabidopsis thaliana is presented, including an assessment of the genetic relatedness of individuals collected from the same field. A hierarchical sample of four individuals from 37 local populations, including North America, England, Eastern and Western Europe, and Asia, and a selection of ecotypes, were analysed for variation in Adh, ChiA, FAH1, F3H, Rpm1, Rps5, and five microsatellite loci. Twenty-eight of the 37 population samples contained individuals with identical multilocus haplotypes, 12 of which were fixed for a single haplotype. These monomorphic populations were evenly distributed over the species range. Only in North America did we find a single multilocus haplotype shared among different populations, perhaps indicating a continental founder event. Despite the occurrence of local inbreeding, a considerable amount of genetic variation was found segregating within and among local populations. A novel analysis of haplotype differences reveals that genetic differentiation occurs at every geographic scale in A. thaliana, where we find a surprising under-representation of recent migrants between local populations. This leads us to hypothesize that most dispersal between A. thaliana populations is by pollen rather than seed. Based on the structure of A. thaliana populations, it appears that regional groups of local populations may provide the most appropriate genetic material for linkage disequilibrium mapping of adaptive traits. [ABSTRACT FROM AUTHOR]

Abstract: Fusarium fujikuroi and Fusarium proliferatum are two phylogenetically closely related species of the Gibberella fujikuroi species complex (GFC). In some cases, strains of these species can cross and produce a few ascospores. In this study, we analyzed 26 single ascospore isolates of an interspecific cross between F. fujikuroi C1995 and F. proliferatum D4854 for their ability to produce four secondary metabolites: gibberellins (GAs), the mycotoxins fusarin C and fumonisin B1, and a family of red polyketides, the fusarubins. Both parental strains contain the biosynthetic genes for all four metabolites, but differ in their ability to produce these metabolites under certain conditions. F. fujikuroi C1995 produces GAs and fusarins, while F. proliferatum D4854 produces fumonisins and fusarubins. The segregation amongst the progeny of these traits is not the expected 1:1 Mendelian ratio. Only eight, six, three and three progeny, respectively, produce GAs, fusarins, fumonisin B1 and fusarubins in amounts similar to those synthesized by the producing parental strain. Beside the eight highly GA3-producing progeny, some of the progeny produce small amounts of GAs, predominantly GA1, although these strains contain the GA gene cluster of the non-GA-producing F. proliferatum parental strain. Some progeny had recombinant secondary metabolite profiles under the conditions examined indicating that interspecific crosses can yield secondary metabolite production profiles that are atypical of the parent species. [Copyright &y& Elsevier]

The article informs that variations in DNA sequence, or polymorphisms, between and within species are thought to harbor the genetic basis of adaptive events. The study of natural selection at the molecular level has long been dominated by Kimura's theory of neutral evolution, which argues that most polymorphisms in both DNA and protein sequence have minor or no selective effect and are governed by random, not selective, processes. The strength of this theory is that it leads to clear predictions that can be tested to identify those polymorphisms that really are subject of selection.