Consumer demand regarding the impacts of conventional agriculture on the environment and human health have spurred the growth of organic farming systems; however, organic agriculture is often criticized as low-yielding and unable to produce enough food to supply the world's population. Using wheat as a model crop species, we show that poorly adapted cultivars are partially responsible for the lower yields often found in organic farming systems when compared with conventional farming systems. Our results demonstrate that the highest yielding soft white winter wheat genotypes in conventional systems are not the highest yielding genotypes in organic systems. An analysis of variance for yield among 35 genotypes between paired organic and conventional systems showed highly significant (P < 0.001) genotype  system interactions in four of five locations. Genotypic ranking analysis using Spearman's rank correlation coefficient (R S ) showed no correlation between genotypic rankings for yield in four of five locations; however, the ranks were correlated for test weight at all five locations. This indicates that increasing yield in organic systems through breeding will require direct selection within organic systems rather than indirect selection in conventional systems. Direct selection in organic systems produced yields 15%, 7%, 31% and 5% higher than the yields resulting from indirect selection for locations 1-4, respectively. With crop cultivars bred in and adapted to the unique conditions inherent in organic systems, organic agriculture will be better able to realize its full potential as a high-yielding alternative to conventional agriculture. Published by Elsevier B.V.

The objective of this study was to determine the Vrn-1 allelic composition of spring wheat germplasm from the Pacific Northwest region of the USA. Individual plants from 56 spring wheat lines were crossed to near-isogenic tester lines carrying the dominant allele Vrn-A1, Vrn-B1 or Vrn-D1. F 2 progeny were evaluated for growth habit in the field and Vrn-1 allelic composition was determined through chisquare analysis. Lines also were analysed with DNA sequence-based Vrn-1 allele-specific markers. A majority of the germplasm carried the dominant allele Vrn-A1a alone or in combination with Vrn-B1, Vrn-D1 or Vrn-B3 alleles. Vrn-B1 and Vrn-D1 were almost always associated with other dominant Vrn-1 allele(s). Based on DNA sequence analysis, a novel Vrn-B1 allele referred to as Vrn-B1b, which carried a single nucleotide polymorphism (SNP) and a 36 bp deletion, was identified in cultivar ÔAlpowaÕ. These results will be useful to wheat breeders for choosing parents with different Vrn-1 alleles for crossing to maximize diversity at the Vrn-1 loci with an expectation of identifying superior Vrn-1 allelic combinations for cultivar improvement.

Hansen, Jennifer L.; Zemetra, Robert S.; Santra, Dipak K.; Campbell, Kimberly G.; and Riera-Lizarazu, Oscar, "Identification of a candidate gene for the wheat endopeptidase Ep-D1 locus and two other STS markers linked to the eyespot resistance gene Pch1" (2008 Abstract Wheat is prone to strawbreaker foot rot (eyespot), a fungal disease caused by Oculimacula yallundae and O. acuformis. The most eVective source of genetic resistance is Pch1, a gene derived from Aegilops ventricosa. The endopeptidase isozyme marker allele Ep-D1b, linked to Pch1, has been shown to be more eVective for tracking resistance than DNA-based markers developed to date. Therefore, we sought to identify a candidate gene for Ep-D1 as a basis for a DNA-based marker. Comparative mapping suggested that the endopeptidase loci Ep-D1 (wheat), enp1 (maize), and Enp (rice) were orthologous. Since the product of the maize endopeptidase locus enp1 has been shown to exhibit biochemical properties similar to oligopeptidase B puriWed from E. coli, we reasoned that Ep-D1 may also encode an oligopeptidase B. Consistent with this hypothesis, a sequence-tagged-site (STS) marker, Xorw1, derived from an oligopeptidase B-encoding wheat expressed-sequence-tag (EST) showed complete linkage with Ep-D1 and Pch1 in a population of 254 recombinant inbred lines (RILs) derived from a cross between wheat cultivars Coda and Brundage. Two other STS markers, Xorw5 and Xorw6, and three microsatellite markers (Xwmc14, Xbarc97, and Xcfd175) were also completely linked to Pch1. On the other hand, Xwmc14, Xbarc97, and Xcfd175 showed recombination in the W7984 £ Opata85 RIL population suggesting that recombination near Pch1 is reduced in the Coda/Brundage population. In a panel of 44 wheat varieties with known eyespot reactions, Xorw1, Xorw5, and Xorw6 were 100% accurate in predicting the presence or absence of Pch1 whereas Xwmc14, Xbarc97, and Xcfd175 were less eVective. Thus, linkage mapping and a germplasm survey suggest that the STS markers identiWed here should be useful for indirect selection of Pch1.