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A linkage mapping approach was used to identify quantitative trait loci (QTL) associated with day-neutrality in the commercial strawberry, Fragaria × ananassa (Duch ex Rozier). Amplified Fragment Length Polymorphism (AFLP) markers were used to build a genetic map with a population of 127 lines developed by crossing the day-neutral (DN) ‘Tribute’ with the short-day (SD) ‘Honeoye’. The population was genotyped with AFLP markers and 429 single dose restriction fragments (SDRF) were placed on a consensus map of 1541 cM with 43 linkage groups. Individuals from the mapping population were observed for their flowering habit throughout the growing season in Michigan (MI), Minnesota (MN), Maryland (MD), Oregon (OR) and California (CA). Eight QTL were found that were either location specific or shared among locations. None of these QTL explained >36% of the phenotypic variation, indicating that the inheritance of day-neutrality is likely a polygenic trait. [ABSTRACT FROM AUTHOR]

Provides information on Ovation, a June-bearing strawberry cultivar which was introduced for propagation to nurseries in January 2003 by the U.S. Department of Agriculture-Agricultural Research Service. Origin and seedling selection; Technical description; Performance; Area of adaptation; Fruit nutritional characteristics.

Soybean (Glycine max L. Merrill) linkage group A2 contains a major resistance gene to the soybean cyst nematode (Heterodera glycines Ichinohe) at the Rhg4 locus near a gene encoding aspartokinase homoserine dehydrogenase (AK-HSDH) and also near the I locus affecting seed coat color. To identify clones related to this region of the genome, we used a PCR assay using primers designed from a gene encoding AK-HSDH to screen approximately 40,000 clones from a bacterial artificial chromosome (BAC) library constructed from genomic DNA of the susceptible cv. Williams 82. The identified BACs were screened with a second PCR assay using primers designed from DNA sequence associated with the I locus to confirm the location of the BACs. Only BAC Gm_ISb001_056_G02 (56G2) was positive for both assays. BAC 56G2 contains several genes previously associated with stress or defense response including genes with high sequence similarity to those encoding chalcone synthase, glucosyl-transferase, a heat-shock transcription factor, a membrane-associated salt-inducible protein, adenosyl homocysteinase, a protein kinase, and a G10-like protein. The map contributes to our understanding of the organization of the soybean genome and to the completion of a physical map of the soybean genome. In addition, the genes identified provide landmarks to identify BAC clones near the Rhg4 locus in resistant soybean genomic libraries and provide a foundation for comparison of soybean cyst nematode resistant and -susceptible DNA sequences in this region. [ABSTRACT FROM AUTHOR]

Profiles several strawberry breeders based in eastern North America. Walter van Fleet; George Darrow; Emmett Brown Morrow; Donald H. Scott; Charles Lewis Ricketson.

Abstract Background The recent development of novel repeat-fruiting types of blackberry (Rubus L.) cultivars, combined with a long history of morphological marker-assisted selection for thornlessness by blackberry breeders, has given rise to increased interest in using molecular markers to facilitate blackberry breeding. Yet no genetic maps, molecular markers, or even sequences exist specifically for cultivated blackberry. The purpose of this study is to begin development of these tools by generating and annotating the first blackberry expressed sequence tag (EST) library, designing primers from the ESTs to amplify regions containing simple sequence repeats (SSR), and testing the usefulness of a subset of the EST-SSRs with two blackberry cultivars. Results A cDNA library of 18,432 clones was generated from expanding leaf tissue of the cultivar Merton Thornless, a progenitor of many thornless commercial cultivars. Among the most abundantly expressed of the 3,000 genes annotated were those involved with energy, cell structure, and defense. From individual sequences containing SSRs, 673 primer pairs were designed. Of a randomly chosen set of 33 primer pairs tested with two blackberry cultivars, 10 detected an average of 1.9 polymorphic PCR products. Conclusion This rate predicts that this library may yield as many as 940 SSR primer pairs detecting 1,786 polymorphisms. This may be sufficient to generate a genetic map that can be used to associate molecular markers with phenotypic traits, making possible molecular marker-assisted breeding to compliment existing morphological marker-assisted breeding in blackberry.

The plant family Rosaceae consists of over 100 genera and 3,000 species that include many important fruit, nut, ornamental, and wood crops. Members of this family provide high-value nutritional foods and contribute desirable aesthetic and industrial products. Most rosaceous crops have been enhanced by human intervention through sexual hybridization, asexual propagation, and genetic improvement since ancient times, 4,000 to 5,000 B.C. Modern breeding programs have contributed to the selection and release of numerous cultivars having significant economic impact on the U.S. and world markets. In recent years, the Rosaceae community, both in the United States and internationally, has benefited from newfound organization and collaboration that have hastened progress in developing genetic and genomic resources for representative crops such as apple (Malus spp.), peach (Prunus spp.), and strawberry (Fragaria spp.). These resources, including expressed sequence tags, bacterial artificial chromosome libraries, physical and genetic maps, and molecular markers, combined with genetic transformation protocols and bioinformatics tools, have rendered various rosaceous crops highly amenable to comparative and functional genomics studies. This report serves as a synopsis of the resources and initiatives of the Rosaceae community, recent developments in Rosaceae genomics, and plans to apply newly accumulated knowledge and resources toward breeding and crop improvement.

Infection of the soybean root by the soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) induces a well-documented, yet poorly understood, response by the host plant. The plant response, involving the differentiation of a feeding structure, or "syncytium," facilitates the feeding and reproduction of the nematode to the detriment of the host. We used a genetic system involving a single dominant soybean gene conferring susceptibility to an inbred nematode strain, VL1, to characterize the nematode-host interaction in susceptible line PI 89008. The restriction fragment length polymorphism marker pB053, shown to map to a major SCN resistance locus, cosegregates with resistance among F2 progeny from the PI 89008 x PI 88287 cross. Cytological examination of the infection process confirmed that syncytium development in this genetic system is similar to that reported by others who used noninbred nematode lines. Our study of infected root tissue in the susceptible line PI 89008 revealed a number of genes enhanced in expression. Among these are catalase, cyclin, elongation factor 1alpha, beta-1,3-endoglucanase, hydroxy-methylglutaryl coenzyme A reductase, heat shock protein 70, late embryonic abundant protein 14, and formylglycinamidine ribonucleotide synthase, all of which we have genetically positioned on the public linkage map of soybean. Formylglycinamidine ribonucleotide synthase was found to be tightly linked with a major quantitative trait locus for SCN resistance. Our observations are consistent with the hypothesis proposed by others that feeding site development involves the dramatic modulation of gene expression relative to surrounding root cells.