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Soon O. Park, Dermot P. Coyne, James R. Steadman, and Geunhwa Jung

White mold, incited by Sclerotinia sclerotiorum (Ss), is an important disease of common bean (Phaseolus vulgaris). Our objective was to identify RAPD markers and seedcoat pattern associated with QTL affecting resistance to Ss isolates 152 and 279 in a molecular marker-based linkage map previously constructed using a recombinant inbred (RI) population from the common bean cross `PC-50' (resistant to Ss) x XAN-159 (susceptible to Ss). White mold reactions were derived from a greenhouse straw test. Continuous distributions for the reactions to Ss isolates 152 and 279 were observed for RI lines, indicating quantitative inheritance. An intermediate (+0.67) Pearson correlation was observed between the reactions to Ss isolates 152 and 279. Low (0.24 and 0.23) narrow-sense heritabilities were found for the reactions to Ss isolates 152 and 279. Three QTL affecting resistance to Ss isolate 152 explained 33% of the phenotypic variation. Four QTL affecting resistance to Ss isolate 279 explained 54% of the phenotypic variation. The seedcoat pattern marker (C) on linkage group I was most consistently associated with resistance to Ss isolates 152 and 279, and explained 10% and 24% of the phenotypic variation for the traits, respectively. This is the first report on detection of QTL for white mold resistance in common bean. The RAPD markers and seedcoat pattern could be useful in breeding for white mold resistance.

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Geunhwa Jung, Paul W. Skroch, Dermot P. Coyne, James Nienhuis, E. Arnaud-Santana, H.M. Ariyarathne, Shawn M. Kaeppler, and Mark J. Bassett

Randomly amplified polymorphic DNA (RAPD) molecular markers were used to construct a partial genetic linkage map in a recombinant inbred population derived from the common bean (Phaseolus vulgaris L.) cross PC-50 × XAN-159 for studying the genetics of bacterial disease resistance in common bean. The linkage map spanned 426 cM and included 168 RAPD markers and 2 classical markers with 11 unassigned markers. The seventy recombinant inbred lines were evaluated for resistance to two strains of common bacterial blight [Xanthomonas campestris pv. phaseoli (Smith) Dye] (Xcp). Common bacterial blight (CBB) resistance was evaluated for Xcp strain EK-11 in later-developed trifoliolate leaves and for Xcp strains, DR-7 and EK-11, in first trifoliolate leaves, seeds, and pods. One to four quantitative trait loci (QTLs) accounted for 18% to 53% of the phenotypic variation for traits. Most significant effects for CBB resistance were associated with one chromosomal region on linkage group 5 and with two regions on linkage group 1, of the partial linkage map. The chromosomal region (a 13-cM interval) in linkage group 5 was significantly associated with resistance to Xcp strains DR-7 and EK-11 in leaves, pods, and seeds. The regions in linkage group 1 were also significantly associated with resistance to both Xcp strains in more than one plant organ. In addition, a seedcoat pattern gene (C) and a flower color gene (vlae) were mapped in linkage groups 1 and 5, respectively, of the partial linkage map. The V locus was found to be linked to a QTL with a major effect on CBB resistance.

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Rebecca C. Lough and R.G. Gardner

During the last century Phytophthora infestans (Mont.) de Bary, which causes the devastating disease late blight of tomato and potato, has been controlled with pesticides. Recently, the difficulty of controlling late blight has increased due to the appearance of new strains of P. infestans that are more virulent and are resistant to metalaxyl. Numerous P. infestans resistance genes exist within the Solanaceae; however, most of these are race-specific and have the potential of being overcome. To achieve durable resistance, it may be necessary to utilize multigenic resistance or gene pyramiding. The Lycopersicon hirsutum Kunth accession LA1033 is highly resistant to P. infestans. To incorporate resistance into a useful background, the L. esculentum Miller inbred line NC215E was used as a recurrent parent in backcrossing with L. hirsutum LA1033. A population of 264 BC3F1 plants derived from 11 BC2F2 families was planted at Fletcher and Waynesville, N.C., in July 1998 in a replicated field trial. BC3F2 seed were collected from a single highly resistant BC3F1 plant. The BC3F2 population was tested for resistance using a detached leaf screen. To verify growth chamber test results, BC3F3 seeds were collected from the BC3F2 individuals and were planted in a field trial at Fletcher in July 1999. The ratio of resistant to susceptible progeny fit the expected ratio for an incompletely dominant trait controlled by two loci. To identify molecular markers linked to the resistance loci, DNA was extracted from the highly resistant and susceptible BC3F2 individuals, and bulks of DNA were constructed. The resistant and susceptible bulks were screened with AFLP (amplified fragment length polymorphism) markers. Results of the AFLP study indicate marker linkage to resistance.

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Milica Ćalović, Chunxian Chen, Qibin Yu, Vladimir Orbović, Frederick G. Gmitter Jr, and Jude W. Grosser

histogram produced by the ploidy analyzer. EST-SSR molecular analysis. Selected somatic tetraploid plants were further tested with molecular markers using EST-SSR method to determine whether they were auto- or allotetraploids. Genomic DNA of recovered

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Michael J. Havey and Yul-Kyun Ahn

polymorphisms in expressed regions of larger genomes useful for diversity analyses and development of genetic maps ( Duangjit et al., 2013 ; Gore et al., 2009 ; Ipek et al., 2015 ; Kuhl et al., 2004 ; Martin et al., 2005 ). Molecular markers, such as

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Christopher S. Cramer and Michael J. Havey

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Melinda A. Miller-Butler, Barbara J. Smith, Brian R. Kreiser, and Eugene K. Blythe

; Lerceteau-Köhler et al., 2003 ), which allows breeders to identify dominant and recessive alleles for these loci. The advent of molecular genetics provided plant breeders with molecular markers to use for identification of alleles linked to disease

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Innocenzo Muzzalupo, Francesca Stefanizzi, and Enzo Perri

/or developmental stages ( Martins-Lopes et al., 2007 ). An ideal molecular marker technique should have the following criteria: 1) to be polymorphic and evenly distributed throughout the genome; 2) to provide adequate resolution of genetic differences; 3) to be

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Carlos Calderón-Vázquez, Mary L. Durbin, Vanessa E.T.M. Ashworth, Livia Tommasini, Kapua K.T. Meyer, and Michael T. Clegg

, 2010 ). Selection on molecular markers such as simple sequence repeats (SSRs) or single nucleotide polymorphisms (SNPs) associated with traits of economic value promise to increase breeding efficiency for beneficial traits, especially in long-lived tree

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Leigh K. Hawkins, Fenny Dane, and Thomas L. Kubisiak

Morphological traits were examined in an F3 generation derived from a cross between C. lanatus var. lanatus [(Thunb.) Matsum. & Nakai] and C. lanatus var. citroides. At least three genes, C (yellow) vs. c (red), i (inhibitory to C) vs. I (non-inhibitory to C), and y (yellow) vs. yw (white), with epistatic and inhibitory actions were found to govern the inheritance of fruit flesh color. The high frequency of yellow-fleshed fruit and low frequencies of white and red fruits can be explained by the presence of a new allele (yw recessive to y) in the multiple allele series at the Y locus. The low frequency of tan colored seeds in segregating populations could be explained by at least three genes governing inheritance of seed-coat color. Single factor analysis of variance was conducted for each pairwise combination of random amplified polymorphic DNA (RAPD) locus and fruit or seed characteristics. Several RAPD loci were identified to be loosely linked to morphological characteristics.