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

Agricultural Research Division journal series paper 12097. Research was conducted under Projects 20-036 and 20-042. We acknowledge financial support from the Title XII Bean/Cowpea CRSP (AID contract DNA-1310-G-SS-6008-00). We also appreciate Anne K. Vidaver

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James S. Beaver, James R. Steadman, and Dermot P. Coyne

Research supported in part by USAID/BIFAD Bean/Cowpea CRSP grant no. AID/DSAN-XII-G-0261. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby

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Carlos A. Urrea, Phillip N. Miklas, and James S. Beaver

High levels of resistance to common bacterial blight caused by Xanthomonas campestris pv. phaseoli (Smith) Dye (Xcp) have been observed for tepary bean (Phaseolus acutifolius A. Gray var. latifolius Freeman). However, the inheritance of resistance from this source is unknown for many lines. The inheritance of common bacterial blight resistance was studied in four tepary bean lines crossed with the susceptible tepary bean MEX-114. Progenies were inoculated with a single Xcp strain 484a. Segregation ratios in the F2 generation suggested that resistance in Neb-T-6-s and PI 321637-s was governed by one dominant gene, and Neb T-8a-s had two dominant genes with complementary effects. These hypotheses for inheritance of resistance were supported by various combinations of F1, F3, BC1Pn segregation data in all lines except PI 321637-s where an additional minor-effect gene with recessive inheritance was indicated. Generation means analyses corroborated that multiple resistance genes were present in PI 321638-s. Lack of segregation for susceptibility among testcrosses for allelism between Neb-T-6-s/PI 321637-s, Neb-T-6-s/Neb-T-8a-s, PI 321637-s/Neb-T-8a-s, and PI 321637-s/PI 321638-s, suggested that one or more loci conditioning resistance to common bacterial blight were in common across the four tepary lines.

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Zhanyuan Zhang, A. Mitra, and D.P. Coyne

Optimization of parameters influencing biolistic transformation is a crucial stage towards repeatable transformation of common beans. However, there has been no published study on such optimization of this crop species in a helium particle delivery system (BioRad). Using an intron-containing β-glucuronidase (GUS) gene as a reporter, we optimized several critical parameters of biolistic PDS-1000/He delivery system for common bean transformation. The target explant tissues included cotyledons, zygotic embryos, and meristemic shoot tips suitable for organogenesis. Thus, pretreatment of target tissues with osmotic medium containing 0.15–0.25 m mannitol and 0.15–0.25 m sorbitol, positioning of target tissues in 4 cm microcarrier flying distance, the use of 1.6-μm gold particle and high concentration of coating DNA, and bombardment of young immature tissues twice at 2000 psi, etc., significantly increased transformation rate and achieved the best coverage and penetration of the meristemic areas involved in direct shoot organogenesis.

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Krista C. Shellie and George L. Hosfield

1 Formerly Dept. of Crop and Soil Sciences, Michigan State Univ., E. Lansing. Current address: USDA-ARS Weslaco, TX 78596. 2 Research Geneticist, USDA, Agricultural Research Service, Sugarbeet, Bean, and Cereal Research Unit and Dept. of Crop and

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Mohamed F. Mohamed, Paul E. Read, and Dermot P. Coyne

20-036. We gratefully acknowledge the financial support of the Title XII Bean/Cowpea CRSP Program (AID Contract no. DAN-1310-G-SS-6008-00). The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations

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

Bean rust, caused by Uromyces appendiculatus, is an important disease of common bean (Phaseolus vulgaris L.). The objective was to identify RAPD markers linked to the gene (Ur-6) for specific resistance to rust race 51 using bulked segregant analysis in an F2 segregating population from the common bean cross pinto `Olathe' (resistant to rust) × great northern Nebraska #1 selection 27 (susceptible to rust). A single dominant gene controlling specific resistance to race 51 was hypothesized based on F2 segregation, and then was confirmed in the F3 generation. A good fit to a 3:1 ratio for band presence to band absence for each of three markers was observed in 100 F2 plants. Three RAPD markers were detected in a coupling phase linkage with the Ur-6 gene. Coupling-phase RAPD marker OAB14.600 was the most closely linked to the Ur-6 gene at a distance of 3.5 cM among these markers. No RAPD markers were identified in a repulsion phase linkage with the Ur-6 gene. The RAPD markers linked to the gene for specific rust resistance of Middle American origin detected here, along with other independent rust resistance genes from other germplasm, could be utilized to pyramid multiple genes into a bean cultivar for more durable rust resistance.

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Antonio Figueira, Kelson Kodama, Isabela Sathler, Eva Mamani, and Siu Mui Tsai

Resistance genes (QTLs and major genes) to various pathogens tend to occur in clusters at specific locations in plant genomes. In common bean (Phaseolus vulgaris), common genomic regions associated with host response to the bacterial pathogen Xanthomonas campestris pv. phaseoli and to the symbiont Rhizobium have been identified. Agrobacterium tumefaciens causes crown gall disease in common bean, and shares similar gene activation mechanisms and host recognition signals with Rhizobium. Genotypic differences in tumorigenesis have been observed and could restrict Agrobacterium-mediated bean genetic transformation. The objectives of this research were: 1) to identify wild Agrobacterium strains inducing contrasting response in bean genotypes; and 2) to identify genomic regions in a core linkage map associated with host response to Agrobacterium infection, in comparison with the position of other symbiont or pathogen resistance genes. Among 10 wild A. tumefaciens strains tested under controlled inoculations of 1-week-old seedlings, Ach5, R10, and mainly Chry5 were virulent to the genotypes tested. The genotype BAT93 was susceptible to Chry5, even at low inoculum concentration, in contrast with JaloEEP558. Increasing levels of N enhanced susceptibility to Chry5, R10 and Ach5. Fifty recombinat inbred lines of BAT93 × JaloEEP558 were inoculated with Chry5 and segregated for tumor formation, with 21 lines not forming tumors. Analysis of variance identified 25 markers in five linkage groups of the core linkage map, significantly associated with Agrobacterium resistance, sharing the same location with QTLs identified for other host-bacteria interactions. (Financed by FAPESP 97/12066-1).

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Scott D. Haley, Phillip N. Miklas, Lucia Afanador, and James D. Kelly

the grant DAN 1310-G-SS-6008-00 from the USAID Bean/Cowpea Collaborative Research Support Program, the Michigan Agricultural Experiment Station, and the USDA-ARS. Mention of a trademark or a proprietary product does not constitute a guarantee or

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Phillip N. Miklas, Valerie Stone, Carlos A. Urrea, and James S. Beaver

A genetic linkage map of 170 RAPD markers mapped across 79 recombinant inbred lines (Dorado and XAN-176) reveal genomic regions that condition multiple disease resistance to fungal (Ashy Stem Blight—Macrophomina phaseolina), viral (bean golden mosaic virus—BGMV), and bacterial (common bacterial blight—Xanthomonas campestris pv. phaseoli) pathogens of common bean (Phaseolus vulgaris). A genomic site on linkage group US-1 had a major effect, explaining 18%, 34%, and 40% of the variation in phenotypic reaction to ashy stem blight, BGMV, and common bacterial blight disease, respectively. Adjacent to this region was a QTL conditioning 23% of the variation in reaction to another fungal pathogen, web blight (Thanatephorus cucumeris). A second genomic site on linkage group US-1 had minor affect on multiple resistance expression to the same fungal (15%), viral (15%), and bacterial (10%) pathogens. It is unknown whether these specific genomic regions represent a series of linked QTL affecting resistance to each disease separately or an individual locus with pleiotropic effect against all three pathogens.