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M.E. Scott and T.E. Michaels

We thank T. Smith and J. Krusky for technical assistance, and the Ontario Ministry of Agriculture and Food and the Ontario Bean Producers' Marketing Board for financial assistance. The cost of publishing this paper was defrayed in part by

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N.N. Wassimi, G.L. Hosfield, and M.A. Uebersax

Mich. Agr. Expt. Sta. Journal Article 13057. Research supported in part by a USAID/BIFAD bean/cowpea gram no. AID/DSAN-XII-G-0261. Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the

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Paul Skroch and Jim Nienhuis

The genetic variation in a population of one hundred Snap Bean varieties, including processing and garden types, was studied using RAPD markers. All one hundred genotypes were distinguished by unique combinations of banding patterns. These unique “fingerprints” were tested for repeatability. Certain bands were very reliable and can be used for varietal identification. The RAPD marker data was also used to estimate genetic relationships among a subset of the one hundred lines. The results of the analysis agreed with known pedigree information. These markers will allow more precise monitering and control of germplasm by those who are involved with the breeding and production of superior seed.

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Mark E. Lewis and Fred A. Bliss

Ten common bean (Phaseolus vulgaris L.) lines—including cultivars, breeding lines, and one wild line—were evaluated for susceptibility to Agrobacterium tumefaciens strain C58 by stab-inoculating intact shoot tips of germinating seeds. Significant differences for tumor frequency and size were found on the resulting 3-week-old seedlings. UW 325, a wild bean, had the highest rate of tumorigenesis; `Olathe', a dry bean cultivar, had the lowest. Uninoculated excised shoot tips cultured in media with BA or BA plus NAA exhibited differences in phytohormone sensitivity, as evidenced by callusing and root initiation. The cultivar Montcalm seemed to be highly sensitive, while `Olathe' was relatively insensitive. Fluorometric GUS assays of shoot tips from germinating seeds inoculated with the disarmed GUS-containing A. tumefaciens strain C58C1(pGV3850/pKIWI105) showed that UW 325 had the highest level of GUS activity. `Montcalm' had a high rate of tumorigenesis but a low level of GUS activity; this anomaly was attributed to its high phytohormone sensitivity. The use of the virulence-inducing compound acetosyringone in the inoculum culture medium did not alter genotypic differences (ranks) in susceptibility. Histochemical GUS assays of inoculated UW 325 shoot tips showed that 60% of the apexes exhibited one or more transformation events. Chemical names used: β-glucuronidase (GUS); α-naphthaleneacetic acid (NAA); N-(phenylmethyl)-1H-purin-6-amine (BA).

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Maricelis Acevedo Román, Albeiro Molina Castañeda, Juan Carlos Angel Sánchez, Carlos Germán Muñoz, and James S. Beaver

The inheritance of resistance to bean golden yellow mosaic virus (BGYMV) was studied in common beans (Phaseolus vulgaris L.). The original cross was made between breeding line PR9556-158, which produces deformed pods when infected with BGYMV, and PR9556-171, which has normal pod development when inoculated with the virus. Pod type was evaluated on plants from six generations (parental lines, F1, F2, F2:3, F3:4, and backcrosses of the F1 to both parents) at mid-pod fill (R8), ≈65 days after planting. The segregation patterns from the F2, F2:3, F3:4, and backcross populations were consistent with the hypothesis that a single dominant gene confers normal pod development in PR9556-171. When inoculated with BGYMV, the deformed pods of PR9556-158 produced fewer seeds per pod than PR9556-171, resulting in lower seed yield. The gene symbol Bgp-1 has been assigned for this dominant resistance gene that controls the normal pod reaction to BGYMV in common bean.

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Mario Crespo, James Nienhuis, Jan Tivang, and Paul Skroch

70 ORAL SESSION 19 (Abstr. 151–158) Breeding/Vegetable Crops I

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Jose J. Velez, Mark J. Bassett, James S. Beaver, and Albeiro Molina

The inheritance of resistance to bean golden mosaic virus (BGMV) in common bean (Phaseolus vulgaris L.) was studied in crosses between susceptible bean variety XAN176 and resistant breeding lines 9236-6 (T446/A429) and 9245-94 (DOR303/T968). Disease response data were taken on plants from four generations derived from each cross (parents, F1, F2, and backcrosses (BCs) of F1 to both parents) at 25 days after plants were inoculated with BGMV, using whiteflies (Bemisia argentifolii Bellows & Perring) as vectors. The segregation ratios obtained from F2 and BC generations were consistent with the hypothesis that resistance in 9236-6, which prevents a chlorotic response, is conferred by a single recessive gene. The disease response in 9245-94 was controlled by two genes—a dominant gene controlling a dwarfing reaction and a recessive resistance gene preventing a chlorotic response to BGMV infection. An allelism test demonstrated that the gene controlling resistance in 9236-6 is nonallelic with the recessive gene controlling resistance in 9245-94. The gene symbol bgm is proposed for the recessive resistance gene (originally from A429) in 9236-6. The gene symbol bgm-2 is proposed for the recessive resistance gene (originally from DOR303) in 9245-94.

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Geunhwa Jung, Paul W. Skroch, Dermot P. Coyne, James Nienhuis, and E. Arnaud-Santana

106 POSTER SESSION (Abstr. 335–343) Breeding and Genetics–Vegetables II (Molecular Markers and Physiological Genetics)

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Mohamed F. Mohamed and Dermot P. Coyne

Pathology, for a Xcp bacterial isolate (V 4 S 1 ), and Kent Eskridge, Dept. of Biometry, Univ. of Nebraska, Lincoln, for statistical advice. We gratefully acknowledge the Title XII Bean/Cowpea Collaborative Research Support Program Project, Univ. of

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Mark J. Bassett

The inheritance of corona and hilum ring color of common bean (Phaseolus vulgaris L.) was investigated in the reciprocal cross `Wagenaar' (a Canario market class dry bean) × `Mayocoba' (Mayocoba market class dry bean), where both parents were known to have seedcoat color genotype P [C r] gy J g b v lae Rk. `Wagenaar' has greenish yellow (GY) seedcoat (due to gy) except for purple (dark) corona (due to v lae) and reddish brown hilum ring (due to J), whereas `Mayocoba' has an entirely GY seedcoat. Seeds produced on the F1 progeny plants had GY corona and reddish brown hilum ring. The F2 segregated for three phenotypic classes, the two parental classes and the F1 class, but the segregation did not fit a 1:2:1 segregation ratio due to disturbed segregation. F3 progeny tests of 35 randomly selected F2 parents demonstrated that the two parental classes were true breeding and the F1 class segregated again (as in the F2) for the same three phenotypic classes. In spite of variable expressivity of GY color and disturbed segregation, the data support a single gene hypothesis, for which the tentative symbol Chr is proposed. Chr is dominant for changing purple corona to GY, but recessive for changing reddish brown hilum ring to GY. Thus, only one gene, Chr, controls the difference in seedcoat color between the market classes Canario and Mayocoba. An allelism test between Chr and Z (hilum ring color factor) is needed before a formal proposal for Chr can be made.