Evaluation location: Colorado, United States
A subset (100 each representing a range of seed colors and origins) of the Phaseolus vulgaris Core Collection - Mexican Subgroup accessions and the combined Latin American Subgroup accessions were screened for reaction to a yellow (B528), orange (B557) and purple (B597) isolate of Bacterial Wilt previously recovered from infected common beans in Colorado or Nebraska and maintained in the laboratory. The purple isolate came from the collection of R. Harveson from the University of Nebraska, and the other 2 isolates were from the collection of H. Schwartz. The core collection subgroups provided by Molly Welsh represent the Central/South American Phaseolus collection maintained at the Western Regional Plant Introduction Station in Pullman, WA. In addition, a subset of current cultivars from various dry bean market classes grown in the United States were also evaluated to assess their risk to this pathogen. These included pinto (Bill Z, Grand Mesa, Kimberly, La Paz, Maverick, Montrose, Othello, Poncho, Shoshone, UI 114, Vision), great northern (Alpine, Beryl, Hungerford, Marquis, Matterhorn, Orion, Sawtooth, UI 59, UI 465, US 1140, USGN-5, Weihing), small red (Le Baron, Merlot, NW 63, Rojo Chiquito, USRM 20), pink (Rosalee), light red kidney (California Early LRK, Pink Panther, Sacramento), yellow (Canario 707, Enola), black (Black Rhino, Condor, Eclipse, Jaguar, Shiny Crow, T-39, UI 911), and Ojo de Cabra (LEF 2RB); additional entries included PIs 136677, 136725, 165078, 177510, 204600, Wilkinson, with great northern Emerson and yellow Myasi included as the resistant and susceptible checks, respectively. The accessions and other candidate germplasm were screened using the cotyledonary node inoculation method. Seven to 8 seeds were sown 2.5 cm deep into potting mix in a 15-cm wide plastic pot and thinned to 5 emerged seedlings prior to inoculation. The point of a sterile dissecting needle bearing inoculum was inserted into the stem at the cotyledonary node of 7 to 10 day old seedlings. The inoculated plants were incubated in a greenhouse with a daily temperature of 28oC / 22oC - 16 hr day / 8 hr night photoperiod with watering as needed. Two pots of 3 to 5 plants provided an average of 9 to 12 replicates (plants) each for evaluation individually with the yellow, orange and purple isolate. Ten plants each of the resistant and susceptible checks were included with each two month-long series with one bacterial isolate, which consisted of planting to emergence to inoculation to final evaluation 4 weeks later. Approximately 200 germplasm and 50 cultivars and other entries were evaluated using a 1 - 4 rating scale: 1 (highly resistant) = no wilt or discoloration, 2 (moderately resistant) = wilt or discoloration at one of the unifoliolate leaves, 3 (susceptible) = wilt or discoloration on both unifoliolate leaves with no symptoms on the 1st trifoliolate leaf, and 4 (highly susceptible) = wilt or discoloration on the 1st trifoliolate leaf. Data are reported as an average severity for the replicated plants per isolate; and the following table lists only those entries that were resistant (less than 1.51 rating) to each of the 3 bacterial wilt isolates.