Evaluation location: Colorado, United States
Accessions were screened using the root dip inoculation method of Salgado and Schwartz, (1993) that was developed to screen dry bean cultivars and germplasm for resistance to Fop. This inoculation procedure was based on a modified root-dip procedure developed by Pastor-Corrlaes and Adawi(1987). Isolates of the three races of Fop used to inoculate all plants have been maintained by H.F. Schwartz at 4 degrees C in culture tubes containing autoclaved, finely sieved sandy soil mixed with 2% powdered oat meal and 15% distilled water. Fifteen to twenty-five days before plant inoculation, two to four milligrams of as stock was plated onto petri dishes containing potato-dextrose agar, pH 5.6 0.2, and stored at room temperature. The day of inoculation, conidia from the cultures was suspended in distilled water and the suspension vortexed for 30 seconds and filtered through cheesecloth into an Erlenmeyer flask prior to use. The inoculum concentration was adjusted to 10 to the sixth conidia per ml with a hemacytometer and poured into a 1000-ml beaker and continually stirred for use as a root-dip inoculum. Sixteen to twenty seedlings of each accession were removed from pots and excess soil removed from the root system by gentle shaking. The roots were then washed to remove any excess soil and their root systems immersed in cool tap water for five to ten minutes, then the distal = to 1/3 of the root system clipped with a scissors. The clipped plants were placed in the 10 to the sixth conidia ml-1 inoculum solution for five minutes to allow conidia to adhere to wounds in the roots. Control plants for each experiment were clipped and placed in sterile, distilled water. After the inoculation , plants are transplanted, two to a pot, in fresh soil and clean pots. The plants were grown in a greenhouse maintained at approximately 16/32 C night/day, respectively. Supplemental lighting was provided the plants 12 hours of light per day. Plants were scored 21 days after inoculation.