Evaluation location: Colorado, United States
Differences among lines were highly significant. There were three replications, which were arranged in randomized complete block designs. Two-row plots were 12 feet long, with 22-inch row spacing and an 8 - to 10-inch within-row plant spacing. The trial was planted on April 20th in Windsor, CO. Inoculation was performed on June 30th and again on July 7th. Evaluations were made on September 22, with the peak of the epidemic occurring on or about the last date. The field was sprayed twice with Betamix Progress, Upbeet, and Stinger (May 14th and 24th) to control weeds. The field was thinned by hand and irrigated as necessary. We had good spring rain in 1999 and emergence was excellent and we got off to an early start. The 1999 leaf spot epidemic started strong and progressed rather slowly, but eventually became more severe by late August. We had a period between of about one month right after inoculation, in which we had relatively high evening temperatures, which helped disease development, however by September or evening temperatures had dropped. At our evaluation, means of the resistant and susceptible internal controls were 3.1 and 6.4 (scale of 0-10), respectively, across the nursery. In 1998 (September 8), these means were 3.2 and 5.3, respectively. Means of contributor lines on September 22 ranged from 2.7 to 9.0, compared with 2.5 to 8.0 in the milder epidemic of 1998.