Assessment of Bacterial Blight Pathogens Prevalent on Dry Bean and Identification of Sources of Resistance to Rhizoctonia Root Rot in North Dakota
Abstract
Bacterial blights and root rots are two major diseases affecting dry edible bean
(Phaseolus vulgaris L.) production in North Dakota and Minnesota (Venette and Lamey
1998). Bacterial blights of dry bean are commonly caused by three bacterial pathogens,
namely Pseudomonas syringae pv. phaseolicola (Psp), Pseudomonas syringae pv. syringae
(Pss) and Xanthomonas axonopodis pv. phaseoli (Xap), which can appear either together or
independently under natural conditions. The bacterial portion of this study involved
ascertaining the extent of incidence of bacterial blight in the major dry bean production
areas of ND through surveys, determining the prevalence of Psp and Pss and screening a
collection of commercial varieties from different market classes for resistance to these two
bacterial pathogens. In this study, more than 50% of the fields surveyed in all the major
dry bean producing counties, including Grand Forks, Pembina, Traill and Walsh from year
2008 to 2010, were found to have been affected by bacterial blight. Among the bacterial
diseases, bacterial brown spot (caused by Pss) appeared to be the most prevalent.
Representative isolates for both Psp and Pss randomly selected from the survey were used
for pathogenicity tests and confirmed to be pathogenic. Race typing of the Psp isolates
confirmed the presence of the races 6 and 8 in the field samples with race 6 being the most
common. Susceptibility of the 11 varieties used in this study was also variable. Difference
in aggressiveness was observed among the Psp isolates.