|Canaday, C - UNIV OF TENNESSEE|
|Wyatt, J - UNIV OF TENNESSEE|
Submitted to: Biological and Cultural Tests for Control of Plant Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 18, 2002
Publication Date: May 1, 2002
Citation: Canaday, C.H., Wyatt, J.E., Bohac, J., Smith, J.R. 2002. Field Evaluation of Bean Cultivars and Lines for Resistance to Rhizoctonia, 2001. Biological and Cultural Tests for Control of Plant Diseases. 17:V02. Interpretive Summary: Plant pathogens living in the soil can cause damping-off, root rot, and post emergence plant death and reduce the seed yield of common bean. Cultivar resistance to the diseases caused by these pathogens can be improved by conventional plant breeding, but it is first necessary to correctly identify bean lines with resistance. The purpose of this experiment was to identify resistant bean lines with potential for use as parents in bean breeding programs. Fifty bean lines from over seven market classes of bean were tested for resistance to naturally-occurring soil-borne plant pathogens. "Dorado" and "Don Silvio", from the tropical small red market class, had very good resistance, whereas several other types were highly susceptible. This study provides bean breeders with information for improving resistance to soil-borne bean pathogens. It demonstrates that is is possible to identify bean lines with resistance to multiple soil-borne pathogens in fields with naturally occurring populations of these organisms.
Technical Abstract: Rhizoctonia solani (Kuhn) can cause damping-off and stem rot in common bean (Phaseolus vulgaris L.), resulting in serious stand and yield losses. Other soil-borne pathogens that may be present with R. solani can intensify stress conditions and yield loss. The purpose of this experiment was to differentiate genotypic response to R. solani in common bean. Fifty diverse (small white, small red, snap, black, pinto, light red kidney, cranberry, etc.) common bean lines were grown in a field previously cultured with snap bean for over ten years and naturally infested with R. solani and Macrophomina phaseolina (Tassi) Goidanich, as well as other Phaseolus pathogens. Beans were planted 24 August 2001 in a Grenada-Calloway silt loam soil in Jackson, TN in single-row plots 1.5 m long. Plots were organized in a randomized complete block design with 6 replications. Healthy stand counts were made 18-19 September, 8-9 October, and 24-25 October 2001 and subjected to analysis of variance. Fisher's LSD was used to differentiate phenotypic response. Based on stem lesions and weather conditions, it was determined that R. solani was the principal pathogen causing plant death prior to 18 September. Several dry and snap bean genotypes, most of tropical origin, had high levels of resistance to R. solani. Stand losses after 20 September were due primarily to a combination of R. solani and M. phaseolina. Tropical small red types "Dorado" and "Don Silvio" appeared to have resistance to both pathogens. These results suggest that it may be possible to identify bean lines with resistance to multiple soil-borne pathogens in naturally infested disease nurseries. It also provides information to bean breeders regarding potential parents for improving resistance to soil pathogens in common bean.