|Pérez-Vega, E -|
|Pascual, A -|
|Campa, A -|
|Giraldez, R -|
|Ferreira, J -|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 16, 2010
Publication Date: January 1, 2012
Citation: Pérez-Vega, E., Pascual, A., Campa, A., Giraldez, R., Miklas, P.N., Ferreira, J. 2012. Mapping QTL conferring partial physiological resistance to white mold in the common bean RIL population Xana/Cornell 49242. Crop Science. 29:31-41. Interpretive Summary: White mold is the most important disease problem plaguing production of dry edible and snap bean production in temperate climates around the world. This paper describes the identification and characterization of resistance genes in the fabada dry bean market class in Northern Spain. The fabada cultivar Xana was found to possess one novel resistance gene and three additional resistance genes previously identifed. This research also determined that morphological traits influenced disease reaction in greenhouse screening trials, which was not known to occur. The new gene will faciliate breeding for resistance to this destructive pathogen in large-seeded dry bean market classes in Europe and North America. Findings also direct breeders and pathologists to screen lines with different growth habits in separate greenhouse straw tests, or use morphological traits for covariate adjustment of disease reaction to enable resolution of physiological resistance differences among segregating lines in the straw test.
Technical Abstract: White mold, caused by the fungus Sclerotinia sclerotiorum (Lib.) de Bary, is a devastating disease in common bean (Phaseolus vulgaris L.). Resistance to this pathogen can be due to physiological or avoidance mechanisms. We sought to characterize the partial physiological resistance exhibited by ‘Xana’ dry bean in the greenhouse straw test using QTL analysis. A population of 104 F7 recombinant inbred lines (RILs) derived from an inter-gene pool cross between Xana and the susceptible black bean Cornell 49242 was challenged by five local isolates of Sclerotinia using the greenhouse straw test. The affect morphological traits (plant height, first internode length, and first internode width) had on response to white mold was examined. The level of resistance exhibited by Xana to five isolates of S. sclerotiorum was similar to that of the well known resistant lines PC50, A195 and G122. Eighteen QTLs, involving the linkage groups (LG) 1, 3, 6, 7, 8, and 11, were found to be significant in at least one evaluation and in the mean of the two evaluations. The number of significant QTLs identified per trait ranged from one to five. Four major regions on LG 1, 6 and 7 were associated with partial resistance to white mold confirming the results obtained in other populations. A relative specificity in the number and the position of the identified QTLs was found depending on the isolate used. QTLs involved in the control of morphological traits and in the response to white mold were co-located at the same relative position on LG 1, 6 and 7. The role of these genomic regions in physiological resistance or avoidance mechanisms to white mold is discussed.