PROGRAM OBJECTIVES

Agronomic traits affecting resistance to white mold in common bean
J. D. Kelly^a, & J. M. Kolkman^b

^aDepartment of Crop and Soil Sciences
Michigan State University, East Lansing, MI 48824, USA

^bDepartment of Crop and Soil Science
Oregon State University, Corvallis, OR 97331, USA

ABSTRACT

Resistance to white mold [caused by Sclerotinia sclerotiorum (Lib.) de Bary] in common bean (Phaseolus vulgaris L.) is complexly inherited, and highly influenced by environmental factors. The identification of agronomically desirable avoidance mechanisms in advanced or elite lines and segregating populations is essential. The objectives of this study were to determine the relationship between nine agronomic traits (growth habit, days to flower, canopy height and width, branching pattern, lodging, days to maturity, seed size, and yield) and resistance to white mold in the field, corresponding heritabilities of resistance and agronomic traits, and the effect of the agronomic traits on disease and seed yield. A group of elite lines, and two recombinant populations derived from crosses between two resistant navy bean cultivars, Bunsi and Huron, to a susceptible cultivar, Newport, were evaluated for disease severity index (DSI) and agronomic traits in multiple field seasons. Heritability estimates for DSI were moderate (0.47) in the Bunsi/Newport population and high (0.82) in the Huron/Newport population. All agronomic traits displayed moderate to high heritability estimates. The agronomic traits that associated significantly with DSI in the three populations differed greatly. The most important agronomic trait that reduced DSI and contributed to yield was indeterminate growth habit. Increased canopy height, width, and lodging were generally associated with an increase in DSI, whereas traits such as days to flower and maturity varied in relation to DSI and yield across environments and populations. The complexity of the relationship of agronomic traits to DSI and yield highlights the difficulties bean breeders face in selecting among elite lines and within segregating populations for resistance to white mold in the field.

Abstracted from:
Kolkman, J.M. and J.D. Kelly. 2002. Agronomic
traits affecting resistance to white mold in
common bean Crop Sci. 42:693-699.

Judith M. Kolkman^a and James D. Kelly^*,b

^aDep. of Crop and Soil Sciences, Oregon State Univ., Corvallis, OR, 97331
^b Dep. of Crop and Soil Sciences, Michigan State Univ., East Lansing, MI, 48824

ABSTRACT

White mold is a serious fungal disease that negatively affects production of common bean. Resistance to white mold in common bean is complexly inherited and comprised of physiological resistance and avoidance mechanisms. The objectives of this research were to discover QTL conferring resistance to white mold in navy beans, determine if a multi-trait bulking strategy was an efficient approach for locating QTL conferring resistance to white mold, and to identify agronomic traits associated with QTL for white mold avoidance in the field. A 98 F₃-derived Bunsi/Newport population was evaluated in three environments for resistance to white mold and agronomic traits. A 28 recombinant inbred line population derived from a Huron/Newport cross was evaluated for the resistance and yield in four environments and was used to confirm marker associations. Marker BC20.1800 on B2 was associated with DSI (12%) across environments, and was confirmed in the second population. Markers linked to QTL were also detected on B7 for DSI (17%), resistance to oxalate (16%), yield (37%), as well as days to flowering (14%), branching pattern (9%), lodging (9%) and seed size (20%). Growth habit unexpectedly mapped to B7, and represents a novel source of determinacy in navy bean. Multiple-trait bulking based on low DSI, high yield, and 40 to 45 days to flowering versus high DSI, low yield, and 40 to 45 days to flowering effectively identified more markers linked to QTL for resistance to white mold than did bulks based on low and high DSI alone. Selection based on QTL that confer resistance to white mold, such as the Bunsi-derived QTL located on B2 and B7 of the bean genome, combined with certain desirable agronomic traits offers the opportunity to develop resistant cultivars and improve our understanding of resistance to white mold in common bean.

Abstracted from: Kolkman, J.M. and J.D. Kelly. 2003. QTL conferring resistance and avoidance to white mold (Sclerotinia sclerotiorum) in common bean (Phaseolus vulgaris). Crop Sci 43:539-548.

WhiteMoldFig1.pdf