Plant Disease (2006) 90, 1167-1170

Howard F. Schwartz, Kristen Otto, Henry Terán, Margarita Lema and Shree P. Singh (2006)
Inheritance of white mold resistance in Phaseolus vulgaris × P. coccineus crosses
Plant Disease 90 (9), 1167-1170
Abstract: The fungus Sclerotinia sclerotiorum, cause of white mold, is known to attack >400 plant species. It is a widespread problem in dry bean (Phaseolus vulgaris) in the United States, causing >30% average yield losses. Low to moderate levels of resistance are found in dry bean. However, some accessions of P. coccineus (commonly known as scarlet runner bean) possess a relatively higher level of resistance. Our objective was to verify the reaction of 13 known white mold-resistant P. coccineus germ plasms and determine inheritance of resistance in accessions PI 433246 and PI 439534. Pinto Othello was crossed with PI 433246, and the resulting interspecific F₁ was backcrossed onto Othello and allowed to produce F₂ seed. Similarly, pinto UI 320 was crossed with PI 439534. The F₁ was backcrossed onto UI 320 and allowed to produce F₂ seed. The two parents, F₁, F₂, and backcross to dry bean of each set were evaluated in the greenhouse using the straw test at Fort Collins, CO in 2004. All 13 P. coccineus accessions and the two F₂ also were evaluated using the modified petiole test at Kimberly, ID in 2005. All 13 P. coccineus accessions were variable in a 2002 straw test when rated for white mold reaction on a 1-to-9 scale, because the mean disease score ranged from 1.9 for PI 433246 to 4.4 for PI 189023 and 8.8 for the susceptible check Bill Z. For the petiole test, when rated on a 1-to-9 scale, the accessions exhibited an intermediate white mold score of 4 or 5 in 2005. In 2004, the susceptible check Othello exhibited a mean score of 7.9 compared with 3.4, 3.2, and 2.1 for PI 433246, UI 320, and PI 439534, respectively. The white mold reaction of PI 433246 and PI 439534 was dominant in their respective F₁. The F₂ segregation further indicated that white mold resistance in PI 433246 and PI 439534 was controlled by a single dominant gene. These two and other white mold-resistant P. coccineus accessions and selected breeding lines from the interspecific crosses should be useful for future improvement of white mold resistance of pinto and other market classes of dry and green or snap bean.
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Database assignments for author(s): Margarita Lema

Research topic(s) for pests/diseases/weeds:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Sclerotinia sclerotiorum	Beans (Phaseolus)	U.S.A. (SW)
	Sclerotinia sclerotiorum	Beans (Phaseolus)	U.S.A. (NW)