Inheritance of Resistance to White Mold Disease (Sclerotinia sclerotiorum (Lib.) de Bary) in the Breeding Line A 195 of Common Bean (Phaseolus vulgaris L.)

Dobroudja Agricultural Institute, BG-9520 General Toshevo, Bulgaria


GENCHEV, D. and I. KIRYAKOV, 2002. Inheritance of resistance to white mold disease (Sclerotinia sclerotiorum (Lib.) de Bary) in A 195 (Phaseolus vulgaris L.). Bulg. J. Agric. Sci., 8: 181–187

The breeding strategy for control of white mold on beans includes combining of physiological resistance and mechanisms preventing or reducing the development and spread of the disease: these are upright habit and open plant canopy. The aim of the study was to determine the genetic control of resistance in the CIAT (Centro Internacional de Agricultura Tropical) breeding line A195 to strain SsPh-2 of Sclerotinia sclerotiorum (Lib.) de Bary.
The study included reciprocal crosses of the CIAT breeding lines A195 (R) and G2883 (S). The resistance of the plants from G2883, A195, F1, F2, BC1 and BC2 was evaluated under greenhouse and field conditions. Plants were grown in pots with diameter 17 cm and 3 soil : 1 sand mixture at 20–25 °C, 4–5 plants per pot, during 2001.
3-day old cultures from isolate SsPh-2 on nutrition medium PDA were used as inoculum. Four weeks after sowing plants were inoculated by the straw method of Petzoldt and Dickson. Results were read 8 days after inoculation. Under greenhouse conditions, the physiological resistance of A195 was controlled by a single recessive gene, and under field conditions – by a single dominant gene. This difference in the gene control is due to the lower air humidity, the avoidance mechanisms under field conditions, and the later and lower formation of tissues from cells with thicker (lignified) walls. The breeding of new cultivars with smaller angle between the leaf petiole and the stem is promising because it is related to avoidance of white mold attack by the bean plant, more intensive photosynthesis and higher productivity.

Key words: Phaseolus vulgaris, Sclerotinia sclerotiorum, inheritance