Inheritance of resistance to white mold disease (Sclerotinia sclerotiorum (Lib.) de Bary) in the breeding line A195 of common bean (Phaseolus vulgaris L.)

摘要

The breeding strategy for control of white mould on beans includes combining 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 Centro Internacional de Agricultura Tropical (CIAT) breeding line A195 to strain SsPh-2 of S. sclerotiorum. 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 [date and place not given] conditions. Plants were grown in pots with a diameter of 17 cm and a 3:1 soil/sand mixture at 20-25degC, 4-5 plants per pot, during 2001. Three-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 whitemould attack by the bean plant, more intensive photosynthesis, and higher productivity.