ASSESSMENT OF VARIETAL RESISTANCE TO CHOCOLATE SPOT (BOTRYTIS-FABAE) INFECTION OF FIELD BEANS (VICIA-FABA L), WITH SOME INDICATIONS OF ITS HERITABILITY AND MODE OF INHERITANCE

Varietal differences in resistance to non-aggressive chocolate spot infection were detected in the field, although complete resistance was not observed. Following artificial inoculation under growth-room conditions, a parent-offspring regression of disease scores for the heterogeneous stock Chivers was estimated as 0.51 + 0.24, and although this cannot be regarded as a reliable heritability estimate, it demonstrates a degree of additive genetic control. An F2 diallel cross, under field conditions, indicated resistance to be controlled mainly by dominant alleles within a system of partial dominance. Detached-leaf tests indicated that within virtually complete dominance systems, dominant alleles facilitate fungal penetration and induce a hypersensitive response within the leaf. Control of further lesion development was indicated to be effected by a virtually complete additive system. © 1979, Cambridge University Press. All rights reserved.