Disease assessment of pea lines with resistance to foot rot pathogens: protocols for in vitro selection

Cultural conditions were optimized so that disease reactions of plantlets and callus tissue from partially resistant and susceptible genotypes of Pisum sativum could be differentiated when inoculated with Fusarium solani f.sp. pisi. Disease was assessed using both semi-quantitative (disease score/fungal diameter) and quantitative methods (ergosterol assay).
After optimization of inoculum concentration and incubation period it was possible to differentiate the disease reactions of plantlets using disease scores and amount of ergosterol in the tissues.
Incubation period, temperature and the auxin added to the media were important in allowing differentiation of callus tissue cultures. These differences were visible by measurement of the diameter of fungal growth on the callus and the amount of ergosterol in the tissues, but not with disease scores.
The plantlet test was also applicable to the other foot rot pathogens Phoma medicaginis var. pinodella and Aphanomyces euteiches , allowing differentiation of the disease reactions of a partially resistant and susceptible genotype using disease scores. The ergosterol assay could be used to quantify infection caused by P. medicaginis var. pinodella , but this sterol was not detectable in mycelium of A. euteiches. In this fungus the presence of cholesterol was detected, which may be used to quantify infection.