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 plantl ets and callus tissue from partially resistant and susceptible genotyp es of Pisum sativum could be differentiated when inoculated with Fusar ium solani f.sp. pisi. Disease was assessed using both semi-quantitati ve (disease score/fungal diameter) and quantitative methods (ergostero l assay). After optimization of inoculum concentration and incubation period it was possible to differentiate the disease reactions of plant lets using disease scores and amount of ergosterol in the tissues. Inc ubation period, temperature and the auxin added to the media were impo rtant in allowing differentiation of callus tissue cultures. These dif ferences were visible by measurement of the diameter of fungal growth on the callus and the amount of ergosterol in the tissues, but not wit h disease scores. The plantlet test was also applicable to the other f oot rot pathogens Phoma medicaginis var. pinodella and Aphanomyces eut eiches, allowing differentiation of the disease reactions of a partial ly resistant and susceptible genotype using disease scores. The ergost erol assay could be used to quantify infection caused by P. medicagini s var. pinodella, but this sterol was not detectable in mycelium of A. euteiches. In this fungus the presence of cholesterol was detected, w hich may be used to quantify infection.