Ma. Gretenkort et Jpfg. Helsper, DISEASE ASSESSMENT OF PEA LINES WITH RESISTANCE TO FOOT ROT PATHOGENS- PROTOCOLS FOR IN-VITRO SELECTION, Plant Pathology, 42(5), 1993, pp. 676-685
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.