FACTORS ASSOCIATED WITH SOIL RECEPTIVITY TO SOME FUNGAL ROOT-ROT PATHOGENS OF PEAS

The relationship between various abiotic and biotic soil factors and t he capacity of the soil to allow soil-borne pathogens to produce disea se ('soil receptivity', SR) was investigated for three major pea root rot pathogenic fungi. Several relationships were established. SR to Th ielaviopsis basicola was shown to be positively associated with the ab undance of pseudomonads, soil pH, organic matter content and C/N ratio . The number of saprophytic Fusarium solani in the rhizoplane was high er in soil less conducive to F. solani f. sp. pisi, whereas the abunda nce of indigenous F: solani in the rhizosphere was unrelated to recept ivity. The amounts of soluble K, P, Mg and total C and N in soil, indi vidually, were higher with increasing conduciveness to F: solani f. sp . pisi. The SR to Aphanomyces euteiches was not well associated with a ny soil aspect investigated, except Gliocladium in the rhizoplane and Acremonium in the rhizosphere, of which populations were higher in soi l less receptive to this pathogen. Experiments with soil sterilization showed that soil biota were the main factor responsible for the inhib ition of investigated pathogens. Therefore, despite its correlation wi th chemical and physical factors, SR to the investigated pathogens can be considered essentially of microbiological nature. (C) 1998 Elsevie r Science B.V.