DIFFERENCES IN THE TIMING AND MECHANISMS OF THE INFECTION PROCESSES OF MICRODOCHIUM NIVALE AND MICRODOCHIUM MAJUS ON WHEAT (TRITICUM AESTIVUM) AND KENTUCKY BLUEGRASS (POA PRATENSIS)

摘要

The infection process for several strains of M.nivale and M.majus,originating from various geographic regions and host plants,was investigated on detached leaves of wheat (Triticum aestivum) and Kentucky bluegrass (Poa pratensis) in three separate experiments.The purpose of these histological experiments was threefold: to determine whether the timing and mechanism of the infection processes of these pathogens may differ on different host plants; to investigate the abilities of conidia and hyphal fragments to cause infection; and to investigate whether specialized structures are produced during infection.In all three experiments,both M.nivale and M.majus,regardless of the plant host species from which they were originally isolated,colonized and penetrated the leaf tissue of both of the host species studied.Penetration occurred by hyphae growing directly into the stomata,and neither appressoria nor haustoria were observed.Hyphal inoculum penetrated plant tissue within 48 hours postinoculation in most cases,whereas conidial inoculum produced infection at a slower rate.Together,these experiments suggest that both M.nivale and M.majus,regardless of the host plant from which they were originally isolated,are capable of penetrating the tissues of both turfgrasses and cereals.The observed host preferences in the field may result from other limiting biotic or environmental effects.