Inhibition of Fusarium moniliforme var. subglutinans, the causal agent of pine pitch canker, by the soil bacterium Arthrobacter sp.

Abstract

A species of Arthrobacter was recovered during culture of the causal organism of pitch canker of southern pines, Fusarium moniliforme var. subglutinans (FMS). Arthrobacter is a relatively common soil bacterium and is lytic to several fungal pathogens in the soil. Soil samples from two seed orchards with pitch canker and one from a healthy pine plantation all yielded Arthrobacter. These isolates were evaluated for their ability to inhibit the growth of FMS isolates from pitch canker tissue and from soil in areas with high pitch canker disease incidence, and to several other species of Fusarium isolated from the same soil samples where Arthrobacter was recovered. Generally the pitch canker isolates were more sensitive to Arthrobacter than the soil fusaria. There was variation in the ability of the Arthrobacter isolates to inhibit the growth of the fusaria recovered from the soil at the three different test sites. Light and scanning electron microscope observations revealed that hyphae of FMS growing near an isolate of Arthrobacter were enlarged, producing many vesicularlike structures. The surface of these hyphae was warped and wrinkled in comparison with normal hyphae.