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POSTERS: Pathogenicity and host specificity

Pathogenicity tests of fungal isolates from Loblolly pine (Pinus taeda) trees growing in southern Mississippi
Frank Mrema - Alcorn State University.

Characterization of fungal isolates obtained from five (5) year old loblolly pine trees was conducted in this study to better understand the pathogenic fungi that cause pine forest decline in southern Mississippi. Fungal isolates with different morphological variations were tested for extra-cellular enzyme production. Comparative pathogenicity tests using juvenile P. taeda seedlings as host were conducted by root inoculation with two of the isolates (ASP1 and ASD18). The control seedlings were mock inoculated with sterile water. To study the fungi infection process, the first (1st) and second (2nd) 10mm root tips were cut from inoculated and un-inoculated (control) seedlings, 3, 6, 10 15 days post inoculation. Of the 19 fungal strains isolated from symptomatic P. taeda, 21% showed a positive Bavendamn reaction, indicating the ability to produce phenol oxidase, and depletion polysaccharide and lignin components in wood. ASP1 and ASD18 fungal strains showed strong enzyme reaction, 36%, and 38% respectively. Both tested fungal isolates caused browning tissues in the roots from 3 days post inoculation. Observations on seedlings, day 15-post-inoculation showed severe browning of the root tissues in both root regions (1st and 2nd mm regions) challenged with ASP1 when compared to similar regions of ASD18 and the controls, indicating that the necrotic cells could not prevent the fungal colonization in loblolly pine seedlings. More studies are proposed to establish the pathogenic capability of ASP1 and ASD18 fungal strains on field-grown loblolly pine seedlings.