Parasitism of Hoplolaimus galeatus on Diploid and Polyploid St. Augustine grasses

R. M. Giblin-Davis, P. Busey, B. J. Center

Abstract


'Floratam' and 'FX-313' St. Augusfinegrasses (Stenotaphrum secundatum) were compared in a time-course experiment for host suitability and susceptibility to the lance nematode, Hoplolaimus galeatus. Nematode densities were determined in the soil and acid-fuchsin stained roots 42, 84, 126, 168, and 210 days after pots containing 230 cm³ of autoclaved native Margate fine sand/pot were infested with 104 ± 9 nematodes and maintained at 25 ± 2 C in the laboratory. 'FX-313' was a more suitable host for H. galeatus. Numbers of H. galeatus reached a maximum at 210 days after inoculation, with 5,550 and 4,120 nematodes (adults plus juveniles)/pot for 'FX-313' and 'Floratam,' respectively. Root and shoot dry weights of both grasses were not affected by H. galeatus throughout the experiment. Three polyploid, 2n = 30 to 32 ('Floratam,' 'FX-10,' and 'Bitterblue') and three diploid, 2n = 18 ('FX-313,' 'Florida Common,' and 'Seville') S. secundatum genotypes were inoculated with H. galeatus (99 ± 9/pot) and compared with uninoculated controls 210 days after inoculation. St. Augustinegrass genotypes differed as hosts of H. galeatus. 'FX-313' and 'Florida Common' represented the high and low extremes, respectively, for nematode reproduction (9,750 and 5,490 nematodes/pot or 4,239 and 2,387 nematodes/100 cm³ of soil). However, differences in root and shoot growth were not detected 210 days after inoculation with H. galeatus. Key words: Hoplolaimus galeatus, lance nematode, nematode, population dynamics, resistance, St. Augustinegrass, Stenotaphrum secundatum, turfgrass breeding.

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