E. A. Des Jardin

Comparison of media and diluents for enumeration of aerobic bacteria from Bermuda grass golf course putting greens

To increase our knowledge of soil and rhizosphere bacteria associated with bermuda grass grown on golf courses, a standardized procedure has been developed. Seven aerobic bacterial groups were selected for enumeration. For each group selected, appropriate media were compared to determine which one was best for enumeration of that group. Six diluents were evaluated across all media for the seven bacterial groups. The best diluent was sodium pyrophosphate with glycerol. The following media were best for enumeration: solidified 10% tryptic soy broth for total culturable aerobic bacteria and heat tolerant bacteria; reduced arginine soluble salts medium for actinomycetes; S1 medium for fluorescent pseudomonads; XMSM for Stenotrophomonas maltophilia; Bacto azide blood agar base for gram-positive bacteria; crystal violet agar for gram-negative bacteria.

Fumigation effects on bacterial populations in new golf course bermudagrass putting greens

Abstract Golf course putting greens in the United States are normally built with a root-zone mix composed of >80% sand and a peat source. Populations of seven aerobic bacterial groups, commonly associated with soil or plant roots, were monitored during the building, planting and establishment of miniature bermudagrass putting greens, with a different set of greens built in each of 2 years. At each phase of construction, including pre- and post-fumigation, the following bacterial groups were enumerated: fluorescent pseudomonads, Gram-positives, Gram-negatives, Stenotrophomonas maltophilia , actinomycetes, heat-tolerant and total aerobic. The fumigants methyl bromide, dazomet and metam sodium were used at either normal or 10× field rates. In both years, by 50–70 days after fumigation, which included 4 weeks after planting, the size of the populations for all of the bacterial groups were either greater than or similar to the size of the populations prior to fumigation. The sand source, peat source, and fumigant source and amount did not have any long-term detrimental effects on size of the populations of any of the bacterial groups evaluated.

Effect of organic nitrogen fertilizers on microbial populations associated with bermudagrass putting greens

Abstract Four natural organic fertilizers, alone or in combination with the synthetic organic fertilizer isobutylidene diurea (IBDU), were compared with IBDU alone for their effect on soil/root microbial populations associated with bermudagrass grown on a golf course putting green in southern Florida, USA. Populations of total fungi, total bacteria, fluorescent pseudomonads, Stenotrophomonas maltophilia, actinomycetes and heat-tolerant bacteria were monitored every 3 months during the 2-year study. On only one sampling date and for only one bacterial population (S. maltophilia) was a significant difference in microbial populations obtained among the fertilizer treatments. However, the S. maltophilia populations associated with the natural organic fertilizer treatments were not significantly different from the synthetic organic IBDU fertilizer treatment.

Fusarium oxysporum f. sp. palmarum, a Novel Forma Specialis Causing a Lethal Disease of Syagrus romanzoffiana and Washingtonia robusta in Florida

A new disease of Syagrus romanzoffiana (queen palm) and Washingtonia robusta (Mexican fan palm) has spread across the southern half of Florida during the past 5 years. The initial foliar symptom is a one-sided chlorosis or necrosis of older leaf blades, with a distinct reddish-brown stripe along the petiole and rachis and an associated discoloration of internal tissue. Within 2 to 3 months after onset of symptoms, the entire canopy becomes desiccated and necrotic but the leaves do not droop or hang down around the trunk. Based on pathogenicity and morphological and molecular characterization, the etiological agent has been identified as a new forma specialis of Fusarium oxysporum, designated f. sp. palmarum. Sequence analysis of a portion of the translation elongation factor 1-α gene (EF-1α) separated 27 representative isolates into two EF-1α groups, which differed by two transition mutations. Members of both EF-1α groups are pathogenic on both species of palm. A phylogenetic analysis inferred from partial EF-1α sequences from a genetically diverse set of F. oxysporum isolates, including three other formae speciales pathogenic on palm (i.e., f. sp. albedinis, f. sp. canariensis, and f. sp. elaeidis), suggested that f. sp. palmarum and f. sp. albedinis may be more closely related to one another than either is to the two other palm pathogens.

Serenomyces associated with palms in southeastern USA: isolation, culture storage and genetic variation.

Serenomyces is a genus belonging to the family Phaeochoraceae, which is known to occur only in association with the plant family Arecaceae (palms). It is presumed to be one of the causes of a leaf disease referred to as either rachis blight or petiole blight, depending on the palm species affected. The fungus is not readily observed, with few reports in the literature; it cannot be readily isolated from tissue, with only one known instance of it being cultured on artificial media and has no DNA sequences deposited in GenBank. Over an 8 y period, leaves symptomatic for rachis or petiole blight were obtained from Florida and South Carolina, USA. The fungus was induced to produce ascospores, and single-spore isolates were obtained in culture and, in some instances, induced to produce ascospores in culture. Based on ascospores size and ITS sequencing, Serenomyces from Phoenix canariensis and P. dactylifera form one group, Serenomyces from Thrinax radiata form a second group and Serenomyces from Sabal palmetto form a third. All three groups are most similar morphologically to Serenomyces phoenicis. Due to the observed instability of Serenomyces in culture, we have suggestions regarding the storage of this fungus.