Related Experiment Video
Updated: Jan 4, 2026
Recessive Lethal Alleles Cause Genetic Disorders in Humans
First Report of Leaf Spot and Blight Caused by Ralstonia pickettii on Bird of Paradise Tree in Italy
G Polizzi1, M Dimartino1, P Bella1
1Dipartimento di Scienze e Tecnologie Fitosanitarie, University of Catania, Via S. Sofia 100, 95123 Catania, Italy.
Abstract:
Bird of Paradise tree (Strelitzia alba (L. f.) Skeels) is an ornamental perennial tropical plant grown in southern Italy. In the summer of 2006 and 2007, a widespread, severe leaf disease was observed on seedlings and 1- to 2-year-old plants in two glasshouses located in eastern Sicily. Disease incidence ranged from 10 to 25%. Symptoms on the leaves consisted of dark brown-to-black stripes of varying length and found between the lateral veins. Lesions sometimes coalesced into a large area of necrotic tissue. Symptomatic tissues were ground in a drop of sterile distilled water (SDW) with a scalpel. Suspensions were streaked on King's medium B (KB), nutrient agar, and yeast extract nutrient agar (2). Isolated strains were gram negative and oxidase positive, non-levan, negative in tobacco hypersensitivity test, white and nonmucoid on yeast dextrose calcium carbonate agar, did not produce fluorescent pigments on KB, and utilized glucose, mannitol, trehalose, arabinose, mannose, and N-acetylglucosamine. Bacterial strains were identified as Ralstonia pickettii by using the Biolog Identification System (MicroLogTM System Release 4.2; Biolog, Inc., Hayward, CA) with a similarity index ranging from 0.52 to 0.67. For an additional confirmation of identity, the small subunit rRNA gene (SSUrDNA) was amplified with primers 530F and Uni 1492R (1). The resulting nucleotide sequence was compared with sequences deposited in GenBank and showed the highest identity (99%) to sequences of R. pickettii strains. Pathogenicity tests were performed on 20 cm tall potted plants. Four S. alba plants were inoculated by infiltrating leaf veins with bacterial suspensions for each of the four isolates (107 CFU ml-1 in SDW) with a 25-gauge needle and syringe. Plants were placed in polyethylene bags 1 day before inoculation and maintained there for 3 days after inoculation. Four control plants were inoculated with SDW. Water-soaked areas in the lateral veins of leaves were observed in all inoculated plants 4 days after inoculation. Within 10 days, dark brown-to-black stripes that coalesced into dark necrotic areas were observed. All isolates induced similar symptoms. Control plants did not show any symptoms. The pathogen was reisolated from symptomatic tissue and identified as R. pickettii by Biolog. A similar disease on S. reginae caused by a Pseudomonas sp. was previously reported from Florida (3). To our knowledge, this is the first record in the world of leaf spot and blight caused by R. pickettii. References: (1) D. J. Lane. 16S/23S rRNA sequencing. Page 115 in: Nucleic Acid Techniques in Bacterial Systematics. E. Stackebrandt and M. Goodfellow, eds. John Wiley and Sons, NY, 1991. (2) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. The American Phytopathological Society, St. Paul, MN, 2001. (3) C. Wehlburg. Plant Dis. Rep. 55:447, 1971.
More Related Videos
Related Concept Videos
Lethal Alleles
Lucien Cuénot discovered lethal alleles in 1905 while studying the inheritance of coat color in mice. The agouti gene is responsible for the color of the coat in mice. This gene codes for an agouti-signaling protein, which is responsible for melanin distribution in mammals. The wild-type allele gives rise to gray-brown coat color in mice, while the mutant allele gives rise to yellow coat color. In addition to coat color, the agouti gene is associated with the yellow...
Mouse Models of Cancer Study
The development of transgenic, knockout, and knock-in mice has led to an exponential increase in their use as model organisms in research,...