A Recurrent Epiphytotic of Guava Rust on Rose Apple, Syzygium jambos, in Hawaii.

A Neotropical rust of the Myrtaceae, Puccinia psidii Winter, was described from Psidium guajava L., or guava, in Brazil in 1884 (1). It was first discovered in Hawaii on potted Metrosideros polymorpha Gaud. on Oahu in April 2005 (2) with pathogenicity and identity established (3). It spread quickly, and by January 2006, severe outbreaks of this rust occurred statewide on new leaves of Syzygium jambos (L.) Alston, or rose apple. Rose apple, a native to South and Southeast Asia, was introduced to Hawaii in 1825 and is locally abundant to invasive from just above sea level to as high as 1,000 m in elevation in wet sites. Healthy, reddish green immature leaves on new twigs become deformed, yellow-red, and covered with masses of yellow urediniospores following infection. As the disease progresses, infected leaves are blackened and defoliate, with no functional leaves formed. Stem tips and branches are killed and the canopy becomes progressively smaller. Repeated mortality of juvenile leaves was observed to kill 8 to12 m tall trees in the Haiku area of Maui. Wind dispersal of urediniospores resulted in heavy infection of even small groups of S. jambos isolated by 1 km or more and billions of urediniospores covered the ground under diseased trees. On Hawaii, Maui, and Oahu, trees with many dead branches are becoming common with concerns about the fire hazard of these dead trees surrounded by dry grasses. At low humidity levels, or on more mature leaves characterized by soft expanded yellow-green tissue, fewer, mostly circular spots are formed that do not expand. S. jambos is an example of a highly vulnerable host in Hawaii and represents one of approximately 3,500 species of Myrtaceae outside the Neotropics growing in Australasia, Southeast Asia, the Pacific, and tropical Africa, which have evolved unexposed to P. psidii. Severely infected S. jambos plants have been the major source of spores in the environment, exposing many Myrtaceae hosts to P. psidii. The pathogenicity of P. psidii has been consistent among and within islands with S. jambos severely infected and M. polymorpha, Melaleuca quinquenervia, Rhodomyrtus tomentosa, Myrtus communis, and Eugenia species commonly infected. Other hosts such as S. cumini, S. malaccense, and Myriciaria cauliflora are also infected, although guava and Eucalyptus spp. are rarely infected. Strain differences within P. psidii are suspected (4). In the tropics, it is rare for mature trees to be killed by a foliar pathogen, but given the devastation of new growth, death of more S. jambos trees is likely. References: (1) T. A. Coutinho et al. Plant Dis. 82:819, 1998. (2) E. M. Killgore and R. A. Heu. New Pest Advisory No. 05-04. Hawaii Department of Agriculture, 2007. (3) J. Y. Uchida et al. Plant Dis. 90:524, 2006. (4) S. Zhong et al. Mol. Ecol. Res. 8:348. 2008.

The value of LYM-1 cells for examining vacuole formation and loss of cell viability induced by culture supernates of Helicobacter pylori.

Some strains of Helicobacter pylori are known to produce an extracellular cytotoxin that causes vacuolation in cultured mammalian cells. Screening for such strains makes use of HeLa cells which may not be sensitive enough to detect minimal changes. The aim of this study was to develop a more sensitive cell line. Vacuole formation was examined in HeLa cells, as well as four other cell lines established in this laboratory by ammonium chloride induction. Among five cell lines tested, LYM-1 cells were most sensitive for the detection of intracellular vacuolation with this agent. Loss of cell viability of LYM-1 and HeLa cells induced by H. pylori culture supernates was also examined: LYM-1 were more sensitive than HeLa cells. Cell death was not always accompanied by vacuole formation. This suggests that the mechanism whereby cell death occurs must be different from that for vacuole formation. LYM-1 cells may be useful when measuring vacuole formation and cell death of the cultured cells induced by culture supernates of clinical isolates of H. pylori.

Comparative Morphology and Pathology of Calonectria theae and C. colhounii in Hawaii.

Calonectria theae is distinguished from C. colhounii by perithecial color, number of ascospores in an ascus, longer stipes, longer conidia, and the formation of a second conidial type that is extraordinarily long, angular, and borne on simple, submerged, dichotomously branching conidiophores. Both species were isolated from ohia (Metrosideros collinus), M. excelsus, and sentry palm (Howea forsteriana). C. theae was also isolated from leather leaf fern (Rumohra adiantiformis) and Strelitzia, while C. colhounii isolates were obtained from Eucalyptus, Leucospermum, and Chrysalidocarpus lutescens. All tested isolates of both Calonectria spp. were pathogenic to ohia, an important native tree species in Hawaiian forests. Both species killed apical shoots, and caused leaf spotting, blighting, and subsequent defoliation. Symptomatically, the diseases caused by these species are indistinguishable on ohia. This disease poses a potential threat to native forests.