First Report in Hawai'i of Xanthomonas citri pv. mangiferaeindicae Causing Bacterial Black Spot on Mangifera indica

Bacterial black spot of mango (Mangifera indica) caused by Xanthomonas citri pv. mangiferaeindicae (Xcm), is an economically important disease in tropical and subtropical areas (3). Xcm can infect a wide range of mango cultivars and induces raised, angular, black leaf lesions, sometimes with a chlorotic halo. Fruit symptoms appear as small, water-soaked spots on the lenticels that become star-shaped, erumpent, and exude an infectious gum (3). The bacterium can also cause latent infections (2). Immature mango fruit with black spots on the epidermis were collected in August 2012 from mango trees of the cvs. Raposa and Pirie at a residence in Pukalani, Hawai'i, on the island of Maui. Similar symptoms were seen on a tree of the mango cv. Common (also known as 'Spanish' or 'Lahaina') at a nearby golf course. Mango fruit with black lesions, and leaves showing black lesions with yellow halos, were collected in August 2012 from mango trees of the cv. Haden at a residence in Kaimuki, Hawai'i, on the island of O'ahu. Xanthomonas-like bacterial colonies were isolated on TZC agar. Suspect colonies were non-pigmented on YDC agar. A fruit strain of the bacterium from Maui (A6081A) and a strain from each of a fruit (A6081B) and a leaf (A6082) from O'ahu were each gram-negative, oxidative, positive for both starch and esculin hydrolysis, and negative for nitrate reduction, resulting in presumptive identification as a Xanthomonas sp. The three strains were further characterized by Microlog (Biolog, Inc. Hayward, CA), which showed the closest match with X. campestris. In addition, 16S rDNA PCR assays showed the closest match (99% similarity) with X. citri strains, and RIF marker analysis of dnaA (4) grouped the three strains with Xcm strain LMG 941 (Accession No. CAHO01000002.1). Hypersensitivity responses typical of xanthomonads were observed when these strains were infiltrated into tobacco leaves, whereas no response was observed using sterile water. Leaves of 3-week-old mango seedlings were infiltrated using 10 μl (~10⁸ CFU/ml) of each strain suspended in sterilized water (six to eight inoculations per leaf, four leaves per plant, and three replicate plants per strain). The negative control treatments consisted of inoculation with sterile water, as well as an incompatible pathogen, X. hortorum pv. vitians (A6076), isolated from lettuce. Typical symptoms of bacterial black spot were observed for all strains assayed approximately 2 weeks after inoculation. No lesions were observed on the negative control plants. Koch's postulates were satisfied following reisolation and identification of the Xanthomonas strains from the infected plant tissues, using the biochemical and PCR methods described above. Results for strains from the two islands confirmed published descriptions of the pathogen, indicating that the pathogen causing symptoms on these mango trees is Xcm (1). Cultures and infected plant samples were sent to USDA APHIS and CPHST NPGLB facilities where this identification was confirmed. To our knowledge, this is the first report of bacterial black spot of mango in Hawai'i or anywhere in the United States. It is unknown whether this disease is a new occurrence or has not been reported previously. The origin of the primary inoculum is unknown. References: (1) B. Manicom and F. Wallis. Int. J. Syst. Bacteriol. 34:77, 1984. (2) O. Pruvost et al. Microbial Ecol. 58:928. (3) O. Pruvost et al. Plant Dis. 95:774, 2011. (4) K. Schneider et al. PLoS 6:e18496, 2011.

First Report of Tomato yellow leaf curl virus in Hawaii

Tomato yellow leaf curl disease, caused by the begomovirus Tomato yellow leaf curl virus (TYLCV; family Geminiviridae), is an economically important disease of tomato (Solanum lycopersicum L.) that can be very destructive in tropical and subtropical regions (1). In October 2009, tomato plants showing stunted new growth, interveinal chlorosis, and upward curling of leaf margins were reported by a residential gardener in Wailuku, on the island of Maui. Similar symptoms were observed in approximately 200 tomato plants at a University of Hawaii research farm in Poamoho, on the island of Oahu in November 2009. The similarity between these symptoms and those of tomato yellow leaf curl disease and the presence of whiteflies (Bemisia spp.), the vector of TYLCV, suggested the causal agent was a geminivirus such as TYLCV. Total nucleic acids were extracted from a tomato plant sample from Wailuku and Poamoho and used in a PCR assay with degenerate primers PAR1c715 and PAL1v1978 for geminivirus detection (4). The ~1.5-kbp amplicon expected to be produced from a geminivirus template was generated from the symptomatic tomato plant samples but not from a greenhouse-grown control tomato plant. The amplicons were cloned by the pGEM-T Easy vector (Promega, Madison, WI). Three clones from each sample were sequenced, revealing 97 to 99% nucleotide identity to TYLCV sequences in GenBank and a 98.9% nucleotide identity between the Wailuku (Accession No. GU322424) and Poamoho (Accession No. GU322423) isolates. A multiplex PCR assay for the detection and discrimination between the IL and Mld clades of TYLCV was also performed on these isolates (2). A ~0.8-kbp amplicon was generated from both isolates confirming the presence of TYLCV and their inclusion into the TYLCV-IL clade (2). Seven symptomatic and three asymptomatic tomato plant samples from Poamoho were tested for TYLCV using a squash-blot hybridization assay (3) utilizing a digoxigenin-labeled probe derived from the ~1.5-kbp PCR amplicon. All symptomatic tomato plants and one asymptomatic tomato plant were found to be infected with TYLCV. How the virus entered Hawaii and how long it has been present is unknown. The most plausible route is through infected plant material such as an asymptomatic alternative host rather than viruliferous whiteflies. It appears TYLCV is not a recent introduction into Hawaii since the Wailuku gardener observed similar disease symptoms for a few years before submitting samples for testing. In January 2010, TYLCV was also detected in two commercial tomato farms on Oahu, posing a serious threat to the state's $10 million annual tomato crop. References: (1) H. Czosnek and H. Laterrot. Arch. Virol. 142:1392, 1997. (2) P. Lefeuvre et al. J. Virol. Methods 144:165, 2007. (3) N. Navot et al. Phytopathology 79:562, 1989. (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.

Auditory nerve and brainstem responses in newborn infants with hyperbilirubinemia

To assess early bilirubin toxicity, a study was made of auditory brainstem responses in relation to total bilirubin levels as well as unbound bilirubin levels in 56 hyperbilirubinemic infants (total bilirubin greater than or equal to 15.0 mg/dL) and 24 infants who did not have jaundice. The latencies of wave I at 85 dB HL (hearing level) in hyperbilirubinemic infants were significantly greater than those in the control group. The latencies of wave I and V in hyperbilirubinemic infants with unbound bilirubin levels greater than or equal to 1.0 microgram/dL (group C) were greater than those in the control group and in the hyperbilirubinemic infants with unbound bilirubin levels less than 0.5 microgram/dL (group A) and with unbound bilirubin levels less than 1.0 microgram/dL (group B). There were no significant differences of the wave I-V interpeak latency between the control infants and the hyperbilirubinemic infants. Thirty of the 80 infants showed prolonged peak latencies (greater than the mean +/- 2 SD for the control infants) of wave I and/or V in one or both ears. The incidences of the prolonged peak latencies in group B (42%) and group C (89%) were significantly greater than that in the control group (12%). The serial determinations of auditory brainstem responses in infants treated with exchange transfusions revealed that the prolonged peak latencies before exchange transfusion improved at 48 and 96 hours after the procedure for wave I, and at 24, 48, and 96 hours after the procedure for wave V. The interpeak latency of wave I-V did not change with exchange transfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of phototherapy on serum unbound bilirubin i icteric newborn infants

Sera from 39 preterm and 35 full-term infants with hyperbilirubinemia, undergoing phototherapy continuously for 48 h, were assayed for unbound bilirubin by the peroxidase oxidation method. Assessment was done to determine the influence of therapeutic exposure to light on the serum unbound bilirubin concentrations in preterm and full-term infants. At 24 and 48 h after initiation of phototherapy, the unbound/total bilirubin ratios, as well, as the serum total and unbound bilirubin levels showed statistically significant declines of values in both preterm and full-term infants. It is concluded that, following phototherapy, the serum levels of unbound bilirubin decline more conspicuously than the decrease in serum total bilirubin levels.