College of Tropical Agriculture and Human Resources

About: College of Tropical Agriculture and Human Resources is a based out in . It is known for research contribution in the topics: Population & Soil water. The organization has 513 authors who have published 604 publications receiving 15798 citations.

Atypical Internal Yellowing of Papaya Fruit in Hawaii Caused by Enterobacter sakazakii.

Abstract: Internal yellowing (IY) caused by Enterobacter cloacae and characterized by yellow discolored tissue surrounding the papaya (Carica papaya L.) seed cavity, diffuse margins, and the presence of a distinctly rotten odor was first reported in 1987 (3). Here we report the formation of atypical internal yellowing (AIY) in ripe papaya caused by the bacterium Enterobacter sakazakii. In surveys conducted from 2006 to 2007, 'Kapoho Solo' papayas grown in the Puna District of Hawaii Island were obtained from various packinghouses. After incubation at 27°C, the papayas were bisected and examined for symptoms of IY. Among papayas that were asymptomatic for IY, a dull, greenish yellow discoloration of the flesh with a distinct margin extending from the seed cavity into the pericarp was noted, along with a pungent odor. These symptoms occurred in 5 of the 500 fruit surveyed and bacterial populations were 102 to 103 CFU/g. Discolored tissue was aseptically excised, weighed, macerated, serially diluted in sterile distilled water (SDW), and plated onto modified peptone yeast extract medium (PT-M4) (4). The plates were incubated at 30°C for 24 to 48 h until single colonies were evident. After 48 h, colonies on PT-M4 were orange-red, convex and circular, and surrounded by a somewhat opaque 1-mm margin. After single colony purification, five strains were obtained. The strains, inoculated into oxidation/fermentation-glucose tubes and API 20E strips (bioMerieux, Inc., Durham, NC) incubated at 30°C, were shown to be facultative anaerobes and identified as E. sakazakii with a 98.4% certainty. Colonies plated onto tryptic soy agar (TSA) and incubated for 72 h at 25°C produced yellow pigmentation, indicative of E. sakazakii. Amplification by PCR with E. sakazakii-specific primers (2) yielded a 929-bp fragment, which was absent with E. cloacae and Pseudomonas aeruginosa template DNA. To confirm pathogenicity, cell suspensions at 109 CFU/ml of putative E. sakazakii strains RK07-05, RK07-06, and RK07-07 and E. cloacae (3) were inoculated by injection (0.5 ml per site) into one-third-ripe 'Kapoho Solo' papayas (six fruit per strain, inoculated at duplicate sites) and incubated at 27°C for 4 days. Control sites were injected with 0.5 ml of SDW. Fruit inoculation experiments were repeated. E. cloacae-inoculated sites produced typical IY as previously described (3), while the sites inoculated with the three E. sakazakii strains produced greenish yellow tissue (26% mean incidence), symptomatic of AIY. Control sites did not produce IY or AIY. Koch's postulates were fulfilled, and the identification of reisolated bacterial strains was confirmed with API 20E, PCR, and pigment production on TSA. Although less prevalent (1% incidence) than the typical IY produced by E. cloacae (3), E. sakazakii has the potential to affect quality and food safety of fresh and processed papaya products. E. sakazakii has been implicated in a severe form of neonatal meningitis, sepsis, and necrotizing enterocolitis (1). Research into the transmission and infection of papaya of this cross-domain pathogen merits further study. References: (1) D. H. Adamson. Clin. Microbiol. Newsl. 3:19, 1981. (2) A. Lehner et al. BMC Microbiol. 4:43, 2004. (3) K. A. Nishijima et al. Plant Dis. 71:1029, 1987. (4) K. A. Nishijima et al. Plant Dis. 88:1318, 2004.

Soil salinity and the growth of macadamia seedlings.

Abstract: Several salt levels were imposed on a silica sand and a soil to determine the tolerance of macadamia (Macadamia integrifolia) seedlings to salinity. Visual symptoms, plant height increases and plant nutrient composition were used to measure plant response. Subsequently, five soils with different mineralogical and chemical properties were subjected to salinization then desalinization to study changes in soil and plant chemical composition. Results suggest that macadamia seedlings are moderately sensitive to soil salinity. A 50% growth reduction occurred at an EC of 5 dS/m in the saturation paste extract. Salinization not only increased the Na concentrations in soil and plant, but also reduced the relative proportion of other nutrients (e.g., Ca and K). When plant K/Na ratios were ≤ 2.5, adverse effects of salinity could be expected. A K/Na ratio of 1.5 corresponded to a 50% growth reduction. Other nutritional problems seemingly unrelated to soil salinity, such as Al and Mn phytotoxicities, were br...

Parent and household influences on calcium intake among early adolescents

Abstract: Calcium intake during early adolescence falls short of requirements for maximum bone accretion. Parents and the home food environment potentially influence children’s calcium intakes. This study aimed to quantify parental psychosocial factors (PSF) predicting calcium intakes of Asian, Hispanic, and non-Hispanic white (NHW) early adolescent children from a parental perspective. This was a cross-sectional study involving the administration of a validated calcium-specific food frequency questionnaire to a convenience sample of children aged 10–13 years and the primary individual responsible for food acquisition in the child’s household. Based on Social Cognitive Theory, parental factors potentially associated with children’s calcium intake were also assessed via parent questionnaires. The total study sample consisted of 633 parent-child pairs (Asian = 110, Hispanic = 239, NHW = 284). Questionnaires were completed at community-based centers/sites. Outcome measures were the association between parent-child calcium (mg), milk (cups/day), and soda (cans/day) intakes and the predictive value of significant parental PSF towards calcium intakes of their children. Sex-adjusted linear regression and multivariate analyses were performed. Calcium intakes of parent-child pairs were positively associated among all ethnic groups (r = 0.296; P < 0.001). Soda intakes were positively associated among Hispanic parent-child pairs only (r = 0.343; P < 0.001). Home availability of calcium-rich foods (CRF), parental rules and expectations for their child’s intake of beverages, and parents’ calcium intake/role modeling were positively associated with children’s calcium intake and overwhelmed all other PSF in multivariate analyses. Significant cultural differences were observed. Parental role modeling was a significant factor among Hispanic dyads only. Multivariate models explained 19–21% of the variance in children’s calcium intakes. Nutrition interventions to improve children’s calcium intakes should focus on parents and provide guidance on improving home availability of CRF and increasing rules and expectations for the consumption of CRF. Among Hispanic families, interventions promoting parental modeling of desired dietary behaviors may be most successful.

Reduced pesticide use in an IPM program for anthuriums.

Abstract: An integrated pest management program (IPM) for anthuriums successfully reduced pesticide applications without reducing production and marketability. During 1986 and 1987, insecticide, acaricide, and fungicide applications at three farms studied were reduced by 45, 79, and 96%, respectively, by economically justifying spray applications. No significant increase in thrips, mite, or anthracnose injuries occurred, nor did total cost for treatment and pest damage increase. Our study indicated that the IPM concept implemented on a floricultural crop can reduce pesticide applications and increase profitability.