Evaluation of Resistance to Asiatic Citrus Canker among Selections of Pêra Sweet Orange (Citrus sinensis).

Asiatic citrus canker (ACC, caused by the bacterium Xanthomonas citri subsp. citri) is a destructive disease of citrus in Brazil and in several other citrus-producing countries. ACC management is problematic, and bactericides such as copper can be reasonably efficacious but do not completely control the disease. Furthermore, injury by citrus leaf miner (CLM) can exacerbate severity of ACC. Host resistance is the most desirable solution for management of ACC; however, evaluations of germplasm indicate that resistance is limited in many popular species and cultivars that are grown commercially. Limited evaluations have been made of sweet orange (Citrus sinensis) selections. We evaluated resistance of 25 Pêra sweet orange selections to X. citri subsp. citri by wound inoculation and measuring lesion diameter under greenhouse conditions (wound inoculation indicates mesophyll resistance which will be valuable in areas where CLM exists). ACC severity was assessed on the same 25 selections at three locations in the field in Brazil, relying on natural inoculum and conditions to cause disease. In the greenhouse experiments, the selections EEL, Bianchi/CC, Ipiguá, Olimpia, IAC 2000/1, and Ovale Siracusa consistently had the smallest diameter lesions, indicating greatest resistance, although differences in lesion diameter were small. Results from the field experiments were less conclusive, although EEL and Ovale Siracusa were consistently numerically least affected by ACC. These results indicate selections of sweet orange that might be preferable to consider in canker-prone areas in Brazil and elsewhere.

Association between seropositivity for Toxoplasma gondii, scholastic development of children and risk factors for T. gondii infection.

BACKGROUND: We evaluated the possible association of seropositivity for Toxoplasma gondii and certain risk factors for T. gondii infection with the scholastic development of children. METHOD: One hundred children aged 6-13 years attending the Hospital Municipal de Maringá Paranáa, Brazil, participated in the study. Serologic tests for IgG and IgM anti-T. gondii (indirect immunofluorescence (capture ELISA) were performed. The Scholastic Performance Test (SPT) for writing, mathematics and reading was applied to each child, and the result was classified as high, average or poor. The guardian of each child responded to a questionnaire about certain aspects of the child's living situation and diet. RESULTS: The prevalence of seropositivity for T. gondii was 8%. An association between seropositivity for T. gondii and scholastic development in the mathematics subtest and also consumption of fresh cheese were observed. Children with exposed soil, sand or grass lawn in their peridomicile were 9.116 times more likely to be infected by T. gondii. CONCLUSION: The findings showed the need to test school-age children for this parasite, educate families with T. gondii-positive children, provide training to educators, monitor recreation areas, and raise awareness of the need for care in handling food.

Trypanosoma cruzi: Different methods of data analysis to evaluate the genetics-biology relationship.

The correlation of genetic and biological diversity in Trypanosoma cruzi was studied. Strains of T. cruzi II, isolated from humans; and of T. cruzi I, isolated from wild-animal reservoirs and from triatomines in the state of Paraná, Brazil, were used. Thirty-six biological parameters measured in vitro and six in vivo, related to growth kinetics and metacyclogenesis, susceptibility to benznidazole, macrophage infection, and experimental infection in mice were evaluated. Data from RAPD and SSR-PCR were used as genetic parameters. Mantel's test, group analysis, principal components analysis (PCA), and cladistical analyses were applied. With the Mantel's test, a low correlation was observed when parameters related to growth kinetics and metacyclogenesis in vitro and development of the experimental infection in vivo were included. The group analysis defined two groups that were separated as to whether they produced patent parasitemia in BALB/c mice. In the larger group, strains derived from wild reservoirs were separated from strains derived from triatomines and humans. The PCA identified two groups that differed as to whether they produced a parasitemia curve in mice. The cladistical analysis supported the previous results. This study shows the importance of the parasite-host relationship for the behavior of the strains, and that the combination of methods supports, extends, and clarifies the available information.