RESUMO
Tomato severe rugose virus (ToSRV) and Tomato chlorosis virus (ToCV) are among the major viruses that affect tomato (Solanum lycopersicum) development and yield in Brazil. ToSRV and ToCV are transmitted in a persistent circulative and semipersistent manner, respectively, by the whitefly Bemisia tabaci Middle East-Asia Minor 1, considered the main vector of these viruses. In this study, the kinetics of systemic invasion and the latent and incubation periods of ToSRV and ToCV were evaluated in singly and doubly infected tomato plants. Both viruses moved systemically into tomato plants as early as 1 day after inoculation. The mean ToCV latent periods in single infections and co-infections with ToSRV were 13 and 11 days, respectively, while incubation periods in single and co-infections were, on average, 30 and 31 days, respectively. For ToSRV, the mean latent period was 7 days in single infections and 6 days in co-infections with ToCV. Incubation periods were, on average, 18 and 17 days in single and co-infections, respectively. Because latent periods for both viruses were shorter than their respective incubation periods, field-infected tomato plants may act as sources of inocula soon after infection and before onset of symptoms.
Assuntos
Coinfecção , Doenças das Plantas/microbiologia , Solanum lycopersicum , Animais , Brasil , Crinivirus , Cinética , Oriente MédioRESUMO
A shift towards declining azoxystrobin sensitivity has been previously documented in a collection of Brazilian Monilinia fructicola isolates, but information on the stability of this trait after in vitro sub-culturing is not available. In this study, one highly-sensitive isolate and two isolates with reduced sensitivity to azoxystrobin, not exhibiting point mutations at codons 129, 137 and 143 in the target gene of cytochrome b were used. Two independent experiments consisted of 10 weekly transfers of each strain in potato dextrose agar (PDA). Conidial production and germination were quantified in the initial culture and, again, after the third, sixth and tenth transfer. Measures of mycelial growth were obtained in colonies growing on PDA amended with azoxystrobin at 1 µg mL-1 and salicylhydroxamic acid at 100 µg mL-1. Data were normalized to mycelial growth rate after each of the 10 transfers. The colony diameter in the less sensitive isolates was stable across the transfers in the PDA amended with the fungicide. The conidial production and mycelial growth rate did not decrease in non-amended media either. Our results suggest that the trait of reduced sensitivity to azoxystrobin is stable under no selection pressure for azoxystrobin.(AU)
Assuntos
Micoses/patologia , Testes de Sensibilidade Parasitária , Prunus , QuinonasRESUMO
A shift towards declining azoxystrobin sensitivity has been previously documented in a collection of Brazilian Monilinia fructicola isolates, but information on the stability of this trait after in vitro sub-culturing is not available. In this study, one highly-sensitive isolate and two isolates with reduced sensitivity to azoxystrobin, not exhibiting point mutations at codons 129, 137 and 143 in the target gene of cytochrome b were used. Two independent experiments consisted of 10 weekly transfers of each strain in potato dextrose agar (PDA). Conidial production and germination were quantified in the initial culture and, again, after the third, sixth and tenth transfer. Measures of mycelial growth were obtained in colonies growing on PDA amended with azoxystrobin at 1 µg mL-1 and salicylhydroxamic acid at 100 µg mL-1. Data were normalized to mycelial growth rate after each of the 10 transfers. The colony diameter in the less sensitive isolates was stable across the transfers in the PDA amended with the fungicide. The conidial production and mycelial growth rate did not decrease in non-amended media either. Our results suggest that the trait of reduced sensitivity to azoxystrobin is stable under no selection pressure for azoxystrobin.
Assuntos
Micoses/patologia , Prunus , Testes de Sensibilidade Parasitária , QuinonasRESUMO
The center of origin of peanut is located in South America, specifically in southeastern Bolivia and northwestern Argentina, where its parental species are found in wild habits. Even though Argentina is only the seventh largest producer of peanut in the world (2% of global production), it is the leading exporter of edible grain and crushed (e.g., flour, butter, and oil) peanut products worldwide. Peanut production was moved to more southern areas of Cordoba in the early 1990s to avoid the consequences of production issues in the northern region. During this migration process, a new disease emerged in commercial plots: peanut smut caused by Thecaphora frezii. Peanut smut was first detected in the northern peanut producing areas in Córdoba Province, and then established on the central region where the main grain processing industries are located. Currently, the prevalence is 100% in Argentinian peanut area. This finding showed evidence that pathogens could also migrate along with peanut production activities and contaminate soil of new production areas.