Sexto ciclo de seleção recorrente fenotípica visando resistência à mancha-angular no feijoeiro.

Neste trabalho são apresentados os resultados obtidos na avaliação de progênies do sexto ciclo de seleção do referido programa

Eight cycles of recurrent selection for resistance to angular leaf spot in common bean.

The genetic progress (GP) was evaluated after eight cycles of recurrent selection for resistance to angular leafspot in common bean and indirect gain for yield and grain type. The base population (Cycle-0) was obtained from the diallelcross of seven lines with carioca grain and ten resistance sources. To obtain Cycle I, the most resistant S0 plants of Cycle 0were intercrossed. The same procedure was adopted in the subsequent cycles. GP for resistance to the pathogen was estimatedby the overall average of the progenies of each cycle in comparison with control Carioca MG and for productivity incomparison to the controls Carioca MG and Pérola. Lines of the first six cycles were used for grain type. No GP was detectedfor resistance to angular leaf spot. However, the indirect yield gain was 2.3% and 2.5% in the selection for grain type, withvalues similar to those obtained by direct selection for these traits

Controle genético da incompatibilidade do cruzamento entre cultivares andinas e mesoamericanas de feijoeiro comum.

Normalmente, ocorre incompatibilidade nos cruzamentos entre feijoeiros de origem andina com mesoamericanas. Há dúvidas no controle genético do caráter. Singh & Gutiérrez (1984) relataram que no controle do caráter estão envolvidos dois genes e ocorre epistasia recessiva dupla. Vilarinho (2004) apresentou resultados, relatando que não seriam apenas dois genes. Para melhor elucidar o controle genético desse caráter foi realizado o presente trabalho. Para isso, a cultivar de origem andina 'Jalo EEP 558' foi cruzada com a 'Small White', que é mesoamericana, porém compatível com a anterior. A cultivar de origem mesoamericana 'Mulatinho da Vagem Roxa' também foi cruzada com a 'Small White'. As gerações F1 desses dois híbridos foram cruzadas entre si. As sementes resultantes foram semeadas no campo e avaliada a ocorrência ou não da incompatibilidade. Constatou-se a segregação de três plantas normais para uma incompatível. Esse resultado evidencia que são dois genes, DL1 e DL2, e que o genótipo das cultivares envolvidas são: 'Jalo EEP 558' dl1dl1DL2DL2 ; 'Mulatinho da Vagem Roxa' DL1DL1dl2dl2 ; 'Small White' dl1dl1dl2dl2

Biotic Indicators for Ecological State Change in Amazonian Floodplains

Riverine floodplains are biologically diverse and productive ecosystems. Although tropical floodplains remain relatively conserved and ecologically functional compared to those at higher latitudes, they face accelerated hydropower development, climate change, and deforestation. Alterations to the flood pulse could act synergistically with other drivers of change to promote profound ecological state change at a large spatial scale. State change occurs when an ecosystem reaches a critical threshold or tipping point, which leads to an alternative qualitative state for the ecosystem. Visualizing an alternative state for Amazonian floodplains is not straightforward. Yet, it is critical to recognize that changes to the flood pulse could push tropical floodplain ecosystems over a tipping point with cascading adverse effects on biodiversity and ecosystem services. We characterize the Amazonian flood pulse regime, summarize evidence of flood pulse change, assess potential ecological repercussions, and provide a monitoring framework for tracking flood pulse change and detecting biotic responses