High-resolution linkage map and chromosome-scale genome assembly for cassava (Manihot esculenta Crantz) from 10 populations

Cassava (Manihot esculenta Crantz) is a major staple crop in Africa, Asia, and South America, and its starchy roots provide nourishment for 800 million people worldwide. Although native to South America, cassava was brought to Africa 400–500 years ago and is now widely cultivated across sub-Saharan Africa, but it is subject to biotic and abiotic stresses. To assist in the rapid identification of markers for pathogen resistance and crop traits, and to accelerate breeding programs, we generated a framework map for M. esculenta Crantz from reduced representation sequencing [genotyping-by-sequencing (GBS)]. The composite 2412-cM map integrates 10 biparental maps (comprising 3480 meioses) and organizes 22,403 genetic markers on 18 chromosomes, in agreement with the observed karyotype. We used the map to anchor 71.9% of the draft genome assembly and 90.7% of the predicted protein-coding genes. The chromosome-anchored genome sequence will be useful for breeding improvement by assisting in the rapid identification of markers linked to important traits, and in providing a framework for genomic selectionenhanced breeding of this important crop.Bill and Melinda Gates Foundation (BMGF) Grant OPPGD1493. University of Arizona. CGIAR Research Program on Roots, Tubers, and Bananas. Next Generation Cassava Breeding grant OPP1048542 from BMGF and the United Kingdom Department for International Development. BMGF grant OPPGD1016 to IITA. National Institutes of Health S10 Instrumentation Grants S10RR029668 and S10RR027303.http://www.g3journal.orghb201

More people, more trees in South Eastern Tanzania: local and global drivers of land-use change

Land degradation in South Eastern Tanzania, the country’s major cashew producing area, has been attributed to deforestation. By comparing land-use/cover maps derived from aerial photographs of 1965 with maps derived from satellite images of 2002, we assessed how land-use changed in six villages, and relate these to local and global drivers. Land-use/cover changes are complex processes, which we analyzed by determining the relative net changes, losses, persistence and gains of each land-use/cover categories. Widespread planting of cashew trees only started in the 1960s; while the ‘villagisation’ program in the 1970s, altered settlement patterns as centrally planned villages were created. Population growth and rural development policies were major local drivers for land-use/cover change; international trade and technological innovations were principal global drivers. Though population increase led to a reduction of natural vegetation, the spread of cashew trees resulted in a case of ‘more people, more trees.’ How far the ensuing deforestation affected the biodiversity of the area and how sustainable the production of cashew nuts actually is, remains yet unresolved questions.status: publishe