Geographic differences in patterns of genetic differentiation among bitter and sweet manioc (Manihot esculenta subsp. esculenta; Euphorbiaceae)

Abstract

Lack of differentiation in Africa is most likely due to postintroduction hybridization between bitter and sweet manioc. Inconsistent transfer from South America to Africa of ethnobotanical knowledge surrounding use-category management may contribute to increased hybridization in Africa. Investigating this issue requires more data on the variation in cyanogenesis in roots within and among manioc populations and how manioc diversity is managed on the farm.

Farmer variety exchange along Amazonian rivers influences the genetic structure of manioc maintained in a regional Brazilian GeneBank

“…Based on the pattern of dispersion in PCoA of the groups identified by Structure and of the 188 varieties characterized by the levels of cyanogenic glycosides using available passport data, we found weak sweet-bitter structure, although errors in the passport identification, partial chemical characterization of manioc accessions and mixture during clonal multiplication (on farm and ex situ) may contribute to this. Bradbury et al (2013) also showed, in African varieties, the occurrence of hybridization, incorrect passport data, and misidentification of sweet or bitter varieties by farmers.…”

Effect of genotype and genotype by environment interaction on total cyanide content, fresh root, and starch yield in farmer‐preferred cassava landraces in Tanzania

“…; Bradbury et al. ). Konzo is the irreversible upper motor neuron damage caused by consumption of high dietary cyanogens especially from insufficiently processed cassava roots.…”

Molecular characterization of 'sweet' cassavas (Manihot esculenta) from a germplasm bank in Brazilian Eastern Amazonia

“…They also harvest 'sweet' cassavas earlier than 'bitter' types, in order to avoid formation of fibers, due to root lignification. Maybe this different type of selection, and the separation that farmers promote in their farms have contributed to generate a slight genetic differentiation detected by molecular markers in South America (Mühlen et al 2000, Elias et al 2004, Alves-Pereira et al 2011, Bradbury et al 2013), which did not occur in Africa (Bradbury et al 2013). Due to these differences in usage, 'sweet' and 'bitter' cassava genetic breeding programs are specific for each type (Fukuda et al 2002, Ceballos et al 2004).…”