Cassava (Manihot esculenta Crantz) is an important source of food in the tropics. Phillips (1974) estimated that by 1980 it would provide 37% of the calories consumed in Africa, 11% in Latin America and 6% in the Far East forming the staple diet of 500 million people. Total world production in 1978 was estimated to be over 119 mill tonnes, mainly distributed among Africa, South America and Southeast Asia (FAO, 1979). Production figures for the major cassava producing countries of the world for the years 1976-1978 are shown in Table 1. Most of the world production of cassava is used for human consumption in tropical countries, the other main uses being for animal feed and the starch industry. The latter 2 markets, however, accounted for only 6.5% of the world production in 1974 (Anonymous, 1977). To an even greater extent than other tuberous crops, cassava is primarily a carbohydrate source containing little protein and as such is often considered as an inferior food. However, in much of the world where severe malnutrition and even starvation exists, the populations suffer not only from protein deficiency but also carbohydrate deficiency. The production of cassava products using traditional methods of preparation goes far to alleviate the problem: indeed it is significant that in areas where cassava is extensively grown, severe famines seldom occur. There are many descriptions of the traditional methods used to prepare foods from the cassava root but most are oriented to particular areas of the world. There is no study of the subject on a worldwide basis. The present paper reviews the literature, bringing together information from all the major cassava-producing areas in order to focus attention on the diversity of the processing techniques and the wide variety of cassava-based foods and beverages that are produced. Cassava leaves are also used as a food particularly in Africa and they are a good supplementary source of proteins and vitamins (Terra, 1964). As such their role in the diet is very different from that of the cassava root and they will not be discussed here. However, there is a need for further studies on the value of cassava leaves in the diet.

Traditional cassava-based foods: Survey of processing techniques

The objective of this work was to quantify the genetic diversity among cassava folk varieties as well as to examine the distribution of the genetic diversity among varieties of different origin and type. Fifty-four cassava varieties were chosen from 4 Brasilian regions: 45 of the Amazon basin (23 from River Negro, 6 of the River Branco and 16 of the River Solimoes) and 9 of the south coast of the Sao Paulo State, Brazil. The modern variety Mantiqueira was also included as a reference. Among these, 38 were bitter varieties and 17 sweet. Three different types of DNA markers were used: RAPD (randomly amplified polymorphic DNA), AFLP (amplified fragment length polymorphism) and microsatellites. Analysis of the results consisted of a description of band patterns, a calculation of similarity indexes (Nei & Li) and a principal coordinate analysis (PCoA) for each marker type. Heterozygosity, diversity indexes (DI, Weir) and genetic differentiation coefficients (GST) were calculated for the microsatellite loci.Genetic variability was more concentrated within regions, then among regions (GST = 0.07). Mean heterozygosity was 56%. Mean similarity indexes were dependent on the marker used: S = 0.89 for RAPD, S = 0.85 for AFLP and S = 0.59 for microsatellites. PCoA analysis revealed groups, distinguishing bitter from sweet varieties.

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Variabilidade genética de etnovariedades de mandioca, avaliada por marcadores de DNA

A monograph of Manihot Esculenta with an explanation of the taximetrics methods used

As variedades de mandioca (Manihot esculenta Crantz ssp esculenta) sao classificadas pela taxonomia popular em bravas e mansas. As bravas tem sabor amargo, contem alto teor de glicosideos cianogenicos (superior a 100 mg de equivalente HCN/kg de polpa fresca de raiz) e sao consumidas apos serem processadas na forma de farinha, fecula e outros produtos. As mansas ou doces nao tem sabor amargo, contem baixo teor de glicosideos cianogenicos, sao consumidas com ou sem qualquer processamento, principalmente por meio de preparados domesticos simples. Neste trabalho, foram feitos cruzamentos para verificar o perfil cianogenico das progenies segregantes visando utilizar variedades bravas no melhoramento de mandiocas mansas. Duas variedades mansas (IAC 289-70 e IAC 576-70) e uma brava (SRT-1330 Xingu) foram polinizadas com uma variedade mansa (SRT-797 Ouro do Vale). Dos cruzamentos entre variedades mansas, 85,7% dos genotipos apresentaram teores abaixo de 100 mg eq. HCN/kg de polpa fresca de raiz. Do cruzamento entre as variedades mansa e a brava, apenas 31,3% dos genotipos mostraram teores abaixo desse valor. A media das progenies foi muito proxima a media dos parentais. Em todos os cruzamentos, a maior frequencia de genotipos esteve na classe entre 50 e 100 mg eq. HCN/kg de polpa fresca de raiz, mesmo no cruzamento entre brava e mansa. Em todos os cruzamentos apareceram segregantes transgressivos para maior e menor potencial cianogenico em relacao a qualquer parental. O tipo de segregacao observada indica ser a cianogenese um carater com heranca quantitativa que, embora tenha algum grau de influencia ambiental, torna possivel a selecao de individuos com maior ou menor teor cianogenico devido a alta herdabilidade oriunda de ampla variabilidade genotipica. Assim, variedades bravas podem surgir como recombinantes de variedades mansas, sendo tambem possivel selecionar variedades com baixo teor cianogenico em cruzamentos de mandiocas mansas com mandiocas bravas.

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Conteúdo cianogênico em progênies de mandioca originadas do cruzamento de variedades mansas e bravas

Summary Field experiments were made in the rainforest zone of Western Nigeria over three cropping seasons on the effects of potassium fertilizer of one local cassava cultivar 53101 and two improved cultivars 60506 and 60447 which were F1 hybrids of the former. The results showed that K-fertilizer increased the starch yields only slightly. Cultivar 60506 produced significantly higher starch yields (P < 0–01) than the local strain, 53101, while cultivar 60447 gave lower starch recovery than the local cultivar. A definite influence of K application on the cyanide (HCN) content of the tuber roots could not be established. The peeled tubers of the improved cultivars contained much less cyanide than those of the local 53101 strain (P < 0–01). Potassium had the highest (0·72–1·28% dry weight basis) while phosphorus had the lowest concentration (0·06–0·12%) in the peeled tuber. Owing to its higher yielding capability the unfertilized 60506 removed larger amounts of potash (average 110·9 kg k20/ha) from the soil than unfertilized 53101 (average 82·2 kg k20/ha).

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0021859600027167

Investigations on Nigerian root and tuber crops: effect of potassium on starch yields, HCN content and nutrient uptake of cassava cultivars ( Manihot esculenta )

/pdf/determinacao-da-toxicidade-da-mandioca-pelo-paladar-das-3vb3kcsl8v.pdf

M. Gomes Pinto

Papers

Determinação da toxicidade da mandioca pelo paladar das raízes "In Natura"