Case of escape in cassava, Manihot esculenta Crantz

Two cassava escapes where collected from cultivated fields near natural habitat in Bolivia. They are described morphologically and analyzed cytogenetically in this study. It is suggested that they are the product of backcrosses of cassava interspecific hybrids with the cultigen itself, and that selective conditions have developed in which certain forms of cassava segregates have adapted to grow wildly in natural habitats near cassava fields. These segregates may hybridize with cultivated cassava upon coming in contact with such varieties. Because these escapes have incorporated useful genes from the wild into their genetic structure, they could be used for cassava improvement since their genetic barriers with other forms of cassava are very weak

Wild cassava, Manihot spp. : biology and potentialities for genetic improvement

Espécies selvagens de Manihot dão origem à mandioca. Elas constituem valioso reservatório genético, com genes mostrando novos caracteres. O exame cuidadoso dessas espécies mostrou que algumas delas têm uma percentagem notavelmente alta de proteína combinada com uma porcentagem baixa de ácido cianídrico. O estudo dos habitats naturais revelou resistência à seca e à toxicidade por alumínio em excesso no solo, assim como adaptação a baixas temperaturas. Alguns dos híbridos obtidos mostraram alta produtividade da raiz e resistência a brocas do caule. A apomixia foi descoberta nas espécies selvagens e transferida com sucesso para as espécies cultivadas.Wild species of Manihot are progenitors of cassava. They constitute valuable genetic reservoirs presenting genes that show new characters. Screening of these species showed some of them to have a notably high percentage of protein combined with a low percentage of hydrocyanic acid. Study of natural habitats revealed resistance to drought and excessive soil aluminum toxicity as well as adaptation to low temperature. Some of the hybrids obtained showed high root productivity and resistance to stem borers. Apomixis was discovered in the wild and transferred successfully to the cultivate species

Cytogenetics and evolution of cassava (Manihot esculenta Crantz)

All Manihot species so far examined, including cassava (Manihot esculenta), have 2n = 36. Interspecific hybrids between cassava and its wild relatives show fair regular meiosis, and backcrossed generations exhibit high fertility. Electrophoresis shows affinity between species of different sections, as well as between some of them and cassava itself. Polyploidy has apparently contributed to the rapid speciation of this genus, while apomixis has offered a means of perpetuating new hybrid types adapted to different environments. It is assumed that cassava originated by hybridization between two wild Manihot species followed by vegetative reproduction of the hybrid

Técnicas novas na produção da mandioca para melhorar o bem-estar dos pequenos agricultores no DF e Goiás

Durante quatro anos de execução, o projeto para melhorar o bem-estar dos pequenos agricultores forneceu mais de 6 mil mudas, híbridos e estacas enxertadas, desenvolvidas pelo Projeto da Mandioca da UnB. Onze famílias de pequenos agricultores no Distrito Federal (DF) e sete assentamentos no Estado de Goiás (GO), totalizando 700 famílias foram beneficiadas com esse germoplasma. Este trabalho de extensão objetivou melhorar a produtividade e a renda dos agricultores proporcionando monitoramento dos plantios de mandioca e aconselhamento técnico. Os estagiários coordenados pelo pesquisador Nagib Nassar e acompanhados por técnicos de Emater/DF (Empresa de Assistência Técnica e Extensão Rural do Distrito Federal) acompanharam mensalmente os plantios e forneceram recomendações técnicas sobre adubação, controle de pragas e valor nutritivo das variedades. Além de variedades melhoradas, os agricultores receberam mudas de mandioca enxertadas com espécies silvestres. Foram realizadas três reuniões nas quais os agricultores opinaram sobre desempenho e qualidade das variedades distribuídas e avaliaram o impacto do projeto em suas rendas e condições de saúde. Entre estes cultivares, UnB 201, UnB 205 foram as variedades mais elogiadas pelos agricultores devido ao alto valor nutritivo nutritivo e palatabilidade e sabor excelentes. Os cultivares enxertados com M. glaziovii mostraram maior produtividade, dando 15 kg por planta após dois anos. A alimentação do gado por partes vegetativas resultou em aumento da gordura no leite de 3,1% até 4,5%. Foi concluído ter sido alcançado com sucesso o objetivo de melhorar a produtividade de seus plantios e suas rendas. Resultados deste projeto foram recebidos com entusiasmo pelo Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) e publicados em sua página enfatizando o impacto positivo no bem-estar de pequenos agricultores no DF e em Goiás.During four years, this project to improve small farmers welfare distributed more than 6000 cuttings of cassava hybrids and grafted seedlings, developed by Cassava Program University of Brasilia. Eleven farmers families in Federal District (DF) and 7 rural settlement in Goiás state (GO) totaling about 700 families made benefit of this germplasm. This extension work aimed to improve productivity and the income of the farmers providing monitory of cassava plantation and technically advising to them. The students accompanied by coordinator (N. Nassar) and Emater/DF extension agents monitored monthly plantations and provided technical recommendations on fertilization, pest control and nutritive value of varieties. In addition to improved cultivars, grafted seedlings of wild species onto cassava were received too by small farmers. Three meetings were held with small farmers where they opined about performance of varieties and evaluated project impact on income and healthy conditions. Among these varieties, UnB 201 and UnB 205 were the most ones praised by farmers due to high vitamin content and excellent palatability and flavor too. Cassava cultivars grafted by M. glaziovii showed higher productivity, giving 15kg per plant after 2 years. Feeding cows by vegetative parts resulted in increasing fat content in milk from 3.1% to 4.5%. It is concluded that objective of improving plantations productivity and incomes were successfully reached. Results of this project were received enthusiastically by the National Council of Technological and Scientific Development-CNPq and published it at its homepage emphasizing the positive impact on welfare of small farmers in the DF and Goiás state