-The objective of this work was to evaluate corn cultivars grown in the state of Amazonas, Brazil, which simultaneously show high grain yield, adaptability, and stability. The trials were carried out in seven environments in the state of Amazonas, in a randomized complete block design, with two replicates. The grain yield of 30 corn cultivars was evaluated in four growing seasons, from 2011/2012 to 2014/2015. The genetic parameters were estimated by the REML/Blup methodology. The selection for adaptability and stability was based on the predicted genetic value and on the harmonic mean of the relative performance of the genetic values. Despite the existence of genotype x environment interaction, cultivars with high adaptability and stability were identified. Iranduba -lowland, in

RESUMO -Neste trabalho procura-se destacar as principais características das várzeas que ocorrem no Estado do Amazonas e suas influências sobre as atividades agrícolas, tomando-se como base trabalhos desenvolvidos nesse ecossistema. No Amazonas são diferenciados dois grandes ecossistemas: "terra firme" e "várzeas". Terra firme é um termo genérico, usado na Amazônia, para designar locais que não sofrem inundações provocadas pelos rios. O termo "Várzea" é utilizado para designar áreas situadas às margens dos rios de água "barrenta" ou "branca", sujeitas a inundações periódicas causadas pelos rios. Essas enchentes contribuem anualmente com novos depósitos de sedimentos, oferecendo uma camada de solo novo e fértil, às margens do rio Solimões e afluentes. Nas margens dos rios de água clara ou preta, não há formação de várzeas. As que se formam às margens desses rios são por influência dos rios de água barrenta e são menos férteis do que aquelas que ocorrem às margens desses rios. As várzeas, por apresentarem solos de fertilidade mais elevada, são intensivamente utilizados para fins agrícolas, no período em que não estão inundadas. As produtividades das culturas nesse ecossistema são mais elevadas do que nas terras firmes mas, o cultivo contínuo, sem inundação dos rios, leva a decair essa produtividade. Um dos principais fatores limitantes para o uso contínuo da várzea é a infestação por ervas daninhas. A distância dos mercados consumidores é um fator que deve ser considerado, quando da definição da utilização das várzeas, para fins agrícolas.Palavras Chaves: Região Amazônica; Várzeas Amazônicas; Regime de Enchente de Várzeas; Solos de Várzeas. Characteristics, Potential and Actual Agricultural Use of Floodplains in the Amazonas State, Brazil.SUMMARY -In this work we try to stand out the main characteristics of the floodplains that occur in the Brazilian State of Amazonas, and its influences on the agricultural activities, based on works developed in that ecosystem. In Amazonas State two great ecosystems arc to designate local that don't suffer floods provoked by the rivers. The term "Várzea" designate areas at the margins of the rivers of "loamy" or "white" water , subject to periodic floods caused by those rivers. By means of the floods of the "Várzeas" new contributions of sediments are registered, particularly to the margins of the rivers of "white" water as the Solimões river. In the margins of the rivers of clear and black water, there is not "Várzeas" formation. The ones that are formed are by influence of the rivers of "white" water, and they are less fertile. The "Várzeas", due to present soils of higher fertility, are intensively used for agricultural purpose, in the period that are not flooded. The productivity of the crops in the "Várzeas" are higher than that in "Terra Firme" but, in the continuous cultivation, without flood of the rivers, the

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Sugary cassava (Manihot esculenta) represents a type of cassava that accumulates sugar in its root due to a deficiency to convert sugar into starch.

ABSTRACT. Manioc, Manihot esculenta, is economically important in many tropical and subtropical countries. The genetic variability of the species has not been fully explored, and new information may help expand its use. Molecular markers based on retrotransposons have good potential for analysis of genetic diversity given their abundance in the genome. Eight long terminal repeat retrotransposons were selected for the development of interretrotransposon-amplified polymorphism markers. To test these primers, we analyzed 32 varieties from Anori, 30 from Manicoré and 10 Mandiocabas from the Manioc Germplasm Bank at Embrapa Western Amazonia. The six informative primer pairs yielded 20-60 polymorphic bands, averaging 92% polymorphism (51.7-98.4) and 0.37 heterozygosity (0.17 to 0.40), with a Shannon information index of 0.54 (0.26-0.59). These markers can be used to explore the genetic diversity of manioc.