The culture of yuca is traditionally rustic and adapted to soil and climate marginal conditions. It is also one of the most important sources of carbohydrates for 600 million people in tropical countries worldwide. Although the entire plant is consumed, the root is the most important part of the plant (Fukuda et al., 2008), and in Pará, the area destined to the cultivation of yucca is rather expressive, reaching 326,000 hectares in the year 2007, with a production of 5,211,503 root tons, a fact which makes the state yuca´s largest producer in the country. This production supplies internal demand and exports the culture´s surplus to the Amazonian region’s neighbouring states and other regions in Brazil. The increase in production is a result of not only the incorporation of new areas to the productive process, but also of the increase in productivity, which has grown from 12.74 tons/hectare to 16 tons/hectare during the period (IBGE, 2007), thus reflecting appropriation of technological innovation along the productive chain. However, once current production is compared with its potential, which is estimated in 60-70 tons/hectare, the availability and incorporation of considerable technological innovation becomes necessary to raise productivity. The culture’s profile in the region is highly associated to family farming, once its cultivation is done in small estates and with the use of family labor. Throughout the counties in which the producers depend on subsistence agriculture, yuca represents their agricultural base, especially by means of table-flour sale. Although this cultivation possesses advantages when compared to other food cultures, in regard to tolerance towards acidic and low fertility soils which occur in humid climate cultivations, the little technology employed in these areas, in which successive cultivation occurs, and with little set-aside periods, has been contributing to the outbreak of diseases caused by fungus, such as the root decay caused by the Fusarium and Phytophthora genera, thus compromising production, in addition to the planting of a mixture of cultivares with low productive potential. In short term, production tends to increase due to the state’s incentives by means of the Support and Development of Yuca’s Productive Chain Program (2004 administration), executed by Pará’s State Secretary of Agriculture (SAGRI) in partnership with EMATER-PA (State Technical Assistance and Rural Extension Company), which projects ambitious goals of productivity and production increase as well as quality, of both products and byproducts, in addiction to market support. Without changing the state’s culture profile, there won’t be any mechanisms to increase yuca production and productivity, these goals will only be met with solid support of technical assistance (established technology transfer) and research, linked with the provision of genetic material which is productive and adapted to the greatly diverse climate conditions found in the state. The project under execution, having been implanted and coordinated by SAGRI in partnership with EMATER, consists of implanting small multiplication orchards (seeds and seedlings), belonging to yucca varieties listed by producers from varied locations, actions which may be considered as an initial step towards the culture’s genetic improvement program. However, considering that the following evaluation and selection stage is the longest most burdensome (and is the project´s main goal), the use of scientific methods which increase accuracy is thus of extreme importance. Another fact to point out is that the state of Pará and its territorial extension, shows great soil and climate variability among the most productive regions, and thus the cultivares’ adaptations show great variation throughout these areas, a phenomenon called genotype x environment interaction.