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There are several structural and technical factors that determine rice production. Among others, we have to take into account weed management. Red rice (=Oryza sativa L.) is undoubtedly one of the most troublesome weeds in rice production in some regions of Portugal. In order to be able to better control this weed, the knowledge of red rice biological behavior, in relation to different environmental conditions, is considered essential to bring out strategies of weed management fit for an integrated production of rice of a high quality. This experiment was conducted to study the competitive ability of the most important rice varieties (Ariete and Thaibonnet) against red rice, at 2 N rate and 4 densities of the weed. This research allowed besides understanding preliminarily if shattering is related only to the genetic features or depends also on agronomical or environmental conditions, such as N supply and condition of competition.

In order to reach the objectives of the UE project "RESGEN" for conservation, characterisation, collection and exploitation of genetic resources in agriculture, it will be performed the description, collection, employing and organisation of germplasm available at different European institutions. The planned activity was aimed to constitute an operative germplasm gene bank. To perform this goal a number of genotypes have to be described, evaluated and characterised for agrophysiologic, adaptive and technologic behaviour. The first step was to collect and catalogue all the genetic resources currently available in the different European rice countries that at the beginning of the project amounted to about 450 varieties.

Rice is a crop moderately sensitive to salinity (Maas & Hoffman, 1977), that grows in waterlogged conditions. The identification of genotypes resistant to NaCl at specific developmental stages is essential to improve the understanding of the effects of salt stress upon phenology and to elaborate further breeding programs. Five European rice-producing countries pooled their genetic resources in order to evaluate them and subsequently improve national breeding programmes (Project RESGEN CT 95-37). 320 European rice varieties were screened at the young seedling stage (the most sensitive to NaCl during vegetative growth).