1. Acknowledgements This study was performed with financial support of European Social Fund co-financed project 2009/0218/1DP/1.1.1.2.0/09/APIA/VIAA/099. Acknowledgements This study was performed with financial support of European Social Fund co-financed project 2009/0218/1DP/1.1.1.2.0/09/APIA/VIAA/099. Cereal breeding for organic farming: aspect of competitiveness against weeds Dace Piliksere 1, Vija Strazdina 2, Zaiga Vicupe 2, Zaiga Jansone 2 1 State Priekuli Plant Breeding Institute, Latvia dacepil@gmail.com 2 State Stende Cereals Breeding Institute, Latvia Introduction Assessing weed suppression ability of crops became more important with the development of organic plant breeding.This report introduces with first results on the project “Development, improvement and implementation of environmentally friendly and sustainable crop breeding technologies” The aim is to develop the methodology for an estimation of cereal varieties and breeding lines for their competitive capacity against weeds, to establish more effective criteria of the selection by significant crop characteristics in the breeding process. Introduction Assessing weed suppression ability of crops became more important with the development of organic plant breeding.This report introduces with first results on the project “Development, improvement and implementation of environmentally friendly and sustainable crop breeding technologies” The aim is to develop the methodology for an estimation of cereal varieties and breeding lines for their competitive capacity against weeds, to establish more effective criteria of the selection by significant crop characteristics in the breeding process. Material and Methods The investigation is carried out at State Priekuli Plant Breeding Institute and at State Stende Cereals Breeding Institute in Latvia. In organic growing conditions With different varieties and breeding lines of such cereal species as: Barley (fig. 1) oat winter triticale winter wheat Different crop, as well as some weed flora characteristics are taken into account, to evaluate cereal varieties for their competitiveness: field germination crop growth habit at tillering and at stem elongation crop tillering capacity canopy height at the beginning and at the end of stem elongation and crop plant height before the harvesting beginning of such crop phenological phases as tillering, stem elongation, heading and fully ripening, (in days from sowing) crop and weed ground cover several times from tillering to maturity weed dry weights at cereal flowering or maturity crop yields. Harrowing was not used in the trials, to exclude the impact of this factor. Linear correlation method was used for statistical data analysis. Material and Methods The investigation is carried out at State Priekuli Plant Breeding Institute and at State Stende Cereals Breeding Institute in Latvia. In organic growing conditions With different varieties and breeding lines of such cereal species as: Barley (fig. 1) oat winter triticale winter wheat Different crop, as well as some weed flora characteristics are taken into account, to evaluate cereal varieties for their competitiveness: field germination crop growth habit at tillering and at stem elongation crop tillering capacity canopy height at the beginning and at the end of stem elongation and crop plant height before the harvesting beginning of such crop phenological phases as tillering, stem elongation, heading and fully ripening, (in days from sowing) crop and weed ground cover several times from tillering to maturity weed dry weights at cereal flowering or maturity crop yields. Harrowing was not used in the trials, to exclude the impact of this factor. Linear correlation method was used for statistical data analysis. Results Cereals suppress weed growth, as it is evident from field trials (fig. 2). However, diverse cereal genotypes could have different competitiveness against weeds, that depends on crop growth and above-ground characteristics. Therefore we look for the most relevant crop traits that influence weed growth and can be of value in organic crop breeding. Results from first investigation year are shown below (fig. 3). Results Cereals suppress weed growth, as it is evident from field trials (fig. 2). However, diverse cereal genotypes could have different competitiveness against weeds, that depends on crop growth and above-ground characteristics. Therefore we look for the most relevant crop traits that influence weed growth and can be of value in organic crop breeding. Results from first investigation year are shown below (fig. 3). Figure 2. Pure-weed plot versus barley-weed plot at stem elongation. Figure 1. Diverse genotypes of barley differ in their characteristics (stem elongation) Figure 3. Significant correlations between weed observations and different crop traits. Photo by L. Legzdina First Conclusions The first year’s results of investigation show that some crop traits are signifficantly correlated with weed growth. However, these results should be reviewed for correctness in next at least two years more of experiments. Detection of the most important crop characteristics, which provide the competitiveness against weeds for cereal breeding aims in organic growing conditions, is stressed as a desired result. First Conclusions The first year’s results of investigation show that some crop traits are signifficantly correlated with weed growth. However, these results should be reviewed for correctness in next at least two years more of experiments. Detection of the most important crop characteristics, which provide the competitiveness against weeds for cereal breeding aims in organic growing conditions, is stressed as a desired result.