TO NORMAL AND LOW TEMPERATURES

Ryegrass, a plant that produces forage during the winter and spring, is much used in pasture in the south of Brazil. Despite being a cold station specie, low temperatures can restrict their development.. The present work was developed with the objective of comparing the establishment of ryegrass populations submitted to cold temperatures with the same populations in normal conditions and determine the population’s tolerance to lower temperatures. An experimental design of subdivided plots was used. Four months after sowing, plant height, length of the biggest sheet of main tiller, tiller number and number of leafs in the main tiller were evaluated. There were effects of genotype and environment but not genotypeenvironment interaction for the studied traits. The Comum-Ijui and CNPGL130 populations showed the highest values for plant height; Comum-Ijui, CNPGL130, CNPGL136 and Eclipse showed the highest values for number of leafs in the main tiller; CNPGL130, CNPGL136 and Eclipse achieved the highest values for leaf length; whereas Eclipse, LE284 and CPPSUL 001 presented more tillers then the other populations. The populations do not differ with regard to cold tolerance. However, they differ on initial development, which selection helps to ensure the availability of forage during the winter.