Avaliação de cultivares de arroz cultivados no Rio Grande do Sul quanto à tolerância ao frio no estágio germinativo

Abstract

With more than 2 million hectares planted in Brazil, the rice crop stand out in the state of Rio Grande do Sul, where is concentrated the majority of the country’s irrigated rice production. The recommended seeding season for rice in the state of Rio Grande do Sul matches with low temperature periods, damaging the establishment of the crop and limiting the yield. The optimum temperature range for rice to germinate sets between 20ºC and 35ºC, it is also known that the temperature of 10ºC, is the critical minimum value, below which germination does not occur. Therefore it is indispensable the study of the changes caused in the plants by the low temperatures in the germination phase. The objective of this work was to evaluate the behavior of some of the most cultivated irrigated rice cultivars in Rio Grande do Sul, when exposed to low temperatures during the germination phase. The work was carried out at the Federal University of Pampa, Itaqui Campus, Rio Grande do Sul, Brazil, in the laboratory of Phytopathology and Soil Microbiology, in a germination chamber, using temperatures of 25ºC and 13ºC. The experimental design used was entirely at random, in factor scheme (2x4), with two temperatures and four cultivars, where the observation unit was constituted of 20 plantas for each cultivar. Were evaluated four rice cultivars: IRGA 417, IRGA 424 RI, IRGA 426 e GURI INTA CL, and the analyzed variables were coleoptile length, dry matter of seedlings and percentage of germination. Stress by cold caused reduction in the variables CC, MS, and PG. The variable coleoptile length was efficient to distinguish the genotypes as the tolerance for stress by cold, and the cultivars IRGA 417 E IRGA 424 RI those that have had the highest values for coleoptile length in low temperature conditions.