Seleção de genótipos de sementes de arroz de terras altas submetidos ao estresse hídrico

Abstract

The rice (Oryza Sativa L.), it is the most cultivated cereal in the world, being China the bigger producer and the Brasil occupyng the ninth position between the producers around the world. Although it shows high suceptibility to water stress, around 59% of the brazilian rice is cultivated in the upland ecossystem, without irrigation. In Maranhão the producers’ reality is characterized by the use of rustic varieties and absence of thecnologies in the production system. Therefore, the drop of 70% in upland rice production, in part, becouse of inherent crop factors, both of the point of view of the soil and climate. So that the farmer suceed in the rice cultivation, it is necessary the use of good quality seeds and adapted to climate variations to provide better productivity indexes. The purpose of this study, it is to avaluate the fisiological potential in order to classificate upland rice genotypes tolerant to water stress and with and high vigor. The experimente was conducted in the seeds analysis laboratory of the Universidade Estadual do Maranhão - UEMA. Ten upland rice seeds genotypesproduced in the State of Maranhão were sown in substrate with osmotic potentions of 0.0; -0.2; -0.4 and -0.6 Mpa. Were avaluated the water contente, germination test, firs count and germination rate index and seedlings aerial and root length. The physiological potential of upland rice seeds and seedlings, becoming sensitive to water deficit induced by PEG 6000 from the osmotic potential -0.4 Mpa. Germination tests, first germination counts, germination speed index, and shoot and root lengths are efficient in assessing the physiological potential of upland rice seed lots, providing sufficient information for the classification of lots the level of vigor. Rice genotypes respond differently to water stress, with lot 2 being the most tolerant to waterrestriction