Avaliação de cruzamentos de arroz tolerantes/sensíveis à baixa temperatura no estádio de germinação e estudo do transcriptoma

Abstract

Rice is a tropical crop widely grown in a variety of areas, is currently the second most-produced cereal in the world. The presence of low temperatures is a common stress in rice crops in temperate regions, so the tolerance to low temperatures is a desirable characteristic in Brazilian rice genotypes cultivated in the south, where low temperatures damage germination, establishment of the crop and decrease grain yield. Therefore, this paper aims to study the behavior of rice crossings tolerant and sensitive to cold tolerance at the germination stage and identify differentially expressed genes through the transcriptome. Controlled crosses with 5 contrasting genotypes were performed. The parents and segregating populations in F3 and F4 were subjected to treatments with different temperatures (13C e 25C) and compared for their relative performance, as measured by germination, germination speed index in the laboratory and in the field, length coleoptile length and root. The transcriptome analysis was performed through the RNAseq two genotypes BRS SCS Tio Taka and Oro, submitted to treatment with different temperatures (13C e 25C). The results show that the germination speed index obtained in the laboratory, has higher efficiency and populations to identify genotypes compared with the field evaluation. The length of the coleoptile and the germination speed index are the most appropriate methodologies due the high association with germination at low temperatures. The results of the correlations in the generation F3 differed from the results shown in the F4 generation due to segregation populations. In tolerant cultivar Oro, few genes have increased gene expression significantly. A list of 55 genes with common expression difference in the two cultivars and a list of 17 genes with only difference in the expression for the tolerant cultivar Oro, were selected due to responses of these genes to cold tolerance in rice germination.