Caracterização de mutantes M3 de arroz derivadas da cultivar BRS Pampeira sob déficit hídrico

Abstract

Rice is one of the most grown and consumed crops worldwide, and Brazil produces 12 to 13 million tons every year. In this country, the largest part of the cereal production takes place in the Southern region. Paddy system predominates at this region and also around the globe, however it requires a large use of water. High using of water brings environmental issues, increases the production cost and, taking into account the current climate change, there is a concern that the availability of this resource for agriculture may be under risk. Thus, efforts towards breeding rice for rainfed system are needed. However, this system shows risk for water deficit. This study aimed to 1) develop a protocol for evaluating rice genotypes for tolerance to drought in the field, for conditions in southern Brazil; 2) characterize mutant rice families in terms of tolerance to stress due to water deficit, as well as to agronomic performance; 3) evaluate a population of rice mutant lines regarding chlorophyll indexes under drought conditions, associating these traits with yield, and selecting promising lines. The experiments were carried out at field (under a rainout shelter), at the Estação Experimental Terras Baixas, belonging to Embrapa Clima Temperado, Capão do Leão / RS, during the 2019/2020 crop season. The mutant families assayed were at M3 generation and were obtained from the elite cultivar BRS Pampeira, through the seed treatment with gamma rays (60Co) (148 and 146 families obtained from the doses of 250 and 300 grays, respectively). For the drought tolerance assessment protocol, four contrasting cultivars were subjected to water stress (-50kPa) in the vegetative and reproductive periods, and different traits of growth, development and productivity were evaluated. To characterize the mutant families and evaluate the chlorophyll indices, the water deficit (100 kPa at 10 and 15 cm) started from the R2 stage until 10 days after R4. Plants were evaluated during and at the end of the reproductive cycle for photosynthesis parameters and agronomic and yield traits. The results of protocol testing demonstrate that the contrasting genotypes studied did not show significant differences under the applied drought stress (-50kPa) at the reproductive periods. The studied population has a wide genetic variability for drought tolerance and promising mutants were identified for the development of improved cultivars for the different agronomic traits studied. There was also a low correlation magnitude between agronomic traits and chlorophyll indices in populations evaluated under drought stress conditions