Fenotipagem e expressão de proteínas de linhagens de arroz de terras altas para à tolerância a deficiência hídrica

Abstract

Water deficiency stress, especially during the flowering period, can reduce upland rice yield in 100%. One way to overcome this problem is to use drought tolerant genotypes. Conventional breeding combined with other tools, such as studies of enzyme expressions involved in the drought tolerance process, can contribute greatly for the success of selection in order to increase the stability of production under the occurrence of water deficits. Therefore, this study aimed to phenotype upland rice lines cultivated in environments with and without water deficiency, verifying the enzymatic mechanisms involved in stress tolerance and to identify the greatest lines for drought tolerance. Twenty lines of upland rice from the VCU trial (value of cultivation and use) belonging to UFLA’s Rice Breeding Program, in partnership with Embrapa Arroz e feijão and EPAMIG, were evaluated. The experiments were conducted in Nossa Senhora das Dores/SE in the 2015, 2016 and 2017 seasons and in Lavras / MG and Patos de Minas/MG in the 2014/2015 season. The experiments implanted in Minas Gerais were conducted under irrigation throughout the crop cycle. Two experiments were implemented in Nossa Senhora das Dores, one of them was conducted under supplementary irrigation throughout the development of the crop, maintaining the optimal water conditions, and the other one the water deficit in the reproductive period was induced before the panicle emission, which was confirmed by daily readings of tensiometers installed in the experiment, and irrigation was performed when the mean of these readings were around -50 kPa , which indicated water stress for rice. In all experiments, a randomized complete block design with three replications, was used the plots consisted of 3 lines of 4 m spaced in 0.35 m. and 80 seed / meter seeding density. The grain yield (kg/ha), plant height (cm), number of days for flowering (days), head rice yield (%), milled rice (%), spikelet sterility (%), chalkiness and 1000 grain weight were evaluated. A statistical analysis, was performed, with the obtainment of phenotypic correlations and studies of phenotypic plasticity by the GGEBiplot method. After harvesting, grain samples from Nossa Senhora das Dores, 2016 season, were analyzed to enzymatic expression of catalase, superoxide dismutase and heat resistant protein. The water deficit caused a reduction in grain yield and plant height, an increase in the percentage of broken grains, chalkiness and spikelet sterility. The CMG 2085, CMG 2093 were the least affected by the water deficit, showing the greatest performance under the different water conditions, being considered tolerant to the water deficit. The enzymatic expression was influenced by water stress and each line can react to the water deficit in different way and with different defense mechanisms. The CMG 2168 line presented a better mechanism to protect against oxidative damage under drought stress and may be classified as tolerant to water deficit.