Ariano Martins de Magalhães Júnior

Characterization of herbicide tolerant rice genotypes under hydroponic culture

Authors declare no conflict of interest The use of nutrient solution combined with different herbicide concentrations allows the evaluation and discrimination of tolerant and non-tolerant genotypes to imidazolinone herbicides. The objectives of this research were to identify possible morphological characteristics to be used as markers of resistance to imidazolinones, as well as the identification of herbicide doses and evaluation time to discriminate sensitive and tolerant genotypes of rice under hydroponic systems. Six rice genotypes four characterized as sensitive, BRS Querência, BRS Border, BRS Atalanta and BRS Pampa and two as tolerant, BRS Sinuelo CL and PUITA INTA CL to imidazolinones were tested in a hydroponic system. Four doses of herbicide were tested, which were evaluated at 7, 14, 21 and 28 days after transplantation. The insertion of the first leaf was the most responsive variable and can be used as morphological marker in experiments for selecting rice genotypes tolerant to imidazolinones. The best time to discriminate genotypes is the 7 day of development. The concentration of herbicide that enables better discrimination between tolerant and sensitive genotypes is 25 μg L, according to the methods described in this bioassay.

Response of rice genotypes subjected to salt stress

Authors declare no conflict of interest Soils with high salt concentrations (NaCl) may affect plant development and nutrient uptake in rice. The objective of this experiment was to evaluate the response of rice cultivars released by Embrapa Clima Temperado to salt stress at the germination and seedling stages. Four NaCl concentrations (0, 40, 80 and 120 mM) and a random factorial design 4×6 (dose × genotype), the cultivars belonging to the Embrapa germplasm collection were evaluated, BRS Bojuru (the only tolerant variety), BRS Pampa, BRS 7 Taim, BRS Querência, BRS Atalanta and BRS Sinuelo CL, with three replicates. After 14 days, the levels of Na, K, Ca and Mg absorbed by the plant shoots and roots were determined. NaCl was not significantly present in the germination stage. In the first germination count, BRS Bojuru and BRS 7 Taim decreased the germination with the increase in salt. The length of the first leaf in the 40 mM dose at 14 days of development (vegetative stage) is indicated as morphological marker for discriminating sensitive and tolerant genotypes to salinity in hydroponic system. The cultivar BRS Pampa showed higher ability of leaf Ca and Mg translocation under salt stress conditions.

Hyperthermotherapy in the Rice Emasculation Process

Aims: The objective of this work was to evaluate the emasculation by hyperthermotherapy method in irrigated rice genotypes, and to compare it with the emasculation by vacuum suction. Study Design: The experimental design used to compare the two methods was completely randomized, with two treatments (emasculation by hyperthermotherapy and vacuum suction) and six replications. To analyze the emasculation by hyperthermotherapy, this design was also used with three replications. Place and Duration of Study: The study was carried out in the agricultural years of 2012/2013 (1st year) and 2013/2014 (2nd year), at the Terras Baixas Experimental Station of Embrapa Clima Temperado, in the municipality of Capão do Leão, RS (31o48’15.47” S and 52°24’47.11” W). Original Research Article Aguiar et al.; JEAI, 18(4): 1-10, 2017; Article no.JEAI.37597 2 Methods: In the emasculation by hyperthermotherapy, 48 treatments were analyzed, consisting of the combination of 6 water temperatures (40°C, 42°C, 44°C, 46°C, 48°C and 50°C), 4 panicle immersion times (2.5 min, 5.0 min, 7.5 min and 10 min) and two cultivars (BRS Pampa and IAS 12-9 Formosa). Results: The progressive increase in the temperature and time decreases the formation of grains until a certain condition in which the total sterilization of rice flowers occurs, being possible execute the emasculate before this occurs. This condition is 46°C for 2.5 minutes of panicle immersion. The genotype IAS 12-9 Formosa showed higher tolerance to high temperatures. Conclusion: The condition that presented the best result to perform the hybridization was a temperature of 46°C for a panicle immersion time of 2.5 minutes for both cultivars. The hyperthermotherapy produces a smaller amount of grains, but presents a lower percentage of selffertilization, thus, being more effective in the artificial rice hybridization process.