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).

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 self-fertilization, thus, being more effective in the artificial rice hybridization process.