Effects of the growth regulator and chemical control of diseases on the physiologic and sanitary quality of rice seeds

This study aimed to evaluate the effects from the application of the growth regulator ethephon and the tebuconazole fungicide on the physiologic and sanitary quality of rice seeds cropped at different sowing densities. A factorial combination (2x2x4) of two varieties (IRGA 417 and El Paso L 144), two sowing densities (50 and 150kg.ha-1) and four chemical treatments (1-control, 2-ethephon, 3-tebuconazole, 4-ethephon + tebuconazole) was used on a randomized block experimental design with three replicates. Both the physiologic and sanitary quality of the seeds were evaluated at two different times (just after harvesting and at 120 days under storage) by applying the tests for germination, first germination count, cold, emergency, emergence speed index and health test. The germination of the seeds cropped under tebuconazole pulverization showed a better performance in the El Paso L 144 variety, since this cultivar was shown to be more susceptible to diseases. The vigor tests showed the seeds cropped with application of the tebuconazole performed better in both cultivars. The seed health test revealed high incidence of fungi in the treatments without fungicide pulverization, and their incidence was also higher in the El Paso L 144 variety compared to the IRGA 417 variety. The varied sowing density did not affect the seed quality.

Oryza sativa; seed pathology; vigor; fungicide