In vitro germination of urediniospores of Puccinia psidii Winter on water and mineral oil

The variability observed in P. psidii urediniospores germination is possibly related the pathogen itself, the host and the environment. The urediniospores of P psidii present a poor germination in water, nevertheless in mineral oil it is possible to observe higher levels of germination, probabily due to the dissolution of the self-inhibitor present in the spores. This work intended to investigate the percentage of germination ofP psidii urediniospores in both water and mineral oil at four temperatures and on different days after inoculation (d.a.i.). The temperatures tested were 10, 15, 20 and 25°C and urediniospores were collected at 12, 14, 17, 24 and 31 d.a.i.. Germination in oil was evaluated at 12, 24 and 48 hours of incubation with its levels increasing up to the temperatures of 17.3; 17.84 and 17.76°C, respectively, and corresponding to 0.54; 0.62 and 0.64%. The above values of temperature and germination were transformed by arcsen x/100. The maximum and minimum germination of urediniospores were detected spores with 10 and 31 d.a.i., respectively. For germination in water, mean test was performed. Urediniospores colleted 24 d.a.i. and submitted to the temperature of 15°C yielded greater germination. These results point out to a possible dissolution of inhibitors in contact with the mineral oil. The youngest spores provided higher germination percentages in oil, probably due to their lower amount of self-inhibiting substances and their easier dissolution in the medium.