Physiological characterization of Cochliobolus bicolor (sin. Bipolaris bicolor) from wheat BRS 264 seeds.

Several diseases cause a reduction on the wheat (Triticum aestivum L.) yield, among which is helminthosporiosis, which infects the plant in all its stages of development. The objective of this work was to carry out the physiological characterization, under different temperature regimes of Cochliobolus bicolor isolates from BRS 264 wheat seeds. The six isolates of C. bicolor were recovered from the mycoteca stored in the Plant Pathology Laboratory of the Goiás State University. For the physiological evaluation, C. bicolor isolates were inoculated in Petri dishes containing PDA medium and subjected to six temperatures: 10°, 15°, 20°, 25°, 30° and 35°C. The evaluations were carried out obtaining the measurements of mycelial growth during 5 days. At 8 days after inoculation (DAI), a total of 10 mL of sterilized distilled water was added to each Petri dish, followed by the release of spores with a Drigalsky loop, the suspensions obtained were measured in a Neubauer chamber. For the germination tests, plastic Petri dishes containing agar-water medium were used, to which 100 µL C. bicolor spores suspension were added. Then the plates were taken to BOD at 25°C and constant light. The germ tube length of five spores per Petri dish was measured during five hours. The experimental design was completely randomized, with five replications (Petri dishes) for each C. Bicolor isolate. The temperature of 25°C provided greater mycelial growth area, sporulation and spore germination.