Reduction of meiotic homologous chromosome pairing due to high temperature in common wheat.

Effect of high temperature on meiotic homologous chromosome pairing of common wheat was examined. According to the experimental results, constant high temperature of 30°C significantly reduced homologous pairing compared with 15, 20 and 25°C, and such effect was recognized only when the PMCs of some limited stage immediately before premeiotic S phase were exposed to the temperature. Besides, the high temperature did not affect the pairing of both arms of an isochromosome (1A-long-arm) at all.It was strongly suggested from these results that (1) high temperature of 30°C disturbs the process of pairing at a step which controls premeiotic inter-homologues attraction, creating such a situation as homologues are spatially kept away each other, and (2) this step may closely be connected with a peculiar stage sensitive to the high temperature. A similarity of acting mechanism among high temperature, colchicine and Ph allele was also discussed.