Studies on the resistance to pink snow mold in winter wheat [Triticum aestivum]
1998
Nakajima, T. (Tohoku National Agricultural Experiment Station, Morioka (Japan))
The objectives of the present studies were (i) to develop efficient assessing method for resistance to pink snow mold caused by Microdochium nivale in winter wheat, (ii) to elucidate environmental factors affecting resistance and (iii) to clarify mechanisms involving resistance. Incubation of inoculated plants at the optimum temperature of 15 decrees C for the growth of M. nivale could reduce the incubation period considerably. the level of resistance was quantitatively expressed as LI50 (duration of incubation in days to achieve 50% mortality). The relative order of resistance among the cultivars was consistent with that obtained from field trials. This method that involves optimum temperature incubation was found to be suitable for the screening of resistant lines. I traced the resistance from sowing to snow thaw and proposed stereo-typing of winter wheat cultivars based on the curve of the progression of resistance. These ecological analyses should be useful for determining the: regional adaptability of wheat cultivars. The upper limit of conditioning temperatures for the expression of snow mold resistance varied among the cultivars. The resistance increased with increasing duration of the period of pre-hardening growth. Light intensity was essential for the expression of the resistance but not a limiting factor. Penetration of M. nivale occurred though the stomata at 0 degrees C but M. nivale could not penetrate leaf at -3 degrees C. No varietal differences in resistance were observed in leaf. We tested the hypothesis according to which key materials involved in the resistance might translocate from leaf to crown and found that cold hardening induced chlorophyll degradation under snow
显示更多 [+] 显示较少 [-]