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Discussion
The differences among genera and species in the level of
resistance to scab were closely related to the ecological conditions
where they grow. The most resistant genera, Roegneria, is
distributed in temperate and subtropical zone, and usually
thrives in meadows, open shrublands and forests, beside streams and
on moist mountain slopes. Other genera that showed good resistance
grow in humid area during the flowering stage. Hystrix is
distributed in sparse forests. The four analyzed species of
Kengyilia are distributed in high mountain plateau area, from
1100 m to 4750 m altitude, where rain showers are relatively
common during their flowering stage. Elymus is distributed in
temperate zone of the Northern Hemisphere, and grows in the open
shrublands and forests, or on moist mountain slopes. Agropyron
occurs mainly in prairie, slope or hilly land of Asia. On the
other hand, the annual wild species of Hordeum, Aegilops,
Eremopyrum, Heteranthelium, Henrardia, Crithopsis, Taeniatherum
and Haynaldia, which are susceptible to scab, are
distributed in Mediterranean-Central Asiatic regions (Sakamoto,
1973) where it is hot and dry during the flowering period of
these genera and species. These results suggest that during the
process of mutual adaptation and coevolution of the host and
pathogens, genes for scab resistance might have accumulated in
particular genera.
Ae. tauschii and T. monococcum, which are diploid donor
species of D and A genome of the common wheat, respectively, showed
high susceptibility to scab. No materials with high resistance to
spread were found in tetraploid wheat. However, we found 3.43% of
hexaploid common wheat as highly resistant to spread. Most of common
wheat resistant to scab are Chinese landraces from Zhejiang, Jiangsu,
Hunan, Hubei proveniences and Shanghai City located in the middle and
lower reaches of the Yangtse River. Out of 82 landraces,
among which 17 were highly resistant to spread, including
Wangshuibei from Jiangsu, Gunmai from Hunan, Bagutao from Hubei,
Yazitou from Shanghai, Changmangmai from Zhejiang, etc. In Guizhou,
Sichuan and Yunnan provinces which locate in southwest of China,
eleven out of 98 landraces were highly resistant to spread, including
Wuyangmai from Sichuan, Changmangmai from Guizhou, Zimai from Yunnan,
etc. No landraces showed high resistance to spread in Hebei, Shanxi,
Shaanxi provinces and Beijing City that locate in northern China.
Along the middle and lower reaches of the Yangtse River, there is a
rainy season called Plum Rains, that affects the climate of southeast
of China and results in continuous humid and warm weather during the
blooming stage of wheat, while in northern China the weather is dry.
The results indicated that variation in resistance to scab is closely
related to the ecological conditions where they grow.
References
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Mesterhazy A (1987) Selection of head blight resistant wheats through
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Sakamoto S (1973) Patterns of phylogenetic differentiation in the
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Shroeder HW and Christensen JJ (1963) Factors affecting resistance of
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