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Molecular Basis of Resistance to s-Triazine Herbicides in Poa annua L. and Its Photosynthetic Properties under Different Light Conditions
Shuji KUMATA, Koichi YONEYAMA, Masaru OGASAWARA, Yasutomo TAKEUCHI, Makoto KONNAI, Yoshihiro NAKAJIMA, Takeshi NAKANO and Shigeo YOSHIDA
J. Pestic. Sci.
26, 236-243 (2001)
A simazine resistant biotype of Poa annua L. was found in a golf course in Shizuoka prefecture, Japan. The biotype was highly resistant to s-triazines, almost equally susceptible to the phenylurea, diuron, and more susceptible to the phenol, dinoseb, than the susceptible biotype both at whole plant and at isolated thylakoid levels. The molecular basis of resistance to s-triazine herbicides in the resistant biotype was identified as a mutation in psbA gene giving rise to the replacement of serine 264 by glycine in the D1 protein of photosystem II (PS II). The resistant biotype showed a reduced capacity of photosynthesis when grown under full-sunlight conditions. However, no differences were observed in photosynthetic performance of susceptible and resistant biotypes when grown under shaded conditions. The resistant biotype also showed increased sensitivity to photoinhibition both at whole plant and at isolated PS II membrane levels, indicating that the increased susceptibility in the resistant biotype to the photoinhibition is due to the substitution of serine 264 to glycine in the D1 protein.
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