Diquat Resistance of Different Paraquat Resistant Conyza canadensis (L.) Cronq. Biotypes

Zoltán Szigeti, Éva Darkó, Erika Nagy, Endre Lehoczki

Research output: Contribution to journalArticle

7 Citations (Scopus)


Photosynthetic responses of paraquat/atrazine coresistant (PqAR) and only paraquat resistant (PqR) biotypes of horseweed [Conyza canadensis (L.) Cronq.] on diquat (Reglone) treatment were investigated. Both resistant biotypes showed a transitory inhibition of photosynthetic activity characterized by in vivo CO2 fixation and Fv in the first 2 hours after spraying of the intact plants with 0.5 mM diquat. Similar to the kinetics observed after paraquat spraying of the resistant plants this transitory inhibition was also followed by a gradual recovery. Comparison of paraquat and diquat treatment of paraquat/atrazine coresistant plants showed that recovery after diquat spraying was slower. Ultrastructure of chloroplasts from resistant plants treated by floating the leaves on 10 μM diquat solution showed only moderate changes, while chloroplasts from sensitive Conyza plants seemed to be severely damaged. Paraquat/atrazine coresistant Conyza biotypes of different origin exhibited different, but relatively high resistance against diquat (resistance factor of PqAR1 = 50, PqAR2 = 102). Resistance factors for paraquat were higher (PqAR1 = 210, PqAR2 = 650).

Original languageEnglish
Pages (from-to)686-690
Number of pages5
JournalJournal of Plant Physiology
Issue number6
Publication statusPublished - Jan 1 1994


  • Conyza canadensis (L.) Cronq.
  • Dq
  • F
  • F
  • F
  • I
  • PAR
  • PS
  • Pq
  • PqAR
  • PqR
  • Rf
  • S
  • chlorophyll fluorescence
  • chloroplast structure
  • concentration necessary to achieve 50 % inhibition
  • diquat
  • diquat resistance
  • horseweed
  • maximum fluorescence yield
  • minimum fluorescence yield following dark adaptation
  • paraquat
  • paraquat resistant biotype
  • paraquat/atrazine coresistant biotype
  • photosynthesis
  • photosynthetically active radiation
  • photosystem
  • resistance factor
  • susceptible biotype
  • variable fluorescence

ASJC Scopus subject areas

  • Physiology
  • Agronomy and Crop Science
  • Plant Science

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