ABSCISIC-ACID IS A POTENT INHIBITOR OF GROWTH AND SPORIDIAL FORMATIONIN NEOVOSSIA-INDICA CULTURES - DUAL-MODE OF ACTION VIA LOSS OF POLYAMINES AND CELLULAR TURGIDITY

The inhibition of polyamine biosynthesis in Neovossia indica (Mitra) M undkur by D,L-alpha-diffuoromethylornithine (DFMO) caused an effective reduction of mycelial growth and sporidial production under in vitro conditions, which was reversed by ornithine application. Abscisic acid proved to be similarly effective, not only in inhibiting mycelial gro wth and sporidial formation but also the germination of teliospores, w hich constitute the primary inoculum of the pathogen. ABA-mediated inh ibition resulted in decreased polyamine levels and loss of cellular tu rgidity of, mycelial cultures. Scanning electron microscopy of ABA-tre ated cultures revealed extremely shrunken hyphae, in marked contrast t o the turgid controls. It is suggested that the manipulation of ABA le vels and/or tissue sensitivity in wheat could be a strategy to combat 'Karnal' bunt, the disease caused by N. indica.