STRESS-INDUCED FORMATION OF HAPLOID PLANTS THROUGH ANTHER CULTURE IN CORK OAK (QUERCUS-SUBER)

Induction of haploid embryos and regeneration of plantlets have been o btained, for the first time, in cork oak (Quercus suber L.) by combini ng a starvation treatment in anther culture with a mild heat shock at 33 degrees C for 5 days, followed by culture at 25 degrees C in a simp le agar medium without growth regulators. The same conditions had been shown previously to be optimal for embryogenic induction in isolated microspore cultures of several model species such as tobacco and wheat . These results support the notion that stress, particularly sucrose s tarvation, a heat shock or a combination of both treatments could be t he major and general signal responsible for the inhibition of normal g ametophytic development of the microspores and for the induction of th e alternative embryogenic pathway. A similar approach may be used for the production of haploid and doubled haploids for plant breeding in o ther species that, like most forest trees, are still recalcitrant in a nther culture.