Transfer of amiprophosmethyl resistance from a Nicotiana plumbaginifolia mutant by somatic hybridisation

Transfer of resistance to the phosphorothioamidate herbicide, amiprophosmet hyl (APM), from the P-tubulin mutant of Nicotiana plumbaginifolia to the in terspecific N, plumbaginifolia (+) N, sylvestris is and to the intertribal N, plumbaginifolia (+) Atropa belladonna somatic hybrids has been demonstra ted. Transfer to the recipient species was accomplished by: (1) symmetric h ybridisation and (2) asymmetric hybridisation using gamma-irradiation of do nor protoplasts. Cytogenetic analysis confirmed the hybrid origin of the hy brids obtained. It was established that most of them typically inherited no more than three donor chromosomes, although it was possible to obtain symm etric hybrids in the case of symmetric fusion. Immunofluorescent microscopy analysis has shown that protoplasts of the mutant, and of the N. plumbagin i-folia (+) N. sylvestris and N. plumbaginifolia (+) A. belladonna hybrids, retained the normal structure of interphase microtubule (MT) arrays and mi totic figures after treatment with 5 mu M APM, whereas MTs of protoplasts o f the recipients were destroyed under these conditions. It was also shown t hat hybrid clones contained an altered beta-tubulin isoform originating fro m the N. plumbaginifolia mutant. The selected hybrid clones were characteri sed by cross-resistance to trifluralin, a dinitroaniline herbicide with the same mode of anti-MT action. Some of the somatic hybrids which could flowe r were fertile. It was established that seeds of some fertile hybrids were able to germinate in the presence of 5 mu M APM. The results obtained thus support the conclusion that the technique of somatic hybridisation, especia lly asymmetric fusion, can be used to transfer APM resistance from the N. p lumbaginifolia mutant to different (related and remote) plant species of th e Solanaceae, including important crops.