Nodulation patterns of actinorhizal plants in the family rosaceae

Abstract

Patterns of nodulation, growth, and Frankia - host specificity have not been well characterized for the actinorhizal genera in the family Rosaceae because of the scarcity of Frankia isolates from these taxa. Furthermore, the few isolates available from actinorhizal Rosaceae have consistently failed to nodulate plants from the host genus. In a series of experiments, species of rosaceous Dryas, Cowania, Cercocarpus, Fallugia, and Purshia were inoculated with Frankia isolates, crushed Dryas actinorhizae, and neoglacial soils to ascertain whether any of these inocula would effectively induce nodulation. Neoglacial soils from Alaska and Canada nodulated not only the local Dryas drummondii, but also Cercocarpus betuloides, Cowania mexicana and Purshia tridentata from distant and ecologically diverse locales as well as nonrosaceous, actinorhizal species of Alnus, Elaeagnus, Myrica, and Shepherdia. But of eight Frankia isolates, including two from Purshia tridentata and one from Cowania mexicana, none were able to induce nodulation on Purshia or Cowania species. Globular, actinorhizae-like nodules incapable of acetylene reduction were produced on C. betuloides inoculated with Frankia isolates. Crushed nodule suspensions from Dryas drummondii nodulated rosaceous Cowania, Dryas and Purshia, as well as non-rosaceous Elaeagnus, Myrica, and Shepherdia species. Nodules produced by inoculation of Cowania mexicana and Purshia tridentata with crushed, dried nodule suspensions from Dryas drummondii reduced acetylene to ethylene, indicating nitrogenase activity for these nodulated plants. These data suggest that a similar microsymbiont infects the actinorhizal genera in the family Rosaceae. © 1994 Kluwer Academic Publishers.